FIELD OF THE INVENTION

The present invention relates to a disposable oxygenating apparatus and in particular to a single use disposable positiv pressure oxygenating apparatus for assisting in a patient's recovery after anaesthesia or a patient otherwise requiring respiratory support.

BACKGROUND OF THE INVENTION

When patients are waking from anaesthesia they typically have an endotracheal tube (ETT) or laryngeal mask airway (LMA) .in situ, and their breathing is usually relatively slow and shallow. This means that they are under-ventilating their lungs and are at risk of desaturation, the condition of low blood oxygen concentration. Medical personnel combat this problem by increasing the patient's fraction of inspired oxygen (FiO _≥ ). This can be achieved by attaching an oxygenation device to the end of the endotracheal tube or laryngeal mask airway. An existing device disclosed in WG1997/010018 and sold under the T-Bag trade mark, comprises a 'T-shaped' pipe having an open outlet, an inlet connected to a collapsible reservoir bag and a coupling for attachment to an end of the ETT or LMA. Oxygen is delivered into the collapsible reservoir bag and the oxygen is entrained into the inflow of air as the patient breathes in. However because the oxygen is only entrained into the inflow of air, and the patient's breathing may only be shallow, the fraction of inspired oxygen may not be very high. The effectiveness of this currently used device is therefore limited and there is still the significant risk of desaturation occurring.

Furthermore, as the patient wakes from anaesthesia the volume of each inspired breath increases. The patient's respiratory rate increases from around 8-12 breaths per minute to around 20-30 breaths per minute, and the minute volume increases from around 2 litres (L) to around 9 litres (L), or more. Additionally, as the patient awakes they may be in acute pain, which means their respiratory rate and heart rate both significantly increase. The collapsible reservoir bag disclosed in th above prior art, is however relatively small and can be quickly emptied during inspiration, under such circumstances. Other medical issues occur because the vocal cords of patients with a L A in situ can close in the time between when a patient is anaesthetised and when they are fully awake. During this waking process the vocal cords are hyper-reactive and they may go into spasm when foreign matter (eg. saliva, sputum, blood etc) come into contact with them. At this time the patient may not be sufficientiy awake to clear the foreign matter. The full or partial closing of the vocal cords can lead to respirator difficulty, desaturation and negative pressure pulmonary edema.

Although positive end expiratory pressure (PEEP) or continuou positive airway pressure (CPAP) can foe used to increase the pressure within the pharynx to maintain the vocal cords open, none of the existing disposable oxygenating devices have the capacity for GPAP or PEEP,

Similar desaturation issues may occur with patients that have other medical conditions, such as but not limited to, heart failure or chronic obstructive pulmonary disease, and accordingly requiring respiratory support. Furthermore many respiratory support devices are costly.

It should be appreciated that any discussion of the prior art throughout the specification is included solely for the purpose of providing a context for the present invention and should in no way be considered as an admission that such prior art was widely known or formed part of the common general knowledge in the field as it existed before the priority date of the application.

SUMMARY OF THE INVENTION

In one aspect of the invention, but not necessarily the only or broadest aspect, there is proposed a disposable oxygenating apparatus for use on a patient recovering from anaesthesia or otherwise requiring respiratory support, where a respiratory device is in situ or is to be used, including,

a body portion having a coupling for attachment to said respiratory device,, a passageway or passageways for fluid communication with the respiratory device, the passageway or passageways extending through said body portion between said coupling and both a primary inlet and a secondary inlet, and extending through said body portion between said coupling and an outlet, for fluid communication therebetween,

a collapsible reservoir bag attached over said primary inlet, said collapsible reservoir bag in fluid communication with a source of oxygen or oxygen rich air, an expiratory valve or valves located in or adjacent said outlet for controlling the passage of an expired breath from said patient during expiration, wherein a positive pressure is applied to the airway of said patient during expiration and rest, a primary inspiratory valve located in or adjacent said primary inlet, for controlling said oxygen or oxygen rich air flowing in through said passageway or passageways from said collapsible reservoir bag, for at least a period of time during inspiration by said patient, and

a secondary inspiratory valve located in or adjacent said secondary inlet in fluid communication with said passageway or passageways for controlling entry of an ambient air in through the passageway or passageways from an exterior of said apparatus during inspiration when said collapsible reservoir bag has been substantially emptied.

The respiratory device may be an endotracheal tube or laryngeal mask airway, wherein the apparatus is attached at an end of an endotracheal tube or a tube of said laryngeal mask airway, which extends outwardly from an airway of said patient, in another form the respiratory device includes a face mask that is attached over said patient's mouth and nose, wherein the apparatus is attached to said face mask or a tube connected to said face mask. In still another form the respiratory device may be a nasal airway respiratory support device. It should be appreciated that the phrase respirator device includes all types of invasiv and non-invasiv respiratory support devices, including but not limited to, Laryngeal Mask Airway (LIMA), and Endotracheal Tube (ETT).

