GB2214088A - Heated nebulizer system - Google Patents

Abstract

A nebulizer system for producing a humidified and heated breathing gas to be inhaled by a patient undergoing inhalation therapy, includes a nebulizer module 12 and a heater module 14 detachably connected to each other. The nebulizer module is connectable to an oxygen source 46, a liquid water supply 22, and, through an outlet 16, to a breathing apparatus 18. A throat or conduit 48 in the system serves to direct an aerosol spray produced in the nebulizer module to the heater module in a conical pattern. The heater module includes an annular heated surface 50 upon which the aerosol spray impinges. The heated surface volatilizes at least a portion of the aerosol spray discharged from the conduit while allowing the remainder to coalesce and return throught port 70 to the reservoir 22. <IMAGE>

Description

HEATED NEBULIZER SYSTEM Technical Field This invention relates to inhalation therapy devices and, more particularly, to a nebulizer system for producing a heated aerosol spray.

Background of the Invention The administration of oxygen to a patient usually has an adverse drying effect on the patient's respiratory system. Therefore, various humidifying or nebulizing devices have been used to condition oxygen being administered to a patient by mixing it with water or other fluids.

A typical nebulizer system for inhalation therapy comprises a bottle or like container of sterile liquid, such as water, and a nebulizer assembly. The nebulizer assembly is usually connected to a supply of pressurized oxygen through appropriate throttling valves. As the oxygen flows through an orifice or venturi, it creates a negative pressure which draws liquid from the container through a suction tube to the nebulizer assembly and generates an aerosol spray.

The nebulizer assembly admixes the oxygen with the water to produce a humidified oxygen stream which is delivered to a patient through an outlet.

The outlet is connected to a delivery hose extending to the patient to be supplied. However, only a small portion of the water drawn to the nebulizer assembly humidifies the oxygen. The majority of the water is returned to the same container from which it was drawn. Most nebulizer systems also use ambient air to dilute the oxygen in the gas stream.

In inhalation therapy, the humidified oxygen flow usually is warmed before it is administered to the patient. To that end, various heater devices have been proposed to warm the spray to near body temperature. Such heater devices, however, are not very efficient.

Heaters used in combination with nebulizer systems warm the liquid used to humidify the oxygen as it travels to the nebulizer assembly. The warmed liquid not converted into spray is returned to the reservoir or container. This results in a rising reservoir temperature which subsequently causes a rising aerosol spray temperature. As will be readily recognized, this condition may result in spray temperature control problems.

As mentioned hereinabove, most nebulizer systems use ambient air to dilute the oxygen content of the gas stream inhaled by the patient. When air is entrained to dilute the oxygen content, total gas flow to the patient is a function of the amount of air entrained. Obviously, not as much heat input will be required to warm the humidified spray at zero entrainment (pure oxygen) as at full entrainment.

The heater of the nebulizer system, however, may not be properly adjusted by the practitioner when the entrainment is modulated. This can result in undesirably high aerosol temperatures. Moreover, heaters that warm the liquid supply along its path to the aerosol-generating station usually lack sufficient heating capacity to raise the liquid temperature adequately when room air is entrained to dilute the oxygen stream.

On the other hand, in a humidifier system the heater vaporizes a small reservoir of liquid by boiling within the system. A drawback of these particular heaters is that if the oxygen flow to the humidifier is inadvertently interrupted, the heater may provide too much heat to the reservoir thus overheating the gas stream to be inhaled or otherwise creating a hazardous condition.

While various advances in the art of inhalation therapy have been made, problems with currently known nebulizer devices remain. For example, existing nebulizers are limited in the moisture input they can provide to the oxygenenriched breathing gas. Known nebulizing systems also have problems in maintaining a particular temperature for the humidified oxygen stream when it is administered to the patient. Due to the lack of accuracy of prior art devices and the many variables involved in the inhalation therapy environment, no prior art device has proven capable of providing an adequate output of humidified breathable gas having a controlled temperature when administered to the patient.

