Mechanical ventilator comprising a pneumatically driven pump module, a pneumatic mode control and an exhalation module

Abstract

The present invention provides a mechanical ventilator comprising a pneumatically driven pump module (40-62), a pneumatic mode control (1-35) and an exhalation module (72-97). The mechanical ventilator is configured to be fully driven and controlled by compressed air.

Description

[0001] MECHANICAL VENTILATOR COMPRISING A PNEUMATICALLY DRIVEN PUMP MODULE, A PNEUMATIC MODE CONTROL AND AN EXHALATION MODULE

[0002] Technical field

[0003] The present invention provides a mechanical ventilator comprising a pneumatically driven pump module, a pneumatic mode control and an exhalation module. The respirator is designed so that its control functions and energy requirements are taken care of in their entirety by supplying pressure-stabilized compressed air.

[0004] Background of the invention

[0005] All respirators are dependent on motive power and ventilation control. As of today, this is commonly achieved by a combination of a propellant gas system and electronic control. This in turn requires a stable resource situation including a well-functioning logistics system. During war and disasters, this is made clear in a brutal way. The purpose of the invention has been to produce a ventilator that can be operated independently of a functioning logistics system. The present invention works completely independent of electricity, as compressed air both drives and controls the system. The required amount of compressed air can be produced on site, e.g. by using a manual pump. The system will thereby be ideal for emergency purposes, both in the event of a loss of logistics, electricity and / or an increase in the number of patients.

[0006] Monitoring of the patient can be carried out with independent monitoring equipment (measurement of oxygen and carbon dioxide) which can be operated at e.g. small solar panels / batteries. In extreme cases, monitoring of the patient can be replaced by clinical expertise. This ventilator therefore does not need a digital display to achieve correct setting of the various ventilation parameters

[0007] Known technology

[0008] GB 1357635 A, US 6591835 Bl and US 6237594 Bl describe pneumatic respirators based on the use of pneumatic actuators and ventilation control using pressure-controlled valves.

[0009] The purpose of the present invention is to provide an improved respirator which is powered only by compressed air as an energy source.

[0010] Summary of the invention

[0011] The present invention is defined by the attached patent claims and in the following:

[0012] In a first aspect, the present invention provides a mechanical ventilator comprising a mode control (or mode controller), a pump module and an exhalation module, wherein the mode control has an outlet port connected to the pump module and is configured to control the ventilator between an expiratory mode and an inspiratory mode with / at a desired ventilation frequency by alternating between providing a lower and an upper pressure level, respectively, in the outlet port, the pump module comprises a single-acting pump that cooperates with a pneumatic actuator (i.e. the pump module may comprise a single acting pump and a pneumatic actuator), the singleacting pump is configured to be controlled by the pressure level in the outlet port of the mode control to switch between inspiratory mode and expiratory mode, in that the pneumatic actuator comprises a housing in which an axially displaceable drive piston forms a leak-free barrier between a pressure device and a drive chamber, the pressure device applies to the drive piston a pressure set to a level below the upper pressure level in the outlet port (in other words, during use the pressure device is configured to apply to the drive piston a pressure set to a level below the upper pressure level in the outlet port), and the drive chamber is connected to the outlet port so that the actuator (i.e. the drive piston of the actuator) will reciprocate with a controlled speed in that it, during use, alternates between the drive chamber receiving a controlled supply of compressed air via / from the outlet port and the drive chamber being vented (to the lower pressure level and / or approximate atmospheric pressure), during inspiration mode, the actuator's drive chamber receives a controlled supply of compressed air from the outlet port via a flow regulating valve (in other words, the actuator's drive chamber is configured to receive a controlled supply of compressed air from the outlet via a flow regulating valve), so that the singleacting pump will deliver air at a desired rate via an air outlet, during exhalation mode, air is dumped from the actuator's drive chamber into the surrounding atmosphere, so that the single-acting pump can take in fresh breathing air from the surrounding atmosphere and any supplement of oxygen-enriched air via an air intake, the pump module comprises a first sensor device which is adapted / arranged to produce a pressure signal which causes a shut-off valve to interrupt the supply of compressed air to the drive chamber if the pressure in a patient's airways exceeds a given level, the given level of the pressure in a patient's airways (Peak Inspiratory Pressure) can optionally be set by a maneuvering device, the pump module comprises a second sensor device which is adapted / arranged to produce a pressure signal which causes the shut-off valve to close for the supply of compressed air to the drive chamber when the amount of insufflated breathing air corresponds to a tidal volume which is set by means of a maneuvering means, the shut-off valve is configured so that when one of the sensor devices has produced a pressure signal that causes the shut-off valve to close, the shut-off valve will automatically be opened before the next inspiratory mode is initiated, and the exhalation module is connected to the single-acting pump (in other words, the exhalation module is connected to an air outlet of the single-acting pump) and is configured so that the patient can receive breathing air from the single-acting pump in inspiration mode and release air via the exhalation module to the surrounding atmosphere in expiration mode.

[0013] The mechanical ventilator is configured to use compressed air (or another suitable compressed gas) as the sole source of energy to operate and control all relevant ventilation variables related to switching between an inspiratory mode consisting of an insufflation phase and an inspiratory pause and an expiratory mode consisting of an expiratory phase and an expiratory pause.

[0014] The mode control includes an inlet port which is connected to a source of the compressed air during use.

[0015] The lower pressure level at the outlet port of the mode control can be equal to the surrounding atmospheric pressure.

[0016] In other words, the drive chamber is connected to the outlet port so that the drive piston, during use, may reciprocate at a controlled speed by alternating between providing a controlled supply of compressed air via the outlet port to the drive chamber and venting the drive chamber to any of the lower pressure level and approximate atmospheric pressure.

