GB2612607A

GB2612607A - A respiratory assistance apparatus, and valves for respiratory assistance apparatuses

Info

Publication number: GB2612607A
Application number: GB2115876.1A
Authority: GB
Inventors: Henry Cawood John; Phillips Russell
Original assignee: Nelson Mandela University
Current assignee: Nelson Mandela University
Priority date: 2021-11-04
Filing date: 2021-11-04
Publication date: 2023-05-10

Abstract

A respiratory assistance apparatus comprising a blower 12, a vented pressure limiting valve (PLV) 14 regulating the pressure of air, a flow limiting valve (FLV) 16 regulating the flow of air in proportion to the pressure of air from the PLV, and a shuttle aspiration valve (SAV) 18 in fluid communication with the FLV and a user interface 20 to engage about the mouth and nose. The SAV operates in an inhalation configuration initiated by negative pressure generated at the user interface, and an exhalation configuration initiated by a predetermined internal pressure being reached. The FLV may comprise a flow regulator with a member displaceable proportional to the internal pressure and a connected airfoil to control the air flow in response to the displacement. The SAV may be attached to a plunger and have a detent to retain the shuttle in the inhalation position until the predetermined pressure is reached.

Description

A RESPIRATORY ASSISTANCE APPARATUS, AND VALVES FOR RESPIRATORY ASSISTANCE APPARATUSES

FIELD OF INVENTION

THIS INVENTION relates to a respiratory assistance apparatus, and valves for respiratory assistance apparatuses.

BACKGROUND OF THE INVENTION

Respiratory assistance apparatuses or devices, or the like, are medical devices which provide respiration or breathing assistance to patients in need thereof. Some types of respiratory assistance apparatuses are colloquially referred to as "ventilators" and are typically expensive and technically complex electro-mechanical equipment which provide ventilation to patients in need thereof. These ventilators along with other respiratory assistance apparatuses are not widely available in many settings, including healthcare settings particularly in developing countries, due to cost and/or availability thereof.

The availability of and need for respiratory assistance apparatuses, for example, ventilators became more pronounced during the Global COVID-19 Pandemic, where a large number of COVID-19 infected persons required hospitalisation and a smaller subset that experienced lung dysfunction of a severity requiring high care attention which in most cases included mechanical respiration assistance. Sadly, a percentage of these serious patients succumbed to the pneumonic effects of the infection due to lack of respiratory assistance.

In the case of the Global COVID-19 Pandemic, considering that a large number of the hospitalised cases recover with assistance, it is estimated that, should assisted breathing facilities not be available due to an excessive requirement therefor, the proportion of patient mortality in a populace would be significant.

In this regard, it is an object of the present invention to provide a human respiratory assistance or ventilation apparatus or device, particularly, though not necessarily exclusively, one which could be used outside the hospital environment which is relatively simple to manufacture and/or operate, is functionally effective, is re-usable, has several power supply options, has a long life, and/or can be mass produced using readily available materials.

SUMMARY OF THE INVENTION

According to one aspect of the invention, there is provided a shuttle aspiration valve (SAV) for a respiratory assistance apparatus comprising: a body comprising: a user interface device port connectable to a user interface device configured to sealingly engage a nose and a mouth of a wearer; an inhalation port connectable to and in flow communication with a source of air at positive pressure; an exhalation port through which exhaled air flows; and a common port in flow communication with the user interface device port and communicable with the inhalation port and the exhalation port in a selective manner; and a respiration control arrangement comprising: a shuttle displaceable within the body between a first position in which the SAV is operated to an inhalation configuration in which the shuttle permits flow communication between the inhalation port and the common port and seals the exhalation port, and a second position in which the SAV is operated to an exhalation configuration wherein the shuttle permits flow communication between the exhalation pod and the common pod and seals the inhalation pod, a plunger operatively connected to the shuttle and disposed adjacent the user interface device pod, wherein the plunger is configured to displace the shuttle between the first and second positions, in use; and a detent arrangement configured to engage the shuttle and releasably lock the same in the first position with a predetermined locking force, wherein, in use, with the detent arrangement locking the shuttle in the first position, flow of at least air to the user is permitted from the inhalation port until the predetermined PIP is reached in the breathing zone, wherein at the predetermined PIP in the breathing zone, a force on the plunger exceeds the locking force of the detent arrangement thereby causing the shuttle to be displaced from the first position to the second position in which the user is permitted to exhale via the exhalation port, and wherein, further in use, negative pressure generated in the breathing zone by inhalation of the user causes the plunger to displace the shuttle from the second position to the first position until the detent arrangement locks the shuttle to the first position.

The detent arrangement may be a ball detent arrangement comprising a resiliently biased ball which is engageable with a suitable slot defined by the shuttle thereby to lock the shuttle in the first position. The detent arrangement may in the form of a ball detent comprising a ball and a resilient biasing member to urge the ball resiliently against the shuttle. The detent arrangement may comprise a trigger adjuster operatively connected to the resilient biasing member so as to adjust the resilient biasing member thereby to vary or adjust the locking force of the detent arrangement. The resilient biasing member may comprise a suitable spring under tension operatively connected or engageable with the ball. In particular, the spring may be under compression. The tension of the spring may be adjustable by way of the trigger adjuster to make the valve more or less responsive to the PIP in the breathing zone.

The body may define a channel which intersects the inhalation and exhalation ports and terminates adjacent the user interface device port, wherein the shuttle is receivable in and slidably displaceable within the channel. To this end, the body may define a detent arrangement chamber which houses the detent arrangement, wherein the detent arrangement chamber intersects the channel.

The inhalation and exhalation ports may be isolated or sealed from each other and may terminate at one end of the common port, wherein the inhalation and exhalation ports are selectively sealable from being in flow communication with the common port and each other by way of the shuttle. An opposite end of the common port may terminate adjacent the user interface device port.

According to another aspect of the invention, there is provided a pressure limiting valve (PLV) comprising: a housing defining an interior and comprising: an inlet port in flow communication with a source of a gas such as air with a positive pressure, e.g. from the blower as described herein; an outlet port to output pressure regulated air therefrom; and a wastegate, and a pressure regulating arrangement comprising: a suitable displacement member located in the interior of the housing, wherein the displacement member is resiliently displaceable in response to the predetermined pressure threshold being reached or exceeded; and a suitable plug operatively connected to the displacement member, wherein the plug is configured to control discharge of air from the interior of the housing via the wastegate in response to displacement of the displacement member, in use.

According to another differently stated aspect of the invention, there is provided a pressure limiting valve (PLV), wherein the PLV comprises: a housing defining an interior and comprising: a first chamber having an inlet port in flow communication with a source of a gas such as air with a positive pressure, e.g. from the blower as described herein; and an outlet port to output pressure regulated air therefrom; and a second chamber in controlled flow communication with the first chamber, wherein the second chamber comprises a wastegate; and a pressure regulating arrangement comprising: a suitable displacement member operatively located in the first chamber, wherein the displacement member is resiliently displaceable in response to the predetermined pressure threshold being reached or zo exceeded; and a suitable plug operatively connected to the displacement member, wherein the plug is located in the first chamber of the housing and is configured to control flow of air from the first chamber to the second chamber in response to displacement of the displacement member, wherein the air received in the second chamber is vented via the wastegate.

