This disclosure relates to two-way valves and in particular though not exclusively to valves suitable for use with breathing assistance equipment and patient ventilator systems.

Critically ill patients often require artificial ventilation to assist or replace spontaneous breathing. This can be provided manually or via a mechanical ventilation system. Mechanical ventilation is termed "invasive" if it involves any instrument penetrating the mouth or the skin. There are two main modes of mechanical ventilation: positive pressure ventilation, where air (or another gas mix) is pushed into the trachea, and negative pressure ventilation, where air is, in essence, sucked into the lungs, e.g. by exerting a sub-atmospheric pressure on the external chest wall.

A patient may need to be temporarily disconnected from a breathing circuit and ventilator for a number of reasons, for example: (i) to change the ventilator e.g. to a portable ventilator for intra- and inter-hospital transfers; (ii) to manually ventilate the patient e.g. with a Water’s circuit to improve oxygen saturations; (iii) to change the breathing circuit; (iv) to move or roll the patient.

There can be a number of problems associated with disconnecting a breathing circuit.

A first potential problem relates to staff safety. When a breathing circuit is disconnected, potentially infected aerosols of secretions and water within the breathing circuit can be released into the room (potentially under pressure) and attendant clinical staff or healthcare workers may be sprayed with these aerosols whilst temporarily disconnecting ventilated patients from their breathing circuit.

A second potential problem relates to patient safety. When a breathing circuit is opened to atmosphere, it becomes depressurized and the patient’s lungs lose positive end expiratory pressure (PEEP). PEEP is required during ventilation to prevent the collapse of alveoli in the patient’s lungs. If alveoli collapse, oxygen levels in the blood may drop and the collapsed alveoli may become more susceptible to infection. It can be difficult to re inflate the alveoli. In patients with severe lung disease, when a breathing circuit is disconnected, it is not uncommon for the oxygen saturations to drop precipitously to dangerous levels within seconds. Historically, the loss of PEEP during breathing circuit disconnection was mitigated by applying a clamp to the endotracheal tube prior to and during disconnection, but this practice may have contraindications. If a patient makes an inspiratory effort whilst a clamp is applied, the negative pressure generated can lead to life threatening complications.

It is an object of the invention to provide an improved method and apparatus for mitigating some or all of the above problems.

According to one aspect, the present invention provides a valve comprising: first, second and third ports; a bistable valve mechanism having (i) a first stable configuration in which the first port is in fluid communication with the second port and not the third port and (ii) a second stable configuration in which the first port is in fluid communication with the third port and not the second port; and an actuator configured to transition the bistable valve mechanism between the two stable configurations and prevent the valve mechanism from maintaining a stable intermediate position between the first and second stable configurations.

