WO2011144543A1

WO2011144543A1 - Pneumatic transient handler and a transient handling method

Info

Publication number: WO2011144543A1
Application number: PCT/EP2011/057812
Authority: WO
Inventors: Göran Cewers
Original assignee: Mindray Medical Sweden Ab
Priority date: 2010-05-17
Filing date: 2011-05-15
Publication date: 2011-11-24

Abstract

A pneumatic transient handler unit (20) for connection to a breathing system and control of pressure therein, comprising: - at least one actuator element (30); - at least one container having a volume with an outlet channel (34); - at least one pressure sensor (35); and - wherein a motion of the actuator element (30) compresses or decompresses the container in dependence of the pressure measured by the pressure sensor (35), and wherein the outlet channel (34) of the container is in use connected to the breathing system, in such a manner that undesired pressure variations in the breathing system are compensated by the unit (20).

Description

TITLE: PNEUMATIC TRANSIENT HANDLER AND A TRANSIENT HANDLING METHOD

Related Applications

The present application relates to the following applications of the same inventor/applicant as the present application with the following titles and filing numbers: "MECHANICAL AMPLIFIER, SYSTEM OF SAID AMPLIFIERS AND METHOD FOR MECHANICALLY AMPLIFICATION OF A MOTION"

US61/345,625; "METHODS, SYSTEMS, AND DEVICES FOR MECHANICAL MOTION AMPLIFICATION" US13/105,661 ; and "PNEUMATIC TRANSIENT HANDLER AND A TRANSIENT HANDLING METHOD" US61/345,825; which are incorporated herein by reference in their entirety for all purposes.

BACKGROUND OF THE INVENTION

Field of the Invention

The invention pertains to breathing apparatuses, and more precisely to a device and method for compensating or controlling transient pressures and flow processes in a breathing system. The invention also pertains to a device for carrying out said method.

Description of Prior Art Breathing apparatuses are used to artificially ventilate mammals. These breathing apparatuses, like medical ventilators, have a breathing system for connection to a patient and for providing the artificial ventilation to the patient.

One of the most predominant breathing system configurations in medical ventilators of today is illustrated in Figure 1 . A ventilator 100 has the primary task of alternatingly in phases delivering a quantity of gas into the patient's lung 17 during inspiration, and to subsequently release the delivered volume during expiration. The gas flows during these phases are usually controlled by valves 12 and 13, which are connected to tubes 14 and 15, which feed together into a Y- piece 16 and then flow through a tube or mask to the patient. Tube 14 is an inspiratory tube. Tube 15 is an expiratory tube. Valve 12 is an inspiratory valve fluidly connected to a gas inlet 10. Valve 13 is an expiratory valve fluidly connected to a gas outlet. Since the valves 12, 13 come with a control system and a power supply, and thus are relatively bulky, they are usually assembled in a housing remote from the patient's lungs 17, constituting the ventilator 100.

The ventilator 100 is generally placed a few metres from the patient, and the latter are connected to each other by tubes 14, 15. Consequently, the ventilator tubes 14, 15 are often a metre or more in length. This is not an insuperable issue in terms of dosing, as one tube is always filled with inhalation gas and the other with exhalation gas, and new gas being supplied to the patient merely displaces the gas volume which is already present in the tubes without any major faults in volume, as induced pressure changes do not result in any serious volume changes.

However, pressure changes are induced into the tubes when the flows change. The weight of the gas mass in the tubes in combination with the gas's compressibility may under certain operative conditions cause undesired harmonic pressure oscillations in the tube system. The patient may experience discomfort from these undesired pressure oscillations.

Moreover, the said pressure changes also tend to cause some issues to be solved in certain respiratory modes. For instance, in pressure controlled respiratory modes, these pressure oscillations or transient pressure changes provide for a major challenge to the control system of breathing apparatuses.