[0017] The single-acting pump comprises a pump chamber and a piston. The pump chamber has a pump air outlet and a pump air inlet, and the piston is connected to cooperate with the pneumatic actuator, e.g. the piston can be connected to the drive piston of the pneumatic actuator. The interaction between the pneumatic actuator and the single-acting pump is configured so that air is led / pressed out of the pump chamber via the pump air outlet when the drive chamber is supplied with compressed air, and air is drawn into the pump chamber via the pump air inlet when the drive chamber is vented to approximate atmospheric pressure.

[0018] In other words, the pressure device applies to the drive piston a force which is directed towards the drive chamber and which is set to a level that is lower than the oppositely directed force which the drive gas (i.e. the compressed air from the outlet port) can produce against the drive piston by connecting the drive chamber to the outlet port, whereby the drive piston will reciprocate at a controlled speed in that it alternates, during use, between the drive chamber receiving a controlled supply of compressed air when the outlet port has its upper pressure level and venting when the outlet port has its lower pressure level. In other words, the single-acting pump is configured to be controlled by the pressure level in the outlet port of the mode control via the cooperation of the pneumatic actuator.

[0019] The innovative solution of controlling the single-acting pump with a pneumatic actuator, as defined above, where the pressure device is set to apply an almost constant pressure to the drive piston provides both a simple regulation of the single-acting pump and ensures that it will run smoothly.

[0020] In an embodiment of the mechanical ventilator, the pump chamber air outlet is in fluid communication with an exhalation module air inlet.

[0021] In an embodiment of the mechanical ventilator, the pressure device may comprise a first chamber which is kept permanently pressurized. The first chamber may preferably be pressurized to a level of approximately half of the upper pressure level in the outlet port. In alternative embodiments, the pressure device may, for example, comprise a spring that applies the desired pressure to the drive piston.

[0022] In an embodiment of the mechanical ventilator, the mode control may comprise a housing with an adjustable chamber which is adapted to change the ventilation frequency of the ventilator by regulating the volume of the adjustable chamber by means of a maneuvering means, wherein the pressure of the adjustable chamber alternates, during use, between a selected upper level and a selected lower level by means of valve devices, a first nozzle device and a second nozzle device, the mode control switches from expiratory mode to inspiratory mode by pressurizing the outlet port to its upper level when the pressure in the adjustable chamber reaches the selected lower level, and switches to expiratory mode by venting the outlet port to atmospheric pressure when the pressure in the adjustable chamber reaches the selected upper level, and the mode control is arranged so that the time required to increase the pressure in the adjustable chamber from the selected lower level to the selected upper level is regulated by adjusting the flow resistance of the first nozzle device, and that the time required to decrease the pressure in the adjustable chamber from the selected upper level to the selected lower level is regulated by adjusting the flow resistance of the second nozzle device, the first and second nozzle devices representing a first nozzle set which mutually determines the duration of inspiratory mode relative to expiratory mode.

[0023] In an embodiment of the mechanical ventilator, the mode control may comprise several nozzle sets which are adjusted to give different durations of inspiratory mode relative to the duration of expiratory mode and where only one nozzle set can be engaged at a time by means of a maneuvering means and a mechanism, each nozzle set being adjusted so that the total time to complete a ventilation cycle remains the same. In an embodiment of the mechanical ventilator, the mode control valve means may comprise a switching valve with an activation chamber, a first pressure-sensing valve means, and a second pressure-sensing valve means, wherein the switching valve can alternate between a first state in which the outlet port is in open communication with an exhaust port and separate from an inlet port which is permanently connected to a supply of compressed air, and a second state in which the outlet port is in open communication with the inlet port and separate from the exhaust port, the switching valve is in the first state when the activation chamber is depressurized and in the second state when the activation chamber is pressurized, and where the first pressure sensing valve device senses (i.e. is configured to sense) the pressure in the adjustable chamber and cooperates (i.e. is configured to cooperate) with a valve body and a spring to pressurize the activation chamber when the pressure in the adjustable chamber has reached the selected lower level, thereby placing the outlet port in open communication with the inlet port so that the activation chamber is supplied with compressed air via the first nozzle device, and the second pressure sensing valve device senses the pressure in the adjustable chamber and cooperates with a valve body and a spring to vent the actuating chamber to ambient atmosphere when the pressure in the adjustable chamber has increased to the selected upper level, thereby setting the outlet port in open connection with the surrounding atmosphere with the result that the adjustable chamber dumps air into the surrounding atmosphere via the second nozzle device.

[0024] In an embodiment of the mechanical ventilator, the mode control may include a line that supplies (i.e. is configured to supply) the upstream side of the valve body with compressed air, on the line there is arranged a trigger valve which can be set by means of a maneuvering device so that the patient must produce a certain adjustable negative pressure in relation to the set defined excess pressure for expired air (PEEP) for the supply line to receive a supply of compressed air so that the inspiratory phase can be initiated.