The apparatus is preferably a single use disposable apparatus.

The apparatus ma be used on non-invasive positive pressure devices having a face mask to help the patient breath, as a result of heart failure, chronic obstructive pulmonary disease, etc.

In one form the expiratory vaive, located i or adjacent said outlet, is an inline check valve. The in-line check valve may indude a disc attached to a shaft and a helical spring positioned around the shaft for biasing the disc against a valve seat. Preferably the expiratory valve opens at low pressure to inhibit over pressurisation of the patient's airway. The expiratory valve preferably maintains a positive end expiratory pressure, wherein the pressure within the airway of the patient is between 4-14 centimetres of water {cmH ₂ 0) and more preferably 8-12 centimetres of water (cmH ₂ 0).

The expiratory valve is opened at a low pressure and can rapidly dissipate the expired air in the event of a sudden increase in the rate of expiration, being the exhalation of breath from the lungs, or a peak in expiration volume and/or pressure, such as hen the patient coughs.

The expiratory valve may be a biased check valve, swing check valve or tilting disc check valve.

The primary and secondary inlets may be spaced apart from each other at different locations along a single passageway, or along different passageways.

Alternatively, the primary and secondary inlets may be located at the same location along the single passageway. In one form the prtmary and secondary inlets may be coaxiaily aligned in that the primary inlet is centrally located within the secondary inlet and separated from the secondary inlet by an annular, or otherwise shaped, wall. The collapsible reservoir bag being secured to said wall such that it covers the primary inlet.

The primary inspiratory valve may be a diaphragm check valve and in one form is an umbrella valve. The diaphragm check valve includes a flexible rubber diaphragm positioned over at least one aperture in the primary inlet. At rest the flexible rubber diaphragm seals the at least one aperture in the primary inlet. In another form the primary inlet includes a plurality of apertures. The flexible rubber diaphragm i one form is a disc that is secured at a central location to a mount, the mount including or forming said at least one aperture. Preferably the flexible rubber diaphragm is resiliently flexible around at least its edge.

The secondary inspiratory valve may be a diaphragm valve and in one form is an umbrella valve.

The primary inspiratory valve preferentially opens before the secondary inspiratory valve. In this way the oxygen or oxygen rich air in the collapsible reservoir bag is inhaled first, and once the collapsible reservoir bag is substantially emptied, the secondary inspiratory valve opens to provide the patient with a source of breathable air to inhibit injury to the patient. The primary inspiratory valve preferably has a lower opening pressure compared to the secondary inspiratory valve so that it is preferentially opened before the secondary inspiratory valve.

The primary and secondary inspiratory valves may be recessed into the side of the passageway or passageways to inhibit saliva, condensation, or blood fouling the valves during use. Although the addressee should appreciate that the valves may not be recessed and a filter or filters may be used to inhibit saliva, condensation, or blood fouling the valves during use.

In another form the expiratory valve and the secondary inspiratory valve are a combination valve or are formed in a unitary device that comprises art expirator outlet valve portion and an ambient air inspiratory inlet valve portion.

The combination valve may comprise an expiratory outlet valve of a diaphragm umbrella valve type configuration and an ambient air inspiratory inlet valve of a duckbill valve type configuration, having an end that extends into the passageway or passageways.

In another form a combination primary and secondary inspirator valve or a two-stage inspiratory valve, can be used. The combination or two-stage inspiratory valve may be located within a casing having a frame including central apertures extending therethrough, in fluid communication with the collapsible reservoir bag, and peripheral apertures in fluid communication with the ambient air. A disc shaped flexible diaphragm may be attached to the frame and configured to reversibly seal the central apertures, and the ring-shaped flexible diaphragm configured to reversibly seal the peripheral apertures.

The two-stage inspiratory valve is configured such that the disc shaped flexible diaphragm opens first, and air is preferentially drawn from within the collapsible reservoir bag, during inspiration, in the event that the collapsible reservoir bag is substantially emptied the ring-shaped flexible diaphragm moves to open peripheral apertures to allow ambient air to be drawn in from the exterior of the apparatus.

The disc shaped flexible diaphragm may be located centrally of the ring- shaped flexible diaphragm wherein the disc shaped flexible diaphragm is attached to a centra! protrusion and the ring-shaped flexible diaphragm is attached to the frame around an inner edge such that an outer portion of the ring-shaped flexible diaphragm is permitted to flex.

