GB2641362A

GB2641362A - Device for relieving pain and/or delivering sedation

Info

Publication number: GB2641362A
Application number: GB2407489.0A
Authority: GB
Inventors: Neil Miller Andrew; Stacey Luke; Darwood Alastair
Original assignee: Intersurgical AG
Current assignee: Intersurgical AG
Priority date: 2024-05-24
Filing date: 2024-05-24
Publication date: 2025-12-03
Also published as: WO2025242883A1; GB202407489D0

Abstract

A device 1 for providing pain relief and/or sedation to a patient, the device comprising a handset 301 and a patient delivery interface 10 e.g. mask, the handset having a patient-controlled initiator and electronic dosage control means and being engaged, in use, to a reservoir 322 configured to contain a liquid pain relieving and/or sedative substance, the patient delivery interface being, in use, fluidly connected to the reservoir via a conduit 307, wherein, on actuation of the patient-controlled initiator, an input is provided to the dosage control means, the dosage control means consequently providing an output which controls the transfer of a portion of the liquid pain-relieving and/or sedative substance from the reservoir 322 to the patient delivery interface 10.

Description

Device for relieving pain and/or delivering sedation This invention relates to a device for relieving pain and/or delivering sedation. In particular, this invention relates to a device for relieving pain and/or delivering sedation through the administration of a pain-relieving and/or sedative substance.

The use of sedation, rather than general anaesthesia, is beneficial for patients, clinicians and healthcare organisations. It has been shown to result in a lower incidence of postoperative cognitive dysfunction, shorter hospital stays, and a reduced environmental impact (Anaesthesia and Perioperative Medicine Getting It Right First Time Programme National Specialty Report (2021)). However, sedation remains underutilised as an alternative to general anaesthesia, possibly due to patients' and clinicians' concerns about safety and intraoperative awareness and recall (Chatman N, Sutherland JR, van der Zwan R, Abraham N. A survey of patient understanding and expectations of sedation/anaesthesia for colonoscopy. Anaesth Intensive).

Sedation also has utility outside the hospital and surgical setting. GP surgeries often perform minor procedures such as mole removal and IUD insertion which cause pain and/or discomfort for the patient, but for which there are currently limited options for effective pain relief. Outside the clinical setting, acute situations such as sports injuries or injuries resulting from accidents can lead to severe pain, for which significant pain relief may not be available until the patient has been removed to a clinical setting. In such situations, effective, portable sedation would have a significant impact on alleviating pain. Furthermore, given a suitable sedation approach many medical and surgical procedures currently conducted under general anaesthetic could be carried out in an outpatient setting. This would provide significant operational efficiency improvement and better utilise operating theatre resources.

Effective sedation is a balancing act between awareness and anaesthesia. If too little sedation is given patients may continue to experience discomfort, and be able to recall intraoperative events. On the other hand, if too much sedation is given, patients may become fully anaesthetised and require airway, respiratory or cardiovascular support. Sedation can be delivered with intravenous or inhalational drugs and the drug doses can be controlled by clinicians or by the patients themselves, with clinician-delivered intravenous sedation being the most common.

However, there are benefits associated with patient-controlled sedation/analgesia, including minimisation of drug doses and improved patient satisfaction (Sheahan CG, Mathews DM. Monitoring and delivery of sedation. Br J Anaesth. Dec 2014;113 Suppl 2:1137-47. doi:10.1093/bja/aeu378). Likewise, inhalational drugs offer advantages over intravenous delivery, including less inter-individual dose response variability and faster recovery (Sahinovic MM, Struys M, Absalom AR. Clinical Pharmacokinetics and Pharmacodynamics of Propofol. Clin Pharmacokinet. Dec 2018;57(12):1539-1558. doi:10.1007/s40262-018-0672-3; Ibrahim AE, Ghoneim MM, Kharasch ED, et aL Speed of recovery and side-effect profile of sevoflurane sedation compared with midazolam. Anesthesiology Jan 2001;94(1):87-94.

doi:10.1097/00000542-200101000-00018). However, potentially due to concerns about safe dosages, suitable administration apparatus and an increased risk of disinhibition-excitation, patient-controlled and inhalational delivery have not been widely adopted.

Patient-controlled analgesia devices are known in the art, and generally comprise a means for requesting a dose of analgesia (eg a button), a reservoir of medicament, a means for transferring the medicament from the reservoir to the patient, and a means of patient delivery (most commonly infusion). For example, US2004127860 discloses a patient-controlled drug delivery device comprising a cylindrical handset having a button located on one end of the handset, the handset being connected both to a medication source and to an IV infusion. Pressing the button mechanically initiates the axial movement of a wall within the handset, thus compressing a reservoir of medication and delivering a bolus infusion to the patient. The reservoir contains a single dose of medication, and is refilled from an external source of pressurized liquid medicament via an inlet conduit. However, the need for a clinician to oversee the IV infusion, and the requirement for an external source of liquid medicament, mean that it is not suitable for use outside a clinical setting. Furthermore, many medicaments required for IV sedation or strong analgesia have complex side effect profiles and require trained operatives to prescribe and administer these agents.

Inhaled volatile anaesthetic agents are useful in the provision of analgesia and/or sedation due to their easily managed side effect profiles and relative safety at low concentrations. However, their administration usually requires an anaesthetic machine, which includes a medication storage vessel and a vaporiser, wherein the vaporiser is used to provide a defined inspired partial pressure of the medicament with a high degree of precision, at a range of temperatures and atmospheric pressures. While effective, they are cumbersome and expensive, and are not portable or suitable for use outside a hospital setting and not configured for patient control.

There is thus a need for an improved handset for a patient-controlled analgesia device which overcomes or substantially mitigates the above mentioned and/or other problems associated with the prior art and, advantageously, may be configured for the delivery of volatile anaesthetic agents.

According to a first aspect of the invention there is provided a device for providing pain relief and/or sedation to a patient, the device comprising a handset and a patient delivery interface, the handset having a patient-controlled initiator and electronic dosage control means and being engaged, in use, to a reservoir configured to contain a liquid pain-relieving and/or sedative substance, the patient delivery interface being, in use, fluidly connected to the reservoir via a conduit, and wherein, on actuation of the patient-controlled initiator, an input is provided to the dosage control means, the dosage control means consequently providing an output which controls the transfer of a portion of the liquid pain-relieving and/or sedative substance from the reservoir to the patient delivery interface.

The device and reservoir may be supplied together, and there is therefore also provided a kit of parts comprising device for providing pain relief and/or sedation to a patient and a reservoir, the device comprising a handset and a patient delivery interface, and the reservoir being configured to contain a pain-relieving and/or sedative substance, the handset having a patient-controlled initiator and electronic dosage control means and being engaged, in use, to the reservoir, the patient delivery interface being, in use, fluidly connected to the reservoir via a conduit, wherein, on actuation of the patient-controlled initiator, an input is provided to the dosage control means, the dosage control means consequently providing an output which controls the transfer of a portion of the liquid pain-relieving and/or sedative substance from the reservoir to the patient delivery interface.

There is further provided a device for providing pain relief and/or sedation to a patient, the device comprising a handset, a patient delivery interface and a reservoir, the reservoir being configured to contain a liquid pain-relieving and/or sedative substance, the handset having a patient-controlled initiator and electronic dosage control means and being engaged, in use, to the reservoir, the patient delivery interface being, in use, fluidly connected to the reservoir via a conduit, and wherein, on actuation of the patient-controlled initiator, an input is provided to 15 the dosage control means, the dosage control means consequently providing an output which controls the transfer of a portion of the liquid pain-relieving and/or sedative substance from the reservoir to the patient delivery interface.

The device of the invention provides pain relief and/or sedation to a patient, a pain-relieving and/or sedative substance being transferred from a reservoir engaged with a handset to a patient delivery interface via a conduit. The self-contained nature of the device, wherein the reservoir is engaged with the handset rather than being a vessel or other container separate from the device, makes the device of the invention portable and able to be used outside of a hospital setting. Moreover, only a portion of the liquid pain-relieving and/or sedative substance is transferred from the reservoir to the patient delivery interface, that is, the reservoir is not emptied in a single dose. Thus, a single reservoir can be used over a period of time to deliver multiple doses of a medicament for the relief of pain allowing, for example, for use of the device in a non-hospital setting to provide pain relief for a minor medical procedure, or to allow an acute patient to reach hospital.

By 'handset' is meant a device which is of a size that can be held by the user, and be operated by hand.

The invention concerns a device for relieving pain and/or delivering sedation. These effects may be achieved through the administration of medicaments of a variety of types, but in particular through the administration of sedatives, analgesics and/or anaesthetics. These medicaments may be administered alone or in combination to achieve the desired physical effect. In the context of the invention, 'sedative' is intended to refer to a medicament which induces a state of calm or sleep, 'analgesic' to a medicament which induces pain relief without the loss of consciousness and without total loss of feeling or movement, and 'anaesthetic' to a medicament which induces the loss of physical sensation with or without loss of consciousness.

The device of the invention may relieve pain and/or deliver sedation through the administration of one or more analgesics, anaesthetics and/or sedatives. Suitable pain-relieving or sedative substances are known in the art and may include sevoflurane, methoxyflurane, remifentanil, fentanyl, remimazolam, propofol and/or isoflurane. The pain-relieving and/or sedative substance used in the present invention may particularly be a volatile fluid, and may be selected from the list comprising sevoflurane, methoxyflurane and isoflurane. The volatile pain-relieving and/or sedative substance may be inhaled by the patient.

Different analgesics, anaesthetics and sedatives take varying lengths of time to take effect in the body after administration begins (onset) and to cease acting on the body once administration finishes (offset). This depends at least in part on the way in which the medication is metabolised by the body and/or eliminated, the method of administration, and/or the way in the medication is redistributed within the body, eg whether it circulates in the bloodstream or migrates to fat and muscle tissues, reducing the clinical effect.

The medication for use in the present invention may particularly be a pain relieving and/or sedative substance having rapid onset and rapid offset, that is, that it begins acting in the body quickly after administration begins, and only remains clinically active for a short time after administration ceases. This enables rapid, responsive changes in the delivery of the pain-relieving and/or sedative substance, with changes in dosage being rapidly felt by the patient.

Typically, the pain-relieving and/or sedative substance used in the present invention has rapid offset, and exhibits complete reversal of clinical effect within 15 minutes, or within 10 minutes, or within 7 minutes, or within 5 minutes of the administration of a clinically effective dose.

In particular, the medication may be an anaesthetic, for example sevoflurane. While commonly used as an anaesthetic, low doses of sevoflurane have been found to be an effective analgesic and sedative, with a typical offset time of 5 minutes or less, leading to quick patient recovery. Some memory loss of events occurring whilst under the influence of sevoflurane has also been reported by patients, which may be beneficial for patients in severe pain or undergoing a potentially traumatic procedure.

The user of the device is typically a patient. A clinician may initially set up the device for the patient and assist the patient in correctly donning the device, following which it is used by the patient.

The patient delivery interface provides an interface through which the pain-relieving and/or sedative substance is delivered to the patient, and may be any suitable interface known in the art.

The patient delivery interface may be an interface suitable for the inhalational delivery of medication. The patient delivery interface may be a face mask or a nasal mask. The patient delivery interface may be a face mask. The face mask may cover the mouth and nose of the wearer.

The face mask or nasal mask may comprise a seal about its periphery which abuts the patients face to create a seal and prevent the loss of medication to the atmosphere and increase comfort for the patient.

The face mask or nasal mask may comprise one or more filters to remove exhaled medicament from the air prior to exhaust to atmosphere. The one or more filters may be affixed to the mask, and may be removable. The one or more filters may contain activated carbon. The mass of activated carbon contained within the filter(s) is typically sufficient to absorb the volume of medication contained within the reservoir. The mass of activated carbon in the filter(s) may only be sufficient to absorb the volume of medication contained within the reservoir, thus reducing the cost of manufacture.

A pain-relieving and/or sedative substance in the form of a volatile fluid may be transferred from the reservoir to the patient delivery interface in liquid form. The volatile fluid may be vaporised in the patient delivery interface. The volatile fluid may be exposed to the atmosphere in the patient delivery interface, whereupon it evaporates and can be inhaled. The volatile fluid may be deposited on a substrate in the patient delivery interface, from which it evaporates for inhalation by the patient. Substantially all of the medicament deposited on the substrate may be inhaled in a single inhalation by the patient. The substrate may be textile, and may be, for example, a pad comprising cotton and/or gauze.

It will be appreciated that the device of the invention may be used in combination with other patient delivery systems.

The handset typically comprises a housing, and may be shaped to provide greater comfort for the patient and to be easier to use, even where a patient is in severe pain or has limited mobility. It has been found that a gripping motion is a common response to an increase in pain, and therefore that a handset which responds to a gripping motion by the patient with an increase in the delivery of a pain-relieving substance is desirable.

Thus, according to a further aspect of the invention there is provided a device for providing pain relief to a patient, the device comprising a handset having a patient-controlled initiator and a grip, the grip having a surface which is at least partially spherical or spheroidal and which, in use, is held by the patient, wherein the spherical or spheroidal surface carries the patient-controlled initiator and wherein squeezing of the grip causes actuation of the patient-controlled initiator, a reservoir configured to contain a pain-relieving substance and being engaged, in use, with the handset, a patient delivery interface, and dosage control means, wherein, on actuation of the patient-controlled initiator, an input is provided to the dosage control means, the dosage control means consequently providing an output which controls the transfer of a portion of the liquid pain-relieving and/or sedative substance from the reservoir to the patient delivery interface.