[0025] In an embodiment of the mechanical ventilator, the exhalation module may comprise an exhalation module air inlet, an exhalation module air outlet, a valve device and an isolation valve, where the isolation valve is connected to the outlet port of the mode control and is arranged so that air is not released via the exhalation module to the environment via the exhalation module air outlet when the mode control is in the inspiratory mode, and the valve device has a maneuvering device that can be set so that the pressure in expired air must have a defined excess pressure (=P EEP) in order to pass through the exhalation module when the ventilator is in exhalation mode. The isolation valve is arranged between the exhalation module air inlet and the exhalation module air outlet. In an embodiment of the mechanical ventilator, the second sensing device may comprise a sleeve which is rotatably arranged around a fixed cylindrical tube, and which during an ongoing insufflation (i.e. inspiratory mode) is adapted to achieve mechanical contact with an outgrowth (in other words, a protrusion or projection) which is mechanically coupled to the actuator's drive piston, in that the sleeve is designed so that a length, by which the drive piston must be displaced before mechanical contact with the outgrowth is achieved, is determined by how much a maneuvering member has rotated the sleeve in relation to the cylindrical tube, where the sleeve, having made contact with said outgrowth, will be pressed upwards and produce rotation of a rocker arm which thereby moves a valve body away from a seat, and opens for connection between a first port which is fixedly connected to the outlet port of the mode control, and a second port which is fixedly connected to the shut-off valve's control chamber. The outgrowth can for instance be a rod mounted perpendicular to the actuator's drive piston. The rod may be connected to a guide which ensures that the rod does not rotate relative to the sleeve when the drive piston is displaced. The sleeve may have recesses for contact with the outgrowth / rod. The recesses can be arranged at different distances to the drive piston so that the length that the drive piston must be displaced before the protrusion / rod comes in touch with the sleeve can be adjusted by rotating the sleeve around the cylindrical tube.

[0026] Brief description of drawings

[0027] Embodiments of the present invention are described with reference to the following drawings:

[0028] Fig. la shows a diagram of the respirator's mode control in a preferred basic design.

[0029] Fig. lb shows a drawing which illustrates how the mode control can be arranged to alternate between different mutual durations of inspiratory mode and expiratory mode.

[0030] Fig. lc and Id show a drawing of a relevant embodiment of a flow reducing nozzle.

[0031] Fig. 2a and 2b show drawings of a switching valve that is part of the mode control.

[0032] Fig. 3a shows a diagram of a pump module in a preferred basic design.

[0033] Fig. 3b shows an enlarged section of a sensor device in the pump module which is designed to initiate an inspiratory pause when the pump module has delivered a set upper amount of breathing air during an insufflation.

[0034] Fig. 4a and 4b show drawings of an expiration module in two different modes.

[0035] Fig. 5a and 5b show drawings of a trigger valve in two different settings. Detailed description of the invention

[0036] Overall mode of operation for a respirator according to the invention

[0037] The respirator is composed of three main elements in the form of a mode control, a pump module and an exhalation module. The function and structure of these three main elements will be explained with reference to the attached figures.

[0038] The mode control causes the ventilator to switch between inspiration mode, which means that the patient's lungs are insufflated using the pneumatically driven pump module, and expiration mode, which means that the pump module is filled with fresh breathing air while the patient can exhale via the expiration module, which is designed to produce a defined back pressure (= PEEP = Positive End Expiratory Pressure).

[0039] Inspiratory mode is composed of a first phase of insufflation, and a second phase of inspiratory pause. During an inspiratory pause, the insufflation is interrupted to give the lungs time to distribute the insufflated air in the lungs, thereby improving the absorption of the oxygen.

[0040] The ventilator according to the invention is designed for efficient utilization of compressed air as the only source of energy, with the aim that a suitable manual air pump should be able to produce enough compressed air for the continuous operation of 6 - 8 respirators. To achieve a uniform pressure, the compressed air can be fed to an intermediate buffer or a pressure equalizer, for instance a pressure tank.

[0041] Important properties of the invention are that set values regarding ventilation frequency and mutual duration of inspiratory mode and expiratory mode are not affected by other ventilation variables. This means that the ventilator is easy to operate, and functionally it differs little from electronically controlled ventilators.

[0042] Cooperation between the mode control and the pump module

[0043] The mode control 1-35) causes the change between inspiration mode and expiration mode to occur when a pressure that rises and falls in an internal chamber I) reaches resp. a selected upper level and a selected lower level. In the further description, this chamber (I) is referred to as the time measuring chamber.

[0044] In a preferred embodiment, the mode control switches to inspiratory mode when the pressure in the timing chamber has dropped to the lower level. This causes the pressure in an outlet port 8) in the mode control to change from atmospheric pressure to the stabilized supply pressure of the compressed air that controls the respirator's functions. Correspondingly, the mode control switches from inspiratory mode to expiratory mode as the pressure in the internal chamber reaches the upper level. When this happens, the pressure in the outlet port 8) changes back to atmospheric pressure. The output port 8) has a permanent connection to the pump module's actuator 40-43) via a pipe connection 12,58) and branches 48,50) on this. This connection causes the actuator's drive chamber IV) to receive a controlled supply of compressed air from said outlet via a flow regulating valve 51) when the mode control is in inspiration mode. The actuator 40-43) will thereby cause the single-acting pump 43-47) to insufflate the patient's lungs at a defined speed which is determined by how the single-acting pump's maneuvering device is adjusted. Correspondingly, the coupling will cause the actuator's drive chamber IV) to be vented when the output port 8) is open to atmosphere, whereby the pump module is expanded to take in fresh air while the patient can breathe out via the exhalation module.

[0045] The time required to vary the pressure up and down between the two levels is determined from the adjustment of a nozzle device 27-30). The time taken to increase the pressure from the lower level to the upper level corresponds to the duration of the inspiratory mode and is determined by the set flow resistance in one half 27,29) of the nozzle device. Correspondingly, the time required to reduce the pressure from the upper to the lower level corresponds to the duration of the expiratory mode and is determined by the set flow resistance in the other half 28,30) of the nozzle device.

[0046] For a given adjustment of the first - and the second half nozzle device, both the ventilation frequency and mutual duration of inspiration mode in relation to expiration mode will be unambiguously determined.

[0047] If the timing chamber volume is increased, the time required to complete expiratory mode and expiratory mode will both increase proportionally to the volume change. This means that changing the volume of the time measurement chamber will change the ventilation frequency without changing the mutual duration of inspiratory mode and expiratory mode.

