GB2602500A - Respiratory device - Google Patents

Abstract

A respiratory device 20 for providing a positive end expiratory pressure (PEEP) for a user, comprising a conduit 24 connecting an inlet 21, for receiving respiratory gases, and an outlet 22, through which respiratory gases can exit the device. A blocking member 24 is arranged within the conduit, with a biasing means 27 arranged to bias the blocking member into a blocking position, preventing gases flowing through the conduit. Wherein the blocking member is arranged to translate away from the blocking position when an air pressure force acting on the blocking member overcomes the biasing force, thereby permitting respiratory gases to flow through and exit the device. Stabilisation means serve to fix the rotation and/or tilt angle of the blocking member. The stabilisation means may comprise a protrusion 25 on the blocking member, the protrusion extending into a groove 26 in a wall of the conduit. Alternatively, or in addition, the stabilisation means may comprise a spigot 27 protruding from the blocking member, the spigot being received within a spigot tube 28. The respiratory device is particularly suited for use as a PEEP valve or lung trainer.

Description

RESPIRATORY DEVICE

Technical Field of the Invention

The invention relates to respiratory devices for providing positive end respiratory pressure (PEEP) for a user or patient.

Background to the Invention

Positive end respiratory pressure (PEEP) is a positive pressure that remains in a patient's airways at the end of the respiratory cycle. It is a variable that can be controlled by mechanical ventilators to mitigate the risk of lung collapse at the end of a patient's breath. In mechanical ventilation, PEEP can be applied through the use of respiratory PEEP valves. These valves need to have excellent reliability owing to their medical use with patients often in critical conditions. This necessitates precision manufacturing that can make PEEP valves relatively expensive to produce, despite the requirement in certain applications for PEEP valves to be disposable.

Lung trainers also exploit PEEP to assist with the therapy of certain lung conditions such as chronic obstructive pulmonary disease and asthma. In addition, lung trainers now have an established market in sports and other recreational activities for improving endurance performance. These mechanical devices comprise an inlet for receiving respiratory gases from a user and an outlet through which respiratory gases are released into the environment. The inlet and outlet are connected by a conduit within which a piston biased to block the flow of gases can be translated to an open position by an air pressure force. The air pressure force is generated as a result of a user breathing through the device. The threshold air pressure force to cause translation of the piston is typically set by a spring biasing the piston towards a position in which air flow is blocked, thereby enabling a plurality of different resistance levels to be set. Owing to their primarily therapeutic and recreational use, lung trainers can be manufactured more economically and to lower precision than is necessary for medical PEEP valves.

Whilst the reduced manufacturing costs of lung trainers is advantageous, the potential reduction in precision and reliability can be problematic. For instance, unwanted piston motion during use can compromise the ability of a lung trainer to maintain a reliable PEEP/resistance level. In particular, when a user breathes through a lung trainer the resultant air pressure force acting on the piston can cause vibrational effects that compromise the seal of the piston with other parts of the lung trainer. This affects the performance of lung trainers when their pistons are in both the open and blocking positions, and renders them inappropriate for certain medical applications.

Therefore it is an aim of the present invention to provide a respiratory device for use as a PEEP valve or lung trainer that mitigates these issues.

Summary of the Invention

According to a first aspect of the invention there is provided a respiratory device for providing a positive end expiratory pressure (PEEP) for a user, comprising an inlet part for receiving respiratory gases from a user and an outlet part through which respiratory gases can exit the device, a conduit connecting the inlet part to the outlet part, a blocking member arranged within the conduit, and a biasing means arranged to apply a biasing force to urge the blocking member into a blocking position in which respiratory gases are prevented from flowing through the conduit from the inlet to the outlet part, wherein the blocking member is further arranged to translate away from the blocking position along an axis of translation when an air pressure force acting on the blocking member overcomes the biasing force, thereby permitting respiratory gases to flow through and exit from the device, wherein the respiratory device further comprises stabilisation means for fixing the rotation and/or tilt angle of the blocking member relative to the axis of translation, such that the blocking member is stabilised in angle when the respiratory device is in use. In prior art respiratory devices comprising blocking members or pistons that can undergo translation, air pressures acting on the blocking member can cause vibrational effects owing to the freedom of the blocking member to rotate or tilt. This can be as a result of manufacturing tolerances, or uneven loading of a bias force, combined with a lack of rotational stability of the blocking member. This can compromise the ability of the blocking member to reliably seal with other parts or facets of the respiratory device during use. Resultantly respiratory gases can leak past the blocking member leading to unreliable PEEP or resistance conditions. By providing stabilising means for fixing the rotation and/or tilt of the blocking member, leakage is minimised and the air pressure force can only cause translation of the blocking member in the intended direction against which the blocking member is biased. This leads to more accurate and reliable PEEP conditions throughout translation of the blocking member that may also enable lower cost lung trainer designs to be suitable for use as medical PEEP valves in certain medical applications.