Alternatively, the ring-shaped fiexib!e diaphragm may include a central webbing that is used to attach the ring-shaped flexible diaphragm to the central protrusion and the ring-shaped flexible diaphragm is configured to flex around an outer edge. In this form the disc shaped flexible diaphragm is located on the downstream side of the ring-shaped flexible diaphragm and overlays the webbing.

In still another form the expiratory valve could be understood to comprise a two-stage expiratory valve or cooperating first and second expiratory valves. The expiratory valve comprises a central flexible portion or first expiratory valve, and a larger outer donut shaped flexible diaphragm portion or second expiratory valve. The central flexible portion or first expiratory valve may be disc shaped and be attached to a central projection or may include a plurality of cooperating leaflets. The two-stage expiratory valve is configured such that the centra! flexible portion or first expiratory valve opens first, and air is preferentially expelled therethrough, from within the passageway or passageways during expiration. I the event that the patient coughs the outer donut shaped flexible diaphragm portion or second expiratory valve is then configured to open to thereby rapidly dissipate the expired air,

Accordingly the central flexible portion or first valve assists in maintaining a positive airway pressure during normal expiration of around 8 cmH ₂ 0, while the larger outer donut shaped flexible diaphragm portion or second expiratory valve, controls the pressure during high flow or high pressure events, such as when the patient coughs, to thereby inhibit injury to the patient or disiodgement of the oxygenation apparatus, ETT or LMA,

The two-stage expiratory valve or cooperating first and second expiratory valves may comprise a valve frame including an outer ring-shaped valve seat, connected to an inner ring-shaped valve seat by radially extending arms. The outer ring-shaped valve seat may be 5cm in diameter and the inner ring-shaped valve seat may be 2cm in diameter. The skilled addressee will appreciate that other types of vaives and differently shaped valves or valve seats may be used without departing from the scope of the invention.

In one form the valve or vaives may be check valve assemblies that permit control of fluid flow (liquid or gas) along a flow path. A check valve or one-way valve allows fluid flow in a single direction while inhibiting backfiow. The check valve may comprise a diaphragm valve or may include a disc-shaped head that is biased against a valve seat, wherein a guide controls movement of the disc-shaped head so that it can reseat properly when the pressure on the upstream side reduces, thereby preventing reverse fluid flow. Accordingly the expiratory valve, primary inspiratory valve and secondary inspiratory valve may each be a diaphragm check vaive, ball check valve, duckbill valve, tilting disc check valve, lift-check valve or in-line check valve of similar configuration or different configurations.

A plurality of cooperating leaflets may be connected to the inner ring-shaped vaive seat and extend inwardly thereof to form the central flexible portion or first expiratory valve. For discussion purposes the plurality of cooperating leaflets may open at about 12 cmH ₂ 0 and closes at about 8 cmH ₂ 0.

The outer donut shaped flexible diaphragm portion or second expiratory valve may have a larger surface area than the central flexible portion or first expiratory vaive. The outer donut shaped flexible diaphragm portion or second expiratory valve is attached to the inner ring-shaped valve seat and is able to seal against the outer ring-shaped valve seat. For discussion purposes the outer donut shaped flexible diaphragm portion or second expiratory valve opens at about 16 cmH¾0 and closes at about 12 cmH ₂ 0, Accordingly, in the event of a rapid increase in expiratory pressure and/or flow, the larger vaive or valve portion would open to further increase the size of the opening for the expiration of air. Once the pressure within the passageway drops to around 12 cmH ₂ 0, the larger valve or valve portion closes and leaves the smaller valve or valve portion open, to thereby maintain a positive end pressure within the apparatus.

The apparatus further includes an oxygen input port positioned upstream of the primary inspiratory valve or combination/two-stage inspiratory valve. In this way the collapsible reservoir bag is refilled from the source of oxygen or oxygen rich air when the primary inspiratory valve is closed. The first inspiratory valve may open during expiration if the pressure within the collapsible reservoir bag reaches a predetermined level. This will mean that some of the oxygen rich air will be allowed to escape the apparatus to inhibit over pressurisation and rupturing of the collapsible reservoir bag. The first inspiratory valve will therefore act as a pressure release valve for the collapsible reservoir bag during expiration. The first inspiratory valve may open when the pressure within th collapsible reservoir bag reaches 16 centimetres of water (cmHaO).

Therefore during expiration there ma be a flow of air/gas out of the patient's airway into the passageway/s and through the expiratory valve, and out of the collapsible reservoir bag into the passageway/s and through the expiratory valve. Accordingly, under some circumstances the primary inspiratory valve would be open during expiration, although the direction of the flow of air/gas would still be exiting the apparatus through the expiratory valve.