The valve may be particularly suited for use with for breathing assistance apparatus, breathing assistance equipment and/or patient ventilator systems. The first port may be configured for connection to a patient airway maintaining device. The second and third ports may be each configured for connection to a ventilator breathing circuit or breathing assistance device. The first port may have a 22 mm tapered outer diameter connector surface. The second and third ports may each have a 22 mm tapered internal diameter connector surface. The bistable valve mechanism may comprise a moveable valve core defining a ported chamber for establishing fluid communication paths between selected ones of the first, second and third ports in each of the first and second stable configurations. The valve core may be coupled to and drivable by the actuator via a spring loading mechanism. The actuator may be configured to move from a first position relative to the valve core up to a first release position to load the spring loading mechanism, and to trigger transition of the valve core from the first stable configuration to the second stable configuration by the spring loading mechanism upon reaching the first release position. The actuator may be configured to move from a second position relative to the valve core up to a second release position to load the spring loading mechanism, and to trigger transition of the valve core from the second stable configuration to the first stable configuration upon reaching the second release position. The actuator may comprise at least a first locking pin engaged with the moveable valve core to lock the valve core in the first stable configuration. The actuator may be configured to disengage the first locking pin from the valve core upon reaching the first release position. The actuator may comprise a second locking pin engaged with the moveable valve core to lock the valve core in the second stable configuration. The actuator may be configured to disengage the second locking pin from the valve core upon reaching the second release position. The valve core may comprise a valve core rotatable about a valve axis. The actuator may comprise a lever rotatable about the valve axis, the lever being coupled to the valve core by a torsion spring between the lever and an axially extending peg on the valve core. The valve may further comprise a cam drive element disposed adjacent the valve core. The cam drive element may comprise a first cam surface engaging the first locking pin and a step feature engageable by the actuator as it approaches the first release position to drive the first locking pin to disengagement from the valve core when the actuator reaches the first release position. The valve core may further include a first pin ramp surface within a channel extending between a first deep end and a first pin-receiving hole at a shallow end. The valve core may further include a second pin ramp surface within a channel extending between a second deep end and a second pin-receiving hole at a shallow end. The first and second pin-receiving holes respectively may be configured to block further motion of the valve core beyond the respective bistable positions. At least one of the first, second and third ports may comprise a bore housing and an axially displaceable sealing member within the bore housing. The axially displaceable sealing member may have a face seal at one end for engagement with the valve core and a sliding seal for sliding engagement with the bore housing. The sealing member may be coupled to be driven from an extended position having said face seal engaged with the valve core when the actuator is in the first position to a retracted position when the actuator moves past the first release position. The sealing member may be coupled to be driven back to the extended position having said face seal engaged with the valve core as the valve core reaches the second stable configuration.

At least one of the first, second and third ports may comprise a bore housing and an axially displaceable sealing member within the bore housing having a face seal at one end for engagement with the valve core and a sliding seal for sliding engagement with the bore housing. The sealing member may be coupled: (i) to be driven from an extended position having said face seal engaged with the valve core when the actuator is in the first position to a retracted position when the actuator moves past the first release position, and (ii) to be driven back to the extended position having said face seal engaged with the valve core as the valve core reaches the second stable configuration. The sealing member may be coupled to be driven from an extended position having said face seal engaged with the valve core when the actuator is in the second position to the retracted position when the actuator moves past the second release position. The sealing member may be coupled to be driven back to the extended position having said face seal engaged with the valve core as the valve core reaches the first stable configuration. The face seal of the sealing member may be biased towards the valve core by a spring bias.

Each of the first, second and third ports may comprise a respective said bore housing and axially displaceable sealing member. The one or more axially displaceable sealing members may be driven by the actuator via a cam drive element disposed adjacent to the valve core.

The valve as described above may further include a ventilation apparatus couplable to at least one of the second and third ports. The valve as described above may further include an endotracheal tube couplable to the first port.

According to another aspect, the invention provides a method of configuring breathing assistance apparatus for a patient comprising: providing a valve having: first, second and third ports; a bistable valve mechanism having (i) a first stable configuration in which the first port is in fluid communication with the second port and not the third port and (ii) a second stable configuration in which the first port is in fluid communication with the third port and not the second port; and an actuator configured to transition the bistable valve mechanism between the two stable configurations and preventing the valve mechanism from maintaining a stable intermediate position between the first and second stable configurations, coupling a patient breathing tube to the first port, coupling a first ventilation device to the second port, while the valve is in the first stable configuration, coupling a second ventilation device to the third port; switching the valve to the second stable configuration; and disconnecting the first ventilation device from the second port.

Embodiments of the present invention will now be described by way of example and with reference to the accompanying drawings in which:

Figure 1 shows a schematic diagram of a three-port connector in use with patient breathing assistance apparatus; Figure 2a shows a perspective view of a three-port bistable valve for use with patient breathing assistance apparatus;

Figure 2b shows a top view of the three-port bistable valve of figure 2a;

Figure 2c shows a bottom view of the three-port bistable valve of figure 2a;

Figure 3a shows a perspective view of the bistable valve of figure 2a in a first stable configuration and figure 3b shows a perspective view of the bistable valve of figure 2a in a second stable configuration;

Figure 4a is a perspective view, from the side and above, of a rotatable valve core element of the bistable valve of figure 2a;

Figure 4b is a perspective view, from the side and above, of a sectioned rotatable valve core element of the bistable valve of figure 2a;

