HK1189524B - Breathing assistance apparatus - Google Patents

Description

FIELD OF INVENTION

The present invention relates to the use of a pressure regulator in conjunction with a breathing assistance apparatus, particularly though not solely, for regulating the pressure of gases supplied to a patient from a Positive End Expiratory Pressure (PEEP) apparatus or for an infant resuscitation device.

BACKGROUND

At the moment of their first breath, a baby's lungs are collapsed and filled with fluid. The pressures needed to open such lungs, and keep them open, are several times that of a normal breath until the fluid is displaced and the lungs have filled with air. To generate these large pressures, the baby must have strong respiratory muscles, as well as a chemical called surfactant in their alveoli. Surfactant reduces the surface tension of the fluid within the alveoli, preventing the alveolar walls from sticking to each other, like coasters to coffee cups when there is water between them.

Neonates have difficulty in opening their lungs and keeping them open. Reasons for this include:

1. a) Weak respiratory muscles and low surfactant levels. This means that they cannot generate enough pressure to open the lungs and, should they be resuscitated, tire quickly with the effort of keeping open alveoli lacking in surfactant.
2. b) Underdeveloped internal tissue structure to support the alveoli.
3. c) Slower clearance of lung fluid. In very premature neonates, fluid may continue to be secreted in the alveoli even after birth.
4. d) A soft chest wall, horizontal ribs, and a flatter diaphragm contribute to reduce the inspiratory capacity.
5. e) The mixing of oxygenated and deoxygenated blood raises blood pressure in the lungs, increasing fluid movement from the blood vessels into the lung tissue. The reduced blood oxygen level starves tissue of oxygen and further weakens respiratory muscles.
6. f) Weak neck muscles and a lack of neck fat reduce upper airway stability so that collapse on inspiration may occur.
7. g) Collapsed, damaged alveoli secrete proteins that reduce surfactant function.

To alleviate this it is known to apply Positive End Expiratory Pressure (PEEP) during respiration, resuscitation or assisted respiration (ventilation). In applying PEEP, the neonate's upper airway and lungs are held open during expiration against a pressure that stops alveolar collapse. Lung fluid is pushed back into the circulating blood, alveolar surfactant is conserved, and a larger area of the lung participates in gas exchange with the blood. As blood oxygenation and carbon dioxide removal improves, more oxygen is delivered to growing tissues, while less oxygen and energy is consumed by respiratory muscles. In the case of resuscitation or ventilation the pressure is varied between a Peak Inspiratory Pressure (PIP) and the PEEP value until the patient/infant is breathing spontaneously.

In order to provide the PEEP across a range of flow rates, some method is required to regulate the pressure. It is known in the art to provide a valve near the infant, which actuates at a level of pressure (ie: the PEEP value) to allow the gases to vent externally. Such valves may employ a spring-loaded valve, which in turn requires the use of high quality springs, which have been individually tested to give a high tolerance spring constant in order to ensure that it actuates at a value substantially that of the maximum safe pressure. Both the manufacture and testing of such a spring necessitates that its cost will be correspondingly high. Accordingly it would be advantageous to provide a pressure relief valve for a breathing assistance system which did not involve the use of such a high tolerance spring.

Also such valves are known to have substantial variation of the relief pressure with flow rate. For example as seen in Figure 5 the delivered pressure is shown for a range of valves. Over a given range of flow rates shown in the graph 50 of Figure 5, a variable orifice valve as shown by line 52 gives a wide range of delivered pressure. An improvement on this is a prior art umbrella valve (for example the "umbrella check valve" manufactured by Vernay Laboratories Inc. shown in Figures 4a & 4b) which delivers a lower variation in delivered pressure, as shown by line 54. However in all cases the variation in delivered pressure of prior art valves would desirably be reduced for this application.

US 4 655 213 relates to a mask for treating sleep apnea with an adjustable screw PEEP valve.

US 5 701 886 relates to a non-rebreather 02 mask with separate 02 and medicament inlet ports.