Preferably the collapsible reservoir bag has a volume of between 100-600 mi!lilitres (ml_) and more preferably has a 500 millt!itre (ml_) volume. The collapsible reservoir bag may be secured over the inlet and attached to the body by use of an adhesive, or the bag may be heat welded to the body to inhibit it from becoming dislodged during use.

The collapsible reservoir bag may provide both visual and auditory evidence of respiration, in one form the collapsible reservoir bag is constructed from a materia! that emits a noise when it is being filled or emptied. The bag may be constructed from a polyethylene materia! and may be between 10-20 microns in thickness. In another form the passageway or passageways may include a noise emitting device that is activated when air flows thereover. The coupling ma be a female socket, having an opening extending therethrough, the socket may be configured to fit over the end of the ETT or tube of the LMA, and has an internal diameter of 15mm. The coupling may be tapered such that it friction-ally engages the end of the ETT or tube of the LMA, or face mask or nasal airway respiratory support device, or the apparatus may be of unitary construction with the face mask or nasal airway respiratory support device. In another form the coupling is configured to engage a filter member positioned intermediate of the respiratory device and said apparatus. The filter member may comprise a Heat Moisture Exchanger with Filter (HMEF) that uses the patient's own moisture and humidity from expiration to humidify anaesthetic gases during inspiration. Although it should be appreciated that other filters could also be used to inhibit saliva, condensation, or blood fouling the inspiratory or expiratory valves during use.

In one form the filter member is attached to the end of the ETT or tube of the LMA and the apparatus is attached to the filter member, wherein the filter member is intermediate of the apparatus and the ETT or LMA. Alternatively, the apparatus may include an integral filter member. The coupling ma be integral with the body portion and be of unitary construction, or the coupling may be connected to the body portion.

Preferabl positive end expiratory pressure (PEEP) is used to maintain the pressure in the airway of the patient above atmospheric/ambient pressure. PEEP is produced in the patient by a non-complete or restricted exhalation, wherein the resistance to expiration is used to maintain the vocai cords open with a LMA in situ. PEEP also minimises airway and alveolar collapse distal to the vocal cords and increases compliance by increasing functional residual capacity (FRC). This improves oxygenation and reduces the degree of pulmonary shunt, where ventilation is mismatched to the lung perfusion, with either an ETT or LMA in situ. Other ways of producing increased pressure in the lungs of the patent may be used such as, but not limited to, extrinsic PEEP that is applied by a ventilator, pressure support where pressure is applied or increased during an inspiration cycle, or continuous positive airway pressure (CPAP) where a pressure is applied at all stages of respiration to maintain an open airway. In another aspect of the invention there is proposed a method of providing positive pressure to a patient's airway during recovery after anaesthesia or otherwise requiring respiratory support, including the steps of:

providing a disposable oxygenating apparatus including a body portion and a collapsible reservoir bag, the body portion having a passageway or passageways connecting an outlet, a coupling, a primary inlet and a secondary inlet, said collapsibl reservoir bag attached over the primary inlet;

attaching said coupling at an outwardly extending end of an endotracheal tube or tube of a laryngeal mask airway, positioned within the airway of said patient, or to a face mask or a tube attached to said face mask, or a nasal airway respiratory support device, whereby said passageway or passageways are in fluid communication with the endotracheal tube, laryngeal mask airway, face mask or nasai airway respiratory support device,

filling the collapsible reservoir bag, from a source of oxygen or oxygen rich air, wherein upon inspiration by said patient a primary inspiratory valve, located in, or adjacent, the primary inlet, opens to permit the oxygen or oxygen rich air to be drawn in through the passageway or passageways from said collapsible reservoir bag and into the patient's airway, wherein if the collapsible reservoir bag is substantially emptied, a secondary inspiratory valve, located in, or adjacent the secondary inlet, opens to permit ambient air to be drawn in through said passageway or

passageways from an exterior of said apparatus; and

refilling the collapsible reservoir bag during expiration by the patient, wherei the primary and secondary inspiratory valves are closed for at least a period of time during expiration and an expiratory valve positioned in or adjacent the outlet opens to permit movement of an expired air therethrough, the expiratory valve being configured to close at a selected pressure to maintain positive pressure in the patient's airway relative to an ambient atmospheric pressure. The method may include the additional step of adjusting the expiratory valve by way of an adjustment member or the expiratory valve being an adjustable expiratory valve to maintain a desired pressure within the patient's airway.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an implementation of the invention and, together with the description and claims, serve to explain the advantages and principles of the invention. In the drawings,

Figure 1 is a perspective vie of one embodiment of the oxygenating

apparatus of the present invention; Figure 2 is an exploded view of the oxygenating apparatus of figure 1 ;