According to a second aspect of the invention, there is provided a PEEP valve for a ventilator comprising the respiratory device of the first aspect of the invention.

According to a third aspect of the invention, there is provided a lung trainer comprising the respiratory device of the first aspect of the invention.

The respiratory device comprises an inlet part for receiving respiratory gases from a user or patient. The inlet part may be a mouthpiece into which a user breathes directly, such as is provided with most lung trainers. Alternatively the inlet part may comprise a port connectable directly or via intermediary hoses to other respiratory apparatuses such as mechanical ventilators. The inlet part, regardless of embodiment, is intended to be the part of the device that receives respiratory gases.

The inlet part and outlet part of the respiratory device are connected by a conduit. Respiratory gases can only enter via the inlet part, and exit the device via the outlet part. The conduit therefore is a sealed connecting part providing passageway for respiratory gases. The conduit may have any suitable form or shape provided that it maintains such a passageway, and permits functioning of the blocking member. For instance, the conduit may be a cylindrical tube like structure housing a circular cross section piston member.

Additionally the respiratory device comprises an outlet part through which respiratory gases can exit the device. The outlet part may be an opening or vent that permits respiratory gases, having passed through the device, to exit to the exterior of the device (i.e. into the ambient environment). Alternatively the outlet part may be a port connectable to subsequent respiratory apparatuses or hoses. It is intended that respiratory gases flow from the inlet to the outlet when the respiratory device is in use and operated appropriately.

A blocking member is arranged within the conduit with a biasing means arranged to urge the blocking member into a blocking position in which respiratory gases are prevented from flowing through the conduit. In such a blocking position, respiratory gases entering the inlet part cannot exit from the outlet part -airflow is prevented. The blocking member therefore has dimensions and shape such that it can block the passageway provided by the conduit. The blocking member may therefore conform to the interior dimensions of the conduit, for instance a disc shaped blocking member may be provided inside a cylindrical tube shaped conduit. In other embodiments the conduit may provide a passageway wider than a port of the inlet part, and the blocking member in these embodiments may be dimensioned to seal over the port of the inlet part, but may not necessarily conform to the interior surface of the conduit itself. The biasing means may be a resilient means such as a spring or deformable material that urges against the blocking member forcing it into the blocking position. The blocking position is that in which airflow from the inlet part to output part is prevented. This may be achieved by translating the blocking member to seal over a port in the inlet part, or may be achieved by translating the blocking member to seal over an opening defined by a transversal wall within the conduit, for instance. Alternatively the blocking position may be a position of the blocking member in which airflow cannot reach a groove or channel in the interior surface of the conduit. It is intended that the blocking member can be translated to the blocking position by the biasing means and not rotated or pivoted into the blocking position.

The blocking member can be translated away from the blocking position by the action of an air pressure force overcoming the biasing force exerted by the biasing means. When respiratory gases build up in the inlet part (for instance when a patient breathes into the inlet), an increase in air pressure occurs between the inlet and the blocking member in the blocking position. The air pressure acts on the blocking member as an air pressure force. Ambient air pressure at the outlet part also acts on the blocking member opposing the air pressure force. Furthermore the biasing means creates a biasing force opposing the air pressure force. However, at a particular threshold air pressure, the air pressure force will exceed the ambient and biasing forces and cause the blocking member to translate away from the blocking position. This then permits respiratory gases to flow from the inlet part to the outlet part and out of the respiratory device. As the respiratory gases flow out of the device, the air pressure in the inlet part will decrease, such that the air pressure force no longer exceeds the biasing force. Resultantly the blocking member will return to the blocking position, until a sufficient air pressure can be generated in the inlet part to repeat the translation. It is intended that the blocking member can be translated away from the blocking position by the air pressure force and not rotated or pivoted out of the blocking position.