[0048] Relevant nozzle design

[0049] Figs lc and Id show a relevant embodiment of a nozzle 28) with adjustable flow resistance. The nozzle consists of a housing 28a) where the gas can flow in both directions through an axially arranged channel 28f) and a port 28d). An adjustment screw 28b) is threaded into the housing so that it can be screwed back and forth axially in the housing's axial direction. The most important part of the flow resistance through the nozzle is determined by the clearance between the channel 28f) and a rod which is fixed axially in the adjustment screw, fine adjustment being made by shifting the adjustment screw in the axial direction to thereby change the flow resistance in the passage between the adjustment screw and the port 28d). Fig lc and fig. lc indicates normally selected extreme points with respect to the position of the adjustment screw at minimum and maximum flow resistance.

[0050] Mechanism for connecting several nozzle sets

[0051] A nozzle device consists of two half nozzle devices which control the amount of air which is respectively supplied to the timing chamber when the mode control is in inspiration mode, resp. emitted from the timing chamber when the mode control is in expiratory mode. It is desirable to be able to choose between options for mutual duration of inspiration mode and expiration mode. Fig. lb shows how the module control can include two nozzle devices 31a, 33a). Fig. lb shows how the nozzle set 33a) is engaged by means of a rotatable maneuvering member 32a) which is here oriented so that an outgrowth 32b) pushes a valve body 33b) out from its seat 33c) and causes the nozzle set 33a) to be activated by in fluid connection with the timing chamber. In a preferred embodiment, this solution is used to be able to switch between five differently adjusted nozzle devices.

[0052] The following considerations illustrate how a nozzle set can be adjusted.

[0053] We imagine that the volume of the time measurement chamber is made adjustable from 8 cm3to 32 cm3by means of a first maneuvering device, so that the ventilation frequency can be changed by a factor of 4. The lowest ventilation frequency can, for example, be set to 6 ventilation cycles per minute at volume = 32 cm3, and 24 ventilation cycles per minute at volume = 8 cm3. The control device for the ventilation frequency is now designed to be able to adjust the ventilation frequency from a minimum of 6 cycles per minute to a maximum of 24 cycles per minute, and the control device's scale is adapted to this.

[0054] We now want the option of being able to switch between two nozzle devices that are adjusted so that the mutual duration of inspiratory mode in relation to expiratory mode can switch between 1:1 and 1:1.5.

[0055] The ventilation frequency is set to ventilation frequency = 6 cycles per minute. Duration of a ventilation cycle is 10 seconds. In other words, the first nozzle device must be set so that both inspiratory mode and expiratory mode have a duration of 5 seconds. The second nozzle device is set so that inspiration mode lasts 4 seconds, and expiration time lasts 6 seconds.

[0056] If, after doing this, you turn on the maneuvering device so that the ventilation frequency becomes 15 ventilations per minute, the volume of the time measurement chamber will be reduced to 20 cm3. In this situation, both inspiratory mode and expiratory mode will last for 2 seconds for the first nozzle device, and last for respectively 1.6 seconds and 2.4 seconds for the second nozzle device. Both modes will have their duration changed for both nozzle devices, but the ratio of the duration of inspiratory mode to expiratory mode will still be the same for both.

[0057] We further assume that the operator chooses to set the tidal volume to 0.6 liters, and the insufflation rate to 0.4 liters / second. This will mean that the patient is insufflated with the set time volume within 1.5 seconds. For the first nozzle device, inspiration mode lasts for 2 seconds. Consequently, the inspiratory pause will last for 0.5 seconds before the ventilator switches to expiratory mode.

[0058] For the second nozzle device, the inspiratory mode will last for 1.6 seconds, and the inspiratory pause will consequently be reduced to 0.1 second.

[0059] Based on monitoring the patient or clinical competence, the operator will quickly find out whether the set parameters should be changed. He can, for example, choose to use a higher insufflation rate to increase the duration of the expiratory pause. It is a significant advantage for the operator that he can change the insufflation speed, the tidal volume or the ratio between the mutual duration of the inspiratory mode and the expiratory mode without causing this to change the ventilation frequency.

[0060] A ventilator according to the invention is thus designed so that the ventilation frequency is regulated by means of a first maneuvering device 34) which is designed to change the volume of the time measurement chamber by leak-free displacement of a piston 35). In this way, the ventilation frequency is changed without this changing the mutual duration of the two modes. At the same time, the duration of the inspiratory mode in relation to the expiratory mode can be changed step by step by means of a second maneuvering device 32a). This second maneuvering device makes it possible to change between several nozzle devices 31a, 33a) which are set for different durations of the two modes, without changing the overall duration of these. When the nozzle devices are correctly adjusted, such switching can be carried out without changing the ventilation frequency. The mode control is thus designed so that the ventilation frequency and mutual duration of inspiration mode and expiration mode can be set independently of each other, and that these two parameters are not affected by how the ventilator's other ventilation parameters are set.

[0061] The pump module comprises at least a first sensor device 60-70) and a second sensor device 52-55) which are arranged to be able to initiate an inspiratory pause. The first sensor device 60-70) can set the desired tidal volume and ensures that the sensor device gives a pressure signal that initiates an inspiratory pause as soon as the insufflated amount of air corresponds to the set tidal volume. The second sensor device 52-55) senses the pressure in the patient's airways and generates a pressure signal that triggers an inspiratory pause as soon as the sensed pressure reaches this value. Once Inspiratory Pause has been enabled, it remains enabled until the mode control switches to Expiratory mode.