The first and second chambers may be separated by a wall defining an opening to provide flow communication between the first and second chambers, wherein the plug is receivable in the opening so as to control flow of air from the first chamber to the second chamber, in use.

The PLV may comprise a biasing arrangement to resiliently bias the displacement member to be responsive to the predetermined pressure threshold, wherein the biasing arrangement is controllable so as to vary the pressure at which the displacement member is responsive. The biasing arrangement may comprise a suitable tensioner, and spring operatively connected to the displacement member, wherein the tensioner is operable to tension the spring so as to vary the pressure at which the displacement member is responsive, in use. The displacement member may be in the form of a diaphragm, or a plunger.

According to another aspect of the invention, there is provided a flow limiting valve (FLV) comprising: a housing defining an interior and comprising: an inlet port in flow communication with a pressure limiting valve (PLV); and an outlet port to output flow regulated air therefrom and a flow regulating arrangement comprising: a suitable displacement member located in the interior of the housing, wherein the displacement member is resiliently displaceable in proportion to the pressure of air received from the PLV; and a suitable airfoil operatively connected to the displacement member, wherein the airfoil is configured to control flow of air from the interior of the housing to the outlet port in response to displacement of the displacement member, in use.

According to another differently defined aspect of the invention, there is provided a flow limiting valve (FLV), wherein the FLV comprises: a housing defining an interior and comprising: a first chamber having an inlet port in flow communication with a pressure limiting valve (PLV); and a second chamber in controlled flow communication with the first chamber, wherein the second chamber comprises an outlet port; and a flow regulating arrangement comprising: a suitable displacement member operatively located in the first chamber, wherein the displacement member is resiliently displaceable in proportion to a pressure of the air received from the PLV; and a suitable airfoil operatively connected to the displacement member, wherein the airfoil is located in the second chamber of the housing and is configured to control flow of air from the first chamber to the second chamber in response to displacement of the displacement member, wherein the air received in the second chamber exits the valve via the outlet port.

The first and second chambers may be separated by a wall defining an opening to provide flow communication between the first and second chambers, wherein the airfoil may be receivable in the opening so as to control flow of air from the first chamber to the second chamber, in use.

The FLV may comprise a biasing arrangement to resiliently bias the displacement member to be responsive to the predetermined pressure threshold, wherein the biasing arrangement is controllable so as to vary the pressure at which the displacement member is responsive. The biasing arrangement may comprise a suitable tensioner, and spring operatively connected to the displacement member, wherein the tensioner is operable to tension the spring so as to vary the pressure at which the displacement member is responsive, in use. The displacement member may be in the form of a diaphragm, or plunger.

It will be appreciated that the airfoil may be configured to control flow of air from the outlet port of the FLV in a manner which is inversely proportional to the pressure of the air received from the PLV via the inlet port of the FLV.

According to another aspect of the invention, there is provided a respiratory assistance apparatus comprising: a blower configured to provide a supply of air at a positive pressure; a pressure limiting valve (PLV) in flow communication with the blower, wherein the PLV is configured to regulate pressure of air flowing therethrough by permitting flow of air below a predetermined pressure threshold therethrough and discharging air above the predetermined pressure threshold therefrom; a flow limiting valve (FLV) in flow communication with the PLV, wherein the FLV is configured to regulate flow of air therethrough in proportion to a pressure of air received from the PLV; and a shuttle aspiration valve (SAV) in flow communication with the FLV and a suitable user interface device that is configured to sealingly engage with a face of the user so as to cover their nose and mouth, wherein the SAV is configured to be operated between an inhalation configuration and an exhalation configuration, wherein the SAV is configured to be operated to the inhalation configuration in response to negative pressure being generated in a breathing zone between at least the user interface device, the user, and the SAV, by inhalation of the user thereby to permit at least flow of air from the FLV to the user up to a predetermined peak inhalation pressure (PIP) in the breathing zone, wherein once the predetermined PIP is reached, the SAV is automatically operated to the exhalation configuration in which at least flow of air to the user is restricted thus allowing the user to exhale, in use.

The SAV, PLV, and FLV may be the same or similar to those described herein. In this regard, it will be understood that the PLV may be located downstream from the blower, in a flow path defined by a suitable conduit, wherein the FLV may be located downstream from the PLV, in a flow path defined by a suitable conduit, and wherein the SAV may be located downstream from the FLV, in a flow path defined by a suitable conduit. The conduits may be suitable conventional pneumatic piping or tubing conventionally used with medical equipment to provide respiratory support to users.

It will be understood by those skilled in the art that having components in flow communication with each other via flow paths, either downstream or upstream, does not preclude intermediate components from being arranged in the flow paths between the same. For example, the apparatus may comprise a suitable pressure and flow measurement arrangement located downstream from the FLV to measure flow and pressure of air.

The apparatus may comprise a suitable a post exhalation excess pressure (PEEP) valve in flow communication with the SAV to prevent full exhalation by the user by restricting flow of exhaled gas/es below a predetermined PEEP therethrough. The PEEP valve may be in flow communication with the exhalation port of the SAV, downstream thereof. The apparatus may comprise a disposable bag in flow communication with the PEEP valve, downstream thereof, wherein the bag comprises disinfectant material to disinfect exhaled gases and condensate associated therewith. The bag may be disposable.

The apparatus may comprise a suitable filter in flow communication with the blower to filter air provided thereby.

The blower may comprise a housing having one or more inlet/s to receive natural air from an ambient source; and an outlet to supply air at a positive pressure. The blower may be a curved vane blower or a turbine type blower. 32. The blower may be configured to intermittently operate.

The user interface device may be in the form of a mask which is sealing engageable with a face of the user so as to cover the nose and mouth thereof. The SAV is operatively attached to the mask via the user interface device port.

The apparatus may comprise a power supply unit.

It will be understood that the apparatus may be portable, wherein some components thereof are housed in a suitable housing.

The apparatus may comprise a lightly loaded check valve to atmosphere in a flow path to the SAV which opens if pressure in the flow path reduces below atmospheric pressure. In this way, if air supply in the flow path to the SAV reduces below atmospheric pressure, the user's inhalation impulse will operate the SAV to the inhalation configuration and air will flow via the check valve and into the mask.

On exhalation, the user's exhalation impulse will operate the SAV to the exhalation configuration and exhaled air from the user will be discharged through the SAV exhalation port to the PEEP valve, thereby retaining PEEP integrity without powered flow. The check valve may be referred to as an anti-suffocation valve and may be located within the suitable housing and/or a separate enclosure to prevent contamination.