The stabilisation means is provided to fix the rotation and/or tilt angle of the blocking member. In prior art devices the blocking members have been observed to tilt relative to the axis of translation. This means the blocking members, often conformal to the interior surface of a conduit, no longer provide a matching fit to the interior surface. As a result, respiratory gases can flow past the blocking member, even when in the blocking position. Furthermore, the blocking members can shift in angle about the axis of translation. This can make minor manufacturing tolerances more substantial, as a blocking member having been manufactured to precisely fit a conduit in a particular orientation, does not provide such a reliable fitment when tilted or rotated. This leads again to gases leaking past the blocking member in use. These angular effects can be even more dramatic when combined with uneven application of biasing force (for instance from a spring or other biasing member that is not concentric to the piston member) encouraging angular motion. Combined, the two angular degrees of freedom can lead to a vibrational effect when the respiratory device is in use, which is realised in fluctuation of the PEEP value/resistance level. The inventors have shown that stabilising the blocking member in angle when in the blocking position and during translation away from the blocking position, yields reliable PEEP values and resistance levels by mitigating unwanted respiratory gas leakage

S

through the device. As the inventors have shown, this can be achieved without compromising the ability to translate the blocking member towards and away from the blocking position.

Some embodiments of the respiratory device further comprises a transversal wall extending around the interior of the conduit and defining a through-hole, the blocking member being translatable along the through-hole from the blocking position. The transversal wall protrudes inwards from the interior surface of the conduit to define a relatively narrower aperture than the conduit itself. The transversal wall provides a guide for the blocking member when being translated from the blocking position. The transversal wall may encircle an inlet port of the inlet end, or may be arranged part way along the conduit.

Preferably at least one vent channel is provided extending along the transversal wall, such that when the blocking member is translated away from the blocking position respiratory gases can flow through the vent channel from the inlet part to the outlet part. This allows respiratory gases to flow from the inlet part through the channel and thereby around the blocking member, when the blocking member is translated away from the blocking position. The channel extends towards the outlet part, but may only extend partially towards the inlet part, such that the blocking member must translate a set distance along the transversal wall and the translation axis before the channel is reached and gas flow is enabled. This provides further assurance that respiratory gases cannot flow past the blocking member when in or proximate the blocking position. Alternatively the channel may extend entirely along the length of the transversal wall in embodiments where the blocking member seals against a port of the inlet part. In these embodiments as soon as the blocking member is moved away from the blocking position, respiratory gases are enabled to flow through the channel, around the blocking member, and out of the outlet part. This ensures gas flow is enabled immediately after a set air pressure threshold in the inlet part is reached. Preferably there are a plurality of vent channels thereby enabling respiratory gases to flow more readily from the inlet part to the outlet part, when the blocking member is translated away from the blocking position.

In preferred embodiments the stabilisation means comprises at least one groove extending along the transversal wall parallel to the axis of translation and having received therein at least one cooperating protrusion from the blocking member, such that the rotation of the blocking member about the axis of translation is fixed. The protrusion/s from the blocking member mate with corresponding grooves in the transversal wall to prevent rotation of the blocking member about the axis of translation. This can be achieved with a single protrusion and groove, but more preferably a plurality of protrusions and grooves are provided for greater stability. The protrusions can freely slide within their respective grooves so as not to hinder the translation of the blocking member when the respiratory device is in use. The protrusions and grooves may have any cooperating shape, however a groove with a curved cross section, and a corresponding protrusion, are less prone to snagging as the blocking member is translated In some embodiments comprising the transversal wall, the through-hole has a substantially circular cross section and the blocking member has a substantially circular cross section. A circular blocking member is less prone to stress concentration causing by biasing and air pressure forces when in use, owing to the lack of sharp corners or edges as may be present in other designs of blocking member. Additionally, a circular blocking member and corresponding through-hole is easier to manufacture. Elliptical blocking members and corresponding through hole designs may be used in other embodiments, owing also to the lack of sharp corners for stress concentration and because such designs also contribute to preventing rotation of the blocking member about the axis of translation.

The respiratory device of any preceding claim, wherein the stabilisation means comprises a spigot protruding from the blocking member and extending parallel the axis of translation, the spigot being received within a spigot tube arranged within the conduit to constrain movement of the spigot to be parallel the axis of translation. This fixes the tilt angle of the blocking member relative to the axis of rotation. The spigot is elongate and can have any suitable cross sectional shape. The spigot tube defines a spigot aperture having a cooperating cross section. When the blocking member is induced to tilt relative to the axis of translation, the spigot also is induced to tilt. However the spigot is constrained from tilting by virtue of being received within the spigot tube, thereby also constraining the tilting of the blocking member. For simplicity of manufacture the spigot and spigot tube may be arranged concentric to the blocking member.