Figure 4c is a top view of the cross-section of the rotatable valve core element of figure 4b;

Figure 5 is a partial cross-sectional schematic top view of the valve of figure 2a useful in illustrating features of the bistable mechanism;

Figures 6a and 6b are schematic cross-sectional top views of the valve of figure 2a respectively in first and second bistable configurations;

Figures 7a and 7b are schematic cross-sectional views of the valve of figure 2a illustrating respectively the first configuration and a transition towards the second configuration;

Figure 8a is a perspective schematic view of the valve of figure 2a illustrating various sealing features;

Figure 8b is a partial cross-sectional side view of sealing features in figure 8a;

Figure 9 is a perspective view of components of the valve in figure 8a with the body and top cover removed, revealing operation of those components;

Figure 10 is a perspective schematic view of components of the sealing features of figures 8a and 8b;

Figures 11a to 11c show plan views of the sealing features of figure 10 during various stages of operation.

Throughout the present specification, the descriptors relating to relative orientation and position, such as "top", "bottom", "horizontal", "vertical", "left", "right", "up", "down”, "front", "back", as well as any adjective and adverb derivatives thereof, are used in the sense of the orientation of a valve as presented in the drawings. However, such descriptors are not intended to be in anyway limiting to an intended use of the described or claimed invention. The expression 'clockwise' and 'anticlockwise' are used herein in the sense of directionality as viewed from above the valve, for the purpose of illustration and explanation of specific embodiments as illustrated, and are not intended to limit to those specific embodiments.

Figure 1 illustrates practical use of a patient ventilator system. As seen in figure 1 a, patient 1 is provided with a breathing tube such as an endotracheal tube 2 placed through the mouth into the trachea to deliver oxygen and/or other gases to the lungs. Although the invention is described herein in connection with an endotracheal tube 2, other forms of breathing tube such as a tracheostomy tube can be applicable to the invention. A closed suction device 3 connects the patient to a ventilator breathing circuit 4. In circumstances as discussed above, it can be desirable to facilitate connection of the patient 1 to an alternative ventilation device, such as ventilation bag 6 (figures 1c and 1d). This can be achieved using a T-shaped valve 5 as seen in figure 1b which has first branch 11 connected to the patient breathing tube 2 (via the suction device 3), a second branch 12 connected to the ventilator breathing circuit 4 and a third branch 13 suitable for connecting to a further ventilation device. In figure 1b, the T-shaped valve 5 has a valve mechanism rotated to a first configuration in which the first branch 11 is fluidly coupled to the second branch 12 by way of a first fluid passage and in which the third branch 13 is isolated from the first fluid passage between the first branch 11 and the second branch 12.

As seen in figure 1c, an alternative ventilation device 6 is coupled to the third branch 13 while the valve mechanism remains in the first configuration coupling the first branch 11 and the second branch 12.

As seen in figure 1 d, the valve mechanism is then rotated to a second configuration in which the first branch 11 is fluidly coupled to the third branch 13 by way of a second fluid passage and in which the second branch 12 is isolated from the second fluid passage between the first branch and 11 and the third branch 13. In this configuration, the ventilator breathing circuit 4 is then disconnected as seen in figure 1d. The disconnection occurs after the patient's airway has been connected to the third branch 13 of the T-shaped valve and thus to the alternative ventilation device 6 and isolated from the ventilator breathing circuit 4.

In one aspect, a valve suitable for implementation in the context of figures 1a - 1d may have a mechanism in which the transition from the first configuration to the second configuration occurs quickly such that the valve does not remain, for any appreciable period of time, in an intermediate position between the first configuration and the second configuration. The expression "intermediate position" may encompass a position in which fluid communication between the first branch 11 and the second branch 12 and the third branch 13 might coexist simultaneously, or a position in which there is no fluid communication between any of the first branch 11, the second branch 12 and the third branch 13 (the fluid pathway between each of the first, second and third branches is blocked). The expression "any appreciable length of time" may be understood to be relative to the normal pressure changes within a patient's airway. In another aspect, a valve suitable for implementation in the context of figures 1a to 1d may have a mechanism in which a user cannot statically position or leave the valve in such an intermediate position.