The apparatus may comprise a suitable filter to filter air to the user. The filter may be a suitable bio-filter to filter air entering into the blower.

The apparatus may comprise a suitable filter or scrubber in flow communication downstream from the PEEP valve.

According to another aspect of the invention, there is provided a mask device for a respiratory assistance apparatus comprising: a mask body configured to be attachable to a face of a wearer to define an enclosed breathing zone which encloses at least a mouth and nose of the wearer, wherein the mask body comprises an inlet port; and a SAV as described herein operatively attached to the inlet port of the mask.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a high-level block diagram of a respiratory assistance apparatus accordance with an example embodiment of the invention; Figure 2(a) shows a high-level schematic sectional diagram of pressure limiting valve (PLV) in accordance with an example embodiment of the invention; Figure 2(b) shows a high-level schematic sectional diagram of flow limiting valve (FLV) in accordance with an example embodiment of the invention; Figure 3 shows an image of a prototype of the PLV and FLV of Figure 2 with control fascia in accordance with an example embodiment of the invention; Figure 4 shows another image of a prototype of the PLV and FLV of Figure 2 in accordance with an example embodiment of the invention; Figure 5 shows a high-level schematic sectional diagram of shuttle aspiration valve (SAV) in accordance with an example embodiment of the invention; Figure 6 shows a high-level schematic sectional diagram of the shuttle aspiration valve (SAV) in an inhalation configuration in accordance with an example embodiment of the invention; Figure 7 shows a high-level schematic sectional diagram of the shuttle aspiration valve (SAV) in an exhalation configuration in accordance with an example embodiment of the invention; and Figure 8 shows an image of a mask operatively attached with an SAV of Figures 5 to 7 in accordance with an example embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The following description of the invention is provided as an enabling teaching of the invention. Those skilled in the relevant art will recognise that many changes can be made to the embodiment described, while still attaining the beneficial results of the present invention. It will also be apparent that some of the desired benefits of the present invention can be attained by selecting some of the features of the present invention without utilising other features. Accordingly, those skilled in the art will recognise that modifications and adaptations to the present invention are possible, and may even be desirable in certain circumstances, and are a part of the present invention. Thus, the following description is provided as illustrative of the principles of the present invention and not a limitation thereof.

It will be appreciated that the phrase "for example," "such as", and variants thereof describe non-limiting embodiments of the presently disclosed subject matter. Reference in the specification to "one example embodiment", "another example embodiment", "some example embodiment", or variants thereof means that a particular feature, structure or characteristic described in connection with the embodiment(s) is included in at least one embodiment of the presently disclosed subject matter. Thus, the use of the phrase "one example embodiment", "another example embodiment", "some example embodiment", or variants thereof does not necessarily refer to the same embodiment(s).

Unless otherwise stated, some features of the subject matter described herein, which are, described in the context of separate embodiments for purposes of clarity, may also be provided in combination in a single embodiment. Similarly, various features of the subject matter disclosed herein which are described in the context of a single embodiment may also be provided separately or in any suitable sub-combination.

The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims. For brevity, the word "may" is used in a permissive sense (i.e., meaning "having the potential to"), rather than the mandatory sense (i.e., meaning "must").

The words "include," "including," and "includes" and the words "comprises", "comprising", and "comprises" mean including and comprising, but not limited to, respectively. Additionally, as used herein, the term "coupled" may refer to two or more components connected together, whether that connection is permanent (e.g., welded) or temporary (e.g., bolted, screwed), direct or indirect (i.e., through an intermediary), mechanical, chemical, optical, or electrical.

Referring to Figure 1 of the drawings, a high-level block diagram is shown which diagrammatically illustrates various components of a respiratory assistance apparatus, denoted by reference numeral 10, in accordance with an example embodiment of the invention. The apparatus 10 may also be referred to as a ventilator which provides air to a user, for example, a patient in needs of ventilation or respiratory assistance. In particular, the apparatus 10 is a Bi-level Positive Airway Pressure (BiPAP) respiratory assistance apparatus 10 which is configured to source air, clean the sourced air, pressurise the cleaned air and deliver the pressurised air to a user in a manner in which the air flow to the patient is to be supplied only as required and so must be triggered by the patient's impulse to inhale during an inhalation phase of operation of the apparatus 10. It follows that the tidal flow of respiration must be reversed and as such, the apparatus 10 is configured to sense the user's impulse to exhale provide a flow path for exhaled gases to be released at a lower level of pressure during an exhalation phase of operation of the apparatus 10. The apparatus 10 is largely mechanical with mechanical valves controlling flow through the apparatus 10 as described herein.

To this end, the apparatus 10 comprises a blower 12 configured to provide a supply of air at a positive pressure. The blower 12 may be a conventional blower 12 of the turbine type configured to draw in ambient air from the atmosphere via one or more suitable inlets and output air at a positive pressure via a suitable outlet. In one example, embodiment, the blower 12 is a compact blower 12 with a rotor of 40mm diameter with inlet and outlet vane angles of 60 and 15 degrees and purely radial vane curvatures. The rotor may be driven by a 40W brushless DC motor and runs at speeds up to 22 000 RPM. This arrangement was found to be more suitable than low speed large radius blowers which have high power consumption due to large internal recirculation flow, caused by necessary clearances between fixed and rotating parts of the blower.

The blower 12 typically draws in ambient air which it pressurises and conveys in the flow path through the apparatus 10. The blower 12 is typically configured to provide air at a higher pressure than what is required by a user, for example, to cater for pressure losses in the flow path to the user. However, the pressurised air supplied by the blower 12 cannot be provided to user as it may damage lung tissue of the user.

It will be understood that the pressure of air from the blower 12 is a function of the blower speed and flow. For an intermittent flow, the blower speed will increase when flowrate is reduced, such as during an exhalation period For this reason pressure regulation is required immediately after the blower.

In this regard, a pressure limiting valve (PLV) 14 is provided in flow communication with the blower 12, for example, via suitable tubing defining a flow path. The PLV 14 is configured to limit and/or regulate pressure of air flowing therethrough by permitting flow of air below a predetermined pressure threshold therethrough and discharging air above the predetermined pressure threshold therefrom. In one example embodiment, the PLV 14 is configured to reduce pressure of the air received from the blower 12 from a potential 7.5kPa down to a minimum of approximately 0.8 kPa.

The apparatus 10 further comprises a flow limiting valve (FLV) 16 in flow communication with the PLV 14 via suitable tubing. The FLV 16 is configured to regulate flow of air therethrough in proportion to a pressure of air received from the PLV 14. In some example embodiments, the PLV 14 and the FLV 16 are provided as a coupled pressure and flow regulating valve assembly. In this regard, the valves 14 and 16 act in concert to provide pressure regulated and flow-controlled flow of air at positive pressure.

It will be understood by those skilled in the art that the phrase "flow path" may be understood to mean the path which air flows in the apparatus 10. The flow path 30 may be provided by suitable tubing which connects various components in the apparatus such that they are in flow communication with each other.