This is because a pressure control is usually obtained by means of a so-called closed loop technology. In order for closed loop control to be performed distinctly and accurately, the loop must be kept short. This can be done by positioning the pressure sensor in the loop close to the valve which controls the gas which is to be pressure controlled. Unfortunately, the pressure profile will be different at the Y-piece to that at the pressure sensor due to the transfer function of the long tubes. If, instead, one attempts to place the pressure sensor at the Y-piece 16, the pressure regulation loop becomes large, due to the intermediate patient tubing between such a positioned pressure sensor and the valve, with the consequent impaired pressure control.

Yet another cause of an undesirable pressure profile at the Y-piece may be that the gas source control is slow, which is often the case if the gas source comprises of a flow variable turbine, or if the inspiration valve is slow.

For instance, in United States patent application no. US 2002/0104537 a tracheal pressure ventilation system is disclosed for automatically and variably controlling the supply of a pressurized breathing gas to a patient via a breathing circuit that is in fluid communication with the lungs of the patient. However, transient pressure changes are not handled by the system of US 2002/0104537 and may become an issue with dire consequences for ventilated patients.

The aforementioned pressure oscillations or transient pressure changes are thus an issue that needs to be technically solved.

One object of the invention is thus to provide a device and/or method to avoid, eliminate or reduce the abovementioned pressure changes. In particular, such pressure changes should advantageously be preferably avoided, eliminated or reduced in close proximity to the patient, at the patient or even in the patient's airways or lungs.

Summary of the Invention These objects are met by means of the device and the method in accordance with in the appended independent claims, while particular embodiments are dealt with in the dependent claims.

Accordingly, embodiments of the present invention seek primarily to mitigate, alleviate or eliminate one or more of the above-identified deficiencies or disadvantages in the art, singly or in any combination, and solves at least partly the abovementioned issues by providing a device and method according to the appended patent claims. According to aspects of the invention, a device and a method are disclosed. The device and method provide for a desired flow profile to be generated in a breathing apparatus. The flow generated based on the flow profile is used to compensate or correct a gas pressure in conduits. This is performed at sufficient control speed to compensate for pressure transients.

The flow profile is advantageously generated at the Y-piece or a breathing mask, i.e. in close spatial proximity to the patient. The flow profile may also be provided in the airways of the patient in certain embodiments. The flow profile may also be provided in the lungs of the patient in certain embodiments.

Thus the gas pressure is corrected, and/or adjusted, in conduits, such as tubes, to provide a desired pressure profile.

The abovementioned issues are in some embodiments solved by an active element which generates a flow that compensates for undesirable pressures or pressure curves. A device of this kind can generate a flow profile which it is not possible to obtain from a distant positioned inspiration valve. For example, this method may be implemented in High Frequency oscillation (HFO) or High frequency ventilation (HFV) applications.

In advantageous embodiments of the invention, a transient handler unit generating the flow, i.e. the aforementioned flow generating device is fluidly connected to the gas channel in close spatial proximity to the patient.

The flow generated in this way is provided bi-directional and has a broad bandwidth, but may have a mean value of zero, as a mean value different to zero can be generated by the inspiration valve. Thus the transient handler unit does not need an own source of gas to provide the gas flow.

The transient handler comprises an actuator unit that provides for a gas volume displacement for providing the afore described compensation flow for controlling a desired pressure of gas delivered to a patient during inspiration.

In some embodiments, the flow generating device may comprise a loudspeaker element as an actuator, but having a specific design adapted to the application is preferable with regard to control speed requirements. A

loudspeaker element, i.e. a coil with a connected membrane for providing the gas volume displacement, has the advantage that it is readily available at low manufacturing costs while allowing for a quick control loop compensating undesired pressure patterns, oscillations, and/or transient processes.

An advantageous alternative to an ordinary loudspeaker element is to replace the coil with a piezoelectric actuator combined with a mechanical amplifier. This alternative will considerably improve the bandwidth of the device thanks to the characteristics obtainable by piezoelectric elements, in particular with regard to actuating speed and thus bandwidth.

The pressure is in embodiments measured close to the patient in order to properly control the device flow. The pressure signal provided by the pressure sensor is thus a measure for the pressure close to the patient. The pressure signal is a control input parameter to the transient handler unit for actively providing the flow thereof. This allows for the compensated, transient free or transient reduced, pressure profile of the gas delivered to the patient.

