WO2009112076A1

WO2009112076A1 - Respirator having variable pressure support

Info

Publication number: WO2009112076A1
Application number: PCT/EP2008/053012
Authority: WO
Inventors: Helmut Hoffrichter
Original assignee: Hoffrichter Gmbh
Priority date: 2008-03-13
Filing date: 2008-03-13
Publication date: 2009-09-17

Abstract

The invention relates to a respirator having variable pressure support, comprising a differential pressure sensor 14 for determining the current pressure loss V1 at a reference resistor 3, at least one calculation element for calculating at least one additional pressure signal V4 from the current pressure loss V1, and an addition unit 21 for adding the at least one additional pressure signal V4 having a signal for a base pressure p0 to a control variable V5 of the pressure regulating device 11, 12, 13. The invention enables the simultaneous compensation for pressure losses at the breathing tube 5 and at the flow resistances of the airways of the patient. The limiter 18 enables tri-level respiration with settable end-inspiratory pressure reduction and pressure transitions controlled in the auto-biofeedback. By calculating a support factor, the pressure support as a function of the breathing depth can be influenced.

Description

description

[0001] Ventilator with variable pressure support

Technical area

The invention relates to a ventilator with variable

A pressure support incorporating an internal breathing system with a breathing gas generator in a pressure control device, wherein a gas outlet for providing pressurized breathing gas and any external accessories for directing the breathing gas via a patient interface into a patient's airway.

State of the art

A ventilator for the treatment of obstructive sleep apnea contains a pressure generator, which is usually a radial fan. The fan preferably aspirates the ambient air and compresses it to the ventilation pressure required for the therapy. In order for a given set ventilation pressure to be maintained, the ventilator includes a pressure control device with an actuator for driving the pressure generator. The task of the pressure control device is the production of an actual ventilation pressure, which is measured with a pressure sensor and regulated so that it deviates as little as possible from a predetermined target ventilation pressure. The desired ventilation pressure is the controlled variable of the pressure control device. The compressed breathing gas is introduced via a gas outlet and a breathing tube in the patient interface, which is preferably a face mask.

The pneumatic duct system of a ventilator is called

Respiratory system referred to and has a flow resistance, which is composed of the sum of several flow resistance at deflection points, cross-sectional changes, filters and mufflers. One distinguishes between an internal and an external respiratory system. The inner breathing system starts at the fresh air inlet and ends at the gas outlet. It consists in particular of air filters, noise dampers the blower and the Air entertainment system. The external breathing system starts at the gas outlet and ends at the patient interface. It consists in particular of the breathing tube, an exhalation valve and a humidifier. The patient interface is typically a face mask and serves to introduce the breathing gas into the respiratory tract of the patient.

The physiological flow channels are the respiratory tract. The

Sleep medicine deals in particular with the condition of the upper respiratory tract. These consist in particular of the nasal passages and the airway through the throat into the trachea and into the bronchial system.

All elements of the internal and external breathing system have

Flow resistance and obstruct a gas flow. Each flow resistor consumes exactly as much pressure as is needed to overcome it. The pressure generated by the blower therefore becomes smaller on the way into the bronchial system of the patient after passing through each flow resistance as a function of the flow intensity.

In a CPAP ventilator, the pressure in the face mask should be constant. In order to achieve this, one can supply the pressure sensor, which is arranged in the pressure control device for measuring the actual pressure, the pressure prevailing in the face mask. As a result, the blower always generates the target pressure to be produced in the face mask, and in addition, due to the action of the pressure control device, the sum of all pressure losses on the flow path from the blower to the face mask. Assuming a small control deviation, this happens regardless of the size of the flow resistances on the way.