The grip has a rounded surface which is at least partially spherical or spheroidal such that it can be comfortably held by the patient with the rounded surface being held within the palm and/or fingers of the patient. The spherical or spheroidal surface is typically held in the palm with the fingers curving round the surface, in the same manner as a small ball may be held The patient-controlled initiator is carried on or forms part of the rounded surface of the grip so that, when the patient responds to an increase in or acute pain by clenching or gripping their hand, they actuate the patient-controlled initiator and cause the pain-relieving and/or sedative substance to be administered. The motion required by the grip does not require particular mobility in any individual digit, or accuracy of motion, and hence is usable by patients with decreased mobility.

The grip may have any suitable shape which is at least partially spherical or spheroidal, and which can be comfortably retained within the hand and/or palm. In particular, the grip may be a sphere, spheroid, or a part of or restricted form of any of these shapes. For example, the grip may be a hemi-sphere or hemi-spheroid, a three-quarter sphere or spheroid, or a sphere or spheroid having a reduced diameter in a portion of the three-dimensional form, eg in a middle section.

The patient-controlled initiator is carried on or forms part of the spherical or spheroidal surface. The patient-controlled initiator may be mounted on or in the spherical or spheroidal surface, and the nature of the patient-controlled initiator is discussed in more detail below. The patient-controlled initiator may cover a substantial portion of the spherical or spheroidal surface, and may be of a sufficient size that two, or three, or four fingers can contact the patient-controlled initiator at once.

While the grip is held by the palm and/or fingers, the handset may further comprise a rest portion for the patient's wrist and/or lower arm, to accommodate the user's hand and wrist in a supportive manner and increase the comfort of the patient during use. The rest, or wrist, portion, may extend from the grip and provide a surface on which the patient's wrist and, optionally, a portion of their forearm can rest. The rest portion may be substantially cuboid in shape.

The rest portion may be integrally formed with the grip, or may be produced separately. Alternatively, where the handset is produced in parts, a portion of the rest portion and a portion of the grip may be integrally formed, engaging with further section(s) also comprising a part of both portions. Thus, the upper surfaces of the grip and rest portions may form a continuous surface, with a convex curve joining the spherical or spheroidal form of the grip to the rest portion. Equally, the underside of the rest and grip portions may be integrally formed, forming a continuous surface on the underside of the handset.

The handset may further comprise one or more sensors positioned on a surface of the housing, for monitoring one or more parameters of the patient. The one or more sensors may include pulse oximetry, ECG, non-invasive glucose sensor, wrist-based blood pressure monitor and/or skin temperature, and the one or more parameters to be monitored may include respiratory rate, heart rate, oxygen saturation (spO2), temperature and/or blood pressure. The one or more sensors may be positioned such that, during normal use of the device, the patient contacts the one or more sensors. The one or more sensors may typically be located on a front or upper surface of the handset, or on the patient-controlled initiator, where the patient's hand and fingers are positioned during normal use. The one or more sensors may be positioned on the device where the heel of the user's hand and/or their wrist is placed during normal use, as these parts of the patient's anatomy are likely to remain in constant contact with the device. In particular, in the embodiment described above the one or more sensors may be positioned on the rest portion and/or on the convex curve joining the spherical or spheroidal form of the grip to the rest portion.

The handset of any aspect of the invention may comprise a housing. The housing may comprise an attachment point for the engagement of the reservoir, which may be shaped to provide a secure connection between the housing and the reservoir.

This connection may be any suitable connection, including a push-fit, friction-fit, screw-fit or snap-fit. The attachment point may be located on an outer wall of the housing, or within a recess in the housing. When engaged, the reservoir may be at least partially contained within the housing, or the reservoir may be wholly contained within the housing.

The housing may comprise a a recess. The recess may receive the reservoir, with the reservoir engaging with the handset within the recess. The recess may be concealed by a door, which may be secured to the housing by any suitable means. For example, the door may be a hinged door, or may be secured by means of clips, or a snap-fit and/or other locking means. The attachment point may be located within the recess.

The housing may further comprise an aperture or window through which an indication of the remaining level of medication is visible. The aperture or window may expose at least a portion of the reservoir, such that the remaining level of medication contained within the reservoir is visible. The aperture or window may be located in a wall of the housing.

The handset of any aspect of the invention may further comprise attachment means to retain the handset on the hand and/or arm of the patient. This ensures that, even where the patient is distracted or struggles with movement and/or mobility, they will not drop the handset during use. The attachment means may also retain the handset in the correct position in relation to the patient's hand, such that the patient's fingers naturally rest on the patient-controlled initiator.

The attachment means may comprise one or more straps, eg two straps, or three straps, the one or more straps forming one or more loops extending from a first outer wall of the housing to a second, outwardly opposing outer wall of the housing which, in use, retain the patient's hand and/or wrist and/or lower arm. The one or more loops may be adjustable in size, to ensure a firm and comfortable fit for the patient. The attachment means may comprise two loops extending from a first outer wall of the housing to a second, outwardly opposing outer wall of the housing, retaining the patient's arm in two locations and thus ensuring that the device cannot swing free from the patient's grip.

The one or more straps may extend outwardly from a first outer wall of the housing, with the free end being attached to a second, outwardly opposing outer wall of the housing, forming a loop. Alternatively, first and second straps may extend outwardly from each of the first and second outer walls of the housing, joining together to form a loop which extends between the two outer walls.

The device may be powered by mains power, or by a battery. The device is typically battery powered, enabling it to be used in situations with no access to mains power, eg out of doors. The battery may be retained within the housing. Where present, the recess may receive the battery.

The handset comprises a patient-controlled initiator. The patient-controlled initiator is a means by which the patient can signal a need for more medication, for example because they are experiencing higher pain levels, or respond to a prompt from the device. Actuation of the patient-controlled initiator provides an input to the dosage control means, the dosage control means consequently providing an output which controls the transfer of a portion of the liquid pain-relieving and/or sedative substance from the reservoir to the patient delivery interface with no need for external input from a clinician, thus reducing the delay between the patient request and the administration of the analgesic or sedative. The patient-controlled initiator may be any suitable means of activating the device, operable by a patient. The patient-controlled initiator should be easily operable by a patient who may have limited mobility and/or who is in pain. Thus, the patient-controlled initiator should typically require a simple action by the patient, which is operable by a patient even under duress.

The patient-controlled initiator may be a sensor, a compressible surface, or a button.

The patient-controlled initiator may be a button or compressible surface which is pressed or squeezed by the patient when further medication is required, or if prompted to do so by the device (eg to ascertain the consciousness level of the patient). The button or compressible surface may be of a substantial size, such that multiple fingers may simultaneously rest on it, reducing the co-ordination required.

The patient-controlled initiator may be actuatable from almost any angle, again reducing the co-ordination required by the patient to activate the patient-controlled initiator, either to request medication or (where relevant) to respond to a stimulus. The patient-controlled initiator may be actuatable when interacted with at any angle within a 200° span, or within a 180° span.

Where the patient-controlled initiator is a button, the button may be mounted on or in the housing, for example on the grip, where present. The button may be mounted on the housing such that, when pressed, an activation member (eg a switch, sensor or microswitch) is engaged within the housing, resulting in an input being provided to the dosage control means.

The button may be mounted in the housing above a spring which acts to return the button to its original position after it has been pressed, releasing the activation member. The spring may comprise a resilient member, biased towards the button. Pressing of the button may cause the button to press on and deform the spring such that, when pressure is released, the spring returns to its original shape and returns the button to its original position.

The activation member may be activated by the button, or by the spring. Movement (eg distortion, or compression) of the spring in response to the user pressing the button may cause the spring to activate the activation member, eg through applying pressure to it or by it moving within range of a sensor. Alternatively, the button may directly engage with the activation member (eg by pressing on it, or by moving within range of a sensor), the engagement between the button and activation member being removed when the button is returned to its original position by the spring. The button may comprise one or more engagement tabs which engage with the wall of the housing or handset about the periphery of the button, forming points about which the button can pivot, enabling the button to be pressed from almost any angle and still apply pressure to the underlying spring.

Alternatively, where present, the spherical or spheroidal surface itself may form the patient-controlled initiator. At least a portion of the spherical or spheroidal surface may be resiliently compressible, such that compression of the resilient surface causes actuation of the patient-controlled initiator. Thus, the handset may comprise a resiliently compressible sphere or spheroid, which is held by the user and compressed (eg gripped or squeezed) to activate the patient-controlled initiator. Such a compression may be registered and transmitted to the dosage control means via a pressure sensor.

Actuation of the patient-controlled initiator may be indicative of a demand for pain relief and/or sedation. Actuation of the patient-controlled initiator by the patient may therefore be indicative of the patient requiring greater pain relief and/or sedation, and/or the amount of pain and/or sedation the patient is experiencing. The number and/or frequency and/or duration of actuations of the input arrangement may be indicative of the patient requiring greater pain relief and/or sedation, and/or the amount of pain and/or sedation the patient is experiencing. Similarly, the force and/or velocity and/or acceleration and/or audio volume of actuations of the input arrangement may be indicative of the patient requiring greater pain relief and/or sedation, and/or the amount of pain and/or sedation the patient is experiencing. The patient may therefore be instructed to actuate the patient-controlled initiator to demand greater pain relief and/or sedation.

Actuation of the patient-controlled initiator provides an input to the dosage control means, the dosage control means consequently providing an output controlling the transfer a portion of the sedative and/or pain-relieving substance to the patient. The dosage control means acts to control the volume and/or the rate of medication delivered to the patient at any point, responding to the inputs from the patient-controlled initiator. The input(s) may be processed using a control algorithm to determine the output.

The output may initiate the delivery of medication to the patient. The control algorithm may determine a high response delivery parameter (eg a bolus delivery) and/or a low response delivery parameter (eg a background rate). A high response delivery parameter may determine an output that leads to the transfer of a high dose of a pain-relieving and/or sedative substance, to provide fast and/or strong pain relief for a patient in acute pain. A low response delivery parameter may determine an output that leads to the transfer of a low dose of a pain-relieving and/or sedative substance, and/or to the transfer of a low dose of a pain-relieving and/or sedative substance that is sustained over a period of time, to provide sustained pain relief to the patient. Repeated actuation of the patient-controlled initiator may result in repeated delivery of medication according to the high and/or low response delivery parameters.

The control algorithm may determine a high response delivery parameter (eg a bolus delivery) and a low response delivery parameter (eg a background rate). An output signal may be generated from the high response delivery parameter and low response delivery parameter depending on the number of patient inputs, the length of time since the last patient input, or the frequency, velocity force and/or duration of patient inputs. This enables the device to provide both high and low levels of pain relief, both of which are dependent on and responsive to patient input.

Continuing delivery of the medication to the patient may be dependent upon the patient responding to a regular stimulus, for example a visual (eg light) or audible stimulus. The response to the stimulus required of the patient may be activation of the patient-controlled initiator. Failure to appropriately respond to the stimulus may indicate either reduced pain levels, or that the patient has a reduced or low level of consciousness, and delivery of the medication will reduce and/or cease.

The output may additionally be affected by one or more additional delivery parameters. These may include, for example, a lockout period during which more medication will not be transferred, or only a decreasing or lower level of medication may be transferred, to prevent overdose, or preset dosage limits.

Typically, only a proportion of the total contents of a full reservoir (a reservoir which has been fully charged with a pain-relieving and/or sedative substance) is transferred to the patient as a result of any individual output from the dosage control means. That is, the entire contents of a full reservoir are not transferred to the patient in a single dose.

The device of the invention comprises dosage control means, which are typically electronic. The dosage control means may comprise an electronic controller which receives an input from the patient-controlled initiator indicative of a patient request or response, and provides an output which controls the transfer of medicament between the reservoir and patient-delivery interface. The electronic controller may apply a control algorithm to the input to generate an output signal, and transmit the output signal to the device to control the delivery of the pain-relieving and/or sedative substance to the patient. The output may dictate a dosage of medication to be transferred from the reservoir to the patient delivery interface.

The output may be supplied to a delivery means, which may be a pump, valve, pressurised system, or other known delivery means, and/or to a user display. The delivery means may transfer the pain-relieving and/or sedative substance from the reservoir to the patient delivery interface according to the output from the dosage control means. The delivery means may be wholly or partially located within the handset (eg the housing). The delivery means may be wholly contained within the housing.

The delivery means may comprise a means of mechanically transferring a portion of the pain-relieving and/or sedative substance from the reservoir to the patient delivery interface, and of regulating the flow of that substance. Such means may comprise a 20 pump, one or more valves, one or more pistons and/or a pressurised system.

The delivery means may comprise a pump. The pump may be any suitable pump for the transfer of medication, which enables the transfer of controlled doses of medication, and may be located within the housing of the handset, and may be a peristaltic pump, a piezoelectric pump, a syringe driver or a diaphragm pump.

The pump may particularly be a peristaltic pump. A peristaltic pump typically comprises a tube through which the fluid to be pumped passes. The tube is compressed at regular intervals by the pump, typically by a rotating arm or arms, forcing the fluid along the tube. A peristaltic pump has a fixed displacement, and so the quantity of medication transferred by the pump can be carefully controlled. In addition, in a peristaltic pump the liquid passing through the pump passes through a tube within the pump, rather than coming into contact with the pump itself.

It will be appreciated that references to a fluid connection between a pump and another component may refer to a fluid connection between a tube passing through 10 the pump and that component.