With reference to figures 2a - 2c, a valve 20 suitable for the above purposes is described.

Valve 20 comprises a valve body 25 defining three ports 21 , 22, 23 extending radially outward from a cylindrical core portion 24 of the valve body 25 and a top cover 26 extending axially upward from the core portion 24 of the body 25. Rotatably mounted within the core portion 24 is a valve core 27 which is rotatable about a valve axis 28 and secured to the top cover 26 by a securing feature 29 such as a screw, rivet, pin or other device which allows rotation of the valve core 27 relative to the valve body 25 but prevents axial displacement of the valve core relative to the valve body along the valve axis 28. The valve core 27 has a flanged base portion 27b with flange 27a extending radially outwards to cover the cylindrical bottom end 24b of the core portion 24 and be in sliding engagement therewith as the valve core rotates within the body 25. The base portion 27b of the valve core 27 may also include a direction indicator 27d disposed thereon which can provide a visual indication of the state of rotation of the valve core 27 externally of the body 25. In the arrangement shown, the direction indicator 27d comprises a lug extending axially downwards from the base portion 27b and extending diametrically across the base portion 27b. The direction indicator 27d could alternatively be provided by way of an embossed surface or surface marking on the base portion 27b, for example.

As best seen with reference to figures 4a to 4c, the valve core 27 defines a ported chamber 40 having openings 41 , 42, 43 respectively at 0, 180 and 90 degree positions relative to one another about the valve axis 28. These openings 41 , 42, 43 are positioned to generally align with selected ones of the ports 21 , 22, 23 when in certain angular positions within the valve body 25, as will be discussed later. Also seen in figure 4a is a central shaft 44 extending axially upwards to engage with the securing feature 29 (figure 2a) when the valve core 27 is installed within the body 25. Also seen in figure 4a is a peg 45 extending in an axially upward direction parallel to the central shaft 44 and radially displaced therefrom. The peg 45 has a clockwise-facing surface 45c and an anticlockwise- facing surface 45a. Also provided on the valve core 27 is a pin ramp 46 comprising a channel or groove 46c cut into the circumferential surface 47 of the valve core. The channel 46c has a depth which varies as a function of circumferential position on the valve core 27 and terminates at a shallow end 46s with a locking pin hole 48 and terminates at a deep end 46d with a step surface 46e.

As seen in the cross-sectional views of the valve core 27 in figures 4b and 4c, a further pin ramp 56 comprising a channel or groove 56c is cut into the circumferential surface 47 of the valve core 27 and the channel 56c also has a depth which varies as a function of circumferential position on the valve core 27 and terminates at a shallow end 56s with a locking pin hole 58 and terminates at a deep end 56d with a step surface 56e.