Summary of the Invention The present invention provides a nebulizer system for humidifying and efficiently heating a breathable gas, such as oxygen-supplemented air, to be inhaled by a patient undergoing inhalation therapy. The nebulizer system of the present invention includes a nebulizer module, a heater module associated with the nebulizer module, and a liquid receptacle removably attached to the heater module and supplying liquid water to the nebulizer module.

The nebulizer module is connectable to an oxygen supply source and, through an outlet, to a breathing apparatus. The nebulizer module includes a nebulizing chamber wherein pressurized oxygen gas, ambient air, and water are combined to form an aerosol spray which, in turn, impinges upon an annular heater element in the heater module where water in the aerosol spray is vaporized.

More specifically, pressurized oxygen is passed to a nozzle which opens to a nebulizing chamber defined in the nebulizing module. A liquid supply conduit, extending from the liquid receptacle, is provided with a dispensing port which is likewise arranged in the nebulizing chamber adjacent to the oxygen nozzle. As the pressurized oxygen passes in a stream or flow from the nozzle, it creates a localized region of negative pressure at the dispensing port in a manner drawing liquid from the receptacle, through the supply conduit, and into the nebulizing chamber. As a result of the "Bernoulli Effect", the oxygen flow or stream breaks the liquid flowing from the dispensing port into fine particles or droplets to produce an aerosol spray. Ambient air may be drawn into the nebulizing chamber through an air intake to combine with the aerosol spray.An air intake regulator, arranged in combination with the nebulizing chamber, controls the amount of ambient air introduced to the nebulizing chamber to dilute the oxygen flow.

The aerosol spray generated in the nebulizing chamber is directed downwardly into an axially extended spray directing conduit or throat.

The aerosol spray is exhausted in a conical flow pattern from a distal end of the conduit. At least a portion of the spray impinges onto the planar heater element which, when hot, converts liquid droplets of water in the aerosol to water vapor. The conical flow pattern exhausted from the conduit can be modulated by adjusting the configuration, e.g., length or diameter, of the conduit and/or by regulating the amount of ambient air drawn into the nebulizing chamber. That is, the more ambient air introduced into the nebulizing chamber, the greater the total volume of aerosol flow. A greater aerosol flow volume, in turn, is reflected in a relatively larger flow cone being exhausted from the conduit.

The heater module is detachably connected to the nebulizer module beneath the distal or exhaust end of the conduit. The heater module includes a heater chamber having an annular heating element disposed in the path of aerosol flow exhausted from the conduit. The heating element is provided with a central aperture which is substantially coaxial with the longitudinal axis of the conduit or throat and in registry with a central bore in a heater support, which bore communicates with the liquid container.

The heating element's surface area can have any convenient contour and is selected to contact in a direct heat transfer relationship a predetermined outer peripheral portion of a conical aerosol spray discharged from the conduit. Those particles of the aerosol spray which impinge upon the heating element are volatilized and retained in a heated and humidified gas stream which exits through the outlet in the nebulizer module and, ultimately, to the patient.

The remainder of the aerosol spray coalesces and passes substantially unheated into the liquid receptacle through the central bore in the heater support.

The total flow from the nebulizing chamber may be modulated by the amount of air introduced into the nebulizing chamber. As an example, total flow with no air entrainment (i.e., only oxygen and water) averages approximately 7 liters per minute. This flow increases geometrically as the oxygen concentration is diluted by air so that at 28 per cent oxygen (full entrainment) the total flow approximates 80 liters per minute. Clearly, not as much heat is required to volatilize the aerosol spray at zero entrainment (pure oxygen) as at full entrainment; thus, the heat output duty of the heating element can vary considerably. The heater design contemplated by the present invention mitigates the problem of such changing heat requirements.Because a smaller size flow cone is exhausted from the conduit or throat as the entrainment of the nebulizer is reduced, fewer aerosol droplets or particles are vaporized by the heater element. Conversely, as a larger size flow cone is exhausted from the conduit or throat as a result of higher entrainment and, thus, increased total flow, more particles strike the heated surface of the heating element. As such, a greater heat output is automatically generated to match the higher flow rate.

