DE2432932A1 - METHOD AND DEVICE FOR TRIGGERING THE INHALATION PHASE IN A VENTILATION DEVICE - Google Patents

Description

MANITZ, FINSTERWALD & GRÄMKOW

S / sch - A 3024

B. July

f !

AlRCO INC.

85 Obestnut Ri & ge Road, Montvale, H.T. 07645, USA

Method and device for triggering

the inhalation phase for a ventilator

The invention relates to ventilators and relates in particular to a method and an apparatus for Triggering of the inhalation phase of a ventilator of the kind that has an exhalation overpressure level in the patient's lungs only at the end of the exhalation phase, with the inhalation phase in response is triggered on the patient's attempt to inhale.

The intensive care units of most medical institutes are now equipped with a device to deal with the critical

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see functions of supporting or entertaining the patient, who is too weak, sick or badly injured to maintain his own function. Such a critical function is of course breathing.

Ventilators have been used for a period of time to assist or fully control breathing, by forcing a patient's respiratory cycle. In particular, a gas that contains oxygen or pure oxygen can be brought into contact with the patient's lungs under pressure, in Response to the patient's attempt to inhale »Typically, the patient's airway or respiratory system equipped with a pressure sensor that actuates a device, to deliver pressurized gas to the patient's lungs in response to a predetermined negative pressure in the Respiratory line or airway is detected.

A ventilator is sufficient for most patients, which has a pressure sensor which responds to a negative pressure or a slight vacuum in the airways or the breathing line, in some cases it is in a patient however, it requires positive pressure in the patient's lungs to maintain, for reasons that, for example, the collapse of the alveoli is prevented. In such cases, the ventilator should be triggered by a pressure drop in the patient's line, when the patient tries to inhale; however, the pressure may be within the patient's line or within the patient's airway does not drop below atmospheric pressure, but should

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rather, at a certain overpressure to trigger the inhalation process to lead. The basic trip sensors as they have already been used are therefore not effective, to determine a pressure drop that occurs above atmospheric pressure, especially in patients who are too are weak to overcome the overpressure level to create a vacuum to respond to the probe and the ventilator into an inhalation phase.

To overcome these difficulties, various devices have been used to the triggering device in such a way bias so that a patient can switch the ventilator to an inhalation phase without the need insists that it should create a vacuum, it being sufficient if a certain attempt is made to inhale will.

There is a disadvantage of such release systems with a preload in that the biasing force has to be adjusted beforehand and has no relation to the changing pressure in the In the patient's airway or in the patient's breathing line exists, although a slow or small leak can cause a change. Accordingly a serious disadvantage of such facilities is that that a slow-acting or minor leak that would not be detected by a vacuum alarm system is one Could create pressure drop that could be detected by a triggering system as a patient attempting to inhale could. This in turn would lead to the ventilator being switched prematurely into an inhalation phase.

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The object of the invention is therefore to provide a method and a device to create to switch a ventilator from an exhalation phase to an inhalation phase only when actually a patient's attempt to inhale is determined, regardless of a slow-acting or a minor leak in the breathing line or can occur in the patient's airway.

To solve this problem, the invention provides a device which is able to do so at the end of the exhalation process Maintain positive exhalation pressure in the patient's lungs and still maintain it safely and effectively through a Attempt by the patient to inhale can be switched from the exhalation phase to the inhalation phase, the Pressure in the respiratory line or the patient's airway does not have to be below atmospheric pressure, but rather rather, it can be kept at an overpressure, with a gradual pressure drop in the breathing line or the airway of the patient, for example caused by a leak in this line or path can, whereby it is ensured that thereby no switching of the ventilation device takes place.

According to the invention, the triggering takes place in the case of an exhalation positive pressure ventilation device in that the trip system has differential inputs to increase the rate of pressure drop determine. A first input signal represents the pressure of the patient's breathing line or airway while a second input signal represents a variable reference pressure derived from a pressure of a delayed breathing line

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which is diverted during most of the patient's exhalation phase. The pressure of the delayed Breathing line gradually approaches the pressure of the breathing line, even if there is a leak in the breathing line. As a result, the system adapts automatically the pressure drop in the breathing line and triggers the inhalation cycle only off if a predetermined rate of decrease in the respiratory line pressure in relation to the variable reference pressure is detected.