The apparatus 10 advantageously comprises a shuttle aspiration valve (SAV) 18 in flow communication with the FLV 16, wherein the SAV 18 is operatively connected to a user interface device in the form of a mask 20 as shown in Figure 8. In particular, the SAV 18 is in flow communication with the FLV 16 via an anti-suffocation valve 22 in the form of a check valve to atmosphere as will be explained below. The mask 20 sealingly engages with a face of the user so as to cover their nose and mouth.

The SAV 18 is configured to be operated between an inhalation configuration and an exhalation configuration, wherein the SAV 18 is configured to be operated to the inhalation configuration in response to negative pressure being generated in a breathing zone between at least the mask 20, the user's face, and the SAV 18, by inhalation of the user thereby to permit at least flow of air from the FLV 16 to the user up to a predetermined peak inhalation pressure (PIP) in the breathing zone, wherein once the predetermined PIP is reached, the SAV 18 is automatically operated to the exhalation configuration in which at least flow of air to the user is restricted thus allowing the user to exhale, in use.

The apparatus 10 further comprises a suitable Post Expiration Excess Pressure (PEEP) valve 24 in flow communication with the SAV 18 to prevent full exhalation by the user, in use, by restricting flow of exhaled gas/es below a predetermined PEEP therethrough. The PEEP valve 24 may be a commercially available PEEP valve 24 and may be operatively attached to a suitable filtration unit/disposable 26 condensate bag containing a suitable disinfectant to disinfect condensate from exhaled gases from the user.

Instead, or in addition, the unit 26 may comprise an exhauster filter which comprises a chamber with a filtered exit to atmosphere. A plastic vessel with a layer of plastic foam surrounding the exhalation tube in a bath of dilute disinfectant serves as an outlet scrubber. The foam wicks the disinfectant above the liquid level and exhausted air must follow a torturous path through the saturated foam, entraining disinfectant vapour and effectively sterilising the flow. The exhaust sterilisation vapours cannot return to the patient so that an aggressive concentration can be used. This filter is placed at a low elevation so that any accidental back-flow is impossible.

It will be understood that most of the components of the apparatus 10 is typically housed in a portable housing H which may permit easy transport of the apparatus 10. The apparatus 10 also includes a suitable power supply unit 30. The power supply unit may be a conventional power supply and may in some example embodiments comprise a rechargeable battery unit to permit operation of the apparatus 10 without being connected to an electrical outlet.

The apparatus 10 further comprises a suitable filtration unit 32 comprising a suitable biofilter to filter air drawn in to be pressurised by the blower 12. It will be 10 understood that in some example embodiments, the filtration unit 32 may be provided at or adjacent an outlet of the blower 12 In one example embodiment, the housing H is in the form of an aluminium casing which is compartmentalised and made practically airtight to enable light pressurisation, for exclusion of dust and other contaminants. Though not shown, a wheeled exo-frame is configured to engage with the housing H to aide portability and handling strength to the housing. The housing H may be lockable and may comprise several useful features such as draw and carry handles, a wheeled base and sturdy hinges and latches.

The power supply unit 30 may comprise a battery, transformer and power components as alluded to above and are mounted in a compartmentalised housing H which may be ventilated by the PLV 14, particularly a wastegate thereof (see below and Figure 2(a)) during the exhalation phase of operation. The blower 12 may be mounted in its own compartment which draws ambient air through the biofilter 32. Motor cooling is effected by the passage of air through the blower 12, thereby minimising any requirement for additional heating of the air product.

As described herein, flow and pressure control is maintained by the series connected PLV 14 and the FLV 16 which are mounted in a second compartment which also houses the pressure and flow indication sensors and an electrical main power switch. Pressure and flow adjusters and their indicators are accessed from the external control panel, as well as the master power switch.

The mask 20, hoses, tubes, pipes and dry outlet filter casing as well as loose power cables are stored in a lid of the housing H and are secure via suitable clips and holders In one example embodiment, the blower 12 is mounted on a vibration isolating structure and inside a closed compartment which draws flow from the outside via the housing H which holds the biofilter 32. The air is drawn into the inlet of the blower 12 where it is in contact with a motor heat sink and which performs the dual function of raising air temperature whilst cooling the motor. In this regard, the motor is the blower motor as mentioned herein operatively connected to the rotor.

Though not discussed in great detail herein, the apparatus 10 further comprises a sensing unit 28 with suitable electronic sensors, and the like which intersects the flow path of air from the FLV 16 to provide diagnostic measurements relating to the air pressure and/or flow of air from the FLV 16. In particular the sensing unit 28 comprises a suitable non-choking venturi and suitable air pressure and/or flow sensors to measure air flow and pressure from the FLV 16. In one example, embodiment, the venturi comprises a 19° inlet angle and a 4° outlet angle, from a upstream tube diameter of lOmm and a throat size of 8mm. The unit 28 has two tapping points, the first being in the upstream tube (high pressure (HP)) and the second in the venturi throat (low pressure (LP)), both providing local static pressure.

A third sensor is typically provided to allow constant recalibration relative to barometric pressure, for instances wherein barometric pressure may vary. The high-pressure signal from the upstream tube may be split to provide a system gauge pressure signal and the HP signal for electronic comparison of the LP signal to provide a differential pressure value.

The apparatus 10 comprises suitable displays, for example, LCD displays, as can be seen in Figure 3, to display for Pressure and Flow indication for the valves 14 and 16.

In some example embodiments, oxygen may be added via the venturi downstream from the FLV 16 but upstream from the SAV 18.

Turning now to Figure 2 of the drawings, wherein the PLV 14 and FLV 16 are illustrated in greater detail. As mentioned, the PLV 14 and FLV 16 work in concert to provide pressure regulated and flow-controlled flow of pressurised air to the user via the SAV 18 in a manner which does not cause harm to the user's lungs.

More particularly referring to Figure 2(a), the PLV 14 comprises a housing 34 defining an interior and comprises or defines a first chamber 36 having an inlet port 38 in flow communication with the blower 12 to receive air at a positive pressure therefrom; and an outlet port 40 to output pressure regulated air therefrom The PLV 14 housing 34 also comprises or defines a second chamber 42 in controlled flow communication with the first chamber 36, wherein the second chamber 42 comprises a wastegate 44. The first and second chambers 36, 42 are separated by a suitable wall or web 47 which has an opening or throat 49 to enable a flow connection between the first and second chambers 36, 42 as described herein.

The PLV 14 further comprises a pressure regulating arrangement 46 comprising a diaphragm 48 operatively located in the first chamber 36. The diaphragm 48 is resiliently biased by a suitable spring 50 to a first position and may be displaceable in the direction of arrow A to a second position (not shown) in response to a predetermined pressure threshold being reached or exceeded. The diaphragm 48 may be 80mm in diameter.