This pressure signal may be included in another pressure control loop whose desired control value is the desired pressure profile at the patient, and whose output signal controls the device actuator. In these embodiments, the transient handler is integrated into a ventilator system. The transient handler unit and the respiratory valves may be controlled by a single control unit.

Oscillations are cost-effectively avoided and patient comfort and treatment are improved.

Alternatively, the device can also be provided as a stand-alone unit next to the patient. It can then help to actively counteract oscillations according to predetermined criteria.

According to a first aspect of the invention, a pneumatic transient pressure handler unit is provided for connection to and control of pressure in a breathing system. The transient pressure handler comprises at least one actuator element, at least one container having a volume for displacement by an actuator, and an outlet channel, as well as at least one pressure sensor. The movement of the actuator element compresses or decompresses the container, depending on the pressure measured by the pressure sensor. Thus a desired volume is displaced based on input from the pressure sensor signal. The container's outlet channel is fluidly connected to the breathing circuit. The breathing circuit, in turn, is in operation connected to the patient, as described above via e.g. a tracheal tube, breathing mask etc. Thus, the displaced gas volume and hence gas flow is provided to the breathing circuit. The gas volume may be displaced into the breathing system when the actuator compresses the container. The gas volume may be displaced out of the breathing system to fill the container when the actuator decompresses the container. Alternatively, or in addition, the container may be resilient and support the filling thereof, e.g. providing a bias against which the actuator has to work.

In this manner the transient pressure handler compensates for undesired pressure variations in the breathing system.

Thanks to this advantageous design of embodiments of the invention, the pneumatic transient pressure handler may be connected to a flow

generating device, such as a respirator system, and there act as an active element which is both bi-directional and has broad in bandwidth. The desired pressure profiles may be created by controlling the system with a pressure control loop which in turn is connected to another pressure control loop where the pressure is measured close to the patient in a suitable manner.

The container is advantageously designed as a bellows. The bellows is set in motion by the actuator. It may be supported by a spring force of a resilient element, e.g. integrated into the corrugated folds of the bellows. A disk may be provided for pressing on the bellows, which in turn is set in motion by the actuator.

The invention may in some embodiments also be used as a stand-alone unit at a patient and then be used to actively counteract oscillations according to predetermined criteria.

In one advantageous design of the pneumatic transient pressure handler, actuator element 30 comprises piezo actuators.

This design considerably improves the bandwidth of the embodied device compared with e.g. a coil, which may also be used in other embodinnents. When using piezo actuators it is advantageous to connect these in series with a mechanical motion amplifier 31 to amplify the amplitude of a pushing or pulling movement of the piezo actuator.

In another aspect, embodiments of the invention comprise a method for compensating or controlling transient pressures and flow processes in a breathing system. The method comprises providing a pneumatic transient pressure handler connected to a breathing system to control the movement of an actuator unit in a pressure control loop of at least one pressure sensor, and by means of the motion creates a flow in and/or out of the pneumatic transient pressure handler unit in order to generate a desired pressure profile in the breathing system.

The method may be provided as an internal control method in a transient unit handler unit.

In some particular embodiments, the method may be provided for avoiding transient pressures in portions or aspects of breathing apparatuses that are not related to the therapy of a connected patient. For instance, the transient compensation may be applied during a start-up test of a breathing apparatus without a connected patient. Here, the Y-piece may be clogged or a test lung may be connected instead of a patient.

The advantages of this method are the same as for the equipment described above, i.e. this method may produce a desired pressure profile at the patient, e.g. remove pressure oscillations, which are induced in the breathing system tubes by pressure changes and which can give rise to harmonic oscillations. The patient may experience discomfort from these and they may cause problems with pressure controlled respiration methods.

Further embodiments of the invention are defined in the dependent claims, wherein features for the second and subsequent aspects of the invention are as for the first aspect mutatis mutandis.