In some embodiments the blocking member comprises a piston plate and silicone gasket. The piston plate receives the biasing force from the biasing means. The silicone gasket is arranged adjacent the piston plate and seals against the conduit when the blocking member is in the blocking position. The gasket fills the space between the piston plate and conduit to prevent any leakage of respiratory gases when compressed by the biasing force when in the blocking position. The gasket therefore fills any irregularities in the sealing surfaces of components that may arise during manufacture. The silicone gasket is convenient to manufacture from cutting of sheet silicone.

Preferably the biasing means comprising a spring arranged between the blocking member and outlet part. The spring may be configured to have a stiffness for achieving a particular PEEP. The spring may be formed from a suitable material that can tolerate use in a respiratory environment -for instance a material that can tolerate humid environments and not corrode or lose stiffness. In other embodiments the conduit may be formed from two threaded parts such that the length of the conduit can be manually adjusted to adjust the compression and therefore tension of the spring. Such embodiments allow for adjusting of the PEEP value of the respiratory device by a user.

Brief Description of the Drawings

Embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure la illustrates in cross sectional view an embodiment of a prior art respiratory valve prior to use; Figure lb illustrates in cross sectional view an embodiment of a prior art respiratory valve in use; Figure 2a illustrates in cross sectional view an embodiment of a respiratory valve according to the invention prior to use; Figure 2b illustrates in cross sectional view an embodiment of a respiratory valve according to the invention in use; Figure 3a illustrates in exploded view an embodiment of a lung trainer comprising the respiratory valve according to the invention; and Figure 3b illustrates in cross sectional view the inlet part of the embodiment of Figure 3a. Detailed Description Figure 1A provides an illustration in cross sectional view of an embodiment of a prior art respiratory valve 1 prior to use. The respiratory device 1 comprises an inlet part 2 and an outlet part 3 connected by a conduit 4, all of which have cylindrical cross sections. The inlet part 2 and outlet part 3 are of smaller diameter than the conduit 4 and are connected to opposite ends of the conduit 4. The inlet part 2 defines an aperture through which respiratory gases can flow into the conduit 4. The outlet part 3 defines an aperture through with respiratory gases can flow out of the conduit 4. Within the conduit 4 a blocking members is provided. The blocking members is arranged adjacent the inlet part 2 and is sized to block the aperture defined by the inlet part 2. The blocking members is shown in a blocking position in which the flow of gases from the inlet part 2 to the outlet part 3 is prevented. A biasing means in the form of a spring 6 is shown within the conduit 4 between the blocking members and outlet part 3. The spring 6 urges against the blocking members to retain the blocking members in the blocking position.

Figure 1B provides an illustration in cross sectional view of the prior art respiratory valve 1 in-use. Respiratory gases have been provided through inlet part 2 resulting in an increase in air pressure within the inlet part 2. This has generated an air pressure force acting on the blocking members that opposes the biasing force applied by spring 6. The air pressure force is not sufficient to completely overcome the biasing force, and as such blocking member 5 has failed to translate away from the blocking position. However owing to lack of angular stability of the blocking member 5, blocking member 5 has tilted partially away from the blocking position. This has created an undesirable gap through which respiratory gases can leak into the conduit 4 and out of the outlet part 3. Therefore the respiratory device is unable to maintain a reliable PEEP for a user.