The invention is explained below, for example, with reference to the drawing described; in this show:

1 shows a graphical representation which shows the respiratory cycle of a patient in a "control mode ^{11 of} a ventilation device, the inhalation phase being triggered independently of a corresponding exertion on the part of the patient to inhale.

Figure 2 is a graph showing the respiratory cycle of a patient in a "support mode", with an inhalation phase through a corresponding The patient makes an effort to inhale,

Is a schematic representation to generate Fig. 3 a known / non-differential device for a Patiententrigger- and ventilation system which can be used for the respiratory cycle shown in Fig. 2 of the patient,

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Figure 4 is a graph showing the respiratory cycle of a patient illustrated when he is on a ventilator a positive pressure is created in the patient's lungs at the end of the exhalation phase generated and triggered by the patient's exertion to inhale,

Fig. 5 is a schematic representation of a known, mechanical biased, non-differential device that is triggered by the patient and is used to generate the breathing cycle shown in FIG. 4,

Fig. 6 is a schematic representation of a known pneumatic, differential device, which is triggered by the patient and is used to provide a reference input pressure to pretend

7 is a graphical representation of a respiratory cycle of a Patients, as it is reached when the in Fig. 6 and 6 can be used when there is a small leak in the patient's breathing line is,

8 is a graphic representation of a respiratory cycle of a Patients, when the tripping devices shown in FIGS. 5 and 6 are used and when there is a relatively large leak in the patient's breathing line "ö,

9 shows a schematic representation of an inventive

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Device in place during the inspiratory portion an operating cycle,

Fig. 10 is a schematic representation of the switching valve part of the in the device shown in FIG. 9 in an arrangement during an exhalation portion of an operating cycle;

11 is a graph showing a patient's respiratory cycle during operation of the trigger represents according to the invention, as shown in Figs. and 10,

Figure 12 is a graph showing the respiratory cycle represents a patient, specifically when using the device according to the invention, wherein a breathing line has a small leak, and

Fig. 13 is a graphical representation of a patient's respiratory cycle using the methods of the present invention The device and the method according to the invention in conjunction with a breathing line, which is a relatively has a large leak.

In the drawing, the same reference symbols are used to to designate corresponding parts in the various embodiments. Fig. 1 is a graphical representation which shows a patient's respiratory cycle while on a ventilator works in the "control mode" and the patient's inhalation phase is independent of the patient's exertion is triggered to inhale.

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It can be seen that forced ventilation is generated in the control mode and this mode is particularly useful for a patient when a patient is actually unable to breathe to trigger or entertain on their own. Of course, the respiratory cycle generated in the control mode is not necessary synchronized with the patient's natural respiratory cycle and can cause the patient to become hypoxic or can lead to over-ventilation. It is therefore advisable that the patient's respiratory cycle is controlled by natural needs of the patient is controlled for air and thus depending on the normal inhalation and exhalation characteristics of the Patient.

For this reason, most ventilators only generate the above-mentioned control mode during times when the Patient is unable to apply a minimum of breathable! Tat. Accordingly, there is generally a device that can be triggered by the patient in order to then trigger the inhalation phase, if the patient is found to be trying to inhale.

FIG. 2 illustrates the respiratory cycle of a patient, under the influence of a ventilator operating in the assist mode, generally a patient release selected in the V \ feise that the determination of a certain negative pressure difference "s" is used to set the facility to control in such a way that it goes into an inhalation phase.

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It can be seen that the cycle illustrated in FIG. 2 requires that the patient creates a negative pressure, i.e. a vacuum, before the ventilator initiates the inhalation phase. Would be the If the patient was not able to generate the required vacuum, the pressure difference "s" would not have arisen and the machine would be in the control mode illustrated in FIG work, through known equipment technology facilities. With this in mind, the assist mode becomes overplayed by the control mode if the patient is not able to apply the required pressure difference "s", to begin the inhalation phase of his respiratory cycle.