Figure 3 is a cross-sectional view of figure 2 illustrating the body and valves; Figure 4 is a schematic view of the oxygenating apparatus of figure 1, illustrating the opening of the expiratory valve during expiration by a patient;

Figure 5 is a schematic view of the oxygenating apparatus of figure 1 ,

illustrating the closing of the expiratory valve during the later stage of expiration;

Figure 6 is a schematic view of the oxygenating apparatus of figure 1,

illustrating the opening of the primary inspiratory valve during inhalation by the patient; Figure 7 is a schematic view of the oxygenating apparatus of figure 1 ,

illustrating the opening of the secondary inspiratory valve;

Figure 8a is a possible embodiment of the combination vaive in fluid

communication with both the ambient air and passageway, illustrating exhaled air being expelled from the apparatus; Figure 8b is the combination valve of figure 8a illustrating entry of ambient air in throu the passageway;

Figure 9 is a perspective view of a possible embodiment of a two-stage

inspirator valve;

Figure 10 is a cross-sectional view of the two-stage inspiratory valve of figure 9; Figure 1 is an exploded view of the two-stage inspiratory valve of figure 9;

Figure 12 is a partial cross-sectional view of valve of figure 11 ;

Figure 3 is a perspective view of the oxygenating apparatus illustrating two- stage expiratory valve;

Figure 14 is a cut away view of the expiratory valve of figure 13; Figure 15a is a schematic view of the expiratory valve of figure 13 in a closed arrangement; Figure 15b is a schematic view of the expiratory valve of figure 15a in a partially open arrangement;

Figure 15c is a schematic view of the expiratory valve of figure 15a in a

completely open arrangement; Figure 16 is a schematic view of the apparatus attached to a LMA; and

Figure 17 is a schematic view of the apparatus attached to a face mask of a noninvasive positive pressure device.

DETAILED DESCRIPTION OF THE ILLUSTRATED AND EXEMPLIFIED EMBODIMENTS Similar reference characters indicate corresponding parts throughout the drawings. Dimensions of certain parts shown in the drawings may have been modified and/or exaggerated for the purposes of clarity or illustration. Although the detailed description of the invention is directly primarily to the use of ETT and LMA on anaesthetised patients, the reader shouid appreciate that this is in no wa intended to limit the scope of the invention, and the same or similar advantages are envisaged when the apparatus is used on non-invasive ventilation support face masks and nasal airway respiratory support devices.

Referring to the drawings for a more detailed description, there is illustrated a disposable oxygenating apparatus 10, demonstrating by way of examples, arrangements in which the principles of the present invention may be employed. The apparatus 0 includes a body portion 12 having a coupling 14 for attachment to an end 16 of an endotracheal tube, a tube of a laryngeal mask airway, face mask o nasal airway respiratory support device, A passageway 18 extends through the body portion 12 and connects the coupling 14 with primary and secondary inlets 20, 31 , and an outlet 22,

A collapsible reservoir bag 24 is attached over the primary inlet 20 and is in fluid communication with a source of oxygen or oxygen rich air 25, by way of input port 26 that is located upstream of a primary inspiratory valve 28. The collapsible reservoir bag 24 is refilled from the source of oxygen or oxygen rich air 25 when the primary inspiratory valve 28 is closed. It should be appreciated that the inflow of oxygen is generally constant, but can be varied or the volume adjusted by the medical personnel.

The apparatus 10 further includes a secondary inspiratory valve 30 in, or adjacent, the secondary inlet 31 in a side of passageway 18 for controlling entry of ambient air from the exterior of the apparatus, in through the passageway 18 during inspiration when the collapsible reservoir bag 24 has been substantially emptied.

The secondary inspiratory valve 30 acts as a safety va!ve to ensure that the patient is provided with inhalabie air at all times. This configuration inhibits the patient from performing a 'Valsalva ¹ manoeuver, being a forced inspiration against a closed glottis or obstruction, which can be dangerous to the patient.

In the present embodiment both the primary and secondary inspiratory valves 28, 30 are diaphragrn valves, each comprising a respective flexible rubber diaphragm 32 attached to a central protrusion 33 of a respective valve mount 34, 35, having apertures 36 or 37 extending therethrough. An expiratory valve 38 is located within, or adjacent, the outlet 22 and is configured to control the passage of an expired gas out through the apparatus 10 during expiration. In the present embodiment the expiratory valve 38, is an in-line check valve assembly comprising a disc 40 attached to a shaft 42. The disc 40 having a resiliently flexible sealing member 44 attached to a front face, for abutment with an annular valve seat 46. A helical spring 48 is positioned around the shaft 42 for biasing the flexible sealing member 44 against the valve seat 46. The