US 4 898 167 relates to a resuscitation system to assist a rescuer with providing CPR, without having mouth or lung contact with the patient. A rescuer uses a bellows and mask device with two hands to provide PIP and PEEP to the patient and is required to use their entire hand to occlude the PEEP valve of the device.

AU 637 905 relates to a dual function valve assembly.

US 4 952 563 relates to an elbow member for connecting a Y piece to an endotracheal tube, and discloses that the elbow member has a sampling port

SUMMARY OF INVENTION

Aspects and embodiments of the invention are set out in the appended claims.

It is an object of the present invention to provide a pressure regulator which goes some way to achieving the above-mentioned desiderata or which will at least provide the Healthcare industry with a useful choice.

BRIEF DESCRIPTION OF THE DRAWINGS

One preferred form of the present invention will now be described with reference to the accompanying drawings in which:

• Figure 1 is a block diagram showing a typical configuration for supplying breathing assistance to a neonate in accordance with the prior art.
• Figure 2a is a sectional view of a typical layout of a pressure regulator that can be used with the apparatus of Figure 1, according to an example of the present invention.
• Figure 2b is a perspective view of a valve member used with the pressure regulator of Figure 2a, according to an example of the present invention.
• Figure 3 is a side view showing hidden detail of the valve member of Figure 2b, according to an example of the present invention.
• Figure 4a is a side view showing hidden detail of a prior art umbrella valve.
• Figure 4b is a perspective view of the prior art umbrella valve of Figure 4a.
• Figure 5 is a graph showing a comparison of the pressure ranges produced by different types of valve over a flow range of 5-15 litres/minute.
• Figure 6 is a sectional front elevation view of a pressure regulator according to an example of the present invention.
• Figure 7 is an exploded perspective view of the pressure regulator of Figure 6.
• Figure 8 is a front elevation of a pressure regulator according to an example of the present invention.
• Figure 9 is an exploded perspective view of the pressure regulator of Figure 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is a connector including a valve, for use when resuscitating an infant or neonate. The delivered pressure is varied between Peak Inspiratory Pressure (PIP) and Peak End Expiratory Pressure (PEEP) by the occlusion of a PEEP outlet on the valve. The PEEP outlet may either allow variable PEEP, by adjustment, or substantially flow independent fixed PEEP using a novel umbrella valve. In an example, a duck billed valve is included for suctioning of surfactant delivery during resuscitation. In an example, the connector is adapted for one handed use. If using the fixed PEEP valve, this avoids the need for adjustment as flow through the valve changes, and provides more effective therapy.

Referring now to Figure 1 a typical application as known in the prior art is depicted. A Positive End Expiratory Pressure (PEEP) system is shown in which an infant 119 is receiving pressurized gases through a nasal mask 128 (or endotracheal tube or other interface as are known in the art) connected to an inhalatory conduit 121, preferably for resuscitation. Either the mask 128 or the inhalatory conduit 121 can include the pressure regulator 134 of the present invention, to control the pressure of gas delivered to the infant. The inhalatory conduit 121 is connected to the outlet of a resuscitator apparatus 115, which is in turn connected to a flow regulator and air supply 118 (which provides gas to the resuscitator at 50 psi or thereabouts).

It should be understood that the present invention, however, is not limited to resuscitation, or the delivery of PEEP gases but is also applicable to other types of gas delivery systems.

Pressure Regulator

One example of a pressure regulator 134 is shown in Figures 2 and 3 in detail. In the illustrated example the regulator 134 is disposed within a mask 128 although it will be appreciated that it can be located in a separate assembly, so long as it is proximate the infant.

Referring particularly to Figure 2a we see a cross-sectional schematic of an example of the pressure regulator 134. The pressure regulator 134 includes a housing or manifold 300 with an inlet 302 and two outlets 304, 306. The first outlet 304 supplies respiratory gases to the infant. The second outlet 306 is an external orifice which, as described previously, can be used to vary pressure between PIP and PEEP. Located between the inlet 302 and the orifice 306 is an improved PEEP valve 308.