Hence, embodiments of the invention provide a device and method to avoid, eliminate or reduce the abovementioned undesired pressure changes. In particular, such pressure changes are avoided, eliminated or reduced in close proximity to the patient, at the patient or even in the patient's airways or lungs.

It should be noted that the device or method of embodiments of invention does not controlling a gas flow to the lungs of a patient on the level of inspiratory volumes of one or more entire breathing cycles. It does not as such provide breathing gas itself to a patient, which is provided in a mainstream through tube 14 and Y-piece 16 by the breathing apparatus. Embodiments of the invention rather provide for handling undesired pressure variations, including transient pressure variations and/or oscillations (with far higher frequencies than the respiratory breathing rate) during the inspiratory phase of a breathing cycle.

Brief Description of the Drawings

These and other aspects, features and advantages of which the invention at least is capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which

Figure 1 is a schematic view showing an exemplary embodiment of a common breathing system configuration according to the prior art;

Figure 2 is a schematic view showing how a breathing system may be supplemented with a pressure compensation device 20 according to an embodiment;

Figure 3 is a schematic view showing an exemplary embodiment of a pressure compensation device; and

Fig. 4 is a flowchart of a method 200.

Description of Embodiments

Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements.

In some embodiments a pneumatic transient handler unit 20 is provided for connection to a breathing system and control of pneumatic gas pressure therein. The pneumatic transient handler unit 20 comprises at least one actuator element 30. Further, it comprises at least one container having a volume with an outlet channel 34 for connection to the breathing system. At least one pressure sensor 35 is provided. The pressure sensor measures the pneumatic gas pressure at the outlet channel. Alternatively, or additionally, the gas pressure in the breathing system in close proximity to the outlet channel 34 may be measured by one or more pressure sensors (not shown). The actuator element 30 is arranged to change a volume of the container. By motion of the actuator, the volume is changed, i.e. either made smaller or larger. The actuator element 30 compresses or decompresses for instance the container. The volume change is made in dependence of the pressure measured by the pressure sensor 35. Actuation, i.e. timing and extent of a movement of the actuator affecting the container volume, is based on the pressure signal provided by the pressure sensor(s). In this manner, a desired pressure profile is obtained in the breathing system, at least at the location of the transient handler unit in connection to the breathing system. In this manner undesired pressure variations in the breathing system are compensated by the transient handler unit 20. A desired pressure profile in the breathing system may thus be maintained, and pressure distortions like transient pressure spikes or

oscillations may be reduced, minimized, or removed by the transient handler unit, based on a pressure signal from the pressure sensor.

Figure 3 shows in a schematic view an exemplary embodiment of a pressure compensation device 20 with a piezoelectric actuator 30, a mechanical amplifier 31 , a movable disk 32, a bellows 33 and an outlet 34. The bidirectional arrow 36 shows the direction of the bi-directionally controlled flow.

An example of a device according to the invention may be obtained as shown in Figure 3 in that the motion from a piezoelectric actuator 30 is amplified by means of a mechanical amplifier 31 which in turn brings disk 32 into motion. Bellows 33 is then compressed and a momentary flow 36 is then created through outlet 34. Both actuator 30 and movable disk 32 are spring-loaded (not shown in the figures) so that movements and flows can be generated both ways. A pressure sensor 35 provides feedback into the pressure control loop for the device.

The container is thus in some embodiments advantageously designed as a bellows. The bellows is set in motion by the actuator. It may be supported by a spring force of a resilient element, e.g. integrated into the corrugated folds of the bellows.

The transient handler unit may advantageously be arranged in close proximity to the patient. Transient pressures remote to the patient, e.g. in the breathing apparatus 100, may thus still be present, but not relevant for patient comfort and treatment during inspiratory phases of mechanical ventilation.

The pressure sensor is in some embodiments arranged to measure the pneumatic pressure at a Y-piece 16 of the breathing circuit. In this manner, transient handling is made in close proximity of to the patient, seen in the pneumatic tubing system.

The unit maybe fluidly connected to Y-piece, which usually is kept by a holder, supporting the additional weight of the compact unit of the embodiment.