Other features and advantages of the present invention will become readily apparent from the following detailed description, the appended drawings, and the accompanying claims.

Brief Description of Drawings FIGURE 1 is an elevational view, partially broken away to show interior detail, and showing a nebulizer system embodying the principles of the present invention; FIGURE 2 is an enlarged cross sectional elevational view illustrating an interior of the nebulizer system illustrated in FIGURE 1; and FIGURE 3 is a cross sectional plan view taken along plane 3-3 of FIGURE 2.

Description of the Preferred Embodiment While the present invention is susceptible of embodiment in various forms, there is shown in the drawings the presently preferred embodiment hereinafter described, with the understanding that the present disclosure is to be considered as an exemplification of the invention, and is not intended to limit the invention to the specific embodiment illustrated.

Referring now to the drawings, wherein like reference numerals indicate like parts throughout the several views, and in particular to FIGURE 1, there is shown a nebulizing device or system 10. The nebulizer devise 10 comprises a top section 12 defining a nebulizer module, a detachable heater module 14, and an outlet 16 for connecting the nebulizer apparatus to a breathing apparatus 18. A center section 20 may be used to removably secure the nebulizer module 12 to the heater module 14. The nebulizer device 10 further includes a liquid storing container such as supply bottle 22.

Bottle 22 defines a reservoir 24 adapted to contain a sterile liquid, such as water, which may be medicated, and which is ultimately used to humidify breathable gas for a patient as hereinbelow described. As illustrated in FIGURE 2, the supply bottle 22 is attached to the heater module 14 of the nebulizer device 10. Water is delivered to the nebulizer module 14 through a supply conduit 26.

The nebulizer module 12 includes a housing 28 which defines a nebulizer chamber 30. Water supply conduit 26 extends into chamber 30 and terminates in a spray discharge port 32. Similarly, an oxygen nozzle 34 extends into chamber 30 and terminates adjacent to spray discharge port 32.

Nozzle 34 and discharge port 32 are positioned in chamber 30 relative to one another so that an oxygen stream exiting nozzle 34 crosses port 32 in a manner generating a relatively lower pressure region within port 32, thereby generating an aerosol spray when liquid water is present in reservoir 24.

Housing 28 further defines an ambient air intake 36 the effective area of which is adjustable by means of regulator ring 38 mounted about the periphery of housing 28. Display indicia 40 may be provided on ring 38 for repeatable settings of air intake area.

Oxygen nozzle 34 communicates with an oxygen feed conduit 42 provided in a connector 44. Connector 44 may be integrally formed with housing 28 and permits attachment of the nebulizer device 10 to a source of pressurized oxygen gas 46.

A hollow, tapering, open-ended throat or conduit 48 is mounted in housing 28. The throat 48 is positioned to receive and shape an aerosol spray generated by the coaction of nozzle 34 and discharge port 32 as will be described in greater detail herein below. Preferably, the dimensions of the conduit 48 are selected to provide a conical aerosol spray having a diameter of about 1 1/2 inches at no ambient air entrainment to about 4 inches at maximum ambient air entrainment at a distance one inch from the distal end of the conduit.

Water supply conduit 26 extends into nebulizer chamber 30 through conduit 48. The proximal end of conduit 48 flares radially outwardly and is adapted to receive the aerosol spray generated in the nebulizing chamber 30. The distal end of conduit 48, on the other hand, extends into the heating chamber 53 of heater module 14 and dispenses the aerosol spray in a cone-shaped configuration onto a planar, annular heating element such as heated disc 50 mounted in the heater module 14. Throat 48 defines a longitudinally extending passageway 51 which defines a flow path for the aerosol spray generated in the nebulizing chamber 30.