Returning to figure 2a, the valve 20 further comprises an operating lever 30 which is rotatable about the valve axis 28 and extends radially outwards from the top cover 26. The operating lever 30 is rotatable about the valve axis 28 relative to both the valve core 27 and the top cover 26, but in the arrangement shown, motion of the operating lever 30 is limited to an arc of approximately 90 degrees. The operating lever 30 is coupled to the valve core 27 by way of a pair of torsion springs 31 , 32. The upper torsion spring 31 comprises a coil portion 31c around the valve axis 28, i.e. around the central shaft 44 (figure 4a) and a first arm 31a which bears against the clockwise-facing surface 45c of the peg 45 (just visible in figure 2a and fully visible in figure 4a), and a second arm 31 b (visible in figures 8a and 9) which is engaged with the operating lever 30, e.g. affixed to or disposed within the lever 30 on or below the clockwise facing surface 30c of the operating lever 30. The lower torsion spring 32 comprises a coil portion 32c around the valve axis 28, i.e. around the central shaft 44 (figure 4a) and a first arm 32a which bears against an anticlockwise-facing surface 45a of the peg 45, and a second arm 32b which is engaged with the operating lever 30, e.g. affixed to or disposed within the lever on or below the anticlockwise-facing surface 30a of the operating lever 30. In this way, the operating lever 30 is capable of applying both clockwise and anticlockwise rotational forces to the valve core 27 while still being capable of rotational motion relative to the valve core 27, for reasons to be explained hereinafter. With further reference to figures 2a to 2c, the top cover 26 of the valve 20 further includes pin mounts 33a and 33b respectively supporting a first locking pin 34a and a second locking pin 34b. As best seen in figure 5, each locking pin 34 is displaceable along its axis which corresponds to a radial direction relative to the valve axis 28. Each locking pin 34 comprises a shaft 50, a biasing spring 51 , a cam shoulder 52 and a spring adjustment screw mount 53. The cam shoulder 52 bears against the cam surface 61 of a cam ring 60 which extends around the valve core 27. The inner circumferential surface of the cam ring 60 is rotatable around, e.g. in sliding engagement with, an outer circumferential surface of a top portion 25t of the valve body 25. The cam ring 60 and the top portion 25t of the valve body 25 have elongate slots 80 therein (visible in figures 8a and 9) through which the shaft 50 of the respective locking pin 34 can pass to enter the respective locking pin hole 48, 58 when the locking pin 34 is spring-biased towards a radially inward position. As most clearly seen in figure 9, the cam shoulder 52 of the locking pin 34 may be guided into a radially outward position when the cam shoulder 52 rides up a raised cam surface 61a and the cam shoulder 52 of the locking pin may be guided into a radially inward position when the cam shoulder 52 rides down the cam surface to a low cam surface 61b. In this way, the locking pin shaft 50 may be released from engagement with a respective pin hole 48, 58 of the valve core 27 to facilitate rotation of the valve core 27 about its axis.

As seen in figures 6a and 6b, the cam ring 60 has a cam surface 61 which defines two raised cam surfaces 61a which are operable to lift the respective first and second locking pins 34a, 34b out of the respective locking pin holes 48, 58, and also two oppositely facing step features 62, 63. Clockwise-facing step feature 62 is engageable with an anticlockwise facing engagement surface 64 of the operating lever 30 (figure 6a), and anticlockwise facing step feature 63 is engageable with a clockwise-facing engagement surface 65 of the operating level 30 (figure 6b).

Figures 6a and 6b show the valve 20 respectively in the first and second configurations. In figure 6a, the valve 20 is in a first stable configuration in which the first port 21 is in fluid communication with the second port 22 via the ported chamber 40 of the valve core 27, because opening 43 is in alignment with the first port 21 and opening 42 is in alignment with second port 22. See the inset schematic of valve core 27 showing its relative rotation position. It can also be seen that the third port 23 is blocked or occluded by the valve core 27 and therefore not in fluid communication with either the first port or the second port. In figure 6b, the valve 20 is in a second stable configuration in which the first port 21 is in fluid communication with the third port 23 via the ported chamber 40 of the valve core 27, because opening 42 is in alignment with the first port 21 and opening 41 is in alignment with third port 23. Opening 43 is occluded. See the inset schematic of valve core 27 showing its relative rotation position. It can also be seen that the second port 22 is blocked or occluded by the valve core 27 and therefore not in fluid communication with either the first port or the third port. It can be understood from this diagram that in performing the quarter-turn anticlockwise rotation of the valve core 27 when transitioning from the configuration of figure 6a to the configuration of figure 6b, dependent on the diameters of the openings 41-43 and the ports 21-23, and on the circumference of the valve core 27 / cylindrical core portion 24, the valve 20 can be configured as either a "break-before-make" type valve where the fluid flow from one port pair is completely shut off before the other fluid pair communication starts to be made, or vice versa ("make-before-break").

In figure 6a, first locking pin 34a is engaged with the corresponding locking pin hole 48, preventing rotation of the valve core 27. The second locking pin 34b may be positioned over the deep end 56d of the channel 56c, near the step surface 56e, in the valve core 27. It will be understood that the valve core 27 cannot rotate until the first locking pin 34a is released from its locking pin hole 48.