The transient handler may be integrated into a unit inserted into the airways of the patient. In this manner, an even closer and improved transient handling is provided for patients. For instance the transient handler unit may comprise a tracheal tube (not shown), as described in more detail below. In this embodiment, the outlet may be part of the tracheal tube and said pressure sensor may arranged to measure pneumatic pressure in the airways of the patient when connected to said breathing system. ln advantageous embodiments of the invention, a transient handler unit generating the flow, i.e. the aforementioned flow generating device is fluidly connected to the gas channel in close spatial proximity to the patient.

The pressure is in embodiments measured in the breathing system in close proximity to the patient in order to properly control the device flow.

Alternatively, or in addition, the pressure may be measured within the airways of the patient. The outlet of the transient handler unit is preferably arranged integrated with, or close to the measurement point of the pressure sensor (s) in order to properly control the device flow. The pressure signal provided by the pressure sensor is thus a measure for the pneumatic pressure that is present close to the patient. The pressure signal is a control input parameter to the transient handler unit for actively providing the flow thereof. This allows for the compensated, transient free or reduced, pressure profile of the gas delivered to the patient in an advantageous manner.

This pressure signal may be included in another pressure control loop whose desired control value is the desired pressure profile at the patient, and whose output signal controls the device actuator. In these embodiments, the transient handler is integrated into a ventilator system.

The transient handler unit and the respiratory valves may be controlled by a single control unit. A control unit of ventilator may be used for controlling the transient handler too. All that is needed is then transfer means for the signals from the pressure transducers and for the control signals to the actuator unit. The transfer means may be wired or wireless.

Alternatively, the transient handler has own control unit, which provides for redundancy or stand-alone functionality thereof.

Details on suitable piezoelectric actuators and details on mechanical amplifiers can be found in US patent applications numbers US61/345,625 and US13/105,661 of the same inventor, which is incorporated herein by reference in its entirety for all purposes. In US61/345,625 a mechanical amplifier and method are disclosed for converting a small motion amplitude to a larger motion amplitude. The mechanical motion amplifiers devices and methods are well suitable for the present embodiments of transient handling units, in accordance with the following reasoning. The mechanical motion amplification method includes using two or more beams which are connected in series at angles to each other. Undesirable movements arising in the structure are absorbed by the structure through torsion. Each beam is a mechanical motion amplifier, and by connecting these in series, the total amplification is the product of the