[0062] The expiration module

[0063] The expiratory module has the task of establishing a positive end expiratory pressure during the patient's expiration (= PEEP). This is arranged by means of a valve device 72-97) which sets the end expiratory pressure to the desired level by means of a maneuvering device 93). As the insufflation pressure is higher than the end expiratory pressure, it is necessary to prevent air passage through the exhalation module when the ventilator is in inspiration mode. This is arranged by means of an isolation valve 76-81) which prevents air from passing through the exhalation module when its activation chamber 81) is pressurized, this activation chamber being permanently connected to the output port 8) of the mode control. Patient activation of inspiratory mode

[0064] An important function of a ventilator is to make it possible for the patient to breathe on their own again. In a preferred embodiment of the ventilator, this is achieved by implementing a trigger valve 98) which can be set so that the patient, to start a new inspiratory phase, must produce a defined negative pressure in the breathing circuit in relation to the set PEEP. After this negative pressure has been produced, the ventilator will carry out an inspiratory phase with a set duration, followed by an expiratory phase with a set duration. To start the next inspiratory phase, the patient must again create the set negative pressure.

[0065] The negative pressure that must be produced to start the inspiratory phase is stepless adjustable and can be gradually increased up to a level where it can be established that the patient is able to breathe on their own. When the trigger valve is used, the patient will be able to extend the duration of expiratory mode. This is the only situation where the breathing rate can be lower than what the mode control is set to be.

[0066] The design of the respirator's main elements

[0067] Mode Control design

[0068] Fig la shows a principal sketch of a mode control according to the invention. It comprises a switching valve 6) and a housing 1) which contains the timing chamber I), a first pressure-sensing valve device 13-17), a second pressure-sensing valve device 19-24), and at least one nozzle device (27-30) consisting of a half nozzle device (27,29) which controls the air supply to the timing chamber when the mode control is in inspiratory mode and a half nozzle device (28,30) which controls the air release from the timing chamber when the mode control is in expiratory mode. The volume of the time measurement chamber is made adjustable by means of the maneuvering device 34).

[0069] As previously mentioned, the mode control includes an outlet port 8) which during inspiration mode is pressurized corresponding to the supply pressure of the compressed air, and which during expiration mode is vented to a pressure corresponding to the surrounding atmosphere. This outlet port 8) is arranged on the switching valve 6).

[0070] When the switching valve's activation chamber II) is vented to the surrounding atmosphere, the outlet port 8) is also vented to the surrounding atmosphere. The switching valve is then in a first state which corresponds to the mode control being in exhalation mode. When the switching valve's activation chamber is pressurized, the output port 8) is also pressurized. The switching valve is then in a second state, which corresponds to the mode control being in inspiration mode.

[0071] The mode control is based on a switching valve 6) which in cooperation with the two pressure-sensing valve devices 13-17,19-24), causes the pressure in the time measurement chamber I) to rise and fall at an adjustable rate between a defined upper pressure level and a defined lower pressure level. When the pressure in the timing chamber reaches the lower level, the membrane 17) is pushed downwards, and the valve body 13) opens to pressurize the switching valve's activation chamber II). This causes the mode control to change to inspiratory mode by pressurizing the outlet port 8). Thereby, the mode control can deliver compressed air to the actuator's drive chamber via the channel 12), while the timing chamber is supplied with compressed air via the half nozzle device 27,29).

[0072] The respirator remains in inhalation mode until the pressure in the timing chamber has risen to the upper pressure level. As soon as this happens, the pressure in the timing chamber will push the pressure-sensing surface 21) upwards, so that the valve body 23) is lifted from its seat 24) and causes the channel 18) to be vented to the surrounding atmosphere via a venting channel 22). Thereby the activation chamber II) becomes depressurized, causing the outlet port 8) to be vented to the surrounding atmosphere via the exhaust port 5), and the timing chamber I) starts reducing the pressure in time measurement chamber via the other half 28,30) of the nozzle device. The pressure in the time measurement chamber continues to fall until the pressure has dropped to the lower level, whereby the process repeats itself.

[0073] The design of the switching valve

[0074] The switching valve 6) comprises an inlet port 9) for supplying compressed air, an exhaust port 5) for releasing propellant gas to atmosphere and an outlet port 8). Furthermore, it comprises two axially displaceable components in the form of a valve element 39) and a spring-actuated sleeve 36), as well as an activation chamber II). The activation chamber II) is designed so that the switching valve is in the first state where the outlet port 8) is in open connection with the exhaust port 5) and separated from the inlet 9) when the activation chamber is depressurized. Correspondingly, it is designed so that the switching valve is in the second state where the outlet port 8) is in open connection with the inlet 9) and separated from the exhaust port 5) when the activation chamber is pressurized.

[0075] The house of the switching valve has an internal channel, which with varying cross-sections is guided axially along the length of the house. The spring-actuated sleeve 36) has the form of a tube which has a pistonshaped protrusion with a sliding seal 36b) which causes this protrusion to be displaceable in a guide where it forms a leak-free barrier between the activation chamber II) and the exhaust port 5). The tubular part of the sleeve 36) is leak-free guided through the part of the continuous channel that runs between the outlet port 8) and the exhaust port 5), this tubular part having an axially arranged channel 36a) with a transverse opening towards the exhaust port 5).

[0076] The valve body 39) is composed of a first conical valve element 39a) which is arranged to be able to form a sealing contact against a seat 38) which is arranged around the inlet of the part of the internal channel that is led between the inlet port 9) and the outlet port 8), and of a second conical element 39b) which is arranged to be able to form sealing contact with a seat 37) that is arranged around the inlet of the channel 36a). The desired switching function is achieved by the spring tension against the sleeve 36) causing the sleeve to be pressed to its lowest position when the activation chamber II) is depressurized. The switching valve is then in the first state in that the upper conical valve element 39a) is placed in sealing contact with the seat 38), and the outlet port 8) is open to the exhaust port 5) via the opening created between the lower conical valve element 39b) and the seat 37). Correspondingly, the switching valve will be in the second state when the activation chamber II) is pressurized and the spring-loaded sleeve is pressed to its uppermost position. The conical valve element 39b) then makes sealing contact with the seat 37) and presses the valve body 39) upwards so that the outlet port 8) is open to the inlet port 9) via the opening created between the conical element 39) and the seat 38).