3 schematically illustrates a known one Device which can be used to generate the patient respiratory pressure curve shown in the figure. Necessarily the device has a housing 10, which is an inlet chamber for a ventilation line, which is through a flexible Membrane 14 is closed. A gas line 16 provides a connection between the chamber 12 and the breathing line 18 of the Patients, who in turn are connected to the ventilation unit 20. In the present description, the term "Patient's breathing line" is used in the sense that it is understood to mean any gas line that begins with communicates with the lungs of the patient, and this gas line can comprise any other gas line is designed to determine the pressure in the patient's lungs.

A ventilation control unit 22 which is responsive to the movement of the flexible membrane 14 can be provided. It can be

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dear different bodies used to keep the movement the membrane 14 in response to the creation of a vacuum to be determined in the chamber 12 by the patient. Such Motion sensors contain correspondingly sensitive electrical switches, direct electrical contact devices (vot ^ which one moved with the membrane), arrangements of light sources and photocells as well as flow sensors.

An element 24, which extends from the flexible membrane 14 into electrical switching relationship to the electrical control unit 22 extends.

While the release system described above is sufficient for most applications, it is sometimes desirable to have one Constantly maintaining positive pressure in the alveoli of the patient. In such cases, overpressure is created in the Maintain the patient's lungs at all times, including during the entire exhalation phase.

Figure 4 is a graphical representation of a patient's respiratory cycle during which positive pressure is continuously maintained in the patient's lungs. The pressure curve 26 represents the minimum positive pressure that should be maintained in the patient's lungs, except for an instantaneous pressure drop that occurs when the patient attempts to inhale. The pressure level 26 is generally referred to as positive exhalation pressure (AAÜD) and briefly mentioned below as AAÜD.

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From Fig. 4 it can be seen that in a ventilated patient, if an AAUD is maintained, a device according to Fig. 3 is not effective because it would be difficult even for a healthy patient to obtain a suitable sufficient vacuum within the chamber 12 to initiate the inhalation phase of its respiratory cycle. Therefore it becomes a well-known The device according to FIG. 5 is sometimes used to assist the patient in initiating the inhalation phase.

In particular, FIG. 5 illustrates a modification of the FIG the device shown in FIG. 3, in which a mechanical prestress acts on the flexible membrane 14. The bias has the same polarity as the force generated by the patient's attempt to inhale so that the The patient is supported in moving the flexible membrane against the overpressure in the chamber 12. Accordingly, a Spring 28 or similar device may be operatively connected to the diaphragm 14 such that the diaphragm is directed towards a position is biased, which corresponds to the triggering of an inhalation phase. The magnitude of the preload force which is applied by the spring 28 can be adjusted by a corresponding adjusting screw or by a similar device, so that the pressure drop difference in advance can be adjusted, which is required to move the membrane.

The device according to FIG. 6 operates essentially in the In the same way as the device according to FIG. 5, a pneumatic preload is applied to the membrane 14 by a pressurized gas is introduced into a reference chamber 32

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w! rd, which is present in the overall housing 10 of the release device, the reference pressure by means of an adjusting valve 34 can be set. By producing an overpressure in the chamber 32 as a reference pressure, the flexible membrane 14 are moved in the actuating direction in response to the pressure drop in the chamber 12, thereby reducing the pressure to a predetermined pressure difference is reduced below the reference pressure.

During the operation of the release devices shown in FIGS it is generally sufficient if, under ideal conditions, there is an overpressure in the patient's lungs maintained in the event of a leak in the patient's breathing line, however, it is known to exist Facilities run the risk of the inhalation process being triggered too early.

In particular from Fig. 7 it can be seen that when a small leak occurs in the patient's breathing line who Pressure in the patient's breathing line by the amount "s" can drop below the reference pressure (which in this case is equal to AAÜD) and that an inhalation phase is triggered prematurely will. Fig. 8 illustrates the condition which exists would be if there were a major leak in the patient's breathing line, which may not be large enough to trigger an appropriate low pressure alarm or activate another alarm system, as is typically done is provided in known ventilation systems.

It can also be seen from Fig. 8 that a major leak

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would trigger the inhalation phase much too early, whereby the ventilator would be brought into a free-running condition in which there is a risk of over-ventilation of the patient occurs;

Of course, such a condition is highly undesirable.