amplification of the comprised beams. A mechanical motion amplification device thus comprises two or more beams connected together at an angle of 90 degrees in an embodiment. ln one aspect, the US61/345,625 disclosure includes a mechanical motion amplifier for amplification of an amplitude of a motion from an actuator unit. The motion amplifier may include at least two beams connected in a series at an angle, where the thickness of each beam is substantially less than its orthogonal extension, and wherein each beam has at least one supporting element about which the beam is pivotable. When the serial connection is exposed to a pushing or pulling motion having a first amplitude from at least one actuator unit, the amplifier amplifies and generates a second pushing or pulling motion, in parallel in the same plane, with a larger amplitude than the first amplitude. The amplified amplitude and its direction are determined by the gear provided by the design, which depends on how the beams, supporting elements, and at least one actuator unit are positioned in relation to each other. The beams may be described as having properties, which besides being thin, comprise low torsional strength, low weight, and small dimensions. This leads to various properties being obtained, such as the serial beam design having low inertia and thus a rapid amplification response. [0016] Moreover, in some embodiments, the gearing transmission is obtained by a pushing or pulling motion being applied to a first beam, either from one or a plurality of actuator units, or from a second beam adjacent to the first beam, at a position a distance X1 from the supporting element of the first beam support, which in turn is positioned a distance X2 from where the first beam is touching a third beam or the last beam in the series where the final amplified motion is to be applied. Optionally, the device may be designed such that the distances are X1 <=X2 for each serially connected beam. In order to achieve an amplified amplitude of the final motion, the abovementioned relation should be complied with for each beam connected in the series. In some embodiments of the mechanical motion amplifier, the position of each beam's supporting element is adapted to providing a transmitted amplified motion amplitude by the beam that is pushing or pulling. By adjusting where the supporting element for each individual in- series connected beam is positioned, the final amplified motion becomes pushing or pulling. For example, a pushing motion from an actuator unit may be an amplified pushing properties, such as being thin, having low torsional strength, low weight, and small dimensions. In yet another embodiment, the beams connected in series of the mechanical motion amplifier may be made as an integral part of a continuous piece of foil. In still another embodiment, twisting motions and lateral motions that may occur against a first beam, caused by motions of a second adjacent beam, may be absorbed by the first beam by means of lateral bending and torsion. Twisting motions in the structure of beams connected in series are mainly absorbed, due to the angle between the beams, by the first beam by means of torsion. In another aspect of the mechanical motion amplifier, a beam having no amplifying effect of the motion may connect two adjacent beams having an amplifying effect of the motion. Moreover, the in-series connected beams may form part of a system of a plurality of mechanical motion amplifiers, in which the design allows at least two units of in-series connected beams to be linked together in order to, in a compact way, distribute the pushing and/or pulling motions from one or more actuator units, positioned vertically against the at least two units of in-series connected beams, and generate, in at least two zones, parallel pushing and/or pulling motions with amplified amplitude. This type of system, having more than two units of beams connected in series, provides for effectively obtaining an amplified motion amplitude (which may be either pushing or pulling) to occur in parallel, but at the same time, almost simultaneously. From the same system, a combination of pushing and pulling motions may be obtained. For instance, if one alters the position of the supporting elements, the same pushing motion may be converted to an amplified pulling motion. In some embodiments, the beams of the mechanical motion amplifier may be made of a foil. By making beams of foil, they may be manufactured having various properties, such as being thin, having low torsional strength, low weight, and small dimensions. In yet another embodiment, the beams connected in series of the mechanical motion amplifier may be made as an integral part of a continuous piece of foil. In still another embodiment, twisting motions and lateral motions that may occur against a first beam, caused by motions of a second adjacent beam, may be absorbed by the first beam by means of lateral bending and torsion. Twisting motions in the structure of beams connected in series are mainly absorbed, due to the angle between the beams, by the first beam by means of torsion. In another aspect of the mechanical motion amplifier, a beam having no amplifying effect of the motion may connect two adjacent beams having an amplifying effect of the motion. From the same system, a combination of pushing and pulling motions may be obtained. Another aspect of the disclosure includes a mechanical motion amplification method. The method may include using at least two in-series connected beams, wherein each beam is designed to have low torsional strength, low weight, and small dimensions. According to the method, the pushing or pulling motion from at least one actuator unit having a first amplitude, on one of the beams connected in series, is provided with an amplified amplitude as a result of cooperation between the beams connected in series so that the total amplification of the first pushing or pulling motion's amplitude is a product of the cooperating beams' amplifying effect on the motion amplitude. Thus, the final amplified pushing or pulling motion is parallel to the first pushing or pulling motion. The rigidity of a beam having square cross section is increased by the cube of the beam's cross sectional width in the working direction of leverage. Thus, the cross sectional width of the beam has been made greater compared to the orthogonal width in the working direction. This also decreases the mass and provides a high resonance frequency. Metal with a low surface roughness has greater resistance to exhaustion than a processed surface. Therefore, in some embodiments, a low surface roughness is used. In one embodiment, a cross section of the foil is not bent, but only the actual foil orthogonally to it. A thin beam has low torsional strength. This may be exploited to absorb motions in the device. The thickness of the foil may be in the range of 0.1 -1 mm. In some embodiments, the thickness is approximately 0.5 mm. Motions of two beams in a row, which in an undesirable manner are working against each other in a plane, may, by bending one of the beams in an angle relative to the other, be absorbed, so that the motions may be converted to a twisting of the first beam. By making the beams thin, they may be manufactured from foil, and with a design according to the disclosure, it is easy to produce three dimensional structures by bending the foil to the desired structure. To work with large forces, structures may be provided that comprise several parallel beam systems.