The breathable gas outlet 16 is provided in a side wall of nebulizer module 12. The outlet is in communication with an annular space defined by housing 28 and the open-ended throat or conduit 48.

The heater module 14 includes a cylindrical housing 52 which is detachably connected to the nebulizer module beneath the distal end of conduit 48. Housing 52 together with center section 20 defines a heating chamber 53 and an apertured web 54 through which the supply conduit 26 extends. The web 54 also has a threaded connector portion 56.

Connector portion 56 permits attachment of the supply bottle 22 to the heater module 14.

A heater assembly 58 is mounted in the housing 52 of heater module 14. As illustrated, the heater assembly includes the heated annular disc 50, heat input control means 60 for the heated disc, an annular platen 62 positioned over disc 50, and a heat assembly supporting structure for maintaining the heater assembly substantially normal to the flow path of the aerosol stream.

In one form, the heater assembly supporting structure includes an annular support ring 64 disposed in housing 52. The heated annular disc 50 is arranged above the ring 64 and defines a heated surface 66. The heated disc 50 is an annularly shaped element having a central aperture 68 substantially aligned with the flow path. Disc 50 can be planar as shown; however, it can also have a toroidal, radially inwardly beveled, wavy, or like configuration as lon as the central portion of the conical aerosol spray exiting from conduit 48 remains unheated. The central aperture 68 usually is about 1 to about 2 inches in diameter. As illustrated, the annular platen 62 is arranged above the heated annular disc 50. Alternatively, the heated annular disc can be positioned on the opposite side of platen 62, if desired.A plurality of vertically adjustable members 65 are threadably engaged with the ring 64.

The annular platen 62 is concentrically arranged relative to the annular heater disc 50 and defines a tubular extension 69 which extends through the central aperture 68 in the heating element. The tubular extension 69 defines a central port 70 which extends through apertured web 54 of housing 52 and communicates with the liquid reservoir 22. Platen 62 combines with an annular seal ring 72 and a radial projection 74 on housing 52 to define a seal assembly. A series of vertically adjustable members 76 are also threadably engaged with ring 64.

The control means 60 for the heated disc may take the form of a printed circuit board embodying appropriate control circuitry. Control means 60 may be joined or connected to the heated disc 50 through suitable electrical leads 78 to provide the desired electrical energy input thereto. Usually electrical energy input, in the range of about 150 to about 300 watts, is delivered to the disc 50 to provide a latent heat of vaporization input for heating and saturating about 80 liters per minute of breathable gas at 37 degrees C.

In operation, a stream of oxygen is exhausted from the nozzle 34 into the nebulizing chamber. As the oxygen stream passes the discharge port 32 a local negative pressure is generated in the supply conduit 24. This negative pressure draws fluid from bottle 22 into the nebulizing chamber.

The liquid water discharged from port 32 admixes with the stream of oxygen to produce an aerosol spray. At the same time, ambient air may be drawn into the nebulizing chamber through the air intake 36 at a predetermined dilution ratio.

The aerosol stream generated in the nebulizing chamber is received by the conduit 48. As the aerosol spray moves toward the distal end of conduit, ambient air may be entrained therewith. The regulator ring 38 may be modulated to allow a proper mix of ambient air to achieve the desired oxygen content in the inhalation mixture.

The spray is exhausted from the distal end of the conduit in a turbulent, generally conicalshaped flow pattern. The area of heating element 50 is usually selected to allow approximately one-half of the aerosol spray to impinge upon the heated surface 66. That portion of the aerosol spray which avoids impinging on the heated surface coalesces and is conveyed substantially unheated to the reservoir 24 by means of liquid outlet port 70. Only the outer portion of the conical flow pattern strikes the heating surface and is vaporized. The aerosol spray impinging on the heated surface is volatilized as a result, thereby providing a heated gas mixture. This heated gas mixture is passed to a breathing apparatus through the outlet 16.