components of the expiratory vajve 38 are held within valve housing 50 that includes outlet apertures 52 for passage of the expired air and an orifice 54 that s!idably locates shaft 42. The expiratory valve 38 is biased closed by the helicai spring 48 to maintain a pressure within the airwa of the patient of between 8-12 centimetres of water (cmH ₂ 0). This positive end expiratory pressure assists in keeping the vocal cords open during intubation with a LMA and minimises airway and alveolar collapse when the ETT or LMA is positioned within the airway of the recovering patient. The size and configuration of the outlet apertures 52 permit the expired air to rapidly dissipate, even in the event that the patient coughs. The apparatus 10 includes collar 55 that incorporates the input port 26 and to which the opening of the collapsible reservoir bag 24 can be heat welded or glued as illustrated in figure 1.

Turning to figures 4 to 7 there is illustrated the different stages of airflow through the apparatus 10 during use. During expiration, pressure within the passageway 18 increases which causes the expiratory valve 36 to open against the influence of the helical spring 48, as shown in figure 4, The disc 40 moves off the annular valve seat 46 in the direction indicated by the arrow, thereby allowing expired air to move through the passageway 18 and out through outlet apertures 52 into the surrounding environment.

If the patient breathes out rapidly or with a large volume, such as in the event the patient coughs, the expiratory valve 38 opens fully to allow the air to flow through the sidewardly open outlet apertures 52, Therefore the greater the pressure generated within the passageway 18 of the apparatus by the expiration of air, the further open the expiratory valve 38 is pushed and the faster the pressure drops back to the desired 8-12 centimetres of water (cmH _a O) within the passageway 18 or airway of the patient.

It is important that the apparatus 10 can accommodate rapid rises in airflow to inhibit either injury to the patient, or damage/disSodgernent of the oxygenation apparatus, ETT or L A,

As illustrated in figure 5, during the final stages of expiration, as the expired air flow from the patient's airway decreases, the spring 48 forces the disc 40 to close against the annular seat 46, as indicated by the arrow, to thereby dose the expiratory valve 38. This thereby maintains a positive end pressure within the passageway 18 of between 8-12 centimetres of water (cmH ₂ 0).

The collapsible reservoir bag 24 is in constant fluid communication with the source of oxygen or oxygen rich air 25 and is filled by way of input port 26 as indicated by the arrow when the primary inspiratory valve 28 is dosed. As indicated in figure 5 during the expiration cycle, and also between breaths, the collapsible reservoir bag 24 continues to be filled with oxygen. The reader should appreciate that the flow of oxygen rich air in through the input port 26 is preferably constant, however a medical practitioner may vary the flow rate by way of conventional means. In the present embodiment 100% oxygen is used and the bag has a capacity of 5Q0mL. The reader should however appreciate that the oxygen rich air from the source does not need to be 100% oxygen.

As the reader will now appreciate, during inspiration, there are essentially two sources from which the patient receives breathable air or gas. Preferentially, the patient receives oxygen or oxygen rich air through the primary inspiratory valve 28 from th source of oxygen or oxygen rich air 25 at least partially via the collapsible reservoir bag 24. Then, if the bag 24 is substantially emptied, ambient air is drawn in through the secondary inspiratory valve 30 from the surrounding environment. When the patient begins to inhale, as illustrated in figure 6, the diaphragm 32 of the primary inspiratory valve 28 is drawn away from mount 34 by the reduction in pressure within passageway 18. This opens apertures 36 and permits the oxygen or oxygen rich air within the collapsible reservoir bag 24 to be drawn in through the apparatus 0 and into the patient's airway, Typically a sedated or recovering patient will have a tidal volume equal to, or less than SOOmL. Accordingly, a SOOmL bag will be sufficient so that the patient will inspire dose to 00% from the bag, without entraining any ambient air through the primary inspiratory valve 30. However for patients who have large lung capacities or those in pain, the secondary inspiratory valve 30 is provided so that the remaining percentage of required air for inspiration can be drawn in from the surrounding environment, exterior of the apparatus 10, while still permitting the apparatus to maintain pressure to the airway of the patient when the secondary inspiratory valve 30 closes.

As illustrated in figure 7, when the collapsible reservoir bag 24 has been substantially emptied the diaphragm 32 of the secondary inspiratory valve 30 is drawn away from mount 35 to thereby open corresponding apertures 37, which allows ambient air to the drawn into the passageway 18 from the surrounding environment, as indicated by the solid arrow.