Figure 2A provides an illustration in cross sectional view of an embodiment of a respiratory valve 20 according to the invention. The respiratory device 20 comprises an inlet part 21 and an outlet part 22 connected by a conduit 23, all of which have cylindrical cross sections. The inlet part 21 and outlet part 22 are of smaller diameter than the conduit 23 and are connected to opposite ends of the conduit 23. The inlet part 21, outlet part 22, and conduit 23 are formed from polycarbonate and may be integrally formed with each other (for instance from injection moulding or CNC manufacture) or may comprise separate parts attached using adhesive. The inlet part 22 defines an aperture through which respiratory gases can flow into the conduit 23. The outlet part 22 also defines an aperture through with respiratory gases can flow out of the conduit 23. Within the conduit 23 a blocking member 24 is provided. The blocking member 24 is arranged adjacent the inlet part 21 and is sized to block the aperture defined by the inlet part 21. The blocking member 24 is shown in a blocking position in which the flow of gases from the inlet part 21 to the outlet part 22 is prevented. The blocking member 24 comprises a piston plate 24a formed from plastic and a gasket disc 24b formed from silicone. The piston plate 24a and gasket 24b are attached with adhesive. The gasket 24b seals against the inlet part 21 when in the blocking position. The piston plate 24a is shown with a protrusion 25 at its circumference. The protrusion 25 extends into a groove 26 in the conduit 23. The protrusion 25 prevents rotation of the blocking member 24 about an axis of translation T of the blocking member 24. The blocking member 24 also comprises an elongate cylindrical spigot 27 extending from the piston plate 24a of the blocking member 24 towards the inlet part 21. The spigot 27 is integrally formed with the piston plate 24a and concentric thereto. The spigot 27 passes through the silicone gasket 24b and is received snugly into a spigot tube 28 arranged concentrically to the aperture in the inlet part 21. The spigot tube 28 and spigot 27 are permitted to slide relative each other during translation of the blocking member 24 in use. The spigot tube 28 is fixed in position by one or more fixing legs (not visible) connecting the spigot tube 28 to the conduit 23 or inlet part 21. The spigot 27 and spigot tube 28 have a diameter substantially smaller than the aperture defined by the inlet part 21 for flow of respiratory gases. As such the spigot 27 and spigot tube 28 can be considered as providing minimal restriction to the flow of respiratory gases when the respiratory device is in use. The spigot 27 and spigot tube 28 prevent tilting of the blocking member 24 relative to the axis of translation T. A biasing means in the form of a spring 29 is shown within the conduit 23 between the blocking member 24 and outlet part 22. The spring 29 urges against the piston plate 24a of the blocking member 24 to retain the blocking member 24 in the blocking position. The spring 29 is formed of spring steel. The outer diameter of the respiratory valve 20 is approximately 45mm. The inlet part 21 and outlet part 22 have a diameter of approximately 25mm. The piston plate 24a and silicone gasket 24b have a diameter of approximately 30mm. The silicone gasket 24b has a thickness of approximately 1mm. The protrusion 25 and groove 26 have a length and depth respectively of approximately 2mm. The spigot 27 extends from the piston plate 24a a length of approximately 10mm and has a diameter of 5mm.

Figure 2B provides an illustration in cross sectional view of the respiratory valve 20 of Figure 2A in-use. Respiratory gases have been provided through inlet part 21 resulting in an increase in air pressure within the inlet part 21. This has generated an air pressure force acting on the blocking member 24 that opposes the biasing force applied by spring 29. The air pressure force has overcome the biasing force resulting in blocking member 24 translating along the axis of translation T away from the blocking position. The blocker member 24 is stabilised in tilt angle relative the axis of translation T owing to spigot 27 being prevented from rotating by spigot tube 28. The blocking member 24 is stabilised in rotation angle about axis of translation T owing to protrusion 25 being retained by groove 26. Overall the blocking member 24 is free to translate along the axis of translation T because protrusion 25 can slide parallel the axis T in groove 26, and spigot 27 can slide parallel the axis T through spigot tube 28. However any angular rotation about or relative to the axis T is prevented. This ensures a more reliable transition of the blocking member 24 towards and away from the blocking position, and a more reliable seal of the blocking member 24 with the inlet part 21 and conduit 23 when in the blocking position. This ensures the respiratory device 20 can more reliably provide a predetermined and stable PEEP.