The pressure regulating arrangement 46 further comprises a suitable plug 52 operatively connected to the diaphragm 48 and/or the spring 50 via a stem 54 thereof. A free end of the plug 52 is locatable in a suitable seat in the wall 47 to seal the first and second chambers 36, 42 from each other, when the diaphragm 48 is in the first position. The plug 52 is located in the first chamber 36 of the housing 34 and is configured to control flow of air from the first chamber 36 to the second chamber 42, in response to displacement of the diaphragm 48 between the first and second positions, by variably engaging with the opening 49. Air received in the second chamber 42 is vented via the wastegate 44.

In this way, when pressure of air entering into the first chamber 36 via the inlet port 38 is below a predetermined pressure threshold, the air travels through the first chamber 36 and is output via the outlet port 40. It will be appreciated that when the pressure of air entering into the first chamber 36 is below a predetermined pressure threshold, the diaphragm 48 is resiliently urged in the direction of arrow B to the first position via the spring 50 thus urging the plug 52 to seal the opening 49, pneumatically isolating the first and second chambers 36, 42 from each other and allowing air to flow freely from the inlet port 38 to the outlet pod 40.

However, when the pressure of air entering into the first chamber 36 via the inlet port 38 is at and/or above the predetermined pressure threshold, the diaphragm 48 is displaced in the direction of arrow A to a second position (not shown) due to the pressure in the first chamber 36 thus causing the plug 52 to be resiliently displaced in the direction of arrow A thus unseating the plug 52 from sealing the opening 49 and allowing air under pressure to be vented from the first chamber 36 into the second chamber 42 for discharge via the wastegate 44.

The plug 52 typically has a triangular or bullet-like profile to variably engage with the opening 49 to regulate pressure in the manner contemplated herein. For example, when the pressure in the first chamber 36 only slightly exceeds the predetermined pressure threshold, the diaphragm moves slightly from the first position to the second position thus providing a slight gap between the plug 52 and the opening 49 to vent a bit of air via the wastegate 44 as opposed to the plug 52 completely disengaging from the opening 49 and providing free flow of air to be vented via the wastegate 44.

It will be noted that the tension of the spring 50 may be adjusted with a suitable tensioner Ti. In this way, the pressure and extent to the PLV 14 is responsive to regulate may be conveniently adjusted.

Turning now to Figure 2(b) of the drawings, the FLV 16 is similar in construction to the PLV 14. In particular, the FLV 16 comprises a housing 60 defining an interior and comprising or defining a first chamber 62 having an inlet port 64 in flow communication with a source of at least air at a regulated positive pressure, for example, from the PLV 14. The housing 60 also comprises or defines a second chamber 66 in controlled flow communication with the first chamber 62, wherein the second chamber 66 comprises an outlet port 68. The first and second chambers 62, 66 are separated by a suitable wall 70 having an opening or throat 72 provided in the wall 70 to permit flow communication between the first and second chambers 62, 66.

The FLV 16 further comprises a flow regulating arrangement 74 comprising a diaphragm 76 which is resiliently biased by a spring 78. The flow regulating arrangement 74 further comprises a suitable airfoil 80 operatively connected to the diaphragm 76 and/or the spring 78 via a stem 82 thereof. A free end of the airfoil is locatable in a suitable seat in the wall 70 to seal the first and second chambers 62, 66 from each other. The airfoil 80 is located in the second chamber 66 of the housing 60 and is configured to control flow of air from the first chamber 36 to the second chamber 42, in response to displacement of the diaphragm 48, by variably engaging with the opening 72 Air received in the second chamber 42 is output via the outlet port 68.

In this way, flow of air exiting the FLV 16 is in proportion to the pressure of the air entering into FLV 16. In particular the higher the flow or pressure of the air entering the first chamber 62 via the inlet port 64, the lower the flow rate of air exiting the second chamber 66 via the outlet port 68. In particular, if the flow of air or pressure thereof entering into the first chamber 62 is greater than a predetermined flow or pressure threshold, the diaphragm 76 moves in the direction of arrow A thus drawing the airfoil 80 into a more sealing engagement with the opening 72 thus reducing the flow of air from the first chamber 62 to the second chamber 66 and thus reducing the flow of air output from the outlet port of the FLV 68, and vice versa.

The airfoil 80 typically has a triangular or bullet-like profile to variably engage with the opening 72 to regulate flow in the manner contemplated herein It will be noted that the tension of the spring 78 may be adjusted with a suitable tensioner 12. In this way, the pressure and/or flow and hence the extent to the FLV 16 is responsive to regulate flow of air therethrough may be conveniently adjusted.

In Figure 3, the PLV 14 and the FLV 16 may be coupled as illustrated and airflow measurements in respect of pressure and flow therethrough may be indicated by way of a suitable LCD display. To this end, it must be re-iterated that the PLV 14 and FLV 16 may share many parts as they are very similar in construction, apart from the placement of the plug 52 and the airfoil 80, and the blocking of the port 40 in the case of the FLV 16 by way of a friction plug. This reduces the costs of the valves 14, 16.

The airfoil 80 is shaped and/or dimensioned such that when the same is positioned in the path of the airflow in the FLV 16, as biased by the diaphragm 76 with the spring 78, the flow area is reduced as static pressure increases. Once the backpressure has reduced, the flow area increases again.

It will be noted that the FLV 16 may only be required at the start of the inhalation period, when little backpressure exists and blower set pressure is available in the air supply tube. Once the SAV 18 is operated to the inhalation configuration, the trapped air in the supply tube is allowed to expand into the breathing zone without additional supplementary air supplied by the blower 12 and which supplies sufficient pressure to initiate a strong flow into the mask 20 without shock. At this stage of the cycle, the FLV 16 will be almost fully shut due to the excess upstream pressure and may only allow flow once the backpressure is reduced. As already mentioned, the FLV 16 will open proportionally with the receding backpressure but also limits the maximum flow rate.

Referring now to Figures 5 to 6 of the drawings, wherein the SAV 18 is illustrated in more detail. The BiPAP principle of operation of the apparatus 10 relies on a patient's motor impulse to draw a breath, after which the air feed, flow and pressure are supplied up to the set parameters, and exhalation is automatically triggered and controlled down to PEEP pressure. The apparatus 10 maintains a state of rest until the patient initiates a subsequent breath. Unlike enforced ventilation, the BiPAP system is considered to be a semi-automatic process. To this end, the SAV 18 seeks to assist in facilitating such operation.