In figure 6b, second locking pin 34b is engaged with the corresponding locking pin hole 58, preventing rotation of the valve core 27. The first locking pin 34a may be positioned over the deep end 46d of the channel 46c, near the step surface 46e, in the valve core 27. It will be understood that the valve core 27 cannot rotate until the second locking pin 34b is released from its locking pin hole 58.

Now also referring to figure 7a, the operation of the valve will now be described.

From the position of figures 6a and 7a, the operating lever 30 is moved in an anticlockwise direction through approximately 90 degrees. During the course of that movement, which occurs against the bias of the upper torsion spring 31 , the spring 31 stores considerable potential energy which strongly biases the valve core 27 for an anticlockwise rotation to follow the lever 30 motion. However, the first locking pin 34a prevents any such rotation of the valve core 27. However, just prior to the end of the 90 degree anticlockwise motion of the lever 30, the anticlockwise facing engagement surface 64 of the lever 30 engages the clockwise facing step feature 62 of the cam ring 60 causing the cam ring 60 to also rotate in an anticlockwise direction. The raised cam surface 61 drives the first locking pin 34a radially outward by engagement with the cam shoulder 52 thereby disengaging the locking pin shaft 50 from the locking pin hole 48 and thereby causing the valve core 27 to rapidly rotate in an anticlockwise direction under the accumulated spring bias in upper torsion spring 31. As the valve core 27 rotates, the second locking pin 34b travels up the pin ramp 56 to the shallow end 56s where it drops in to the locking pin hole 58. Further rotation of the valve core 27 is prevented by the second locking pin 34b dropping into the locking pin hole 58.

The sudden release of load on the operating lever 30 after the first locking pin 34a release is sufficient to ensure that the lever 30 reaches the fully anticlockwise position where it is stopped by the top cover 26.

A corresponding reverse movement of the operating lever 30 through approximately 90 degrees clockwise from the position of figure 6b uses the second (lower) torsion spring 32, the anticlockwise facing step feature 63 of the cam ring 60, and the second raised cam surface 61a to pre-load the second torsion spring 32 and then disengage the second locking pin 34b to trigger a corresponding reverse snap rotational movement of the valve core 27 from the stable position of figure 6b back to the stable position of figure 6a.

Thus, the valve 20 exemplifies a bistable valve mechanism having (i) a first stable configuration in which the first port 21 is in fluid communication with the second port 22 and not the third port 23 and (ii) a second stable configuration in which the first port 21 is in fluid communication with the third port 23 and not the second port 22. Furthermore, the operating lever 30 and associated features exemplifies an actuator which is configured to transition the bistable valve mechanism between the two stable configurations while preventing the valve mechanism from maintaining a stable intermediate position between the first and second stable configurations. The expression 'fluid communication' is intended to encompass arrangements in which air or other gas flow between the communicating ports 21 , 22, or 23 via the valve core 27 is sufficient in volume and sufficiently unimpeded to have little or no impact on the operation of a breathing circuit delivering gas to a patient's lungs via a breathing tube.

The valve 20 thereby further exemplifies a bistable valve mechanism which comprises a moveable valve core 27 defining a ported chamber 40 for establishing respective fluid communication paths between the first and second or third ports 21,22, 23 in the first and second stable configurations, where the valve core 27 is coupled to and drivable by the actuator lever 30 via a spring loading mechanism exemplified by the torsion springs 31, 32, peg 45 and cam ring 60. The raised cam surfaces 61a of the cam ring 60 and their action on the respective locking pins 34a, 34b respectively determine first and second release positions to trigger transition of the valve core 27 from the first stable configuration to the second stable configuration, using the spring loading mechanism, upon reaching the first release position, and vice versa.

The valve 20 described above can be configured to act as a patient breathing circuit connector and may be configured for particular use with standardised patent assisted breathing apparatus. This may include providing standard fittings on each of the first, second and third ports 21, 22, 23. For example, the first port 21 may be configured for connection to a patient airway maintaining device / breathing tube such as an endotracheal tube 2 or a tracheostomy tube, or via a suction device 3 connected thereto. In this respect, the first port 21 may preferably comprise a male connector with a conical 22 mm outer diameter connector surface with a 1:40 taper and an internal co-axial conical connector with a 15 mm internal diameter (female) conical connector with a 1 :40 taper.