The pump may be battery powered. Indeed, the handset and device as a whole may be battery powered. The battery may be contained within the housing, and may contain sufficient power for a single use of the device. This increases the portability of the device, enabling it to be used out of doors and away from a mains power supply, as well as preventing reuse of the device.

The dosage control means is electronically activated. Electronic activation leads to a quicker, more responsive device, with the ability to adjust the dosage size and/or dosage rate depending on, for example, the sex or weight of the patient, as well as to dynamically adjust the dosage and/or dosage rate depending on patient inputs.

The reservoir is configured to contain a pain-relieving and/or sedative substance, and is engaged, in use, with the handset.

The reservoir is typically removable, and may be attached to and removed from the device, or inserted into and removed from the device. Alternatively, the reservoir may not be removable once it has been correctly engaged with the device without causing damage to the reservoir and/or the handset, in order to prevent reuse. In a further alternative, the device may be supplied with a prefilled reservoir installed.

The reservoir is typically provided separately to the handset and is engaged with the handset (eg to the housing of the handset) prior to operation of the device. The reservoir may be filled with medication by a clinician prior to its attachment to the housing, or may be supplied prefilled. For example, the reservoir may be filled with a pain-relieving and/or sedative substance before it is attached to or inserted into the housing. The reservoir is typically the only source of medication for the device, that is, the device is typically not connected to a further medication source, such as an external bottle of medication. This increases the portability of the device of the invention.

The reservoir may comprise a volume which, in use, is at least partially filled with a pain-relieving and/or sedative substance, and which may be expandable and/or compressible. The reservoir may comprise a compressible volume, wherein compression of the reservoir volume leads to expulsion of the pain-relieving substance held therein. The compressible volume may comprise, for example, a plunger and barrel, or a bladder.

Once engaged with the housing, the reservoir may be in fluid communication with the patient delivery interface. In addition, where present, the reservoir may be in fluid communication with a mechanical delivery means, eg with a pump, or valve system. The delivery means may be located between the reservoir and the patient delivery interface, such that medication travels from the reservoir to the patient delivery interface via the delivery means. The contents of the reservoir may be held at ambient pressure, or may be pressurised.

The reservoir may comprise a plunger and a barrel, the plunger being inserted into the barrel and acting as a piston to move air and/or fluid into and out of the barrel.

The barrel may comprise a proximal end and a distal end, the plunger being inserted into the barrel at the distal end and being slidable longitudinally within the barrel. The proximal end of the barrel may comprise a connection formation to permit connection between the barrel and a supply bottle and/or the handset. The barrel may typically have a circular cross-section (ie be cylindrical), but may alternatively have a square, oval or polygonal cross-sectional shape.

Together, the barrel and syringe form an expandable reservoir, movement of the plunger within the barrel compressing and expanding the volume therein. Where the reservoir is supplied empty, the barrel may be filled with medication from a supply bottle by depressing the plunger, connecting the barrel to the top of a medication supply bottle, inverting the reservoir and bottle together, and drawing the plunger out to fill the barrel with medication. During operation of the device, the pain-relieving substance is drawn out of the barrel by the device, the plunger moving longitudinally along the barrel to reduce the volume as medication is expelled. Where present, the pain-relieving substance may be drawn out of the barrel by the delivery means, eg by a pump.

The reservoir may comprise a connection formation to enable it to connect securely to both the medication bottle and to the device of the invention. In particular, the connection formation may enable the reservoir to connect securely to a proprietary adaptor on a medication bottle, while permitting the transfer of medication between the bottle and reservoir. The connection formation may be integrally formed with the reservoir, or may comprise a separate component.

The connection formation may be located on an inlet of the reservoir. The connection formation may be located on an outlet of the reservoir. The reservoir may comprise a single inlet/outlet on which the connection formation is located. For example, where the reservoir comprises a plunger/barrel configuration as previously described, the connection formation may be located on the proximal end of the barrel.

The connection formation may comprise two concentric rings which extend outwardly from the inlet/outlet of the reservoir, eg from the proximal end of the barrel. The outer ring may extend outwardly from the periphery of the inlet/outlet, such that its outer surface forms a continuation of the outer wall of the inlet/outlet. The outer ring forms a secure connection with the medication bottle, sealing the connection against leaks, eg through a friction fit. The second, inner ring may comprise cut-out sections, such that at least a portion of the ring is broken into two, or three, or four, or five, or more sections. The inner ring may be shorter than the outer ring. When attached to the proprietary connector, the inner ring may press on a spigot of the connector, breaking the seal of the medication bottle and allowing the medication to flow out of the bottle. The cut-out sections provide spaces through which medicament can flow into the centre of the connection formation and through the inner ring into the reservoir.

The connection formation prevents the reservoir from being connected to any vessel which does not carry the standard connector, thus ensuring that the syringe can only be filled with the pain-relieving and/or sedative substance for which the device and its safety mechanisms have been designed.

The reservoir carries sufficient medication to deliver pain relief and/or sedation to a patient for a period of time. The reservoir may contain from 5 to 100m1, or from 5 to 50m1 of medication, or from 5 to 30m1 of liquid medication, or from 5 to 20 ml of liquid medication. Thus, the reservoir may contain, for example, from 5 to 30m1 of a volatile liquid medication such as an analgesic, anaesthetic or sedative, such as sevoflurane.

The volume of pain-relieving substance contained within the reservoir may be sufficient for the device to operate and provide pain relief to the patient for at least 5 minutes, or for at least 10 minutes, or for at least 15 minutes. The volume of medication may be sufficient for the device to operate and provide pain relief to the patient for up to an hour, or up to 45 minutes. This further enables the device to be used in a non-hospital or non-clinical setting, providing pain relief to a patient in need of it during a minor procedure, or during first aid and a transfer to hospital, whilst not requiring a large reservoir of medication for prolonged use.

During use, the reservoir may be contained partially or wholly within the housing. As previously described, the housing of the handset may comprise a recess within which the reservoir may be retained: a reservoir compartment. The reservoir compartment may be accessible through an opening in the housing, such as through a door. The door may be hinged, or may be attached to the compartment by a snap-fit, by clips, or by any other suitable means known in the art. The door is typically openable, enabling the reservoir to be inserted into the reservoir compartment prior to operation of the device. Once inside, the door or lid may be closed to retain the reservoir in place and prevent inadvertent dislodgement or movement of the reservoir.

In use, the reservoir is engaged with the handset. The connection formation on the reservoir may engage with the housing and/or the pump to create a fluid connection between the reservoir and patient delivery interface. The connection formation may engage with a corresponding attachment point on or inside the housing (as previously described), for example inside the reservoir compartment. The connection formation may be received by an attachment point within the handset, for example within or adjacent to the reservoir compartment, which engages with the connection formation to provide a secure join and which is in turn fluidly connected to the patient delivery interface. The connection between the reservoir and the housing, eg the attachment point, may be any suitable, secure connection, such as a push-fit, friction-fit, snap-fit or threaded connection.

The connection portion may further comprise an activation member. When the reservoir is correctly connected to the housing, the activation member interacts with an activation feature on the housing in a manner to activate the device.

According to a further aspect of the invention there is provided a device for providing pain relief and/or sedation to a patient, the device comprising a handset having a patient-controlled initiator and an activation feature, a reservoir configured to contain a pain-relieving and/or sedative substance and being engaged, in use, with the handset, wherein the activation feature is activated on engagement of the reservoir with the handset to cause initiation of the device, a patient delivery interface, and dosage control means, wherein, after initiation of the device, and on actuation of the patient-controlled initiator, an input is provided to the dosage control means, the dosage control means consequently providing an output which controls the transfer of a portion of the liquid pain-relieving and/or sedative substance from the reservoir to the patient delivery interface.

The reservoir may comprise an activation member which, on engagement with the handset, interacts with the activation feature to cause initiation of the device. The activation member may comprise an outwardly extending flange. The outwardly extending flange may extend outwardly from the reservoir, typically from a position on or proximate to the portion of the reservoir which connects to the housing, eg the connection formation. The outwardly extending flange may extend longitudinally along the reservoir, eg along the connection formation. For example, the flange may extend longitudinally along the barrel of a reservoir having a plunger/barrel configuration as previously described. The flange may extend between 0.5 and 5cm along the reservoir, or between 0.5 and 3cm along the reservoir.

Alternatively, the connection formation may also form or comprise the activation member.

In use, when the reservoir is correctly inserted into and engaged with the housing and/or the pump, the activation member interacts with the activation feature on the housing such that it electronically activates the handset. This may be achieved through correct engagement of the reservoir with the housing (eg the attachment point) bringing the activation member into engagement with an activation feature, for example a sensor, button, switch or microswitch, which causes electronic activation of the handset. Incorrect insertion and engagement of the reservoir with the handset may result in the activation member not being brought into contact with the activation feature, and hence the device not becoming active. In the same manner, insertion of an alternative reservoir not designed to operate with the device may not engage with the activation feature, and hence the device won't operate. This safety mechanism prevents the handset from becoming active if the reservoir is not correctly installed, or if an incorrect reservoir is used, reducing the risk of medication leaking from an unsecure or incorrect connection. It also makes the device quick and easy to setup and begin using, as activation of the device occurs as soon as the reservoir is correctly installed.

Initiation of the device may comprise a priming process. The priming process may comprise activating the dosage control means and any delivery means present. It may further comprise transferring a small amount of the pain-relieving and/or sedative substance out of the reservoir and moving it close to the patient delivery interface (eg filling any tube or conduit connecting the two components) such that delivery of the medication to the patient can occur quickly once treatment begins. The progress of the initiation or priming process may be indicated through a user interface, eg a screen or light array, which may be located on the handset and/or the patient delivery interface.

The reservoir may alternatively or additionally comprise means for preventing reuse of the reservoir and/or device. Where the reservoir comprises a barrel and plunger, the plunger may comprise a frangible, narrow, or otherwise weakened section. The weakened section may be positioned such that, when the plunger has been drawn out to fill the barrel with the correct dosage of medication, the point of weakness is located at or just above the distal end of the barrel.

Thus, according to a further aspect of the invention there is provided a device for providing pain relief and/or sedation to a patient, the device comprising a handset a patient-delivery interface, and a reservoir, the reservoir being configured to contain a pain-relieving and/or sedative substance and being at least partially contained, in use, within the handset, the reservoir comprising a plunger received within a barrel, the plunger comprising a point of weakness which, in use, is broken to enable the reservoir to be at least partially contained within the handset, the reservoir, in use, being fluidly connected to the patient delivery interface.

There are notable benefits associated with the presence of an area of weakness on the plunger which may be broken by the user, including reducing the size of the plunger such that it can be received wholly within the housing, preventing the size of the reservoir from significantly changing during delivery of the medication due to depression of the plunger and thus reducing the risk of unwanted movement; and preventing reuse of the syringe.

As previously described, the handset may comprise a housing, the housing having a 20 reservoir compartment. The reservoir compartment may comprise a recess, and may be accessible through an opening in the housing, such as through a door. The door may be hinged, or may be attached to the compartment by a snap-fit, by clips, or by any other suitable means known in the art. The door is typically openable, enabling the reservoir to be inserted into the reservoir compartment prior to operation of the device. The reservoir compartment may be sized such that the reservoir will only fit into the compartment when the plunger has been broken at its point of weakness.

The handset may further comprise a dosage control means (eg an electronic dosage control means) and/or a patient-controlled initiator. The patient-controlled initiator may be carried on the handset as previously described. On actuation of the patient-controlled initiator, an input may be provided to the dosage control means, the dosage control means consequently providing an output which controls the transfer of a portion of the pain relieving and/or sedative substance from the reservoir to the patient delivery interface.

In all embodiments of the invention, the handset is typically electrically connected to the patient delivery interface such that electronic activation of the handset causes electronic activation of the patient delivery interface.

The handset of any embodiment may be connected to the patient delivery interface via a conduit. The handset, or any component contained therein, may be connected to the patient delivery interface by a single conduit. In particular, the reservoir may be fluidly connected to the patient delivery interface via a conduit, typically formed of silicone tubing, the pain-relieving and/or sedative substance being transferred between the reservoir and patient delivery interface through the conduit. Transfer of the pain-relieving and/or sedative substance through the conduit is controlled by the dosage control means, and may be facilitated by a delivery means (eg a pump).

Where it is necessary to also transfer electrical power, for example to power both a pump and a patient delivery interface using a single power source, this may be carried by electrical wires which also pass through or along a conduit or tube. The conduit may permit the passage of liquid medication and/or an electrical connection and/or a gas (eg expired air). The conduit may enable an electrical connection between the handset and the patient delivery interface, such that power is transferred from the handset to the patient delivery interface. This means that a single power source, eg a battery or battery pack, is required to power the device, increasing its portability.

The conduit may comprise a tube having a lumen for the passage of liquid medication. Electrical wires may be attached to or embedded in the walls of the tubing, or may pass through a second lumen. As the liquid medicament cannot be brought into contact with the electrical wires, it has been found that a dual or double lumen tube may be effectively employed to transfer both liquid medicament and electrical power between a reservoir and/or pump (which may be located in a handset) and a patient delivery interface.