The SAV 18 comprises a body 84 comprising a user interface device port 86 connectable to the mask 20, an inhalation port 88 connectable to and in flow communication with a source of air at positive pressure, for example, the FLV 16, particularly the outlet port 68 thereof, an exhalation port 90; and a common port 92 in flow communication with the user interface device port 86 and communicable with the inhalation port 88 and the exhalation port 90 in a selective manner. It will be appreciated that the exhalation port 90 is operatively connected to the PEEP valve 24 The SAV 18 further conveniently comprises a respiration control arrangement 94 comprising a shuttle 96 slidably displaceable within a channel 98 defined by the body 84 between a first position as illustrated in Figures Sand 6 in which the SAV 18 is operated to the inhalation configuration in which the shuttle 96 permits flow communication between the inhalation port 88 and the common port 92 and seals the exhalation port 90, and a second position as illustrated in Figure 7 in which the SAV 18 is operated to the exhalation configuration in which the shuttle 96 permits flow communication between the exhalation port 90 and the common port 92 and seals the inhalation port 88. The shuttle 96 may be generally cylindrical with two parts 96.1 96.2 which are connected by a stem 96.3 of smaller diameter.

It will be understood that the SAV 18 is operated to the inhalation configuration during the inhalation phase of operation of the apparatus 10 and similarly the SAV 18 is operated to the exhalation configuration during the exhalation 10 phase of operation of the apparatus 10.

The respiration control arrangement 94 further comprises a plunger 100 operatively connected to the shuttle 96, particularly a free end thereof, wherein the plunger 100 is operatively disposed adjacent the user interface device port 86, wherein the plunger 100 is configured to displace the shuttle between the first and second positions, in use.

The respiration control arrangement 94 also comprises a detent arrangement 102 housed in a suitable chamber in the body 84 which intersects with the channel 98 defined by the body 84 for the shuttle 96. The arrangement 94 has a suitable ball 102.1 resiliently biased via a suitable spring 102.2 to engage the shuttle 96 and releasably lock the same in the first position with a predetermined locking force. The locking force may be determined by the spring 102.2 and the arrangement 102 may comprise a trigger tensioner 102.3 configured to adjust the tension of the spring 102.2. To facilitate locking the shuttle 96 in the first position, the shuttle 96 comprises a suitable circumferential groove 96.4 within which the ball 102.1 is urged into, once the ball 102.1 is aligned with the groove 96.4, to lock the shuttle 96 in the first position as can be seen in Figure 6.

When the shuttle 96 is locked in the first position, flow of at least air to the user is permitted from the inhalation port 88 via the common port 92 into the breathing zone until the predetermined PIP is reached within the breathing zone. At or around the predetermined PIP in the breathing zone, a force on the plunger 100 exceeds the locking force of the detent arrangement 102 thereby causing the ball 102.1 to disengage from the groove 96.4 and the shuttle 96 to be displaced from the first position to the second position as illustrated in Figure 7. When the shuttle 96 is in the second position, the user is permitted to exhale via the exhalation port 90, which is unsealed. Exhalation flow may be powered by the elasticity of the patient' chest and pressure is limited by the PEEP valve 24.

Further, in use, negative pressure generated in the breathing zone by inhalation of the user causes the plunger 100 to displace the shuttle 96 from the second position to the first position until the detent arrangement 102 is in range of the groove 96.4 to lock the shuttle 96 to the first position. In particular, the arrangement 102 locks the shuttle 96 once the ball 102.1, urged by the spring 102.2, is aligned with and locates within the groove 96.4 of the shuttle 96.

Referring to Figure 8 of the drawings, it will be noted that the SAV 18 and the mask 20 may be operatively attached thereto to form a mask device as illustrated. The mask 20 typically comprises a mask body which envelops the user's mouth and nose to define the breathing zone In this regard, peripheries of the mask may be provided with a cushioned seal.

It will be noted that the apparatus 10 may have a larger outlet tube beyond the SAV 18 which has the effect of delaying the increase in backpressure ahead of the PEEP valve 24 and allowing the initial exhalation flow to be high and initiating some inertial flow.

In use, the apparatus 10 is portable and is able to be used in any location.

Once apparatus 10 is switched on, it receives electrical energy from the power supply unit 30 which powers the blower 12. The blower 12 sucks in ambient air via suitable inlet ports (which may be aligned with suitable inlet vents in the housing H) which it outputs via a suitable outlet at a positive pressure. The air drawn in to the blower 12 may be via a suitable biofilter unit 32 which sanitises the air from pathogens.

The PLV 14, connected in flow communication with the outlet of the blower 12, downstream thereof, via suitable tubing receives air at a pressure which is unsafe for human lungs via the inlet port 38 and as such the pressure of the air in the chamber 36, particularly between the chamber 36 and diaphragm 48, causes displacement of the resiliently biased diaphragm 48 in the direction of arrow A causing the plug 52 to disengage from the opening 49 to vent air through the wastegate 44 but allow air of a desired pressure to exit via the outlet 40.

The FLV 16 located downstream from the PLV 14, and in flow communication with the PLV 14 via suitable tubing connected between the outlet port 40 of the PLV 14 and the inlet port 64 of the FLV. The FLV 16 receives air at a predetermined pressure/s via the PLV 14 and regulates the flow rate proportionally so that the flow of air from the inlet port 64 to the outlet port 68 is regulated.

The flow rate and pressure of the air supplied by the FLV 16 is measured with the sensing unit 28 and is displayed to a user.

Optionally oxygen may be mixed after the FLV 16, for example, via the venturi associated with the unit 28.

The pressure regulated and flow-controlled air is supplied to the SAV 18 via a check valve 22 to atmosphere which is serves as an anti-suffocation valve and is configured to operate to allow air from atmosphere into the flow path to the SAV 18 if the pressure from the FLV 16 is not detected. In this way, a user is saved from suffocation if the air supply under pressure is stopped for whatever reason. The valve 22 is connected via suitable tubing to the outlet port 68 of the FLV.

It will be understood that the various components of the apparatus 10 are in flow communication with each other and are typically downstream from each other in the flow path of pressurised air from the blower 12 to the user via the SAV 18. The flow path between components are defined by the tubing which serve as sealed conduits for pressurised air. Receiving pressurised air from one component may be mean receiving air directly from said component or via any other intermediary component as the case may be.

The SAV 18, located downstream from the FLV 16, is connected to the FLV 16 via the valve 22. In particular, the inhalation port 88 is connected downstream from the FLV 16 and is in flow communication therewith.

As can be seen in Figures 6 and 7, when a user attempts to inhale, a negative pressure in the breathing zone defined by the mask 20, the user's face and the SAV 30 16 causes the plunger 100 to be drawn towards the user thus moving the shuttle 96 to the first position in which the ball 102.1, biased by the spring 102.2 of the arrangement 102, is aligned with and slips into the groove 96.4 thus locking the shuttle 96 in the first position which seals the exhalation port 90 and provides a flow path between the inhalation port 88 for the pressurised air received from the FLV 16 (via the valve 22) and the common port 92 which opens into the breathing zone thus providing air at a desired positive pressure to the user up till a PIP. This is the inhalation phase in which the SAV 18 is operated to the inhalation configuration. The PIP at which the SAV 16 is responsive may be determined by a medical practitioners and may be adjusted by way of a suitable trigger adjuster operatively configured to tension the spring 102.2.