The second port 22 may be configured for connection to a ventilator 4 via breathing circuit tubing and can be left open to air when not in use. The second port 22 may comprise a female connector with a conical 22 mm internal diameter connector surface with a 1:40 taper. The third port 23 may be configured for connection to a second breathing circuit 6 and can also be left open to air when not in use. The third port 23 may comprise a female connector with a conical 22 mm internal diameter connector surface with a 1 :40 taper. In this respect, the valve may be specifically configured to be compatible with relevant national and/or international standards, such as ISO 5356-1 :2004 or ISO 5356-1 :2015 specifying dimensional and gauging requirements for cones and sockets intended for connecting anaesthetic and respiratory equipment, e.g. in breathing systems, anaesthetic- gas scavenging systems and vaporizers.

The operating lever 30 allows switching from one breathing circuit 4 to another breathing circuit 6 while maintaining a closed circuit, thus preventing the release of potentially infected aerosols and minimizing the loss of positive end-expiratory pressure (PEEP) from the circuit. The valve may preferably be formed as a T-shaped device with ports at 90 / 180 degree relative angles, though other angular dispositions of the ports can be envisaged. The valve is preferably made principally from strong, lightweight plastic, e.g. with injection moulded parts, and is preferably a disposable device used fora single patient and for a limited period of time, e.g. up to a few days. Example materials may include polyethylene and polystyrene butadiene.

The valve preferably transitions from one bistable state to the other bistable state in a period of time which is very small compared to the period of normal pressure changes within a patient's airway, e.g. substantially less than 1 second and preferably substantially less than 0.2 second.

The valve arrangements as described herein provide fast-acting transitions with a decisive and unambiguous snap action which provides strong haptic and audible feedback when the valve transitions between its bistable states. This is particularly useful in the clinical context for ensuring ease of use in a potentially noisy and confusing environment. As a further safety feature, the direction indicator 27d also provides clear visual feedback as to the status of the valve and cannot show an ambiguous intermediate indication as it is integrally formed with the bistable valve core 27.

Various modifications and adaptations may be made to the valve 20 as described above. Figures 8a, 8b and 9 illustrate a modification that incorporates higher performance sealing of the ports 21, 22, 23 to the valve core 27. As best seen in the cross-sectional view of figure 8b, one or more (and preferably all) of the first port 21 , second port 22 and third port 23 may comprise an axially displaceable sealing member 81 which is configured to slide (left / right as viewed in figure 8b) within a bore housing 82. A sliding seal 83 provides a sealing interface between the sealing member 81 and the bore housing 82 and a spring 88 biases the axially displaceable sealing member 81 towards the valve core 27. The axially displaceable sealing member 81 also includes an inner end 84 defining a face seal 85 which is brought into sealing engagement with the circumferential surface 47 of the valve core 27 when the sealing member 81 is in the (biased) extended position as shown in figure 8b. Drive pins 86 (see also figure 9) extend downwardly from the cam ring 60 and each engages in a respective profiled slot 87 defining a cam surface in the axially displaceable sealing member 81. Referring to figure 9, as the cam ring 60 rotates under the action of the operating lever 30 (previously described), a respective drive pin 86 on the cam ring 60 engages the profiled slot 87 and, as the cam ring 61 rotates approaching a release position, the drive pin 86 momentarily drives the axially displaceable sealing member 81 away from the valve core 27 so that it can rapidly rotate with minimal friction and impedance. Upon reaching the stable configuration, the spring bias from springs 88 will bias the displaceable sealing members 81 into contact again with the valve core 27.