Thus according to a further aspect of the invention there is provided a device for providing pain relief to a patient, the device comprising a handset having a patient-controlled initiator, a reservoir configured to contain a pain-relieving and/or sedative substance and being engaged, in use, with the handset, a patient delivery interface, a conduit connecting the handset and patient delivery interface and having at least first and second lumens, the first lumen being configured to carry a liquid pain-relieving and/or sedative substance and the second lumen carrying at least one electrical wire, electronically connecting the handset and the patient delivery interface for the transfer of power and/or data between the handset and patient delivery interface, and dosage control means, wherein, on actuation of the patient-controlled initiator, an input is provided to the dosage control means, the dosage control means consequently providing an output which controls the transfer of a portion of the liquid pain-relieving and/or sedative substance from the reservoir to the patient delivery interface.

The conduit (where present in any aspect of the invention) may comprise flexible tubing, and may typically be made of silicone. The tubing may have a degree of stretch, and may stretch to at least 2,4, 6, 8 or 10 times its original length. As electrical wires typically have little to no ability to stretch, this ensures that, in the event that the handset is dropped, thrown or otherwise mishandled and the tubing consequently put under stress, the electrical wire carried within the tubing will snap before the tubing ruptures, breaking the electrical connection between the handset and patient delivery interface.

The first lumen carries a liquid substance for relieving pain and/or delivering sedation. The liquid pain-relieving and/or sedative substance is transferred through the conduit from the reservoir when engaged with the handset, under the control of the dosage control means. The reservoir may be, for example, a flexible bladder or plunger/barrel combination as previously described. A pump, eg a peristaltic pump, may transfer the pain-relieving and/or sedative substance from the reservoir and through the lumen, to the patient delivery interface.

The second lumen carries one or more electrical wires for the transfer of power (eg from a single power source) and/or information (eg regarding dosage level, bolus dosage level and/or remaining medication or power, from the dosage control means) between the handset and patient delivery interface. Information transmitted from the handset to the patient delivery interface may be displayed on an information display, which may be a screen or a light array. This transfer of power and/or information between the handset and patient delivery interface means that only one battery and/or controller is required in the device. The battery and/or controller may be located in either the handset or the patient delivery interface, but will typically be located in the handset in order to reduce the weight of the patient delivery interface.

The conduit may further comprise a third or further lumens. A third lumen may be used, for example, for the transfer of gas between the patient delivery interface and the handset, eg for the transfer of exhaled air from the patient to an end tidal CO2 monitor.

There may be no fluid communication between the first and second (and any further) lumens.

The first and second (and any additional) lumens may extend longitudinally along the tube, and may be of the same or similar diameter. Alternatively, the lumens may have differing diameters, in particular, the second lumen (carrying the electrical wire(s)) may have a greater diameter than the first lumen (carrying medication). The reduced diameter of lumen carrying medication reduces wastage, by reducing the volume of medication remaining in the tube when the device is exhausted (ie the reservoir is empty). It also reduces the time taken to fill the tube when the device is first initiated. The first lumen may have a diameter of between 0.5 and 2mm, or of between 0.5 and 1.5mm, or of about 1mm. The second lumen may have a diameter of between about 2mm and 4mm, or between about 2mm and 3mm, or of about 2.5mm.

The first lumen of the conduit is typically in fluid communication with both the reservoir and the patient delivery interface. Where present, a pump may be positioned between the reservoir and conduit, such that it the pump can mechanically transfer the pain-relieving and/or sedative substance from the reservoir to the conduit.

Practicable embodiments of the invention are described in further detail below with reference to the accompanying drawings, of which: Figure 1 shows a perspective view of a pain management system; Figure 2 shows a front view of a facemask from the system of Figure 1; Figure 3 shows a perspective view of the facemask of Figure 2; Figure 4 shows an exploded view of the facemask of Figures 2 and 3; Figures 5a to 5c show part of an assembly sequence for the facemask of Figures 2 and 3; Figure 6 is a part perspective view of the partly assembled facemask of Figures 2 and 3; Figure 7 is a cross-sectional view thorough a delivery chamber of the facemask of Figures 2 and 3; Figure 8 is perspective view of an air/gas inlet component from the facemask of Figures 2 and 3; Figure 9 is perspective view from the top of the partially assembled facemask of Figures 2 and 3; Figure 10 is a cross-sectional view of the facemask of Figures 2 and 3; Figure 11 shows an exploded view of a filter cartridge from the facemask of Figures 2 and 3; Figure 12 shows a perspective view of a handset from the system of Figure 1; Figures 13a and 13b show front and rear exploded views of the handset of Figure 12; Figure 14 shows a horizontal cross-sectional view of the handset of Figure 8, viewed from above; Figures 15a and 15b show front and rear perspective views of a spring used in the handset of Figure 8; Figure 16 shows a rear perspective view of the handset of Figure 8, with the hinged lid in an open position; Figures 17a and 17b show an expandable reservoir and medicament bottle for use in conjunction with the pain management system of the invention; Figures 18a, 18b and 18c show the connection between the expandable reservoir and medicament bottle of Figures 17a and 17b, Figures 18b and 18c showing a cross-sectional view of the expandable reservoir and medicament bottle during (18c) and after (18b) connection; Figure 19 shows the barrel and plunger which form the component parts of an expandable reservoir for use in conjunction with the pain management system of the invention; Figure 20 shows an underside of the handset of Figure 12; Figure 21 shows a perspective view of a transmission tube from the system of Figure 1; Figure 22 shows an exemplary simulation of medicament delivery in use; Figure 23 shows an exemplary simulation of medicament delivery in use; Figures 24a-24d show a first notification sequence indicated by the mask of Figures 2 and 3 during operation of the pain management system of Figure 1; Figures 25a-25d show a second notification sequence indicated by the mask of Figures 2 and 3 during operation of the pain management system of Figure 1; Figures 26a-26d show a third notification sequence indicated by the mask of Figures 2 and 3 during operation of the pain management system of Figure 1; Figure 1 generally shows a patient-controlled pain relief and/or sedation device 1. Briefly, the device 1 comprises a facemask 10, to be placed around the nose and mouth of a user, and a handset 301 connected to the facemask 10 by a transmission tube 307. As will be described in detail later, the handset 301 comprises a reservoir of sevoflurane, or other medicament, for use as an analgesic and/or a sedative, and a user input to trigger delivery of the medicament to the facemask 10 via the transmission tube 307.

The device 1 provides user-controlled delivery of a medicament for inhalation to manage pain. Numerous design features are provided to address, mitigate, or overcome the concerns and risks associated both with patient-controlled sedation and with the use of inhalational delivery.

The mask 10 is shown in isolation in Figures 2 and 3, and comprises a shell or body and a compliant/compressible seal 25, formed of elastomeric material, around the periphery of the body 100. The outer shape of the body 100 and design of the seal 25 are generally similar to those described in the applicant's earlier patent application WO 2022/122974. As well as a chin cup 26 and nose engaging portion 27, the seal 25 comprises extended side portions 28 that, in use, extend laterally across the cheeks of the wearer. The seal 25 thus provides a large area to engage with the face, including over the softer skin of the cheeks, and thus improves the quality and reliability of the sealing provided. It has been found that extending the seal 25 laterally across the softer tissue of the cheeks allows an effective seal to be provided with a lower than usual degree of flexibility in the sealing member, at least in these regions. The minimal movement of the cheeks/cheekbones during talking or other jaw movement also helps to ensure that the seal is not compromised.

The seal 25 shown in Figures 2 and 3 is more curved at the ends of the side portions 28 than that shown in WO 2022/122974. This curvature at both sides of the seal 25 has been found to further improve the sealing performance across a wider range of face sizes, making a single mask size more universal.

Elasticated straps 20 are provided to secure the facemask 10 to a wearer during use. The ends of the elasticated straps 20 are received in tabs 102 extending from the sides of the mask body 100. The tabs 102 provide a frictional engagement with the elasticated straps 20 so that the tension of the elasticated straps 20 can be adjusted in the conventional way.

The relatively large mask shell/body 100 supports and stabilises the compliant seal 25 where needed and also provides sufficient space for a centrally positioned delivery chamber 200 and for a pair of large capacity filter cartridges 50, one on either side of the delivery chamber 200. The depth and overall size of the chamber and filter cartridges 50 can best be seen in the perspective view of Figure 3.

The delivery chamber 200 comprises a chamber housing 202 secured to the mask body 100. A generally tubular air/gas inlet 204 extends forwardly and downward from a lower side of the chamber 200. A pair of diametrically opposed cut-outs 206 are provided at the free end of the inlet 204, allowing connection to a standard T-piece if/when supplementary oxygen needs to be supplied to the mask 10 during use. Behind the inlet 204 can be seen a gas monitoring connector, e.g. an end tidal CO2 monitor connector 104, which is fluidly connected to the interior of the mask 10 through a monitoring port in the lower part of the mask body 100. It should be understood that the connector 104 could also monitor administered drug concentration, and allow peak concentration and end tidal concentration to be measured.

An outwardly facing display 500 is provided on a front face of the chamber 200 to provide information about operation of the device 1 to an external observer such as a clinician.

Figure 4 shows an exploded view of the various components that make up the mask 10.

The exploded view shows that the mask body 100 can be considered to define separate regions. A central region 120 provides the rear part of the delivery chamber 200, and includes a locating boss 208 for the chamber housing 202. A filter cartridge aperture 150 is provided on either side of the central region 120.

Each filter cartridge 50 is independently insertable into and removable from one of the filter apertures 150 the mask body 100 from the rear or cavity side. This avoids potential tampering or inadvertent disconnection of the filter cartridges 50 from outside the mask 10 during use. A peripheral lip 52 and groove 54 are provided around a rear side of each of the filter cartridges 50. The filter cartridges 50 are received in the mask body 100 with a 'pop' fit, with the periphery of each filter aperture 150 engaging with the peripheral groove 54 of a respective cartridge 50. The peripheral lip 52 then abuts an inner surface of the mask body 100 to prevent removal of the cartridges 50 from the front/outside of the mask 10.

Each filter cartridge 50 comprises an aperture 60 through which a cavity within the cartridge 50 can be supplied with activated carbon granules.

A circular wall 210 extends outwardly from the central region 120 of the mask body 100, and surrounds an opening through the mask body 100. A vertical bar 212 spans the opening and provides support for a locator pin 214 which extends along the central axis defined by the circular wall 210. A flexible inhalation valve member 216 is received on the locator pin 214, followed by a gauze/pad 218 from which a delivered dose of sevoflurane evaporates and is inhaled in use.

Figure 4 also shows that the generally tubular air/gas inlet 204 is a separate component from the mask body 100. A generally circular cup 220 is provided at an upper end of the tubular inlet, and is sized to fit over the end of the circular wall 210 to enclose the inhalation valve member 216 and pad 218. A medicament inlet port 222 is provided through the cup 220 so that sevoflurane can be delivered onto the pad 218 on demand.

Finally, Figure 4 shows a PCB 224 to be mounted in front of the other components within the chamber housing 202. The PCB in the illustrated example comprises a ring 502 of front facing LEDs which form a part of the display 500 visible from the front of the housing 202. Several housing mounting bosses 226 extend forward of the circular wall 210 to support and secure the PCB 224 and chamber housing 202 to the mask body via screw holes 228 provided in the chamber housing 202.

For various reasons, it is important that the mask can provide a reliable seal with a patients' face. As already described, the overall shape and size of the mask body 100 and seal 25 has been found to provide a good level of sealing, but a further consideration is that a single mask should ideally be suitable for a range of different face sizes and/or shapes. It is typically easier to accommodate a range of face sizes and shapes when a mask has a high degree of inherent flexibility, and is thus able to deform and conform to a particular face size and shape. In the present invention, the mask body 100 is required to support several relatively large components/modules, and the required strength and stability of construction is generally incompatible with a desire for a flexible mask body.

The design of the described mask body 100 in three different sections helps to maintain a reasonable degree of flex in the mask body 100 while still providing suitable support for the delivery chamber 200 and the filter cartridges 50. Separately mounting the filter cartridges 50 and the components making up the delivery chamber 200 ensures that these components do not prevent the mask body 100 from flexing as they would if all mounted together. For example, the mask body 100 can still flex between the component mountings, and this particularly helps to maintain a good degree of lateral flexibility, so that the extended side portions 28 of the seal 25 can maintain contact with the cheeks of a wearer.

Figures 5a, 5b and 5c show the assembly of the central components within the delivery chamber 200.

Figure 5a shows the inhalation valve member 216 installed on the locator pin 214 within the circular wall 210. The vertical bar 212 is shown faintly in Figure 5a, but is positioned behind the inhalation valve member 216 as shown. A retaining ring 230 extends inwardly from the circular wall 210 to hold the inhalation valve member 216 in place against the vertical bar. Evenly spaced radial fingers 232 extend inwardly from the retaining ring 230 across the outer face of the inhalation valve member 216. It will be understood that the retaining ring 230 and radial fingers 232 prevent deformation of the inhalation valve member 216 towards the outside of the mask 10, while the single vertical bar 212 still allows deformation and /or deflection of the inhalation valve member 216 to the interior of the mask on inhalation. A one-way valve is therefore provided to allow flow on inhalation but to prevent flow on exhalation.

A hollow tubular boss 234 is centrally provided above the one-way valve, and provides a passageway into the interior of the mask body.

Figure 5b shows the pad 218 also assembled on the locator pin 214. The pad 218 is arranged outside and overlying the inhalation valve member 216 retaining ring 230 and radial fingers 232. The pad 218 thus further helps to prevent outward deflection or deformation of the inhalation valve member 216. The retaining ring 230 and radial fingers 232 maintain a small space behind the pad 218 so that the inhalation valve member 216 does not directly abut a surface of the pad and potentially inhibit the evaporation of a medicament. The spacing also helps to avoid the risk of the inhalation valve member 216 sticking to the wet pad 218 once medicament is delivered.