However, this method of near-patient pressure measurement requires an additional pressure measuring tube. This directs the pressure prevailing in the face mask pressure to the arranged inside the ventilator pressure sensor. The hose length of about 2 m causes additional signal propagation times, causing the Dynamics of the pressure regulator reduced. This leads to dynamic control deviations. Another disadvantage is the impairment of hygiene when the pressure measuring tube is routed as usual inside the breathing tube. A regular cleaning is made difficult. In addition, the cost of an additional hose including all the connecting elements are not negligible, and finally, the additional pressure measuring hose can cause interference when it kinks, dissolves at a junction or when a drop of water settles through condensate from the humid air or simply from the cleaning water.

Therefore, methods are known that the loss pressure on the external

Respiratory system or only on the breathing tube. In conjunction with the pressure control device, the pressure generator continuously provides the target pressure and additionally the determined loss pressure at the gas outlet.

DE 102 53 947 C1 describes a method for compensating the pressure drop across a breathing tube, ventilator and storage medium. The compensation takes place in a first step by measuring the flow and the pressure in the device with remote respiratory mask. From the measured values, a resistance parameter is calculated. In the second step, the measurement of the flow with attached breathing mask and calculation of a correction pressure takes into account the pressure-flow characteristic of the breathing tube, which is then additionally provided by the pressure generator. A disadvantage is the additional expense of calibrating.

A CPAP ventilator can with different

Pressure control algorithms are equipped. The person skilled in the art knows the methods C-Flex or PPAP. US 6105575 describes for C-Flex that a sensor detects the respiratory characteristic and the device controller delivers the respiratory gas to the patient in at least part of the respiratory cycle to a "minimum required pressure". At the device control, which receives the sensor output signal becomes a Intensity adjusted to deliver the "minimum required pressure". In addition, it is described that a sensor detects the physiological conditions of the patient to distinguish between inspiration and expiration. The control of the device provides predefined pressure profiles, which should act at least during the inspiration phase. The shape of the profiles is independent of the breathing characteristics.

A disadvantage of the interconnection of predefined pressure profiles is the occurrence of airtraps. These are caused by a too rapid pressure drop in the face mask, which triggers a steep increase in the expiratory flow. Known in this context is the problem of those suffering from asthma. These are difficult to exhale, because the already constricted airways are almost completely pinched off as a result of the expiratory flow. With a corresponding back pressure on the mouth or nose, the expiratory flow can be reduced and the exhalation can be facilitated. Therefore, asthmatics unconsciously train themselves to exhale with a so-called "lip brake." They squeeze their lips into a narrow gap and allow the air to escape slowly, creating a counterpressure in the mouth that keeps the airways open and allows exhalation However, if a pressure profile is given solely by one device, respiration may be obstructed in many patients.

US6609517 describes a PPAP with a flow sensor, wherein the supplied to the patient pressure addition flow proportional and are set separately for inspiration and expiration. The disadvantage of the flow proportionality of pressure additions lies in the non-linear pressure-flow characteristic of flow resistances. The loss pressure as a function of a flow is described by Bernoulli's equation as Dp = v ² r / 2, where v is the

Flow velocity (v = flow / cross section) and r is the gas density. In practice, a mixed form of a linear and a quadratic component usually results. The purpose of pressure support is in alleviating or eliminating the obstructive effect of flow resistance in the respiratory tract. Therefore, the pressure support should also take the form of the loss pressure above the flow resistance. From rhinomanometry it is known that the loss pressure across the nasal passages increases exponentially with increasing flow. Because CPAP patients are forced to breathe through their nostrils only, assisting breathing in breathing is an advantage because the device helps overcome the flow resistance of the nose. If this pressure support is only proportional to the respiratory flow, its effect will decrease with increasing flow, because the loss pressure across the nasal passages increases exponentially with the flow.

A special form of pressure support is done with bi-level devices. These have a detector or breath trigger to determine the beginning of the two breathing phases of inspiration and expiration. For breath support, a higher IPAP pressure is turned on at the beginning of inspiration. This pressure is reached within a few 10 ms depending on the dynamics of the system and held for the duration of the inspiration. At the end of the inspiration, the signal from the breath trigger will turn on the smaller EPAP pressure. Again, this pressure is maintained during the expiratory phase until the breath trigger turns IPAP pressure back on.