The PIP is adjusted at the resuscitator 115 to a desired level. The gases delivered to the infant 119 are varied between the PIP (with orifice 306 near the infant occluded), and the PEEP (with the orifice 306 un-occluded, so that a portion of the gas from the resuscitator 115 flows through the orifice 306). It can be seen that resuscitation of an infant can be attempted by varying the pressure at outlet 304 between the PIP and PEEP at a normal respiratory frequency.

The purpose of the PEEP valve 308 is to keep the Positive End Expiratory Pressure (PEEP) at a reasonably constant level, independent of changes in the overall flow rate of gases from resuscitator 115.

It is desirable for infant respiratory assistance that the PEEP value should be approximately 5 cmH₂0, independent of the flow rate. Preferably interfaces of the type used for resuscitation need to be simple and cost effective, as these are single-use products. Also, due to the nature of this application, a valve with many small separate parts, such as a spring valve, is not a viable option.

In some examples, the PEEP valve 308 is a small umbrella valve 308, made of an elastomeric material, and positioned on a valve seat 310 as shown particularly in Figure 2a & 2b. Valve seat 310 defines an internal venting aperture 311 which is covered and closed by the valve 308 in a closed position. Preferably the valve 308 and seat 310 are included as part of the nasal mask 128, or as part of an endotracheal tube (not shown). As the overall flow rate is increased, the consequent increase in pressure inside the manifold 300 causes the umbrella valve flaps 312 to lift up from the valve seat 310, thereby letting more air out from inside the manifold 300, and therefore keeping the pressure inside the manifold 300 at a constant level.

The umbrella valve 308 of differs from other prior art umbrella valves in the material and dimensions, the material being Silastic liquid silicone rubber Q7-4840. The overall proportions of the umbrella valve are as shown in Figure 3. In particular, comparing Figure 3 to the prior art valve shown in Figures 4A and 4B, we see the present invention has a characteristic flap 312 which is thicker at the periphery than at the centre. The ratio of the centre thickness to the periphery thickness should be 2:3, giving the cross-sectional shape shown in Figure 3. The valve 308 of the present invention includes a shaft 301, which has a retaining flange 303.

Due to the design used, the umbrella valve 308 does not act as a 'pop-off' valve. Most umbrella valves such as that shown in Figures 4A and 4B are designed to open at a specific 'cracking pressure'. The prior art valve shown in Figures 4A and 4B has a shaft 400 and flap 410. Often prior art valves have a "cracking pressure which will increase as the flow threshold increases". In contrast, the valve of the present invention is designed to open at a predetermined flow rate (in this specific application below 5 litres/minute) and will continue to open further as the flow rate increases, increasing the flow through the internal aperture 311, and thus causing the pressure in the manifold 300 to remain constant as the flow from resuscitator 115 increases. Prior art umbrella valves will open at a certain pressure level, and either will not open any further as the flow rate increases, or their resistance to opening will increase, so that there is substantial variation of the relief pressure with flow rate. This variation causes the pressure in a manifold to increase as the flow from a resuscitator increases.

The improved characteristics of the umbrella valve can be seen in Figure 5. If using a simple variable orifice valve, if the flow rate is changed between 5 and 15 litres per minute a dramatic change in PEEP will also occur, as shown by line 52. The PEEP range for the variable orifice valve is 13 cmH₂0. In tests, the best result obtained from prior art umbrella valves, as shown by line 54, was a PEEP range of 4.9cmH₂0. In the same tests, the best result gained from the valve of the present invention as shown by line 56 is a PEEP range of 2.8 cmH₂0.

Referring to Figure 6 we see an example of the pressure regulator 134. Located between the inlet 302 and the orifice 306 is a PEEP valve 308, preferably the umbrella valve described previously for an example. Included in this example is an inlet 303 which includes a duck billed valve 305, used for introducing tubes down the trachea of the infant 119, for suctioning, delivery of surfactant etc. The duck-billed valve 305 is normally closed.