To establish good thermal contact between the heater element 50 and platen 62, members 65 on ring 64 may be adjusted in a manner abutting element 50 against platen 62. The other adjustable members 76 on ring 64 urge platen 62 and seal ring 72 into sealing contact with radial projection 74 on housing 52.

By such construction, the heated chamber 53, on one side of platen 62, receives the aerosol mist from the throat 48 while that area or chamber 74 on the opposite side of platen 64 remains substantially "dry". The "dry" chamber 74 provides an environment conducive to placement of the control means 60.

As mentioned, not as much heat is required at zero entrainment (pure oxygen) as with full entrainment. The heater design presented by the present invention mitigates the heretofore known problems associated with heat control. As mentioned above, a relatively smaller flow cone of aerosol spray 98 (FIGURE 2) is exhausted from the distal end of conduit 42 when the regulator 38 is adjusted to reduce entrainment. That is, as the entrainment of air in the aerosol spray is reduced, a smaller flow cone results. As such, fewer aerosol spray particles or droplets are volatilized by the heater surface 72. Conversely, when the regulating means 38 is adjusted to allow more air entrainment with the aerosol flow, the total flow through the conduit 42 increases and a relatively larger flow cone 100 (FIGURE 2) or conical flow pattern is exhausted from the distal end of the conduit means 42.As such, more particles or droplets of the aerosol spray strike the heated surface. Thus, a greater heat output is automatically obtained to match -the higher flow rate.

Alternatively, the relative positions of the heated surface 66 and the distal end of the conduit 48 may be modified to likewise effect the size of the flow cone exhausted from conduit 48. A myriad of methods may be used to modify the relative positions of the distal end of conduit 48 and heated surface 66. As an example, the length of conduit 48 may be modified to arrange the heater surface 66 further or closer to the conduit as may be required to effect certain ends. Alternatively, the spacing between the heater assembly 58 in the heater module 14 and the conduit 48 can be adjusted to effect similar ends.

Whatever method is employed, however, a change in the size or shape of the flow cone will be reflected in a change in the heat output obtained from the heater assembly.

From the foregoing, it will be observed that numerous modifications and variations can be effected without departing from the true spirit and scope of the novel concept of the present invention. It will be appreciated that the present disclosure is intended as an exemplification of the invention, and is not intended to limit the invention to the specific embodiment illustrated. The disclosure is intended to cover by the appended claims all such modifications as fall within the scope of the claims.

Claims (6)

1. A heated nebulizer system for a breathing apparatus comprising; a nebulizer module connectable to an oxygen supply, said breathing apparatus, and a liquid water supply, said nebulizer module defining a breathing gas outlet port and a nebulizing chamber; an aerosol generating means positioned in the nebulizing chamber and adapted for communication with said oxygen supply and with said liquid water supply; an elongated, open-ended conduit mounted in said nebulizer module for receiving aerosol spray generated in said nebulizing chamber and exhausting the received aerosol spray from said nebulizing chamber in a substantially conical flow pattern; a heater module in communication with said nebulizer module, said heater module defining a heating chamber and a liquid outlet port for transport of coalesced aerosol from the heating chamber; and a substantially annular heating element positioned in said heating chamber and arranged to receive a portion of the exhausted aerosol spray in a direct heat transfer relationship.

2. The nebulizer system of claim 1 further including an air inflow regulating means in said nebulizer module for modulating entrainment of ambient atmospheric air in said aerosol spray.

3. The nebulizer system of claim 1 or claim 2 wherein said heating chamber communicates with the liquid water supply.

4. The nebulizer system of any preceding claim wherein the nebulizer module and the heater module are detachably connected to one another.

5. The nebulizer system of any preceding claim wherein the heater module includes heater control means.

6. A nebulizer system substantially as hereinbefore described with reference to the accompanying drawings.