[0077] The present invention is described by reference to a mechanical ventilator having a control module as shown in fig. la. However, in alternative embodiments of the mechanical ventilator, the control module may be of any suitable design provided the control module comprises an outlet port connectable to the pump module, wherein a pressure in the outlet port may alternate between a lower and an upper pressure level to control the ventilator between an expiratory mode and an inspiratory mode with a desired ventilation frequency.

[0078] The design of the pump module

[0079] Fig. 3a shows a sketch of the pump module. This module includes a single-acting pump 44-47) which is driven by the pneumatic actuator 40-43). The actuator comprises an actuator housing 41) with an axially displaceable drive piston 42), which via a control rod 43), cooperates with a piston 46) in the single-acting pump. The drive piston 42) divides the actuator housing 4 1) into a first chamber V) and into a drive chamber IV), the first chamber V) being permanently open to a larger chamber VI) which is arranged inside a cylindrical housing 71). Chambers VI) and V) are kept pressurized to typically around 2 bars by a pressure reduction valve 59) which is connected to the propellant gas supply 10). This arrangement means that the drive piston 42) will be able to reciprocate by the actuator's drive chamber IV) alternating between being supplied with compressed air and being depressurized against atmospheric pressure. Such supply and discharge of air from the drive chamber IV) takes place via three components which are arranged in branches to a channel 12,58) which connects the drive chamber IV) with the outlet port 8) of the switching valve. These three components comprise a first shut-off valve 57), a flow regulating valve 51) and a one-way valve 41).

[0080] The shut-off valve 57) will always be in the open position when inspiration mode is activated.

[0081] The outlet port 8) will then supply compressed air to the actuator's drive chamber via the flow-regulating valve 51), which controls the insufflation speed via a maneuvering device not shown. The shut-off valve's activation channel 56) is in a permanently open connection with the signal lines 53,65) from the two sensor devices) and will cause the shut-off valve to close and initiate an inspiratory pause as soon as one of the sensor devices 52-55,60-70) is activated. The mode control switches over to exhalation mode by setting the switching valve's output port 8) in open connection with the surrounding atmosphere. This means that the actuator's drive chamber is vented via the one-way valve 49), the channel 58) and the outlet port 8). At the same time, the pressure reduction in the switching valve outlet 8) causes deactivation of the isolation valve 76-80. This means that the patient can breathe out through the exhalation module against a pressure (PEEP) which is determined by the position of the maneuvering device 93).

[0082] The single-acting pump 43-46) comprises a pump chamber III), which piston 46) is connected to cooperate with the pneumatic actuator. This pump chamber III) is in fluid communication with an air inlet 44) and an air outlet 47). The air outlet is connected to the exhaust module that is described below.

[0083] Design of the pump module's first sensor device

[0084] The pump module's first sensor device comprises a rotatable sleeve 67) which interacts with a maneuvering device 65). This maneuvering device is rotatably arranged around a cylindrical guide 70) which is attached to the actuator housing 41). The actuator's drive piston 42) has an axially arranged operating rod 40) which is mounted on a transverse bolt 69) which, when the drive piston is displaced, is forced to move along two grooves 68) which are arranged diametrically opposite in the longitudinal direction of the cylindrical guide 70). In the event of an upward displacement of the drive piston 42), the bolt 69) will get in touch with the sleeve 67) at two diametrically opposite points and then seek to push this sleeve upwards. The maneuvering device 65) cooperates with the sleeve 67) via two pins 66) which allow a certain upward displacement of the sleeve in relation to the maneuvering device 65), so that the pressure against the sleeve 67) produces rotation of a rocker arm 64) which thereby pushes a valve body 62) away from a seat 63), and opens for connection between a first port 61) which is firmly connected to the switching valve's output port 8) and a second port 60).

[0085] Thereby, the port 60) will be pressurized to the same level as the supply pressure for the compressed gas when the bolt 69) gets in touch with the sleeve 67). The sleeve 67) will typically be designed to vary the maximum amount of insufflated breathing air in 10 steps. Fig 3a shows the sensor device 60-70) set for the smallest amount of insufflated air that can trigger an inspiratory pause. Fig. 3b) shows the sensor device in a position where the bolt 69) first get in touch becomes in touch with the sleeve 67) at two diametrically opposite points at adjustment stage 3. Immediately after this contact is made, the outlet 63) and the control chamber 56) are pressurized, leading to immediate actuation of inspiratory pause.

[0086] Design of the pump module's second sensor device

[0087] The pump module's second sensor device 52-55) is designed to prevent the insufflation pressure from exceeding a defined upper level (Peak Inspiratory Pressure). The sensor device that registers the insufflation pressure is in principle a traditional control valve that senses the pressure via a membrane that is affected by an adjustable spring tension that is directed opposite to the sensed pressure forces. The diaphragm 15) cooperates with a valve mechanism which, when sensed pressure reaches the set level, is arranged to open a valve device so that the outlet 53) of the second sensor device is put into open connection with the inlet 55) which is connected to the outlet 8). Thereby, the control chamber 56) is pressurized and leads to the immediate initiation of an inspiratory pause.

[0088] The design of the exhalation module

[0089] Fig. 4a shows the principal design of the exhalation module in a situation where the ventilator is in exhalation mode. Fig. 4b shows a corresponding situation where the respirator is in exhalation mode. The exhalation module comprises a housing 73) with an inlet (72) and an outlet (82) for dumping exhaled breathing air from the patient, an isolation valve 76-81) which is designed to be able to close for releasing exhaled breathing gas via the outlet 82), as well as a power transmission mechanism 83-94) which is arranged to regulate end expiratory pressure by means of a maneuvering means 93).