The installation of the air/gas inlet 204 is shown in Figure 5c. The cup 220 closes the opening provided by the circular wall 210, leaving the medicament inlet port 222 open to receive an end of the transmission tube 307 for delivering sevoflurane or another medicament to the pad 218. A pair of pegs 225 is also provided on the front/outer surface of the cup 220 to help guide and retain the transmission tube 307, as will be described further below.

It will be understood from Figures 5a-5c that air and/or any supplemental oxygen or other gas can enter only through the air/gas inlet 204 as indicated by arrow 236. Any gas flow must, therefore, pass through the pad 218 and then through the one-way valve to enter the cavity of the mask 10. Directing inhaled air/gas flow through the pad 218 helps to drive evaporation of the medicament, and is more efficient than simply passing a flow over a wicking surface or reservoir.

The gauze/pad 218 in the illustrated example is provided as a disc of material 28mm in diameter and 1.3mm thick. The pad 218 has a multi-layer construction, specifically comprising five layers of perforated cotton, forming a 'core' of the pad 218, faced with unperforated cotton on both sides. The perforations in adjacent perforated layers are offset so that the holes in the core do not line up. Testing has shown that it is possible to deliver a 3-4% concentration of sevoflurane from such a pad 218 by delivering 2m1 per minute onto a pad in a breathing simulator at 20 breaths per minute and 500m1 tidal flow. The evaporation rate has found to be such that a single dose delivered to the pad 218 at the end of an exhalation can fully evaporate during the following inhalation.

The system and its control architecture are designed to avoid a buildup of sevoflurane within the mask, and specifically to try and ensure that each delivered dose from the handset 301 evaporates from the pad 218 and is inhaled in a single inhalation event. Nonetheless, the capacity of the pad 218 can be selected so that a small amount of additional medicament delivered to the pad 218 can be retained if desired, for example if the demanded flow is greater than the evaporation rate for a short time. Retaining a small amount of additional medicament on/in the pad helps to avoid immediate leaking or pooling of liquid, which could result in inhalation or ingestion in excessive or unsafe concentrations.

Cotton provides a good level of fluid retention, strong wicking properties for distributing the medicament across the pad 218, and a relatively low resistance to breathing. However, other similar materials could be used with minimal changes to the design. A foam pad or foam core faced with cotton or similar could, for example, be used.

Figure 6 shows a perspective view of part of the mask 10, from below. The transmission tube 307 is shown entering the mask 10 from below to help minimise the risk of the tube 307 tangling or snagging on other equipment or interfering with movements of a patient or a clinician during use. The tube 307 enters the delivery chamber 200 behind the air/gas inlet 204 and then coils between the pegs 225 and then between the two upper housing mounting bosses 226 and the hollow tubular boss 234 before being received in the medicament inlet port 222. For simplicity, the end of the transmission tube 307 is, in use, received in the medicament inlet port 222 with a friction fit. The tortuous path taken by the transmission tube 307, as shown in Figure 6, provides some additional support and frictional resistance to help avoid inadvertent removal or disconnection from the medicament inlet port 222 during use, for example if a user pulls on the tube 307 or handset 301.

The interior of the delivery chamber 200 of the fully assembled mask can be seen in the cross-sectional view of Figure 7. The cross-section shows the arrangement of the inhalation valve member 216 and pad 218, with a space in between, and additionally shows several sections of the transmission tube 307 as it winds through the delivery chamber 200 and is received in the medicament inlet port 222 for delivering a dose of sevoflurane onto the pad 218 on demand. A grate 238 within the air/gas inlet 204 is also shown.

A pressure monitoring port 134, at the interior end of the hollow tubular boss 234, can also be seen in cross section. The hollow tubular boss 234 provides a fluid passageway from the pressure monitoring port 134 to a pressure sensor 240 mounted on the rear side of the PCB 224, allowing real-time pressure measurements to be taken from within the mask 10, which in turn enables monitoring of the patient's breathing in use. It would also be possible to use a temperature sensor within the delivery chamber 200, adjacent the pad 218, to monitor breathing, based on the temperature changes resulting from evaporation of the medicament from the pad 218 during use, and this may also assist in determining whether medicament is building up on the pad so that delivery rates can be adjusted.

Above the pressure sensor 240, also on the rear of the PCB 224, is a rear facing LED 242b for providing stimuli and/or feedback to a wearer of the mask. The visible LED 242b is a central LED of a group of three laterally spaced LEDs, collectively referred to as 242, provided on the rear of the PCB 224. A light guide may also be provided by the material making up an upper part of the mask body 100, for example the mounting boss 208, to direct the light from one or more of the LEDs 242 towards the eyes of the wearer.

Figure 8 shows a rear view of the air/gas inlet 204 and cup 220. Various features can be seen on the rear of the cup 220, most notably the outlet of the medicament inlet port 222 and a central hole 244 for receiving the end of the locator pin 214. As can be seen from Figure 7, these features contact the outermost face of the pad 218 so that the medicament inlet port 222 opens directly onto the pad 218. This helps to avoid medicament dripping from the port 222 and pooling within the delivery chamber 200 rather than being absorbed by the pad 218. However, it can also be seen from Figure 8 (and from Figure 10 below) that a space/void is provided within the cup 220 to help ensure airflow across the whole diameter of the pad 218. A cutout 207, for receiving the transmission tube 307 as it enters the chamber 200, is also shown in Figure 8.

Figure 9 shows a perspective view from the top of the assembled mask 10 with the housing cover 202 removed. The view shows part of the internal cavity 110 defined by the mask body. It can also be seen that the gas monitoring connector 104 extends into this cavity 110 to monitor readings from within the mask body 100. The inhalation valve member 216 can also be seen, positioned centrally between the two filter cartridges 50. The three spaced LEDs 242a, 242b and 242c (collectively 242) can also be seen on the rear surface of the PCB 224. It will be understood that the left and right LEDs 242a,242c are best placed to be seen by a wearer during use.

However, all three LEDs 242 may be used to send alerts and/or stimuli to a wearer, with the use of light guides allowing even quite directional light from the central LED 242b to be directed towards the eyes of the user. Alternative embodiments may, therefore, use only two laterally spaced LEDs, or even just a single LED. Using more than one LED allows alternate flashing of separate LEDs or some other 'pattern flashing' of a group of LEDs. These more unusual light patterns can be more effective in attracting the attention of a wearer.

A complete cross section through the mask 10 is shown in Figure 10. Unlike in Figure 7, the cross-section of Figure 10 is taken off-centre, and shows that an open cavity/void 246 in front of the pad 218 is provided by the cup 220, as discussed above in relation to Figure 8. The majority of a front surface of the pad 218 is open to this cavity 246 to maximise the area that inhaled air/gas can reach to reduce flow resistance and aid with vaporisation of a medicament, particularly at high flow rates. There is a challenging balance for the pad 218 to strike between providing suitable fluid retention/evaporation characteristics and minimising flow resistance, so it is important to ensure as much of the pad as possible remains open to flow.

The cross-section of Figure 10 also passes through one of the radial fingers 232 that maintains a spacing between the pad 218 and inhalation valve member 216 as previously described, and through the rightmost rear facing LED 242c.

The rear surface of one of the filter cartridges 50 can also be seen in Figure 10, with the peripheral lip 52 abutting an internal wall 106 of the mask body 100. An opening 56 in the rear of the filter cartridge 50 provides a one-way exhalation valve. The mask 10 therefore provides a flow path whereby all inhaled air/gas passes through the pad 218 and the one-way inhalation valve, and all exhaled air and other substances from within the cavity 110 exit the mask 10 through the filter cartridges 50.

One factor potentially preventing or limiting the wider adoption of inhalational analgesics and/or sedatives is the risk of contamination of the atmosphere in an operating theatre. Gases or vapours from volatile liquids that are either not inhaled or remain in a patients exhaled air can, if not controlled, quickly build up in a confined space and be detrimental to clinicians or others in the space. Any breathing mask used in the administration of such substances should, therefore, mitigate these risks by providing a robust/reliable seal (as described above) and through effective/efficient filtration of excess and/or exhaled substances.

The large filter cartridges 50 provided on the mask body help to ensure that the filtering of exhaled gases and/or vapours is sufficient to avoid a build-up. The construction of each filter cartridge 50 is shown in the exploded view of Figure 11.

The filter cartridges 50 comprise a front casing 58, which defines a cavity to receive the activated carbon, and a rear casing 64 to close the cavity. The rear casing 64 comprises the opening 56 which, together with an exhalation valve member 66, forms the one-way exhalation valve. A first hydrophobic scrim 68 is provided on a scrim support 70 located between the front casing 58 and the exhalation valve member 66. A second hydrophobic scrim 74 is provided inside the front casing across the exhaust openings 76 in the front of the front casing 58. The first and second hydrophobic scrims 74,76 in the illustrated example are formed from polypropylene.

Activated carbon is a preferred filter medium in many applications due to its low weight and efficient performance. However, it is typically avoided in moist environments because the adsorbent properties of the material tend to absorb moisture first, leading to reduced capacity or even saturation of the filter. The first and second hydrophobic scrims 74,76 prevent moisture ingress into the cavity of the filter cartridge, ensuring that the filtering remains effective and thus allowing the use of activated carbon to filter moist exhaled air. The scrim support 70 additionally helps to secure the exhalation valve member 66 in place within the filter cartridge 50.

When assembled, the components provide a filter cartridge 50 with a contained internal volume to receive the activated carbon. A cover 62 is provided to close the aperture 60, which is in a wall of the front casing 58 that is obscured from view in Figure 11. this means that the cartridge 50 is potentially refillable/rechargeable. As an alternative, the filter cartridge may be made completely disposable. Various sizes of cartridge, either re-fillable or disposable, may be provided to account for different volumes of sevoflurane stored in the handset.

The rear casing 64 comprises the peripheral lip 52, around the rear of the filter cartridge 50, that engages with an internal wall 106 of the mask body 100 as the filter cartridges 50 are inserted from the cavity 110 side. The rear casing 64 also defines the base of the groove 54 that provides the 'pop' fit with the filter aperture 150.

The capacity or fill level of the filter cartridges 50 may be defined by or selected based on the volume of medicament contained in the handset 301 prior to use. That is, the capacity of the filter cartridges 50 may be specifically selected so that they provide sufficient filtering for the entire volume of sevoflurane available for use during a particular procedure. As will be explained below, the volume of medicament held in handset is set prior to use of the device, and cannot then be adjusted, i.e. the reservoir cannot be refilled once the device is in use. A particular filter volume can thus be selected based on the intended use of the device with confidence that the filter capacity will be sufficient.

The handset 301 of the device 1 is shown in Figure 12. The handset 301 comprises a housing having a wrist portion 302 and an end portion 303. The end portion 303 is rounded, with a bulbous shape which fits comfortably within the user's hand. The wrist portion 302 extends outwardly from the end portion 303, the wrist and end portions 302,303 being joined together by a concave curved surface on an upper side of the housing, and by a substantially planar surface on the underside of the housing.

The construction and overall structure of the handset can be seen in Figures 13a and 13b. The underside of the housing comprises a cradle 409 which forms the underside of both the wrist and end portions 302, 303, and the lower part of the front face of the end portion 303. The cradle 409 comprises mounting bosses 413 which extend upwardly from the cradle, and the lower part of the front face comprises a substantially semi-ovular cut-out 415 with a recessed wall 416 positioned behind.

The cradle 409 further comprises loops 314, 315 and slots for the receipt of the straps 305, 306, as described in further detail in relation to Figure 20.

The cradle 409 receives and engages with a central section 410, the central section 410 comprising the side walls 412 of the handset between which are retained the battery and reservoir compartments 309, 310, guide member 407, horizontal bar 417, activation switch 406 and peristaltic pump 334. The transmission tube 307 is fluidly connected to the peristaltic pump 334 and extends from the rear of the handset 301, and, as described above, is connected to the delivery chamber 200 of the facemask 10. These features are discussed in further detail below.

The upper side of the housing is formed of two components: a domed lid 411 and a hinged lid 308. The domed lid 411 forms the upper side, and the upper part of the front face, of the end portion 303. Similarly to the cradle, the upper part of the front face of the domed lid 411 comprises a substantially semi-ovular cut-out 418 with a recessed wall 419 positioned behind. The domed lid 411 engages with the mounting bosses 413 which support and secure the domed lid 411 to the cradle 409, covering the peristaltic pump 334, guide member 407, horizontal bar 417 and activation switch 406 within the central section 410, but leaving the battery and reservoir compartments 409, 410 exposed.

The hinged lid 308, which forms the upper surface of the wrist portion 302, is hingedly attached to the domed lid 411 and, when closed, covers the battery and reservoir compartments 309, 310 as described in further detail in relation to Figure 16 below.

The handset 301 further comprises a button 304 and a spring 403, which together form the user input.

The button 304 is located on a front face of the end portion 303 of the handset 301. It is retained between the semi-ovular cut-outs 415, 418 of the cradle 409 and domed lid 411. The button 304 is substantially oval in shape, and extends over a significant portion of the front face of the rounded end portion 303, providing a large surface area for the user to press. The button 304 has a convex form, and its shape follows the contours of the bulbous end portion 303 of the handset 301. In use, the user's palm lies across and over the domed lid 411 such that their fingers rest on the button 304 on the front face of the end portion 303, while their wrist rests on the hinged lid 308, which forms the upper surface of the wrist portion 302.