Figure 3A illustrates in exploded view an embodiment of a lung trainer 30 comprising a respiratory valve according to the invention. The lung trainer 30 comprises an inlet part 31 through which respiratory gases are received. The inlet part 31 comprises a cylindrical tube acting as a mouthpiece into which a user can exhale. The inlet part 31 has a diameter of approximately 25mm and length of 15mm and is formed from polycarbonate. A plurality of smaller holes 31a are provided within the inlet part 31 through which respiratory gases can flow into the lung trainer 30. The holes 31a each have a diameter of 5mm. The inlet part 31 is attached to a first section 32a of a conduit 32. The section 32a has a diameter of approximately 40mm, length of approximately 30mm, and is formed of polycarbonate. The first section 32a is intended for attachment to a second section 32b of conduit 32 also formed from polycarbonate and having a diameter of approximately 40mm. The second section 32b of conduit 32 is substantially longer than the first section 32a in order to accommodate a spring 41. The second section 32b of conduit 32 is attached to an outlet part 33 which comprises a cylindrical tube of diameter approximately 25mm, of polycarbonate composition. When the two sections of the conduit 32a and 32h are attached, the inlet part 31 is in fluid connection with the outlet part 33. The two sections of the conduit 32a and 32b may be attached using adhesive or screw attachment. Within the first section 32a of the conduit there is provided a transversal wall 34. The transversal wall 34 defines a substantially cylindrical through-hole into which a blocking member 35 is received. The transversal wall 34 extends inwards approximately 5mm into the through-hole such that the through-hole has a diameter of approximately 30mm. The blocking member 35 has a circular cross section to cooperate with the through-hole. The blocking member 35 comprises a piston plate 35a of polycarbonate attached to a silicone gasket 35b with suitable adhesive. The silicone gasket 35b has a thickness of approximately 1mm. The piston plate 35a has a thickness of approximately 3mm. There are three protrusions 36 extending radially outwards from the circumference of the piston plate 35a by approximately 2mm, the protrusions 36 being spaced equally in angle around the piston plate 35a. The protrusions 36 have a smooth curved shape and are received into corresponding grooves 37 of depth 2mm in the transversal wall 34. During use the protrusions 36 can slide along the grooves 37 in the axis of translation T' of the blocking member 35, but cannot rotationally exit the grooves 37. This stabilises the blocking member 35 in rotation angle about the axis of translation. Protruding approximately lOmm from the piston plate 35a of the blocking member 35 in the direction of the inlet part 31 is a spigot 38. The spigot 38 is integrally formed with the piston plate 35a and is concentric thereto. It has a circular cross section of 5mm and is snugly received into a spigot tube 39 of the first section 32a of the conduit 32. The spigot 38 and spigot tube 39 are arranged to be on the axis of translation of the blocking member 35. Also provided in the transversal wall 34 are three vent channels 40 that resemble the grooves 37. The vent channels 40 extend the length of the transversal wall 34 and have a depth of 2mm. They provide a route for respiratory gases to flow from the inlet part 31, around the periphery of the blocking element 35, through the conduit 32a and 32b, and out of the outlet part 33, when the blocking member 35 is translated along the through hole of the transversal wall 34 and away from the blocking position. As a result, the blocking position for the blocking member 35 is only achieved when the blocking member 35 is in abutment with the inlet part 31 so as to completely block and seal the inlet for respiratory gases. A spring 41 is shown arranged within the second section 32b of the conduit, between the piston plate 35a of blocking member 35 and the outlet part 33. The spring 41 urges the blocking member 35 into the blocking position with a biasing force. The spring 41 is formed from spring steel.

Figure 3B provides an illustration in cross sectional view of the inlet part 31 and first section of conduit 32a from Figure 3A, observed along the axis of translation T. The outer circumference of the first section of conduit 32a is shown, with inner boundary of transversal wall 34 visible as reducing the diameter of the conduit 32a. The transversal wall 34 comprises a plurality of equally spaced alternating grooves 37(a, b, c) and vent channels 40(a, b, c) around it's inner circumference. There are three grooves 37 and three vent channels 40. The circumference of the inlet part 31 is also shown as having a slightly smaller diameter than the transversal wall 34 boundary. At the centre of the inlet part 31 there are 6 inlet apertures 31. Central to the inlet apertures 31 is a spigot aperture 39 for receiving a spigot 38 of the blocking member 35.

During use a user exhales into the lung trainer 30 through the mouthpiece of the inlet part 31. Respiratory gases flow through the plurality of holes 31a but are prevented from flowing through the first part of the conduit 32a by the blocking member 35 which is sealing the holes 31a. As the user continues to exhale the air pressure within the inlet part 31 increases. This increases the air pressure force acting on the blocking member 35. Countering the air pressure force is the biasing force exerted by the spring 41. The blocking member 35 is stable up until the air pressure force exceeds the biasing force. This is because the protrusions 36 of the blocking member 35 prevent rotation of the blocking member 35, and the spigot 38 prevents any tilting or vibration of the blocking member 35. When the air pressure force exceeds this biasing force, the blocking member 35 begins to translate away from the blocking position along the axis of translation T'. This causes the holes 31a in the inlet part 31 to be opened and respiratory gases flow along the vent channels 40 and around the blocking member 35 past the first part 32a of the conduit and into the second part 32b. The respiratory gases flow past the spring 41 in the second part 32b of the conduit and out of the outlet part 33. The outlet part 33 may vent to atmosphere. During translation of the blocking member 35 the blocking member 35 is stable in angle owing to spigot 38 preventing any tilt relative to axis T', and the protrusions 36 and grooves 37 preventing any rotation about axis V. Owing to the flow of respiratory gases from inlet part 31 to outlet part 33, the air pressure in the inlet part 31 begins to decrease below the biasing force exerted on blocking member 35 by spring 41. This causes the blocking member 35 to begin to translate back to the blocking position in abutment with the inlet part 31. The holes 31a in the inlet part are now sealed again and a PEEP is established. The process can be repeated for successive exhalations in the breathing cycle of the user.