According to FIGS. 9 and 10, a device according to the invention according to the schematic representation has a housing 10 which a flexible membrane 14 mounted therein to define a breathing line pressure chamber 12 and a variable reference pressure chamber 32. A gas line 16 brings the chamber 12 with the breathing line 18 of the patient in connection, which in turn is in connection with the ventilation unit 20.

The reference pressure chamber 32 is connected to the patient's breathing line 18 connected via lines 16, 17 and 36. A pneumatic resistor 38 and a pneumatic condenser 40 are operative connected within the lines 17 and 36, respectively, in order to delay the build-up of pressure in the reference pressure cylinder 32, if the chamber 32 with the pressure of the breathing line 18 is in communication. A switching valve 42 serves to control the reference pressure chamber vent to atmosphere through tube 46 when the device is in the position shown in Figure 9, and to bring the reference pressure chamber 32 into communication with the patient's breathing line 18 when the device is in the position shown in Fig. 10 is located. If this latter case is present, both the reference pressure chamber 32 and the associated pneutamic condenser 40 are gradually brought to the pressure that is present in the line 18 is.

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The inventive device operates in such a way that the reference pressure in response to changes in the pressure in the Breathing line 18 is changed so that triggering in Response to a drop in pressure occurs at such "rates" as they do correspond to the rates produced by the patient's effort to inhale, but with no inhalation phase in response to the pressure drop triggered at rates such as that of small or minor leaks in the Overall system originate, which supplies the patient.

For illustration, FIG. 11 shows a pressure curve (solid Line) for a respiratory cycle of the patient, while the AAÜD has a broken curve 44. the Reference pressure curve representing the pressure in chamber 32, is drawn as dashed line 46. It must be taken into account that an inhalation phase is triggered when the The solid pressure curve drops below the reference pressure curve 46 by "s".

During the inhalation phase, the valve 42 is switched in such a way that the reference pressure chamber through the outlet opening 46 into the Atmosphere is vented.

A coil 48 can be connected to the switching valve 42 so that the valve 42 is held in the venting position, as shown in FIG. 9, while a patient is in the inhalation phase. The coil can be turned on a certain time after the start of the exhalation phase. The switching of the valve 42 into the position shown in FIG. 10 must, however, be delayed by a time period T. This period should generally be in the range of 0.2 to 0.5 seconds _e

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During the time period T, the pressure in the lungs decreases Patient and in his airways to about the ideal AAÜD level 44. At the end of the period T, the switching valve 42 is in the in the position shown in Fig. 10 switched, so that thereby the release reference chamber 32 and the pneumatic condenser 40 with the patient's airways and lungs through the patient's breathing line 18 and the pneumatic resistance 38 is connected. The resulting exponential pressure increase in the pneumatic condenser 40 and in the trip reference chamber 32 is gradual because of the time delay effect of the capacitor 40 and the pneumatic resistor 38. The capacitor 40 can with an elastic compliant wall 50 be connected in such a way that the damping effect of a large capacitor is achieved without the correspondingly large physical dimensions of a capacitor with a rigid wall are required that have an equivalent damping or an equivalent time delay effect having.

As can be seen from FIG. 11, the reference pressure force is approaching 46 the pressure level in the patient's lungs (solid curve) during the exhalation phase. if If the patient tries to inhale, the pressure in the inlet pressure chamber 12 drops relatively quickly. The pressure in the Reference chamber 32 cannot fall off as quickly, namely because of the time delay effect of the pneumatic resistance 38, and thus the pressure in chamber 12 will soon drop to a pressure "s" below the pressure in the reference chamber 32 and thereby lifts the diaphragm 14 upwards to the main ventilation unit 20 into the inhalation phase.