Further detail of the profiled slot 87 and the operation of the axially displaceable sealing member 81 is described with reference to figures 10 and 11. The profiled slot 87 in the axially displaceable sealing member 81 defines a cam surface 100 having first and second peak portions 101 , 102 separated by a trough portion 103. With the valve 20 in one of the first and second stable configurations, the positions of the first and second drive pins 86a, 86b of the cam ring 60 are, respectively, aligned with the trough portion 103 and outside the profiled slot 87. The drive pins 86a, 86b do not touch, or do not bear against, the side walls of the profiled slot 87 and thus the sealing member is biased against the valve core 27 under the bias of spring 88, thereby effecting the best possible seal. This is applicable to all the axially displaceable sealing members 81 disposed around the valve core 27. As the operating lever 30 is rotated to the position at which it engages the cam ring (figure 7b) at the release position, and the cam ring 60 also starts to rotate, the cam ring pins 86a, 86b start to move from the rest positions (figure 11a) to a position in which they engage the peak portions 101 , 102 of the profiled slot 87 (figure 11b), thereby pushing the axially displaceable sealing member 81 away from the valve core 27 against the bias of spring 88. The face seal 85 is disengaged from the surface 47 of the valve core 27 thus reducing the resistance to motion of the valve core 27. The valve core 27 rapidly rotates and the operating lever 30 / cam ring 60 rapidly complete their rotations leaving the cam ring pins 86a, 86b in the positions as seen in figure 11c. In this configuration, the first drive pin 86a has passed beyond the profiled slot 87 and the second drive pin 86b is aligned with the trough portion 103, and the displaceable sealing member 81 has been biased once again against the valve core 27 by the spring 88. A corresponding reverse action takes place when the operating lever 30 is rotated back to the first position.

In a preferred arrangement as seen in figure 9, the valve 20 may be formed effectively with four bore housings 82 at 90 degree intervals around the body 25, each with an axially displaceable sealing member 81. In the three-port valve described above, one of the four bore housings 82 can be blanked off. This arrangement keeps the sealing arrangements symmetrical around the valve core 27, and may avoid the need for seals between the valve core 27 and the body 25, potentially reducing friction for a fast acting bistable valve.

In the embodiments shown herein, a three-port valve configuration is shown exemplifying a bistable valve mechanism in which a first port can be connected to either one of a second and third port by a rapidly transitioning valve mechanism. It will be understood that further ports could be added, and the actuator mechanism supplemented with a third position e.g. to provide a tristable valve mechanism. Such a tristable valve could have a position in which the first port can be connected to any one of a second, third or fourth port, or there could be a third stable position corresponding to a full isolated position where the first, second and third ports are all isolated from one another. In this respect, the expression 'bistable valve' is intended to encompass a valve having at least a first and a second stable configuration in which an intermediate stable position between the first and second stable configurations is prevented, but need not exclude the possibility of having a further stable configuration while still meeting the specified bistable requirements.

Although the embodiments of valve described in connection with the drawings are based on a bistable valve mechanism and actuator mechanism which rotate about an axis, it will be understood that the bistable functionality could also be achieved in other ways, e.g. with a valve mechanism deploying linear motion. For example, the valve could be configured as a Y-shaped valve with the stem of the Y-shape corresponding to the first port and the two branches of the Y-shape corresponding to the second and third ports. A linear sliding bistable mechanism may be used to transition the valve from a first configuration in which the first port is in fluid communication with the second port to a second configuration in which the first port is in fluid communication with the third port.

For the purposes of providing low cost disposable valves, the valves herein are preferably manually operated valves and constructed from low cost components. However, other electrically actuated versions may be envisaged.

The valve as described above can be deployed to more safely switch a patient using a breathing support tube and connected to a first ventilation device to a second ventilation device with reduced risk of the problems identified above. The patient's breathing tube is coupled to the first port of the valve and the first ventilation device is coupled to the second port and the breathing apparatus is operated with the valve in the first stable configuration. While the valve is in the first stable configuration, a second ventilation device may be coupled to the third port. The valve may then be switched to the second stable configuration. After the transition of the valve to the second stable configuration the first ventilation device may be disconnected from the second port which has been isolated from the patient's active breathing circuit. Other embodiments are intentionally within the scope of the accompanying claims.