In embodiments where the first part 32a and the second part 32b of the conduit 32 are attached using threaded means, the user can adjust the spring 41 tension by screwing the two parts together or unscrewing the two parts together. This compresses of decompresses the spring 41. By adjusting the tension of the spring 41, the PEEP value for the lung trainer 30 can be varied. Furthermore, whilst the embodiment was described as a lung trainer 30, the inlet 31 and outlet 33 may be configured to fit respiratory hoses or connections on a mechanical ventilator for operation as a PEEP valve. A single spigot 38 and spigot aperture 39 are shown in the embodiments described, but a plurality of such spigots 38 and apertures 39 may be present in other embodiments. Similarly the number of protrusions 36, grooves 37, and vent channels 40, are not intended to be limiting.

Claims (15)

1. CLAIMS1. A respiratory device for providing a positive end expiratory pressure (PEEP) for a user, comprising an inlet part for receiving respiratory gases from a user and an outlet part through which respiratory gases can exit the device, a conduit connecting the inlet part to the outlet part, a blocking member arranged within the conduit, and a biasing means arranged to apply a biasing force to urge the blocking member into a blocking position in which respiratory gases are prevented from flowing through the conduit from the inlet to the outlet part, wherein the blocking member is further arranged to translate away from the blocking position along an axis of translation when an air pressure force acting on the blocking member overcomes the biasing force, thereby permitting respiratory gases to flow through and exit the device, wherein the respiratory device further comprises stabilisation means for fixing the rotation and/or tilt angle of the blocking member relative to the axis of translation, such that the blocking member is stabilised in angle when the respiratory device is in use.
2. 2. The respiratory device of claim 1, further comprising a transversal wall extending around the interior of the conduit and defining a through-hole, the blocking member being translatable along the through-hole from the blocking position.
3. 3. The respiratory device of claim 2, further comprising at least one vent channel extending along the transversal wall, such that when the blocking member is translated away from the blocking position respiratory gases can flow through the vent channel from the inlet part to the outlet part.
4. 4. The respiratory device of claim 3, wherein the at least one vent channel extends only partially along the transversal wall.
5. S. The respiratory device of any one of claims 3-4, comprising a plurality of vent channels.
6. 6. The respiratory device of any one of claims 2-5, wherein the stabilisation means comprises at least one groove extending along the transversal wall parallel the axis of translation and having received therein at least one cooperating protrusion from the blocking member, such that the rotation of the blocking member about the axis of translation is fixed.
7. 7. The respiratory device of claim 6, wherein the stabilisation means comprises a plurality of grooves and protrusions.
8. 8. The respiratory device of any one of claims 2-7, wherein the through-hole has a substantially circular cross section and the blocking member has a substantially circular cross section.
9. 9. The respiratory device of any preceding claim, wherein the stabilisation means comprises a spigot protruding from the blocking member and extending parallel the axis of translation, the spigot being received within a spigot tube arranged within the conduit to constrain movement of the spigot to be parallel the axis of translation.
10. 10. The respiratory device of claim 9, wherein the spigot and spigot tube are concentric with the blocking member.
11. 11. The respiratory device of any preceding claim, wherein the blocking member comprises a piston plate and silicone gasket.
12. 12. The respiratory device of any preceding claim, wherein the biasing means comprising a spring arranged between the blocking member and outlet part.
13. 13. The respiratory device of claim 12, wherein the conduit is formed from two threaded parts, such that the length of the conduit can be manually adjusted to adjust the tension of the spring.
14. 14. A PEEP valve for a ventilator comprising the respiratory device of any preceding claim.
15. 15. A lung trainer comprising the respiratory device of any one of claims 1-13.