Although the fraction of oxygen (Fi0 ₂ ) is decreased by the opening of the secondary inspiratory valve 30, it means that the collapsible reservoir bag does not need to b of too large volume to cope will all patients or circumstances. As the reader will no appreciate, when the pressure on the upstream side of the primary inspiratory valve 28 is greater than the pressure on the downstream side of the primary inspiratory valve 28, which occurs during inspiration by the patient, the valve will open allowing the oxygen or oxygen rich air in the collapsible reservoir bag 24 to flow in through the passageway 18 and in turn into the airway of the patient. During expiration by the patient the pressure on the downstream side of valves 28, 30 will increase thereby closing the respective flexible rubber diaphragm 32 over the aperture/s 36, 37 of valve mounts 34, 35,

The use of a diaphragm check valve also means that if the volumetric flow rate of oxygen or oxygen rich air from the source 25 is set too high, the flexible diaphragm 32 of the primary inspiratory valve 28 will open to permit excess gas to escape during the expiration cycle. This will inhibit the bag 24 from tearing due to over-pressurisation.

The coupling 14 of the present embodiment is a female socket that is configured to fit over the end 6 of the ETT/LMA and has an interna! diameter of 15mm. The coupling 14 may be tapered so that it can frictioriaily engage the end 16 of the ETT/LMA.

As illustrated in the figures the primary and secondary inspiratory valves 28 and 30 are recessed into the side of the passageway 18 to inhibit saliva,

condensation, or blood fouling the valves during use.

The primary and secondary inspiratory valves 28, 30 may be the same size provided the primary valve 28 opens first and allows the collapsible reservoir bag 24 to be substantially emptied before the secondary valve 30 opens.

The expiratory valve 38 and th secondary inspiratory valve 3Q may form parts of a combination valve 60. in one possible embodiment as illustrated in figures 8a and 8b, the expiratory valve 38 includes a flexible skirt 62 and a central portion 64 secured through aperture 66 in the side of body portion 12 and at rest seals openings 68. The secondary inspirator valve 30 incfudes a soft tube 70 that is closed by back-pressure within passageway 18 to cut off a flow of air.

In this way during expiration the pressure within the passageway 18 increases to a point that causes the soft tube 70 to close and the flexible skirt 62 to open to thereby permit the expired air to be expelled through the openings 68, as illustrated in figure 8a. During inspiration the pressure within the passageway 18 decreases which causes the ftexib!e skirt 62 to close over openings 68. In the event the collapsible reservoir bag is substantially emptied during inspiration the pressure drops to a point that the soft tube 70 will open to permit the entry of ambient air therethrough as illustrated in figure 8b.

In another possible embodiment, as illustrated in figures 9 to 12, the primary and secondary inspiratory valves are replaced by a two-stage inspiratory valve 76, which is located within casing 78. The two-stage inspiratory valve 76 includes a disc shaped flexible diaphragm 80, and a ring-shaped flexible diaphragm 82, wherein the disc shaped flexible diaphragm 80 is located centrally of the ring-shaped flexible diaphragm 82,

The flexible diaphragms 80 and 82 are attached to frame 84, the frame including central apertures 86 extending therethrough, in fluid communication with the collapsible bag 24, and peripheral apertures 88 in fluid communication with the ambient air. The disc shaped flexible diaphragm 80 is configured to reversibly seal central apertures 86 and the ring-shaped flexible diaphragm 82 is configured to revers'kly seal peripheral apertures 88.

The two-stage inspiratory valve 76 Is configured so that the disc shaped flexible diaphragm 80 opens first, whereby air is preferentially drawn from within the collapsible bag 24, during inspiration. In the event that the collapsible bag 24 is substantially emptied the ring-shaped flexible diaphragm 82 moves to open peripheral apertures 88 to allow ambient air to be drawn in from the exterior of the apparatus 10. In this way the two-stage inspiratory valve 76 incorporates the functionality of the first and secondary inspiratory valve in a single unit. The disc shaped flexible diaphragm 80 may be attached to a central protrusion 90 and the ring-shaped flexible diaphragm 82 may be attached to the frame 84 adjacent the disc shaped flexible diaphragm 80. wherein the outer edge of ring-shaped flexible diaphragm 82 is permitted to flex.

As illustrated in figure 12, the flexible diaphragms 80 and 82 are of different thicknesses, wherein the disc shaped flexible diaphragm 80 opens first under negative pressure within passageway 18, and the ring-shaped ftexibfe diaphragm 82 opens secondly, when the pressure drops further within passageway 18, as would occur when the collapsible bag 24 is substantially emptied. It should however be appreciated that different thicknesses are not the only way to cause the preferential opening of one inspiratory valve, and other ways of preferential opening could be used, including but not limited to, materia! and size of the valves.

Figure 13 illustrates one embodiment of a two-stage expiratory valve comprising a central flexible portion 100, a larger outer donut shaped flexible diaphragm portion 102, which are protected by cove 104 having sidewardly open apertures 106. The central flexible portion 100 includes three cooperating leaflets 108, 110, 112.