Alternatively, the transfer handling device can also be provided as a stand-alone unit. The stand-alone unit is preferably arrangeable next to the patient. It can then help to actively counteract oscillations and transient handling according to predetermined criteria without interaction with a breathing apparatus. The stand-alone unit may have its own source of energy, e.g. a battery. Battery powered operation is in particularly advantageous in

combination with a pizeo actuator that is very energy efficient. In this manner, a power grid independent unit is provideable. This is in particular advantageous in certain conditions, e.g. power outages, development countries, acute operation, remote area operation, etc. Operation may be provided in combination with purely gas driven pneumatic breathing apparatus, which often are exceptionally sensitive to transient pressure processes as the inspiratory valves are not smoothly electronically controlled.

In certain embodiments, the transient handler may also be operated on the expiration side or during the expiration phase of the breathing circuit. As e.g. shown in Fig. 3, the transient handler unit 20 is provideable in fluid

communication with the expiratory portion of the breathing circuit. In this manner, e.g. oscillations or transient pressures during expiration may be handled. Such pressure disturbances may occur under certain operative circumstance, such as if expiratory valves are defective, or if expiratory valves are slow in regulating an end expiratory positive pressure (PEEP).

In some embodiments the transient handler unit is provided with a tracheal tube (not shown) for compensating transient pressures in the airways of the patient. The tracheal tube is a tube to be inserted into the airways of the patient, e.g. via the mouth using a laryngoscope. The tracheal tube has at least one lumen or channel in fluid communication with a distal end thereof for providing a gas passage into and out of the patient's lungs. ln some embodiments, one or more pressure sensors are provided at a region of the distal end of the tracheal tube.

Alternatively, a second lumen of preferably low compliance is provided in the tracheal tube to a pressure sensor arranged at proximal end of the tracheal tube and in fluid communication with a distal end of the second lumen at the distal end region of the tracheal tube. The distal end of the second lumen may be open. Alternatively, it may be closed with a flexible membrane allowing for transferring pressure changes measureable by the pressure sensor. Thus, gas or other contaminants from the patient can be kept apart from the pressure sensor. The pressure sensor may thus be re-useable between patients while the tracheal tube is advantageously a single use, disposable device.

The container, actuator unit, and maybe a control unit, can be provided externally to the patient to provide gas volume displacement for pressure compensation and providing a desired pressure profile.

The transient handler unit may at least partly be integrated into a tracheal tube and energy for driving the actuator is provided from external to the patient.

The container may be provided as a flexible wall of a tracheal tube. The flexible wall may be integrated into an outer surface of the tracheal tube and may act as a volume displacement unit. Displacement may be actuated remote, conveyed to the flexible wall via a fluid connection channel. Alternatively, or in addition, actuator elements may be integrated into the tracheal tube so as to achieve the desired displacement of the flexible wall.

In this embodiment, the container is integrated into the tracheal tube and does not need to be in direct fluid communication with the breathing circuit

In another aspect, embodiments of the invention comprises a method for compensating or controlling transient pressures and flow processes in a breathing system. The method comprises providing 210 a pneumatic transient pressure handler connected to a breathing system to control 220 the movement of an actuator unit in a pressure control loop of at least one pressure sensor, and by means of the motion creates a flow in and/or out of the pneumatic transient pressure handler unit in order to generate 230 a desired pressure profile in the breathing system. Fig. 4 is a flowchart of a method 200.

The method may be provided as an internal control method in a transient unit handler unit. The method of internally controlling a transient handler unit my be performed when said breathing system is disconnected from a patient, such as during a start up check of a breathing apparatus in order to control a reliable function of the transient handler unit. In some particular embodiments, the method may be provided for avoiding transient pressures in portions or aspects of breathing apparatuses that are not related to the therapy of a connected patient. For instance, the transient compensation may be applied during a start-up test of a breathing apparatus without a connected patient. Here, the Y-piece may be clogged or a test lung may be connected instead of a patient.