[0090] As the insufflation pressure is higher than the expiratory pressure, it is necessary to be able to close for passage through the exhalation module when the ventilator is in inspiration mode. This is provided by means of an isolation valve 71-81). This comprises a spring-loaded piston 80) which is connected to a disc 77) which is fitted with a soft sealing ring. This disc cooperates with a seat 76) which is arranged around the outlet of the channel 75). The piston 80) is leak-free displaceable in a guide 79), so that pressurizing a port 81) which is in permanent open connection with the outlet 8) of the switching valve will cause the disc 77) to be pressed into sealing contact with the seat 76). Accordingly, the isolation valve 71-81) will automatically be activated and close to air passage through the expiratory module when the mode control is in the inspiratory mode, and deactivated when the mode control changes to the expiratory mode.

[0091] Fig. 4a) shows a view of this second shut-off valve in a deactivated state. The adjustment wheel 35) is threaded, and when rotated will increase or decrease the compression of a spring 97). This spring exerts upward pressure against a guide 92) which thereby exerts pressure against a weight arm 89) and seeks to rotate this clockwise. This weight arm in turn exerts a downward pull on a second weight arm 87) and thereby seeks to rotate this weight arm counterclockwise about a shaft 86). This downwardly directed draft means that a downwardly directed draft is produced against a sealing disc 83) via a shaft 94). This pull causes the disc 83) to be pulled downwards towards sealing contact with a seat 97) which is arranged around a second channel 95) which is arranged between the inlet 72) and the outlet 82). In fig. 4a illustrates a situation where the sealing disc 83) is pushed up from the seat 96) by the excess pressure which is produced during the patient's expiration. The power transmission mechanism is designed so that the force that seeks to press the sealing disc 83) against the seat 96) is approximately 1 / 7 of the force exerted by the spring 97). The purpose of the power transmission mechanism in question is to ensure that the expiratory overpressure needed to push the sealing disc 83) away from sealing contact with the seat 96) is well defined, and that the exhaled amount of breathing air can be increased quite significantly without a significant increase in the pressure drop across the sealing disc 83).

[0092] Fig. 4b shows the exhaust module in a situation where the respirator is in inspiration mode. This means that the isolation valve 76-80) is in the closed position against the seat 96) and prevents air from flowing through.

[0093] Patient activation of the insufflation phase

[0094] An important function of a ventilator is to make it possible for the patients to breathe on their own again. To achieve this, a trigger valve 98) has been implemented upstream of the valve body 13) in the mode control.

[0095] This trigger valve comprises a housing 99) with an inlet 109) which is connected to the propellant gas supply 10) and an outlet 106) which is connected to the supply line 3). The trigger valve is provided with a pressuresensing membrane 103) which is affected by a spring 103) which has the compression regulated by an adjustment wheel 101). This membrane senses via a sensor channel 104), the difference between the pressure downstream of the single-acting pump outlet 47) and the atmospheric pressure. The membrane 103) cooperates, via a transmission mechanism 100,105,) with a valve body 108) which is spring biased in the direction of a seat 107), so that a force is exerted which seeks to push this valve body away from the seat 107), and thereby open for connection between the trigger valve's inlet 109) and its outlet 106).

[0096] Fig. 5b shows the trigger valve adjusted for patient-activated switching to inspiratory mode. Here, the adjustment wheel 101) is turned outwards until the tension from the spring 102) has just become so low that the valve body 108) makes sealing contact with the seat 107). In this situation, the patient himself must produce a negative pressure in relation to the set end expiratory pressure to make the ventilator switch from exhalation mode to inspiration mode. The further the adjustment wheel is turned outwards, the greater negative pressure the patient must produce to produce this change.

Claims

Claims1. A mechanical ventilator comprising a mode control, a pump module and an exhalation module, the mode control has an outlet port (8) connected to the pump module and is configured to control the ventilator between an expiratory mode and an inspiratory mode with a desired ventilation frequency by alternating between providing a lower and an upper pressure level, respectively, in the outlet port (8), the pump module (40-62) comprises a single-acting pump (43-46) cooperating with a pneumatic actuator (40-43), the single-acting pump is configured to be controlled by the pressure level in the outlet port (8) of the mode control to switch between the inspiratory mode and the expiratory mode, wherein the pneumatic actuator (40-43) comprises a housing (41) in which an axially displaceable drive piston (42) forms a leak-free barrier between a pressure device and a drive chamber (IV), the pressure device applies to the drive piston a pressure set to a level below the upper pressure level in the outlet port (8), and the drive chamber (IV) is connected to the outlet port (8) so that the actuator will reciprocate at a controlled speed by switching during use between the drive chamber (IV) receiving a controlled supply of compressed air via the outlet port (8) and that the drive chamber (IV) is vented, during the inspiratory mode, the actuator's drive chamber (IV) receives a controlled supply of compressed air from the outlet port (8) via a flow regulating valve (51), so that the single-acting pump (43-46) will deliver air at a desired speed via a pump air outlet (47), during the expiratory mode, air is dumped from the actuator's drive chamber (IV) into the surrounding atmosphere, so that the single-acting pump can absorb fresh breathing air from the surrounding atmosphere and any supplement of oxygen-enriched air via a pump air inlet (44), the pump module comprises a first sensor device (52-55) which is arranged to produce a pressure signal which causes a shut-off valve (57) to interrupt the supply of compressed air to the drive chamber (IV) if the pressure in a patient's airways exceeds a given level, the pump module comprises a second sensor device (60-70) which is arranged to produce a pressure signal which causes the shut-off valve (57) to close for the supply of compressed air to the drive chamber (IV) when the amount of insufflated breathing air corresponds to a tidal volume which is set by means of a maneuvering device (65),the shut-off valve (57) is configured so that when one of the sensor devices has produced a pressure signal that causes the shut-off valve (57) to close, the shut-off valve will automatically be opened before the next inspiratory mode is initiated, and the exhalation module is connected to the single-acting pump and is configured so that the patient can receive breathing air from the single-acting pump in the inspiratory mode and emit air via the exhalation module to the surrounding atmosphere in the expiratory mode.2 A mechanical ventilator according to claim 1, wherein the single-acting pump (43-46) comprises a pump chamber (III) and a piston (46), the piston is connected to cooperate with the pneumatic actuator, and the pump chamber is in fluid communication with the pump air inlet (44) and the pump air outlet (47).3 A mechanical respirator according to claim 1 or 2, where the pressure device comprises a first chamber (V) which is kept permanently pressurized.