Figure 13 also illustrates a filter member 98, in the present embodiment being a heat moisture exchanger with filter (HMEF). The filter member 98 is positioned intermediate of the end 16 of the endotracheal tube or iaryngeal mask airway and the apparatus 0. The reader should however appreciate that the apparatus 10 may include an integral filter or filters to inhibit fouling the valves by saliva, condensation, or blood,

As further illustrated in Figure 14, the central flexible portion 100, and the larger outer donut shaped flexible diaphragm portion 102 are attached to and supported on valve fame 114, which includes an outer ring-shaped valve seat 1 16, connected to an inner ring-shaped valve seat 118 by radially extending arms 120. The outer ring-shaped valve seat 116 may be around 5cm in diameter and the inner ring-shaped valve seat 118 may be around 2cm in diameter.

In the present embodiment, the central flexible portion 100 is attached to the top of inner ring-shaped valve seat 118, and the outer donut shaped flexible diaphragm portion 102 engages with, or is attached to a side of the inner ring-shaped valve seat 18, wherein inner parts of the cooperating leaflets 108, 110, 1 12 are able to flex and outer parts of donut shaped flexible diaphragm portion 102 are able to flex. As shown in Figures 15a to 5c the central flexible portion 100 and larger outer donut shaped flexible diaphragm portion 102 open progressively as the pressure within passageway 18 increases during expiration. Figure 15a illustrates the arrangement of the expiratory valve 38 when the patient is at rest. i.e. between breaths, or when they are inhaling. When the patient is exhaling under normal situations, the cooperating leaflets 108, 110, 112, open when the pressure within passageway 18 reaches around 12 cmH _a O to permit passage of th expired air, as indicated by the solid arrows in Figure 5b.

In the event that the patient coughs, the arrangement of the expiratory valve 38 changes, as illustrated in Figure 15c, such that the outer donut shaped flexible diaphragm portion 102 opens, at around 16 cmH ₂ 0, to thereb rapidly dissipate the expired air, as indicated by the broken arrows, to thereby inhibit injur to the patient or dislodgement of the apparatus, ETT or LMA. The cooperating leaflets 08, 0, 112, also remain open and expired air passes therebetween, as indicated by the solid arrows. The reader should however appreciate that other types of combination valves or two-stage valves could be used without departing from the scope of the invention. Furthermore, a plurality of outlet/expiratory or inlet/inspiratory valves may be used.

Figur 18 illustrates use of the apparatus 10 on a LMA 130 that is positioned within the airway 132 of a patient 134 adjacent the epiglottis 136. The LMA 30 includes a pipe 138 having end 16, an inflatable cuff 140, and inflation line 144.

The apparatus can also be attached to a face mask 146, such as, but not limited to, that of a non-invasive positive pressure device such as those used on patients suffering from heart failure or chronic obstructive pulmonary disease, as illustrated in Figure 17. The face mask 148 includes an inflated or pneumatic skirt 148 and strap 149, and covers the nose 150 and mout 152 of the patient during use. The reader should appreciate that the apparatus and face mask may be of unitary construction, or the apparatus and nasal airway respiratory support device may be of unitary construction.

The apparatus 10 is connected directly to the tight fitting face mask 146 in Figure 17, however it should be appreciated that the apparatus 10 could be connected to a flexible tube (not shown) connected to the face mask 146 worn by the patient. Accordingty the spontaneously breathing patient wearing the face mask 146 would get increased Fi0 ₂ and some PEEP. The use of the apparatus 10 has significant advantages over the existing Continuous Positive Airway Pressure (CPAP) and Bi-Level Positive Air Pressure (BiPAP) systems that can be expensive and require patient tolerance, which is sometimes difficult to achieve. It should also be appreciated that the phrase 'fluid communication', used throughout the specification relates to the flow of air through the apparatus between the airway of the patient and the collapsible bag and exterior environment,

The skilled addressee will now appreciate the advantages of the illustrated invention over the prior art. In one form the invention provides a disposable oxygenation apparatus that can be used to apply an oxygen enriched, positive pressure to a patient's airway when an ETT or LMA is in situ, to thereby decrease the incidence of desaturation, and with a LMA in situ, assist in maintaining the vocal cords of the patient open during recovery after anaesthesia. The apparatus also inhibits injury to a patient or dis!odgement of the oxygenation apparatus, ETT or LMA, when a patient coughs.

Various features of the invention have been particularly shown and described in connection with the exemplified embodiments of the invention, however it must be understood that these particular arrangements merely illustrate the invention and it is not limited thereto. Accordingly the invention can include various modifications, which fall within the spirit and scope of the invention.