The pneumatic transient handler unit used in the method may be any of the herein described embodiments. The generating 230 of a flow into and/or out of said pneumatic transient handler may be made via an outlet of said pneumatic transient handler unit, and wherein said outlet is in direct fluid communication with said breathing system or a separated volume therefrom, such as by a membrane or flexible wall.

In some embodiments it is hence sufficient to have an indirect volume communication between the container and the breathing circuit. A membrane may be arranged between the two gas spaces (container / breathing circuit)

Hence, embodiments of the invention provide a device and method to avoid, eliminate or reduce the abovementioned undesired pressure changes. In particular, such pressure changes are avoided, elinninated or reduced in close proximity to the patient, at the patient or even in the patient's airways or lungs.

The present invention has been described above with reference to specific embodiments. However, other embodiments than the above described are equally possible within the scope of the invention. Different method steps than those described above, performing the method by hardware or software, may be provided within the scope of the invention. The different features and steps of the invention may be combined in other combinations than those described. The scope of the invention is only limited by the appended patent claims.

Claims

A pneumatic transient handler unit (20) for connection to a breathing system and control of pressure therein, comprising:

at least one actuator element (30);

at least one container having a volume with an outlet channel (34); at least one pressure sensor (35); and

wherein a motion of the actuator element (30) compresses or decompresses the container in dependence of the pressure measured by the pressure sensor (35), and

wherein the outlet channel (34) of the container is in use connected to the breathing system, in such a manner that undesired pressure variations in the breathing system are compensated by the unit (20).

Transient handler according to claim 1 , wherein the pneumatic transient handler is arranged and said actuator is controlled to contribute to maintain a desired pressure profile in the breathing system, based on a pressure signal from the pressure sensor.

Transient handler according to any of claims 1 -2, wherein the pneumatic transient handler is configured to operate as a stand alone unit with transient pressure compensation based on

predetermined criteria.

Transient handler according to any of claims 1 -3, wherein the actuator element (30) comprises at least one piezo actuator.

Transient handler according to claim 4, wherein a mechanical motion amplifier (31 ) is serially coupled to the actuator element (30).

Transient handler according to any of claims 1 -5, wherein said container comprises a bellows (33), and/or a resilient element against which said actuator is biased. Transient handler according to claim 6, wherein the actuator element is arranged to bring a disk (32) in motion for changing a volume of said bellows (33) for displacement of a portion of said bellows volume into said breathing system or from said breathing system into said bellows.

Transient handler according to any of claims 1 -7, wherein said pressure sensor is arranged to measure pressure at a Y-piece (16) of said breathing circuit.

Transient handler according to any of claims 1 -7, wherein said outlet is part of a tracheal tube and said pressure sensor is arranged to measure pressure in airways of a patient connected to said breathing system.

0. A method (200) of compensating or controlling transient pressures and flow processes in a breathing system, wherein the method comprises

providing (210) a pneumatic transient handler unit coupled to a breathing system,

controlling (220) a motion of said actuator unit in a pressure control loop by means of at least one pressure sensor, and

generating (230) a flow into and/or out of said pneumatic transient handler unit for generating a desired pressure profile in the breathing system.

1 . Method according to claim 10, wherein said pneumatic transient handler unit is arranged and connected to said breathing system in close proximity to a patient who is connected to said breathing system.

12. Method according to claim 1 1 , wherein said pneumatic transient handler unit is arranged to a Y-piece or a breathing mask in fluid communication with said patient.

13. Method according to any of claims 10-12, wherein said pneumatic transient handler unit is a pneumatic transient handler according to any of claims 1 -9.

14. Method according to any of claims 10-13, wherein said method is a method of internally controlling a transient handler unit when said breathing system is disconnected from a patient, such as during a start up check of a breathing apparatus.

15. Method according to any of claims 10-14, wherein said generating (230) a flow into and/or out of said pneumatic transient handler is made via an outlet of said pneumatic transient handler unit, and wherein said outlet is in direct fluid communication with said breathing system or a separated volume therefrom, such as by a membrane or flexible wall.