In some examples, the manifold 300 is shaped to enable ease of use; and it is designed to enable one handed operation. The manifold 300 is preferably wide and short and in the example shown in Figure 6, it has a generally cylindrical cross-section. At the outlet 304 to the neonate, which is connected to the manifold 300, is a flange 301. When the present invention is used with a mask, the flange 301 enables the operator to apply pressure, pushing the mask into position to seal the mask around the neonate's nose and mouth. The flange 301 also enables an operator to use one digit on their hand to occlude orifice 306, in order that they can vary pressure in the manifold 300 between PIP and PEEP. The operator achieves this variation in the pressure most easily by placing their thumb and middle finger on the flange 301 at 309 and 360 and then using their index finger to seal orifice 306. The orifice branch 321 is shown at an angle 309 to the manifold 300. This angle 309 allows the index finger to be placed in a natural position to occlude orifice 306. The previously described example of the pressure regulator 134 operates in the same way as the example described above.

As has already been described new born neonates often lack surfactant in their lungs. When an example comprising an inlet 303 is used with an endotracheal tube, surfactant can be administered to a patient without the need to remove the breathing assistance apparatus from the patient. By using a syringe or similar, the operator can administer surfactant to the neonate by pushing the end of the syringe through the duck billed valve 305, located opposite the inlet 301, and administer the surfactant to the infant 119.

The duck billed valve 305 is normally sealed against the passage of fluids, but upon insertion of a syringe, the duck-billed valve 305 opens to allow the syringe end to enter the interior of the manifold 307. The bill, or inner end 320, of the duck billed valve 305 seals around the end of an inserted syringe, ensuring that the manifold 300 remains sealed. The valve bill 320 is manufactured from a silicone rubber, or other suitable material as known in the art. It is known that surfactant is a viscous fluid, and therefore this method of administration is advantageous over the method of administering surfactant using multi lumen endotracheal tubes.

The duck billed valve 305 can also be used to suction a neonate or infant 119, to remove airway secretions. Suctioning is performed using a catheter inserted through the duck billed valve 305, inserting the catheter through the duck-billed valve 305, then down the endotracheal tube. The bill 320 of the valve 305 seals around an inserted catheter so that airway pressure is maintained. The duckbilled valve 305 is retained in the manifold 300 in such a way that any instrument inserted into the valve 305 is guided directly into the top of an endotracheal tube (or alternatively, a nasal mask, or other interfaces as are known in the art), one end of the endotracheal tube fitted at the outlet 304.

When resuscitating or ventilating an infant it is desirable to ensure that the expired gases of the infant are not re-inspired by the infant. The portion of gases expired by the infant which can potentially be re-inspired is known as the dead-space. A baffle 342 is exemplified in the present invention between the gases inlet 302 and the orifice 306. The baffle 342 provides a barrier to flow which extends from the top of the manifold to the top of a nasal mask (or endotracheal tube or other interface as are shown in the art). The inclusion of the baffle 342 causes the nominal flow path of gases to pass across the top of a mask (or similar) fitted to the manifold when the orifice 306 is in the unoccluded configuration. When the orifice 306 is occluded, the patient receives oxygenated gas from the gases inlet 302, and once the orifice 306 is unoccluded the expired gases are carried from the top of the mask to the outlet orifice 306 by the nominal flow of gas. This has the effect of greatly reducing the dead space within the manifold interior 307.

Figure 8 and Figure 9 illustrate an example of a pressure regulator 134. The overall shape of the manifold 330 is similar to that previously described with reference to Figure 6, with, in this example, orifice branch 321 is replaced by an alternate orifice branch 326. The pressure of the delivered gases is varied between PIP, with orifice 334 on branch 326 occluded, and PEEP, with the orifice 334 un-occluded. As is best shown with reference to Figure 9, the manifold 330 includes a jet outlet 332 positioned between the inlet 328 and the outlet orifice 334. The flow rate of the gases through the jet outlet 332 is controlled by a screw-on cap 324, which is located screwed onto a thread on the end of the outlet branch 326 of the manifold 330. The traveled distance of the screw on cap on the thread determines the restriction to the orifice 332 and therefore varies the PEEP. That is, the closer the screw on cap 324 is to the jet outlet 332, the smaller the gas flow rate through the orifice 334. The manifold 330 is otherwise as described for the previous examples.