At the PIP, the force on the plunger 100 exceeds the locking force of the detent arrangement 102 and the ball 102.1 disengages from the groove 96.4 allowing the shuttle 96 to travel away from the user into the second position which seals the inlet port 88 from flow communication with the common port 92 and opens the exhalation port 90 so that exhaled gases from the user's lungs can travel and exit the SAV 18 via the exhalation port 90 to the PEEP valve 24 which limits complete exhalation of the lungs as described herein. This is the exhalation phase in which the SAV 18 is operated to the exhalation configuration. Any condensate and expelled air is suitable sanitised by the unit 26 as described herein.

The users inhalation reflex starts the inhalation phase again and the inhalation and exhalation phases follow in a reciprocal fashion to provide fresh air to the user and provides a path for exhaled gases to be channelled away from the user.

The apparatus 10 as described herein is simple, functional and less costly than other more complicated ventilator units.

Claims

Claims 1. A respiratory assistance apparatus comprising: a blower configured to provide a supply of air at a positive pressure; a pressure limiting valve (PLV) in flow communication with the blower, wherein the PLV is configured to regulate pressure of air flowing therethrough by permitting flow of air below a predetermined pressure threshold therethrough and discharging air above the predetermined pressure threshold therefrom; a flow limiting valve (FLV) in flow communication with the PLV, wherein the FLV is configured to regulate flow of air therethrough in proportion to a pressure of air received from the PLV; and a shuttle aspiration valve (SAV) in flow communication with the FLV and a suitable user interface device that is configured to sealingly engage with a face of the user so as to cover their nose and mouth, wherein the SAV is configured to be operated between an inhalation configuration and an exhalation configuration, wherein the SAV is configured to be operated to the inhalation configuration in response to negative pressure being generated in a breathing zone between at least the user interface device, the user, and the SAV, by inhalation of the user thereby to permit at least flow of air from the FLV to the user up to a predetermined peak inhalation pressure (PIP) in the breathing zone, wherein once the predetermined PIP is reached, the SAV is automatically operated to the exhalation configuration in which at least flow of air to the user is restricted thus allowing the user to exhale, in use.
2. The apparatus as claimed in claim 1, wherein the apparatus comprises a suitable a post exhalation excess pressure (PEEP) valve in flow communication with the SAV to prevent full exhalation by the user by restricting flow of exhaled gas/es below a predetermined PEEP therethrough.
3. The apparatus as claimed in either claim 1 or claim 2, wherein the apparatus comprises a suitable filter in flow communication with the blower to filter air provided thereby.
4. The apparatus as claimed in any one of the preceding claims, wherein the blower comprises a housing having one or more inlet/s to receive natural air from an ambient source; and an outlet to supply air at a positive pressure.
5. The apparatus as claimed in any one of the preceding claims, wherein the blower is a curved vane blower or a turbine type blower.
6. The apparatus as claimed in any one of the preceding claims, wherein the PLV comprises: a housing defining an interior and comprising: an inlet port connectable to and in flow communication with the blower; an outlet port to output pressure regulated air therefrom; and a wastegate; and a pressure regulating arrangement comprising: a suitable displacement member located in the interior of the housing, wherein the displacement member is resiliently displaceable in response to the predetermined pressure threshold being reached or exceeded; and a suitable plug operatively connected to the displacement member, wherein the plug is configured to control discharge of air from the interior of the housing via the wastegate in response to displacement of the displacement member, in use.
7. The apparatus as claimed in claim 6, wherein the housing comprises: a first chamber comprising the inlet port and the outlet port, wherein the displacement member and the plug are located in the first chamber; and a second chamber in controlled flow communication with the first portion, wherein the second chamber comprises the wastegate, wherein the plug is configured to control discharge of air from the interior of the housing via the wastegate by controlling flow of air from the first chamber to the second chamber in response to displacement of the displacement member, in use.
8. The apparatus as claimed in claim 7, wherein the first and second chambers are separated by a wall defining an opening to provide flow communication between the first and second chambers, wherein the plug is receivable in the opening so as to control flow of air from the first chamber to the second chamber, in use.
9. The apparatus as claimed in any one of claims 6 to 8, wherein the PLV comprises a biasing arrangement to resiliently bias the displacement member to be responsive to the predetermined pressure threshold, wherein the biasing arrangement is controllable so as to vary the pressure at which the displacement member is responsive.
10. The apparatus as claimed in claim 9, wherein the biasing arrangement comprises a suitable tensioner, and spring operatively connected to the displacement member, wherein the tensioner is operable to tension the spring so as to vary the pressure at which the displacement member is responsive, in use.
11. The apparatus as claimed in any one of claims 6 to 10, wherein the displacement member is in the form of a diaphragm, or a plunger.
12. The apparatus as claimed in any one of the preceding claims, wherein the FLV comprises: a housing defining an interior and comprising: an inlet port connectable to and in flow communication with the PLV; and an outlet port to output flow regulated air therefrom and a flow regulating arrangement comprising: a suitable displacement member located in the interior of the housing, wherein the displacement member is resiliently displaceable in proportion to the pressure of air received from the PLV; and a suitable airfoil operatively connected to the displacement member, wherein the airfoil is configured to control flow of air from the interior of the housing to the outlet port in response to displacement of the displacement member, in use.
13. The apparatus as claimed in claim 12, wherein the housing comprises: a first chamber comprising the inlet port, wherein the displacement member is located in the first chamber; and a second chamber in controlled flow communication with the first chamber, wherein the second chamber comprises the outlet port, wherein the airfoil is located in the second chamber and is configured to control flow of air from the interior of the housing to the outlet port by controlling flow of air from the first chamber to the second chamber in response to displacement of the displacement member, in use.
14. The apparatus as claimed in claim 13, wherein the first and second chambers are separated by a wall defining an opening to provide flow communication between the first and second chambers, wherein the airfoil is receivable in the opening so as to control flow of air from the first chamber to the second chamber, in use.
15. The apparatus as claimed in any one of claims 12 to 14, wherein the FLV comprises a biasing arrangement to resiliently bias the displacement member to be responsive to the predetermined pressure threshold, wherein the biasing arrangement is controllable so as to vary the pressure at which the displacement member is responsive.
16. The apparatus as claimed in claim 15, wherein the biasing arrangement comprises a suitable tensioner, and spring operatively connected to the displacement member, wherein the tensioner is operable to tension the spring so as to vary the pressure at which the displacement member is responsive, in use.
17. The apparatus as claimed in any one of claims 12 to 16, wherein the displacement member is in the form of a diaphragm, or a plunger.
18. The apparatus as claimed in any one of claims 12 to 16, wherein the airfoil is configured to control flow of air from the outlet port of the FLV in a manner which is inversely proportional to the pressure of the air received from the PLV via the inlet port of the FLV.