The button 304 is a floating button which can be pressed from almost any angle, increasing usability for patients with restricted movement. The button 304 comprises a domed surface 401 with an integrally formed central column 402, the central column 402 extending rearwardly from the concave face of the domed surface 401.

A rearwardly extending wall 423 extends outwardly from the periphery of the concave face of the domed surface 401, the rearwardly extending wall 423 further comprising four tabs 424 spaced at regular intervals about its outer circumference. In use, the convex face of the domed surface 401 is pressed by the user to activate the device. A spring 403, comprising an arcuate resilient strip 404, is mounted within the handset and positioned behind the concave face of the domed surface 401, such that the end of the central column 402 distal to the domed surface 401 contacts the resilient strip 404, and the spring 403 is orientated such that the resilient strip 404 is biased towards the central column 402.

The spring 403 is shown in isolation in Figures 15a and 15b, and comprises an arcuate resilient strip 404 retained within a rectangular mount 408. Within the central section 410 of the handset a horizontal bar 417 extends between the sidewalls 412, with a guide member 407 depending from a central point on the horizontal bar 417 and extending outwardly towards the front of the handset 301. When installed in the handset, the rectangular mount 408 of the spring rests against the front of the recessed walls 416,419, and is supported by features on a front face of the lower recessed wall 416 and by notches provided in side walls at either end of the lower recessed wall 416 to locate the spring 403 in the correct position. A hollow post 405 extends rearwardly from the centre of the resilient strip 403 and receives the guide member 407, the hollow post being movable longitudinally along the guide member 407. The end of the hollow post 405 distal to the resilient strip 404 is positioned adjacent to or in contact with an activation switch 406, such that longitudinal movement of the hollow post 405 along the guide member 407 causes the activation switch 406 to be pressed.

The spring 403 is mounted within the handset behind the button 304, such that the end of the central column 402 distal to the domed surface 401 contacts the spring.

When pressure is applied to the domed surface 401 of the button 304 by the user, pushing it towards the spring 403 and pushing the rearwardly extending wall 423 into abutment with the recessed walls 416, 419 on the cradle 409 and domed lid 411, the central column 402 exerts a force on the spring, pushing against the bias of the resilient strip 404. This force causes the resilient strip 404 to deform and consequently move the post 405 longitudinally along the guide member 407, pressing the activation switch 406 and thereby registering a user input. When the pressure on the button 304 is released the resilient strip 404 returns to its original arcuate shape, pushing the central column 402 and domed surface 401 back into their original positions such that the tabs 424 engage with the internal periphery of the semi ovular cut-outs on the dome and cradle 415, 418, retaining the button 304 within the handset. This moves the post 405 out of engagement with and hence releases the activation switch 406. Engagement of the tabs 424 with the internal periphery of the semi ovular cut-outs 415, 418 also creates pivot points about the edge of the button 304 such that, if pressure is only applied to one edge of the button 304 by the user, the button 304 will pivot about the tab or tabs 424 adjacent to an opposing edge of the button. This causes the centre of the button and hence the central column 402 to move towards the spring, ensuring that pressure is still applied to the resilient strip 404 by the central column 402 regardless of the angle or position from which the button is pressed.

Referring back to Figure 12, the handset 301 further comprises straps 305, 306 for attaching the handset 301 to the user's arm and/or wrist. The straps 305, 306 extend from a first side of the handset to a second side of the handset, forming a loop for retaining the patient's arm and/or wrist. The straps 305, 306 are adjustable, and can be adjusted to fit the patient's arm and prevent undue movement of the handset relative to the patient's arm, even if the patient's arm moves or falls. The attachment of the straps 305, 306 to the handset 301 is described in further detail in relation to Figure 20.

The wrist portion 302 of the handset comprises an openable housing, as shown in Figure 16. The openable housing comprises a hinged lid 308 which opens to reveal a battery compartment 309 and reservoir compartment 310 (batteries and reservoir not shown). The reservoir compartment 310 comprises a channel 328 for receiving an expandable reservoir filled with a pain-relieving and/or sedative substance, and an aperture 329 shaped to receive a connecting portion of the reservoir. The aperture 329 is broadly circular, and further comprises a laterally extending cut-out 311 shaped to receive a flange 330 which extends outwardly from the reservoir, as will be described in more detail later. Once inserted through the aperture 329, the reservoir 322 is engaged by a reservoir receiver (not shown), the reservoir receiver being connected to the inlet of the tube 335 of a peristaltic pump 334 housed within the end portion 303 as shown in Figure 13a. A peristaltic pump 334 has a fixed displacement and so, when in operation, the pump draws fixed aliquots of medication from the reservoir 322, transferring it to the transmission tube 307.

Two buttons 312, 313 are also located within the housing, proximate to the hinge of the hinged lid 308. The two buttons 312, 313 may be used to adjust parameters for correct operation of the device, for example to adjust the dosage and/or to set the dose profile of the medicament. Also visible are loops 314, 315, integrally formed with the body of the handset 301, which provide retention means for the straps 305,306 (not shown in Figure 16). The transmission tube 307 is clearly shown extending from the rear of the handset 301.

Figure 17a shows an expandable reservoir 322 for use with the handset 301 of the invention.

The expandable reservoir 322 comprises a barrel 325 having a proximal end and a distal end, and a plunger 326, the plunger 326 being inserted into the barrel 325 at the distal end and being slidable longitudinally within the barrel 325. The proximal end of the barrel 325 comprises a connection formation 323 to enable the syringe to be connected to a proprietary adaptor 324 on a medicament bottle 340, as shown in Figure 17b. The connection formation 323 additionally forms the connecting portion which forms a fluid connection between the reservoir and the handset 301, as described above.

The connection formation 323 enables a secure connection between the proximal end of the barrel 325 and a proprietary adaptor 324 on the medicament bottle 340, while permitting the transfer of a pain-relieving and/or sedative substance between the bottle 340 and reservoir 322. The connection formation 323 comprises two concentric rings 331, 332 which extend outwardly from the proximal end of the barrel 325. The outer ring 331 extends outwardly from the periphery of the proximal end of the barrel 325 and forms a friction fit with the proprietary adaptor 324, creating a fluid-tight seal. The wall of the outer ring 331 comprises two cut-out sections 420 to engage with corresponding formations 421 on the proprietary adaptor 324. The inner ring 332 is shorter than the outer ring 331 and comprises cut-out sections 333, such that at least an upper section of the inner ring 332 is broken into three segments. In use, the inner ring 332 presses on the spigot 422 of the adaptor 324, breaking the seal and allowing medicament to flow out of the bottle 340. The cut-out sections 333 provide spaces through which the medicament can flow to the centre of the connection formation and through a channel 425 which extends through the inner ring 332 and into the barrel 325.

The reservoir 322 is filled with a predetermined amount of a pain-relieving and/or sedative substance prior to insertion in the handset 301. Prior to filling the reservoir 322, the plunger 326 is depressed. Once the reservoir 322 is attached to the proprietary adaptor 324 on the medicament bottle 340, the reservoir 322 and bottle340 are inverted and the plunger 326 drawn out (as shown in Figure 18a, and in cross-section in Figures 18b and 18c), thus creating a vacuum which sucks the medicament into the reservoir 322. The outer ring prevents loss of medicament to the atmosphere during this process.

The connection formation 323 prevents the reservoir from being connected to any vessel which does not carry the proprietary connector 324, thus ensuring that the syringe can only be filled with the medicament for which the device and its safety mechanisms have been designed.

The plunger 326 comprises a narrowed section forming a defined point of weakness 327, which can be seen in Figure 19. The point of weakness 327 is positioned such that, when the plunger 326 has been drawn out to fill the barrel 325 with the correct dosage of medicament, the point of weakness 327 is located at or just above the distal end of the barrel 325. Once the expandable reservoir 322 has been filled with medicament, the plunger 326 is snapped off at the point of weakness 327. Snapping off a portion of the plunger 326 in this manner prevents the reservoir from being refilled and reused. The requirement to snap off the plunger 326 is enforced as the reservoir compartment 310 in the handset 301 is sized such that a full reservoir 322 will only fit into the syringe compartment 310 when the plunger 326 has been snapped off.

The barrel 325 further comprises a flange 330 protruding from a side close to or at its proximal end. The flange 330 extends outwardly from, and extends a short distance longitudinally along, the outer ring 331 of the connection formation 323, as shown in Figure 19. When the full reservoir 322 is inserted into the reservoir compartment 310 on the handset 301, the connection formation 323 and flange 330 on the barrel 325 pass through the aperture 329 and associated laterally extending cut-out 311. When correctly inserted, the flange 330 engages with a micro-switch (not shown) within the aperture 329. Actuation of the micro-switch confirms that the reservoir 322 has been correctly loaded into the handset 301, and activates the device 1.

The underside of the handset 301 is shown in Figure 20. The underside of the handset 301 comprises a window 316 in a position corresponding to the position of the reservoir compartment 310 in the interior of the handset 301, such that the reservoir 322 is visible through the window 316. This enables the level of medicament remaining within the reservoir 322 to be monitored while the device is in use.

Also visible are two loops 314, 315 and two slots 317, 318 for attachment of the straps 305, 306, the straps being used to secure the handset 301 to the user's wrist and hand and prevent dislodgement or dropping during use. Strap 305 passes from the interior of the handset 301, where it is secured, and through the slot 318 to the exterior of the handset. The strap 305 then passes over the upper side of the handset and through the corresponding loop 315. The tension of the strap is adjusted by altering the amount of the strap 305 which is pulled through the loop 315. The free end of the strap 305 (that which has passed through the loop 315) may comprise a buckle, toggle, cleat or other adjustable locking means (not shown) to prevent the strap from sliding back through the loop 315 and permit future adjustment. The second strap 306 is attached to the second slot 317 and loop 314 in the same manner.

The transmission tube 307 (shown in further detail in Figure 21) extends from the rear of the handset 301 and, as described above, is connected to the delivery chamber 200 of the facemask 10, operationally connecting the handset 301 and facemask 10.

The transmission tube 307 comprises a tube having a silicone body, and having first and second lumens 319, 320 extending longitudinally through the tube. The first lumen 319 has a diameter of approximately 2.5mm and carries electrical wires 321, electronically connecting the mask 10 and the handset 301. The second lumen 320 has a narrower diameter than the first lumen 319, of approximately 1mm, and carries the medicament from the handset 301 to the mask 10, where it is evaporated for inhalation by the user as previously described.

The transmission tube 307 enters the rear of the handset 301. Inside the handset 301, the second lumen 320 of the tube is connected to the tube of the peristaltic pump 334 at its outlet. As previously described, the reservoir 322 is fluidly connected to the tube of the peristaltic pump at its inlet 335. Thus, when the pump 334 is in operation, predetermined aliquots of medication are drawn from the expandable reservoir 322, through the peristaltic pump 334, and pass into the second lumen 320 of the transmission tube 307 to be carried to the facemask 10.

In use, delivery of the medicament from the handset 310 to the facemask 10 is controlled by a control algorithm that is carried out by a controller. The control algorithm consists of a number of components that in combination determine an output signal that controls the delivery rate of the medicament. Although described individually below, each of the algorithm components runs simultaneously, each influencing the output signal that controls the delivery rate of the medicament.

Breath detection A breath detection component of the algorithm is initiated upon turning on of the device 1. At regular intervals of approximately 10 milliseconds, the controller requests an input signal from the pressure sensor 240 that is indicative of a real-time pressure within the mask 10. Since fluctuations in the pressure within the mask 10 are indicative of a patient's breathing, the controller is able to sense, from the input signal, whether the mask is being worn by a patient.

Before commencing delivery of the medicament from the handset 301 to the facemask 10, if patient breathing is detected, then delivery of the medicament to the pad 218 is enabled. If patient breathing is not detected, then delivery of the medicament to the pad 218 is disabled. This ensures that medicament is not delivered to the pad 218 when the facemask 10 is not being worn, reducing waste and preventing buildup of medicament on the pad 218, which could otherwise lead to overdose should the mask be temporarily removed and repositioned on the patient after such buildup.

During delivery of the medicament from the handset 301 to the facemask 10, if patient breathing is detected, then delivery of the medicament is allowed to continue. If patient breathing is no longer detected, then delivery of medicament is ceased immediately. This enables detection of the mask having been removed, ensuring that medicament is not delivered to the facemask 10 when not being worn, reducing waste and preventing exposure of the medicament to the ambient environment, as well as preventing buildup of medicament on the pad 218, which could otherwise lead to overdose should the mask be temporarily removed and repositioned on the patient after such buildup.

Fluctuations in the pressure within the mask 10 are also indicative of the patient's breathing cycle, i.e. when they are in an inhalation phase and when they are in an exhalation phase. In particular, a drop in pressure within the facemask 10 is indicative of the patient breathing in, and an increase in pressure within the facemask 10 is indicative of the patient breathing out.

By receiving regular input signals from the pressure sensor 240, the controller is therefore able to determine when the patient is inhaling, and when the patient is exhaling. In some embodiments, this may enable the controller to control the timing of the pump to deliver medicament to the pad 218 of the facemask 10, such that the medicament is available for inhalation from the pad 218 when the patient next inhales.

The medicament delivery can also be controlled to provide a single dose size suitable for a single inhalation event. This individual dose size can be pre-set based on established clinical data, or can be tuned for a specific case (for example based on the age, size, weight, and/or lung capacity of a patient).