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In FIG 12 ₀ a respiratory cycle of a patient during a state is illustrated in which the vent line of the patient has a small leak. It can be seen that the reference pressure 46 has a tendency to follow the decreasing pressure in the breathing line 18 so as to prevent premature initiation of the inhalation cycle in response to such a leak. "

Fig. 13 shows the condition of FIG ₀ 12 wherein in the vent line 18, a larger leak, which may not be sufficient to actuate an alarm system which, however, may be enough to the excess pressure in the patient's lungs at the end to eliminate the exhalation phase. It can be seen, however, that even under such an extreme condition, the reference pressure approximately follows the falling pressure in the patient's breathing line and thus an inhalation phase is not initiated until the patient attempts to inhale himself when the breathing tube pressure line (solid line) "s "with respect to the variable reference pressure 46 drops.

To ensure this type of operation, the pneumatic Resistor 38 may be chosen such that variable reference pressure curve 46 has the proper response time.

It can thus be seen that through the synergetic interaction of the elements of the device according to the invention, the device extraordinary in the preferred embodiment is straightforward, which means that it is very economical to manufacture and very reliable to operate.

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According to the invention, a significant technical advance can be achieved, namely by operating the inventive Apparatus a ventilation system with an AAÜD works, which is crucially controllable in such a way that the inhalation phase triggered in the patient's respiratory cycle only in response to the patient's attempt to inhale. Therefore, the operation of the device according to the invention cannot be impaired by a leak in a line.

While above a preferred embodiment of the subject matter of the invention has been described, it is apparent, however, that various modifications and changes are possible without to leave the scope of the invention.

For example, the input pressures could be converted into other parameters such as electrical voltages, which are then corresponding Phases as shown in FIGS. 11 to 13 is, and would be fed as input signals to an electrical release device in a manner known per se. In a similar way In this way it is not necessary that the variable reference pressure exactly follows the pressure in the breathing line. It is Rather only required · that the reference pressure corresponds to the existing Pressure essentially follows, so that a distance between the two pressure lines from one another is permissible.

-Patent claims-

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Claims (14)