19. The apparatus as claimed in any one of the preceding claims, wherein the SAV comprises: a body comprising: a user interface device port connectable to the user interface device; an inhalation port connectable to and in flow communication with the FLV; an exhalation port and a common port in flow communication with the user interface device port and communicable with the inhalation port and the exhalation port; and a respiration control arrangement comprising: a shuttle displaceable within the body between a first position in which the SAV is operated to the inhalation configuration in which the shuttle permits flow communication between the inhalation port and the common port and seals the exhalation port, and a second position in which the SAV is operated to the exhalation configuration wherein the shuttle permits flow communication between the exhalation port and the common port and seals the inhalation port; a plunger operatively connected to the shuttle and disposed adjacent the user interface device port, wherein the plunger is configured to displace the shuttle between the first and second positions, in use; and a detent arrangement configured to engage the shuttle and releasably lock the same in the first position with a predetermined locking force, wherein, in use, with the detent arrangement locking the shuttle in the first position, flow of at least air to the user is permitted from the inhalation port until the predetermined PIP is reached in the breathing zone, wherein at the predetermined PIP in the breathing zone, a force on the plunger exceeds the locking force of the detent arrangement thereby causing the shuttle to be displaced from the first position to the second position in which the user is permitted to exhale via the exhalation port, and wherein, further in use, negative pressure generated in the breathing zone by inhalation of the user causes the plunger to displace the shuttle from the second position to the first position until the detent arrangement locks the shuttle to the first position.
20. The apparatus as claimed in claim 19, wherein the detent arrangement is a ball detent arrangement comprising a resiliently biased ball which is engageable with a suitable slot defined by the shuttle thereby to lock the shuttle in the first position.
21. The apparatus as claimed in either claim 18 or 19, wherein the body defines a channel which intersects the inhalation and exhalation ports and terminates adjacent the user interface device port, wherein the shuttle is receivable in and slidably displaceable within the channel.
22. The apparatus as claimed in claim 21, wherein the body defines a detent arrangement chamber which houses the detent arrangement, wherein the detent arrangement chamber intersects the channel.
23. The apparatus as claimed in any one of claims 19 to 22, wherein the detent arrangement is in the form of a ball detent comprising a ball and a resilient biasing member to urge the ball resiliently against the shuttle.
24. The apparatus as claimed in claim 19 when dependent on claim 2, wherein the PEEP valve is in flow communication with the exhalation port of the SAV, wherein the PEEP valve only permits free flow of exhaled respiratory gas above the 25 predetermined PEEP pressure.
25. The apparatus as claimed in any one of the preceding claims, wherein the user interface device is a mask, wherein the SAV is operatively attached to the mask via the user interface device port.
26. The apparatus as claimed in any one of the preceding claims, wherein the apparatus comprises a power supply unit.
27. The apparatus as claimed in any one of the preceding claims, wherein the apparatus is portable, wherein some components thereof are housed in a suitable housing.
28. The apparatus as claimed in any one of the preceding claims, wherein the apparatus comprises a lightly loaded check valve to atmosphere in a flow path to the SAV which opens if pressure in the flow path reduces below atmospheric pressure.
29. The apparatus as claimed in any one of the preceding claims, wherein the apparatus comprises a suitable filter to filter air to the user.
30. The apparatus as claimed in claim 24, wherein the apparatus comprises a suitable filter or scrubber in flow communication downstream from the PEEP valve.
31. The apparatus as claimed in any one of the preceding claims, wherein the PLV is located downstream from the blower, in a flow path defined by a suitable conduit, wherein the FLV is located downstream from the PLV, in a flow path defined by a suitable conduit, and wherein the SAV is located downstream from the FLV, in a flow path defined by a suitable conduit.
32. The apparatus as claimed in any one of the preceding claims, wherein the blower is configured to intermittently operate.
33. A shuttle aspiration valve for a respiratory apparatus, wherein the shuttle aspiration valve comprises: a body comprising: a user interface device port connectable to a user interface device; an inhalation port connectable to and in flow communication with a supply of at least air at a positive pressure; an exhalation port; and a common port in flow communication with the user interface device port communicable with the inhalation port and the exhalation port; and a respiration control arrangement comprising: a shuttle displaceable within the body between a first position in which the SAV is operated to an inhalation configuration in which the shuttle permits flow communication between the inhalation port and the common port and seals the exhalation port, and a second position in which the SAV is operated to an exhalation configuration wherein the shuttle permits flow communication between the exhalation port and the common port and seals the inhalation port; a plunger operatively connected to the shuttle and disposed adjacent the user interface device port, wherein the plunger is configured to displace the shuttle between the first and second positions, in use; and a detent arrangement configured to engage the shuttle and releasably lock the same in the first position with a predetermined locking force, wherein, in use, with the detent arrangement locking the shuttle in the first position, flow of at least air to the user is permitted from the inhalation port until a predetermined PIP is reached in the breathing zone, wherein at the predetermined PIP in the breathing zone, a force on the plunger exceeds the locking force of the detent arrangement thereby causing the shuttle to be displaced from the first position to the second position in which the user is permitted to exhale via the exhalation port, and wherein, further in use, negative pressure generated in the breathing zone by inhalation of the user causes the plunger to displace the shuttle from the second position to the first position until the detent arrangement locks the shuttle to the first position.
34. A pressure limiting valve (PLV), wherein the PLV comprises: a housing defining an interior and comprising: a first chamber having an inlet port in flow communication with a source of at least air with a positive pressure; and an outlet port to output pressure regulated air therefrom; and a second chamber in controlled flow communication with the first chamber, wherein the second chamber comprises a wastegate; and a pressure regulating arrangement comprising: a suitable displacement member operatively located in the first chamber, wherein the displacement member is resiliently displaceable in response to the predetermined pressure threshold being reached or exceeded; and a suitable plug operatively connected to the displacement member, wherein the plug is located in the first chamber of the housing and is configured to control flow of air from the first chamber to the second chamber in response to displacement of the displacement member, wherein the air received in the second chamber is vented via the wastegate.
35. A flow limiting valve (FLV) for a respiratory apparatus, wherein the FLV comprises: a housing defining an interior and comprising: a first chamber having an inlet port in flow communication with a source of at least air at a regulated positive pressure; and a second chamber in controlled flow communication with the first chamber, wherein the second chamber comprises an outlet port; and a flow regulating arrangement comprising: a suitable displacement member operatively located in the first chamber, wherein the displacement member is resiliently displaceable in proportion to a pressure of the air received from the source of at least air at a regulated positive pressure; and a suitable airfoil operatively connected to the displacement member, wherein the airfoil is located in the second chamber of the housing and is configured to control flow of air from the first chamber to the second chamber in response to displacement of the displacement member, wherein the air received in the second chamber exits the valve via the outlet port.
36. A mask device for a respiratory assistance apparatus comprising: a mask body configured to be attachable to a face of a wearer to define an enclosed breathing zone which encloses at least a mouth and nose of the wearer, wherein the mask body comprises an inlet port; and a SAV as claimed in claim 33 operatively attached to the inlet port of the mask via the user interface device port.