4. A mechanical ventilator according to any one of the preceding claims, wherein the mode control (1- 39) comprises a housing (1) with an adjustable chamber (I) which is arranged to change the ventilation frequency of the ventilator by regulating the volume of the adjustable chamber (I) by use of a maneuvering device (34), wherein the pressure of the adjustable chamber (I) alternates between a selected upper level and a selected lower level by means of valve devices (5-9, 13-17,19-24), a first nozzle device (27,29) and a second nozzle device (28,30), the mode control switches from expiratory mode to inspiratory mode by pressurizing the outlet port (8) to its upper level when the pressure in the adjustable chamber (I) reaches the selected lower level, and switches to expiratory mode by venting the outlet port (8) to atmospheric pressure when the pressure in the adjustable chamber (I) reaches the selected upper level, and the mode control is arranged so that the time required to increase the pressure in the adjustable chamber (I) from the selected lower level to the selected upper level is regulated by adjusting the flow resistance of the first nozzle device (27,29), and that the time required for lowering the pressure in the adjustable chamber (I) from the selected upper level to the selected lower level is regulated by adjusting the flow resistance of the second nozzle device (28,30), the first and the second nozzle device representing a first nozzle set which mutually determines the duration of the inspiratory mode in relation to the expiratory mode.5 A mechanical ventilator according to claim 4, where the mode control comprises several nozzle sets (31a, 33a) which are adjusted to give a different duration of inspiratory mode relative to the duration of expiratory mode and where only one nozzle set can be engaged at a time by means of a maneuvering device ( 32a) and a mechanism (31b, 31c and 33b, 33c), each nozzle set being adjusted so that the total time to complete a ventilation cycle remains the same.6 A mechanical ventilator according to claim 4 or 5, where the mode control valve devices comprise a switching valve (5-8,36-39) with an activation chamber (II), a first pressure-sensing valve device (13- 17) and a second pressure-sensing valve device (19- 24), as the switching valve (5-9,36-39) can alternate between a first state where the outlet port (8) is in open communication with an exhaust port (5) and separated from an inlet port (9) which is permanently connected to a supply of compressed air, and a second state where the outlet port (8) is in open connection with the inlet port (9) and separated from the exhaust port (5), the switching valve being in the first state when the activation chamber (II) is depressurized and in the second state when the activation chamber (II) is pressurized , and where- the first pressure-sensing valve device (13-17) senses the pressure in the adjustable chamber (I) and cooperates with a valve body (13) and a spring (16) which causes pressurization of the activation chamber (II) when the pressure in the adjustable chamber (I) has reached the selected lower level, thus putting the outlet port (8) in open connection with the inlet port (9) so that the activation chamber (II) receives a supply of compressed air via the first nozzle device (27,29), the second pressure-sensing valve device (19-24) senses the pressure in the adjustable chamber (I) and cooperates with a valve body (24) and a spring (20) so that the activation chamber (II) is vented to ambient atmosphere when the pressure in the adjustable chamber (I ) has increased to the selected upper level, whereby the outlet port (8) is put in open connection with the surrounding atmosphere with the result that the adjustable chamber (I) dumps air into the surrounding atmosphere via the second nozzle device (28,30).

7. A mechanical ventilator according to claim 6, where the mode control comprises a line (11) which supplies the upstream side of the valve body (13) with compressed air, on the line there is arranged a trigger valve (98) which can be set with the help of an adjustment wheel (101) so that the patient must produce a certain adjustable negative pressure in relation to the set defined excess pressure for expired air (PEEP) in order for the supply line (3) to receive a supply of compressed air so that the inspiratory phase can be initiated.

8. A mechanical respirator according to any of the preceding claims, wherein the exhalation module (72-97) comprises an exhalation module air inlet (71), an exhalation module air outlet (82), a valve device (83-97) and an isolation valve (76-86), where the isolation valve (76,86) is connected to the outlet port (8) and is arranged so that air is not emitted via the exhalation module to the surroundings via the exhalation module air outlet (82) when the mode control is in inspiration mode, and the valve device (83-97) has a maneuvering device (93) which can be set so that the pressure in expired air must have a defined excess pressure (=PEEP) in order to pass through the exhalation module when the ventilator is in exhalation mode.

9. A mechanical ventilator according to any one of the preceding claims, wherein the second sensor device (60-70) comprises a sleeve (67) which is rotatably arranged around a fixed cylindrical tube (70), and which during an ongoing insufflation is aligned to achieve mechanical contact with an outgrowth (69) which is mechanically connected to the actuator's drive piston (42), in that the sleeve (67) is designed so that a length by which the drive piston (42) must be displaced before mechanical contact with the outgrowth (69) is achieved is determined by how much a maneuvering member (65) has rotated the sleeve (67) in relation to the cylindrical tube (70), where the sleeve (67), after making contact with said outgrowth (69), will be pushed upwards and produce rotation of a rocker arm (64) which thereby moves a valve body (62) away from a seat (63), and opens for connection between a first port (61) which is firmly connected to the outlet port (8), and a second port 60) which is firmly connected to the shut-off valve's control chamber (56).

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