PATENT CLAIM ^ 1.} Procedure for switching a ventilator off an exhalation phase to an inhalation phase for supplying a gas to a patient through a breathing line, thereby characterized in that the pressure in the patient's breathing line is continuous during the exhalation phase is monitored and that a predetermined rate of pressure drop in the patient's respiratory system is sensed in such a way that that the ventilator is brought into the inhalation phase. 2. The method according to claim 1, characterized in that that a given rate of pressure drop is sensed only during part of the exhalation phase. 3. The method according to claim 2, characterized in that the sensing of a predetermined rate of pressure drop is carried out during a period beginning 0.2 to 0.5 seconds after the start of the exhalation phase and ending at the time the ventilator is in the inhalation phase is switched. 4. A method for switching a ventilator from an exhalation phase to an inhalation phase for a patient to supply a gas through a breathing line, characterized in that the pressure within the breathing line of the patient is monitored in order to monitor a first To generate pressure that is related to the first monitored pressure 5O980 7 / Q724 is delayed in time to produce a second monitored pressure so that the second monitored pressure is substantially the first monitored pressure follows the first monitored pressure in the event of slight pressure changes, and that a predetermined one Pressure difference between the first monitored pressure and the second monitored pressure is sensed to the ventilator switch to an inhalation phase. 5, The method of claim 4, wherein one is based on a pressure difference appealing device is available which is assigned to the ventilation device, characterized in that that when monitoring the first pressure in the breathing line of the patient, the pressure in the breathing line of the patient with the device responsive to a pressure difference is connected as the first input signal that at the delay of the first monitored pressure to generate a second monitored pressure a connection between the breathing line of the patient and the device responsive to a pressure difference is established via a narrowed passage, through which during part of the exhalation phase the a second input signal is provided to means responsive to a pressure difference, and that upon sensing a predetermined pressure difference, which is used to open the ventilator to switch to the inhalation phase, the ventilator by the mode of operation of the on a pressure difference responsive device is actuated when the predetermined pressure difference between the first and the second input is detected. 609807/0724 6, pressure differential trigger system for switching a ventilation mode direction from an exhalation phase to an inhalation phase in response to a patient's effort to inhale, and although via a breathing line of the patient, thereby g e ke η n sign that there are a first and a second enclosed chamber that between the first and the second Chamber a flexible membrane is arranged and designed such that it is in response to a predetermined pressure difference between the pressure in the first chamber and the pressure in the second chamber is deflected that the deflection of the The membrane can be controlled in such a way that an inhalation phase trigger signal can thereby be fed to the ventilation device furthermore there is a device which serves to control the pressure in the breathing line of the patient with the first chamber to bring in connection that there is still a device which serves to control the pressure in the breathing line with the second chamber as a reference pressure during part of the exhalation phase that continues to connect a Means is provided which serves to reduce the effect of pressure changes in the breathing line to the second To retard chamber so that pressure changes in the second chamber in relation to pressure changes in the first Chamber be delayed, causing the pressure in the second chamber to change the pressure in substantially gradual changes follows the first chamber during part of each exhalation phase. 7. Arrangement according to claim 6, characterized in that the device which serves to reduce the pressure in the breathing line to connect to the second chamber, and only during 509807/0724 part of the exhalation phase, has a switching valve, this valve being actuatable by a valve actuating device is, and that the valve actuator works to bring the switching valve into a position in which is the pressure in the breathing line connected to the second chamber for a period that is 0.2 to 0.5 seconds begins after the beginning of the exhalation phase and ends at the beginning of the next inhalation phase. 8. An arrangement according to claim 7, characterized in that the means for delaying the effect of pressure changes one in the breathing line in the second chamber has pneumatic resistance, which throttles the device that connects the pressure in the breathing line serves with the second chamber. 9. Ventilation device for supplying gas to a respiratory system Management of a patient, with an inhalation and an exhalation phase are provided and wherein the ventilation device is designed such that a predetermined excess gas pressure within of the patient is maintained at the end of the exhalation phase and a switching device also serves to to switch the ventilation device from the exhalation phase to the inhalation phase, characterized in that, that there is means to monitor the pressure in the patient's breathing line; and that means is provided to determine a predetermined rate of a pressure drop, namely in the breathing line of a patient, to operate the switching device in such a way that the ventilator is switched in the inhalation phase. 509807/0724 10. A device for triggering a ventilator from an exhalation phase in an inhalation phase of a respiratory cycle in response to a corresponding effort by the patient to inhale, characterized in that a pressure difference responsive device is provided, that further means is provided to the pressure in to connect the breathing line to the device responsive to a pressure difference in order to supply this device with a first input signal that further means is provided which serves to reduce the pressure in the breathing line to the device which is responsive to a pressure difference only during one To connect part of an exhalation phase in order to thus supply a second input signal to the device that is responsive to a pressure difference, that a device is also present which serves to delay any pressure changes in the second input with respect to time, whereby the pressure in the breathing line including the second input signal with respect to the pressure in the breathing line including the first input signal is delayed in phase and that the pressure differential responsive device is operable to operate the ventilator in response to the occurrence of a predetermined pressure difference between the first input signal and the second input signal switches to the inhalation phase. 11. The device according to claim 10, characterized in that that the device responsive to a pressure difference has a housing that it furthermore has a flexible membrane, which the housing in a first chamber for receiving the 509807/0724 first input signal and divided into a second chamber for receiving the second input signal and that the flexible membrane deflects in response to a predetermined pressure drop rate in the first input signal to the ventilator switch to the inhalation phase, 12. The device according to claim 11, characterized in that that the device which serves to control the pressure in the breathing line with the device which is responsive to a pressure difference to connect, and only during part of an exhalation phase, has a switching valve, this switching valve is actuatable by a valve actuating device and that the valve actuating device operates in such a way that it brings the switching valve / a position in which the second input signal responds to a pressure difference with the Device during a period beginning 0.2 to 0.5 seconds after the start of the exhalation phase and ends at the beginning of the next inhalation phase. 13. The device according to claim 11, characterized in that that the means for delaying a change in the magnitude of the second output signal with respect to time includes one has pneumatic resistance which narrows a gas passage which is formed by the device which serves to supplying the second input signal to the device responsive to a pressure differential. 14. The device according to claim 11, characterized in that that the device for delaying any pressure changes in the second output signal with respect to: time 509807/0724 has a pneumatic condenser which has a variable Chamber in communication with the second chamber, the changeable chamber being formed in this way is that it decreases in volume in response to a decrease in the second pressure input signal. 509807/0724 Blank page