Claims (13)

1. A pressure regulating device (134) for use with a breathing assistance apparatus which conveys gases to an infant or a neonate (119) requiring breathing assistance, comprising:

   a housing (300, 330) including a gases inlet (302, 328), an outlet (304) and an aperture (306, 332,334), said gases inlet (302, 328) adapted to in use be in fluid communication or integrated with a breathing assistance apparatus (115, 118), said outlet (304) adapted to be in use in fluid communication with said infant (119), said aperture (306, 332,334) enabling the venting through said aperture (306, 332, 334) of a portion of gases that in use are passing through said housing (300, 330) from said inlet (328) to said outlet (304), and

   said housing (300, 330) also includes an orifice manifold (321) extending from a side of said housing (300, 330), said orifice manifold arranged at an angle to said housing, said aperture (306, 332, 334) provided on said orifice manifold (321);

   wherein the housing (300, 330) includes a flange (301) connected to said outlet which, when used with a mask, enables an operator to apply pressure to fluidicly seal the mask to the neonate's nose and mouth,

   characterised in that

   said gases inlet (302, 328) is located substantially on the opposite side of said housing (300, 330) to said aperture (306, 332, 334), a PEEP valve (308) is located between said gases inlet (302) and said aperture, and

   said aperture (306, 332,334), flange (301) and said housing (300, 330) are adapted so that in use a user can hold said housing (300, 330) in position with one hand, and occlude said aperture (306, 332,334) with one finger of said one hand to vary the pressure at said outlet (304) between PIP with said aperture (306, 332, 334) occluded and all the flow of gases from said inlet passing through said outlet (304), and PEEP with said aperture (306, 332,334) unoccluded, and a portion of said flow of gases from said inlet passing through said aperture (306, 332,334).
2. The device as claimed in claim 1, wherein said gases inlet (302, 328) is arranged at an angle of 60 degrees to said housing (300, 330).
3. The device as claimed in any one of claims 1 or 2, configured to allow a user to place their thumb and middle finger on the flange (301) to apply said pressure.
4. The device as claimed in any one of claims 1 to 3, wherein the finger is an index finger.
5. The device as claimed in claim 4, wherein said orifice manifold (321) is at such an angle to the housing (300, 330) that the index finger is in a natural position to occlude the aperture (306, 332, 334).
6. The device as claimed in claim 5, wherein said orifice manifold (321) is at an angle of 70 degrees to said housing (300, 330).
7. The device as claimed in any one of claims 1 to 6, wherein the housing includes a second aperture adapted to receive a surfactant delivery means and sealing means adapted to in use allow surfactant to be delivered to a patient through said second aperture without said second aperture fluidicly communicating with an interior of said housing while providing breathing assistance.
8. The device as claimed in claim 7, wherein the sealing means is a duck billed valve.
9. The device as claimed in claim 8, wherein said second aperture is adapted to receive a surfactant delivery means, and said surfactant delivery means and said outlet are substantially coaxial.
10. The device as claimed in any one of claims 1 to 9, wherein said housing is part cylindrical and part frustoconical.
11. The device as claimed in claim 10, wherein a width of said housing at said flange is less than a height of said housing.
12. The device as claimed in any one of claims 1 to 11, further comprising a jet outlet positioned in said orifice manifold between said gases inlet and said aperture.
13. The device as claimed in claim 12, wherein said orifice manifold comprises a screw-on cap, and wherein a flow rate of gases through said jet outlet is controlled by the proximity of said screw-on cap to said jet outlet.