Determination of delivery rate A continuous delivery component of the algorithm calculates a continuous medicament delivery rate based at least in part on a patient input received via button 304. The continuous delivery component and the continuous medicament delivery rate may otherwise be referred to as a low response component and a low response medicament delivery rate. A rapid delivery component of the algorithm calculates a rapid medicament delivery rate based at least in part on a patient input received via button 304. The rapid delivery component and the rapid medicament delivery rate may otherwise be referred to as a high response component and a high response medicament delivery rate. These components of the algorithm run simultaneously to provide a combined output delivery rate that is based at least in part on the same patient input received via button 304.

Figure 22 illustrates the response of these components of the algorithm to various patient inputs received during medicament delivery.

In this example, the controller compares the continuous delivery component and the rapid delivery component, and the output delivery rate is equivalent to the higher of the two components. Hence, the output delivery rate is not plotted in Figure 22. Where the continuous delivery component is higher than the rapid delivery component, the device is described herein as delivering medicament in a continuous mode. Where the rapid delivery component is higher than the continuous delivery component, the device is described herein as delivering medicament in a rapid mode.

The graph of Figure 22 is split into four phases 900, 910, 920, 930 for illustrative purposes and ease of description. In reality, the graph represents an ongoing simulation of these components of the algorithm for a given scenario.

At the start of phase 900, medicament delivery is yet to commence, as the button 304 has not been pressed by the patient. Around halfway through phase 900, the patient first presses button 304, initiating medicament delivery. In response to the patient pressing button 304, the controller sends a signal to the rear facing LED(s) 242 to flash, thereby confirming to the patient that the button press has been successful and registered by the device 1.

At this early stage of medicament delivery, both the continuous delivery component and the rapid delivery component experience a small increase, by the same amount, i.e. with a step-like rise, and the output delivery rate is therefore equal to both components, and deemed to be in the continuous mode.

In the second half of phase 900, the patient presses button 304 a further four times, as can be seen by the four incremental step increases in both the continuous delivery component and the rapid delivery component. The increases in the rapid delivery component are much larger than those in the continuous delivery component at this early stage of requesting pain relief and/or sedation, to rapidly respond to the patient's needs.

The step increase in the rapid delivery component is dependent on the value of the rapid delivery component at the time of the button press. In particular, each press of the button 304 increases the rapid delivery component by a fraction or percentage of the difference between the instantaneous value of the rapid delivery component and a maximum delivery rate. The maximum delivery rate may be a maximum delivery rate permitted of the pump, or a preset maximum delivery rate that is dependent on the patient, for example based on their weight. Hence, where the rapid delivery component is higher, the step increase is lower, and where the rapid delivery component is lower, the step increase is higher.

In contrast, the step increases in the continuous delivery component are equal for each press of the button 304, irrespective of the value of the continuous delivery component at the time of the press. For example, each press of the button 304 may increase the continuous delivery component by 0.2m1/min, up to a predetermined maximum threshold.

These four presses of the button 304 in a short time period cause the rapid delivery component to increase at a much quicker rate than the continuous delivery component, and thus the output delivery rate is governed by the rapid delivery component throughout the remainder of phase 900, and the pump is operating in the rapid mode.

In phase 910 of Figure 22, the patient does not press the button 304, and the rapid delivery component decreases towards the continuous delivery component. In turn, the output delivery rate also decreases in the same way, still being governed by the rapid delivery component, because the rapid delivery component remains higher than the continuous delivery component.

The continuous delivery component also decreases, but at a much slower rate such that the decrease is imperceptible in phase 910 of Figure 22. In this embodiment, the rate of decrease of the continuous delivery component is a predetermined constant rate of decrease throughout delivery of the medicament.

However, in alternative embodiments, it is envisaged that the rate of decrease could be variable, for example dependent on the instantaneous rate of delivery, or the rate of delivery at the last press of the button 304.

In this example, because the rapid delivery component is still higher than the continuous delivery component, and thus the pump is operating in the rapid mode, the continuous delivery component continuously decreases throughout the absence of a button press by the patient. However, if the rapid delivery component were to decrease enough to become lower than the continuous delivery component, and the pump began to operate in the continuous mode, then the continuous delivery component would vary as described in relation to the breath detection component of the algorithm and Figure 23 below.

In phase 920 of Figure 22, the process described in relation to phases 900 and 910 is repeated a plurality of times. Each time the patient presses button 304, the continuous delivery component experiences a step increase by the fixed amount, and the rapid delivery component experiences a step increase that is typically larger than the step increase in the continuous delivery component, but varies dependent on the value of the rapid delivery component at the time of the button press.

In the absence of the patient pressing the button 304, the rapid delivery component decreases in the same way as in phase 910, and the continuous delivery component 20 decreases at a constant rate, as described above.

It can be seen from phase 920 of Figure 22 that the rate of the decrease in the rapid delivery component is different for each of the button presses. This rate of decrease in the rapid delivery component is dependent on the time that has passed since the button was last pressed. Specifically, the longer it has been since the button 304 was last pressed, the quicker the rate of decrease in the rapid delivery component. This protects the patient from prolonged exposure to higher doses of medicament when unnecessary for pain relief and/or sedation.

Throughout phase 920, because the rapid delivery component remains higher than the continuous delivery component throughout, the pump continues to operate in the rapid mode. Although the pump is operating in the rapid mode, the algorithm continues to calculate and monitor the continuous delivery component, as can be seen by the continued increases in the continuous delivery component throughout phase 920, in response to the patient pressing button 304.

At the start of phase 930 of Figure 22, a dosage monitoring component of the algorithm determines that the continuous delivery component has reached a predetermined threshold. The dosage monitoring component of the algorithm operates by continuously monitoring the continuous delivery component against said predetermined threshold, and intervening when the continuous delivery component reaches said predetermined threshold, by decreasing the rapid delivery component.

In alternative embodiments, the dosage monitoring component may additionally or alternatively continuously monitor the time the device has spent in the rapid mode against a predetermined threshold, and intervening when the cumulative time the device has spent in the rapid mode reaches said predetermined threshold, by decreasing the rapid delivery component.

Once the dosage monitoring component of the algorithm determines that the continuous delivery component has reached a predetermined threshold, the rapid delivery component is disabled such that further presses of the button 304 do not cause an increase in the rapid delivery component.

Hence, although the patient continues to press the button 304 in phase 930, the rapid delivery component decreases towards the continuous delivery component. In this embodiment, in response to the dosage monitoring component reducing the rapid delivery component, the rapid delivery component decreases at a rate that is slower than the rate of decrease in the rapid delivery component during normal operation of the device 1 in the rapid mode. However, it is envisaged that in alternative embodiments, the rate of decrease may be similar to, or faster than, the rate of decrease in the rapid delivery component during normal operation of the device 1 in the rapid mode.

At the end of phase 930, the rapid delivery component decreases to a level that is below the continuous delivery component, and at this point the pump begins to operate in the continuous mode, i.e. the output delivery rate becomes governed by the continuous delivery component.

This transition from the rapid mode into the continuous mode is illustrated in Figure 23, which illustrates the transition from phase 930 of Figure 22 into phase 935.

Phase 935 represents medicament delivery in the continuous mode, where the continuous delivery component is greater than the rapid delivery component, and the output delivery rate is therefore equivalent to the continuous delivery component. Hence, the continuous delivery rate is not plotted in phase 935 of Figure 23. Phase 935 is described in greater detail in relation to consciousness checks below.

Once the device 1 has been forced out of operating in the rapid mode, the device 1 remains locked out of operating in the rapid mode until the continuous delivery component decreases below the predetermined threshold again, or in the alternative embodiment described above, until the cumulative time spent in the rapid mode by the device 1 decreases below the predetermined threshold.

In the meantime, whilst operating in the continuous mode, continued presses of the button 304 would cause the continuous delivery component to increase by the fixed step increase, until the continuous delivery component reaches a predetermined maximum, or maintain the continuous delivery component at the predetermined maximum if presses of the button 304 are frequent.

Consciousness checks A consciousness component of the algorithm monitors the consciousness of the patient when the pump is operating in the continuous mode. No consciousness checks are carried out when the pump is operating in the rapid mode, because the reduction in the rapid delivery component is quick enough that the device 1 will only remain in the rapid mode if the button 304 is pressed regularly, thereby indicating that the patient is conscious. Indeed, in order to remain in the rapid mode, the patient will typically need to press the button 304 more often than a consciousness check would occur, thus negating the need for consciousness checks in the rapid mode.

However, when the pump is operating in the continuous mode, the controller regularly performs a consciousness check by sending output signals to illuminate the rear facing LED(s) 242, e.g. with a single flash or multiple flashes, or flashing patterns using the three spaced LEDs 242a, 242b and 242c, which indicates to the patient to confirm that they remain conscious, by pressing the button 304. In response to the patient pressing button 304, the controller sends a signal to the rear facing LED(s) 242 to flash, thereby confirming to the patient that the button press has been successful and registered by the device 1.

Once the LED(s) 242 has/have been illuminated, the controller monitors the time taken for the patient to respond by pressing the button 304. The controller then compares the patient response time with a predetermined threshold response time to determine whether the patient is conscious enough. Typically, it is deemed that if the patient presses the button 304 within 0.6 seconds, then they are deemed to be conscious enough.

If the patient response time is less than the threshold response time, then delivery of the medicament continues, and a further consciousness check is conducted in due course. If the patient response time is longer than the threshold response time, then the controller determines that the consciousness check has been failed, and that the patient has become too sedated.

In response to the patient failing a consciousness check, a secondary consciousness check is performed in the same way as the primary consciousness check, for example 15 seconds after the failed primary consciousness check. In response to failing a secondary consciousness check, it is confirmed that the patient has become too sedated and medicament delivery to the facemask 10 ceases. In response to passing a secondary consciousness check, the controller returns to performing primary consciousness checks. This ensures that delivery does not cease where the patient has simply missed the response to a primary consciousness check by accident. In alternative embodiments, the secondary consciousness check may be performed quickly, or immediately, after the failed primary consciousness check, i.e. in a small fraction of the time that would otherwise elapse between primary consciousness checks.

The first consciousness check is performed shortly after the pump starts to operate in the continuous mode, i.e. shortly after the end of phase 930 and shortly after the start of phase 935 in the example of Figure 23. The first consciousness check is typically conducted after a predetermined time interval following the last press of the button 304 in the rapid mode, or following commencement of delivery in the continuous mode. In alternative embodiments, the timing of the first consciousness check may additionally or alternatively depend on the time that has elapsed since the button 304 was last pressed by the patient to request pain relief and/or sedation, and the output delivery rate at that moment. Specifically, in this alternative, the longer it has been since the button 304 was last pressed, and the higher the output delivery rate was at the moment, the quicker the first consciousness check occurs once the pump begins to operate in the continuous mode. This is because as more time elapses, particularly after delivery of a high volume of medicament to the patient, the need to check on the status of the patient becomes more urgent, i.e. because they are more likely to have become too sedated.

When operating in the continuous mode, the consciousness checks are performed at regular time intervals, for example every 15 seconds. In alternative embodiments, the length of the time intervals between consciousness checks may be dependent on the output delivery rate at that moment in time, and may therefore be irregular. In particular, where the output delivery rate is higher, the consciousness checks are performed more regularly, because the risk of losing consciousness is higher. In contrast, where the output delivery rate is lower, the consciousness checks are performed less regularly, because the risk of losing consciousness is lower. Indeed, where the output delivery is particularly low, for example below a predetermined threshold, the consciousness checks may cease altogether, i.e. because the chance of the patient being unconscious is significantly low.

Phase 935 of Figure 23 illustrates the carrying out of consciousness checks, where the output delivery rate is plotted over time. At point in time 940, the device 1 begins to operate in the continuous mode, and thus at point in time 950, it is determined that a first consciousness check should be performed, because 15 seconds has elapsed since commencing operation in the continuous mode. An output signal is sent to illuminate the rear facing LED(s) 242, and because the patient presses the button 304 to confirm their consciousness within 0.6 seconds, the check is deemed to have been passed. In response, at point in time 955, the continuous delivery component, and hence the output delivery rate, are increased, because it is deemed safe to deliver more medicament to the patient to maintain their current level of pain relief and/or sedation.

After the initial step increase in the continuous delivery component and the output delivery rate, the continuous delivery component, and hence the output delivery rate, begin to decrease again. At point in time 960, following a further 15 seconds, a further consciousness check is performed, and an output signal is again sent to illuminate the rear facing LED(s) 242.

Again, the patient presses the button 304 to confirm their consciousness, and because the patient's response is within 0.6 seconds, the check is deemed to have been passed. In response, at point in time 965, the continuous delivery component, and hence the output delivery rate, are increased, because it is deemed safe to deliver more medicament to the patient to maintain their current level of pain relief and/or sedation. After the initial step increase in the continuous delivery component and the output delivery rate, the continuous delivery component, and hence the output delivery rate, begin to decrease again.

Whilst the patient continues to pass the consciousness checks, this process continues until a) the patient presses the button 304 without being requested, indicating that they are in pain and wish to receive more pain relief and/or sedation, triggering the continuous delivery component and the rapid delivery component of the algorithm to function as described above, or b) the patient fails a primary consciousness check and a subsequent secondary consciousness check, thereby triggering cessation of medicament delivery.

In response to each passed consciousness check, the delivery rate is increased by a fraction or percentage of the decrease in the delivery rate enforced between checks. For example, between points in time 940 and 950, the delivery rate is decreased by a predetermined amount, and in response to passing the consciousness check at point in time 950, the delivery rate is increased by 80% of that predetermined amount. This creates a cumulative decrease in the delivery rate during operation in the continuous mode, enabling fine adjustment of the delivery rate to the minimum rate required to maintain sufficient pain relief and/or sedation for the patient, whilst allowing the patient to reduce the delivery rate as they begin to feel more comfortable.

In this embodiment, the output delivery rate decreases at a constant rate between consciousness checks. However, in alternative embodiments it is envisaged that the decrease in the delivery rate may decrease at an alternative rate. For example, the decrease in the delivery rate may be dependent on the instantaneous delivery rate, e.g. at the time of pressing the button 304 in response to the most recent consciousness check. In particular, the rate of decrease may be higher where the delivery rate is higher, and lower where the delivery rate is lower.

In an alternative embodiment, it is envisaged that if the patient fails to respond to a consciousness check, the decrease in delivery rate continues at the same rate, but if the patient successfully responds to the consciousness check, the delivery rate decreases, but at a slower rate. In another alternative embodiment, it is envisaged that if the patient fails to respond to a consciousness check, the delivery rate decreases at a faster rate, but if the patient successfully responds to the consciousness check, the delivery rate continues to decrease at the same rate. In another alternative embodiment, it is envisaged that if the patient fails to respond to a consciousness check, the delivery rate continues to decrease at the same rate, or a faster rate, but if the patient successfully responds to the consciousness check, the delivery rate is maintained at the current or instantaneous rate, e.g. for a predetermined amount of time.

Where the above description of the specific embodiments discusses a "delivery rate" of medicament, in reality, it is envisaged that for some pumps in this field this may be better defined by reference to a volume of medicament delivered in a certain time period. For example, a delivery rate of 2m1/min may be delivered by delivering 4m1/min for 30 seconds, and stopping delivery for 30 seconds. The output rate of the pump is therefore 4m1/min, but the delivery rate of medicament to the facemask 10 is 2m1/min. Increasing the delivery rate to 3m1/min may therefore be implemented by delivering 4m1/min for 45 seconds, and stopping delivery for 15 seconds. Similarly, a delivery rate of 2m1/min may be delivered by alternating between delivering 4m1/min for 3 seconds, and stopping delivery for 3 seconds, for 10 intervals of each, giving an overall delivery rate of medicament to the facemask 10 of 2m1/min. Increasing the delivery rate to 3m1/min may therefore be implemented by alternating between delivering 4m1/min for 4.5 seconds for and stopping delivery for 1.5 seconds, for 10 intervals of each.

Hence, the output of the pump may be the same, but may be pulsed to the facemask 10 over a different time period, to achieve a different delivery rate to the facemask 10. This may be particularly relevant when using a stepper motor to drive delivery of the medicament, which may be beneficial in ensuring accurate and precise dosing/delivery.

LED ring The LEDs of display 500 shown in Figures 2-4 are used during operation to provide various status updates to a user or operator. The following notification sequences are described in relation to the specific LED ring 502 of Figures 2-4, which has eight LEDs in a circular shape. However, it will be understood that the same notification sequences could be provided by a plurality of LEDs provided in a different shape, and/or being different in number, and that different colours could be used to indicate different statuses from those specifically described below.

Figures 24a-24d illustrate a first notification sequence, in which one or more of the LEDs is illuminated in purple to indicate that the device is priming. Once the reservoir 322 has been correctly inserted into the handset 301 and the micro-switch activated by the flange 330 as previously described, provided the battery is connected, the device 1 begins the priming process. During priming of the device 1, the peristaltic pump 334 draws and transmits sufficient medication from the reservoir 322 to the transmission tube 307 to fill the transmission tube 307 between the handset 301 and the mask 10, but does not begin delivery of the medication onto the gauze/pad 218.

During priming, actuation of the button 304 will not cause delivery of medication to the mask 10. During priming, medicament will be delivered to the facemask 10 regardless of the breath detection component of the algorithm, but not to the pad 218.

Here, the number of illuminated LEDs of LED ring 502 corresponds to a proportion or percentage of the priming completed. The number of illuminated LEDs therefore increases in a clockwise direction as priming progresses, starting from the LED positioned towards the top of the outwardly facing display 500.

For example, each LED that is illuminated in purple may be indicative of the device being approximately 12.5% primed. Hence, the first LED showing being illuminated in purple may indicate that the device is approximately 12.5% primed, two LEDs being illuminated in purple may indicate that the device is 25% primed (as illustrated in Figure 24a), four LEDs being illuminated in purple may indicate that the device is 50% primed (as illustrated in Figure 24b), 6 LEDs being illuminated in purple may indicate that the device is 75% primed (as illustrated in Figure 24c), and so on.

These percentages are an example only, and in general, each LED being illuminated is indicative of the device being further towards being fully primed.

Once the device is fully primed, all eight of the LEDs are illuminated in purple, to indicate that priming is complete (as illustrated in Figure 20d). Upon completion of priming, the device 1 checks whether the device battery is full., The device 1 may also check whether the reservoir 322 is full, for example by issuing a request to the operator to confirm that the reservoir 322 is new, thereby confirming that it is full. Upon confirmation of the full battery (and the full reservoir, where applicable), all eight of the LEDs are illuminated in green, indicating to the user or operator that the device is fully primed and ready for normal operation, i.e. the handset 301 is ready to deliver medicament to the facemask 10.

Figures 25a-25d illustrate a second notification sequence, which runs during delivery of the medicament from the handset 301 to the facemask 10. In this second notification sequence, 7 of the 8 LEDs in the LED ring 242 remain illuminated in green, whilst a single LED is illuminated in blue. The LED illuminated in blue changes over time, so that the blue LED appears to move in a clockwise manner around the LED ring over time, as illustrated in Figures 20a-20b, indicating that breathing is continually being detected and delivery of the medicament is ongoing.

Figures 26a-26d illustrate a third notification sequence, which runs in combination with the second notification sequence during delivery of the medicament from the handset 301 to the facemask 10. In this third notification sequence, the number of LEDs illuminated in green is indicative of the amount of medicament remaining in the reservoir 322. The number of LEDs illuminated in green therefore reduces in an anticlockwise direction during delivery of the medicament to the facemask 10, finishing with the LED positioned towards the top of the outwardly facing display 500.

As with the first notification sequence, each LED that is illuminated in green is indicative of how full the reservoir 322 is. For example, each LED that is illuminated in green may represent the reservoir 322 being approximately 12.5% full. Hence, when the eighth LED is the last LED illuminated in green, as in Figure 26a, the reservoir 322 is approximately 100% full. When the sixth LED is the last LED illuminated in green, as in Figure 26b, the reservoir 322 is approximately 75% full. When the fourth LED is the last LED illuminated in green, as in Figure 26c, the reservoir 322 is approximately 50% full. When the second LED is the last LED illuminated in green, as in Figure 26d, the reservoir 322 is approximately 25% full.

Once the reservoir 322 drops to being approximately 10% full, the last two LEDs are illuminated in yellow, and pulse or flash to indicate to the operator that the reservoir 5 322 is almost empty.

Once the reservoir 322 is completely empty, the last LED is illuminated in yellow, and pulses or flashes to indicate to the operator that the reservoir 322 is empty.

A single, yellow, flashing or pulsing LED may be used during the setup of a device 1 to notify the operator that the device 1 has been used before. All 8 LEDs flashing or pulsing in yellow during the setup of a device 1 may be used to notify the operator that the device 1 has a software or hardware fault. That fault may be, for example, that the battery is low, or that a component of the device 1 is missing or misconnected.

Various other modifications of the embodiments described above would also be apparent to a skilled reader. As such, it is emphasised that the forgoing description is provided by way of example only, and is not intended to limit the scope of protection as defined with reference to the appended claims.

Claims

Claims 1. A device for providing pain relief and/or sedation to a patient, the device comprising a handset and a patient delivery interface, the handset having a patient-controlled initiator and electronic dosage control means and being engaged, in use, to a reservoir configured to contain a liquid pain-relieving and/or sedative substance, the patient delivery interface being, in use, fluidly connected to the reservoir via a conduit, wherein, on actuation of the patient-controlled initiator, an input is provided to the dosage control means, the dosage control means consequently providing an output which controls the transfer of a portion of the liquid pain-relieving and/or sedative substance from the reservoir to the patient delivery interface.
2. A device according to Claim 1, wherein the handset comprises a housing, and wherein, in use, the reservoir is at least partially contained within the housing.
3. A device according to Claim 2, wherein the housing comprises an attachment point for engagement of the reservoir.
4. A device according to Claim 2, wherein the housing comprises a recess which, in use, receives the reservoir.
5. A device according to any preceding claim, wherein the device comprises said reservoir, the reservoir being configured to contain from 5 to 100m1 of a liquid pain-relieving and/or sedative substance.
6. A device according to any preceding claim, wherein the pain-relieving and/or sedative substance is a volatile fluid.
7. A device according to any preceding claim, wherein the pain-relieving and/or sedative substance is an anaesthetic.
8. A device according to any preceding claim, wherein the pain-relieving and/or sedative substance has an offset time of less than 10 minutes.
9. A device according to any preceding claim, wherein the pain-relieving and/or sedative substance is sevoflurane.
10.A device according to any preceding claim, wherein the handset comprises a grip, the grip having a surface which is at least partially spherical or spheroidal and which, in use, is held by the patient, wherein the spherical or spheroidal surface carries the patient-controlled initiator and wherein squeezing of the grip causes actuation of the patient-controlled initiator.
11.A device according to Claim 9, wherein the handset further comprises a rest portion which, in use, accommodates the user's wrist.
12.A device according to Claim 11, wherein an upper surface of the spherical or spheroidal form of the grip is connected to an upper surface of the rest portion by a convex curve.
13.A device according to any preceding claim, wherein the patient-controlled initiator comprises a button retained within the wall of the handset and mounted above a resilient member, the resilient member being biased towards the button, such that, when pressure is applied to the button by the user, the button contacts the resilient member and causes it to deform.
14.A device according to Claim 13, wherein the button comprises one or more engagement tabs about its periphery which engage with the surrounding wall of the handset.
15.A device according to any preceding claim, the handset further comprising an activation feature, wherein the activation feature is activated on engagement of the reservoir with the handset, causing initiation of the device.
16.A device according to Claim 15, wherein the reservoir comprises an activation member and wherein, on engagement of the reservoir with the handset, the activation member interacts with the activation feature to cause initiation of the device.
17.A device according to Claim 15 or Claim 16, wherein the activation member comprises an outwardly extending flange.
18.A device according to Claim 17, wherein the outwardly extending flange extends longitudinally along the reservoir.
19.A device according to any preceding claim, wherein the handset and patient delivery interface are connected by a conduit, the conduit having at least first and second lumens, the first lumen being configured to carry a liquid pain-relieving and/or sedative substance and the second lumen carrying at least one electrical wire, electronically connecting the handset and patient delivery interface for the transfer of power and/or data between the handset and patient delivery interface.
20.A device according to Claim 19, wherein the first lumen has a diameter of between 0.5 and 1.5mm, and the second lumen has a diameter of between 2mm and 4mm.
21.A device according to Claim 19 or Claim 20, wherein, in use, the first lumen is in fluid communication with the reservoir.
22.A device according to any preceding claim, wherein the handset further comprises a delivery means, the delivery means receiving the output from the dosage control means, and transferring the pain-relieving and/or sedative substance from the reservoir to the patient delivery interface according to the output from the dosage control means.
23.A device according to Claim 22, wherein the delivery means is a pump.
24.A device for providing pain relief and/or sedation to a patient, the device comprising a handset a patient-delivery interface, and a reservoir, the reservoir being configured to contain a pain-relieving and/or sedative substance and being at least partially contained, in use, within the handset, the reservoir comprising a plunger received within a barrel, the plunger comprising a point of weakness which, in use, is broken to enable the reservoir to be at least partially contained within the handset, the reservoir, in use, being fluidly connected to the patient delivery interface.
25.A device according to Claim 24, wherein the reservoir is, in use, engaged with the handset.
26. A device according to Claim 24 or 25 wherein, in use, the reservoir is fluidly connected to the patient delivery interface.
27.A device according to any of Claims 24 to 26, wherein the handset comprises a recess which, in use, receives the reservoir, the recess being sized to receive the reservoir only when the plunger has been broken at the point of weakness.
28.The device of Claim 27, wherein the recess is concealed by a door.
29.The device of any of Claims 24 to 28, wherein the handset further comprises a patient-controlled initiator and dosage control means and wherein, on actuation of the patient-controlled initiator, an input is provided to the dosage control means, the dosage control means consequently providing an output which controls the transfer of a portion of the pain relieving and/or sedative substance from the reservoir to the patient delivery interface.
30.The device of any of Claims 24 to 29, wherein the handset and patient delivery interface are connected by a conduit, the conduit having at least first and second lumens, the first lumen being configured to carry a liquid pain-relieving and/or sedative substance and the second lumen carrying at least one electrical wire, electronically connecting the handset and patient delivery interface for the transfer of power and/or data between the handset and patient delivery interface.
31.The device of any of Claims 24 to 30, wherein the handset further comprises an activation feature, the reservoir being engaged, in use within the handset, wherein the activation feature is activated on engagement of the reservoir with the handset to cause initiation of the device.
32.The device of Claim 31, wherein the reservoir comprises an activation member and wherein, on engagement of the reservoir with the handset, the activation member interacts with the activation feature to cause initiation of the device.