Disadvantage is the rigidity of the pressure profile. Whether spontaneous breathing is currently deep or currently flat, the amount of pressure support and the speed of transitions from one pressure level to another are always the same and are rigidly controlled by the machine. With its spontaneous respiratory activity, the patient can only influence the onset of the respiratory phase-dependent pressure support, but not its size. The comfort of this pressure support is not optimal and the risk of Airtrapping is particularly important.

US 6948497 describes a bi-level system with a sensor for

Control of breathing, in which the pressure setting of the gas flow in the respiratory tract of the patient with the inspiratory phase and Exspiration phase is synchronized and the pressure during the expiration is set lower than during inspiration.

The US 7100607 also beschriebt a bi-level system with a pressure setting that this is at least in part of the expiratory phase less than in a part of the inspiration phase.

Presentation of the invention

The object of the invention is thus in a better adapted to the natural breathing pressure support of breathing.

Another object of the invention is to compensate for pressure losses on external accessories, in particular on the breathing tube by additional generation of an equal pressure at the gas outlet of the device, without the pressure in the patient interface is measured.

This object is achieved by a ventilator according to claim 1. The claims 2 to 7 indicate advantageous developments.

The ventilator according to the invention includes according to claim 1, an internal breathing system whose flow resistance is adjustable and negative. For this purpose, the pressure generator in the internal breathing system generates a pressure which is the sum of a predefined base pressure and an additional pressure, wherein the additional pressure is greater than the loss pressure on all flow resistance of the respiratory system between the pressure generator by a factor of at least 1.0 and the gas outlet are arranged. The signal for the magnitude of the additional pressure is determined by measuring the pressure loss at a characteristic flow resistance in the respiratory system and multiplied by a factor. This signal is added to the predetermined signal of the base pressure and supplied to the pressure control device as a controlled variable. The pressure control device then produces this pressure at the gas outlet.

The pressure support according to the invention has the advantage that the patient no rigid pressure profile is impressed. Instead, limits are set for maximum pressure assistance with a maximum respiratory tract resistance to be assumed. Whether these limits can be reached, the patient determines with his own breathing activity. Thus, the limits can be exceeded during heavy breathing, whereby the pressure support for the limitation period is no longer required. Hours later, the same patient is able to breathe very calmly, and a limitation of the breathing assistance takes place only to a small extent or not at all.

This type of pressure support has an automatic biological feedback effect by the patient with his own breathing affects the control of the device. A rapid pressure change imposed solely by the device could constrict the airway and make breathing difficult. In the device according to the invention, such a flow limitation would immediately slow down the speed of the pressure change. Breathing becomes more comfortable.

In the ventilator according to the invention, the pressure support is not proportional to the flow but proportional to the loss pressure that causes this flow just at a reference resistor. This reference resistor is disposed in the respiratory system and may have any characteristics that correspond to any external resistance whose effect is to be compensated. The disadvantage of continuous flow-proportional pressure supports, in which the effective pressure support decreases with increasing flow, is thereby avoided.

The invention is in addition to the compensation of the pressure loss of physiological airway resistance at the same time suitable for the compensation of the pressure loss to external devices such as a breathing tube or humidifier. This is done by the fact that their positive flow resistances are canceled by an equal negative flow resistance in the respiratory system. For complete compensation, therefore, the weighting factor for the signal measured at the reference resistor must be so dimensioned that the additional pressure is equal to the loss pressure at the external devices.

Advantageously, the ventilator according to claim 2 a

Computing member, which from the signal of the instantaneous pressure loss Spectral components with a frequency of zero removed. This makes it possible to apply the breathing air support solely to the breathed flow and not to leakage flow.

Particularly preferred is an inventive computing element according to claim 3 is used in combination with an amplitude limiter. This limits the signal remaining behind the arithmetic unit to an arbitrarily adjustable amount. This limitation can be made in negative and positive amplitude both in the same or different heights.

By such a limitation, in particular when it takes place after a gain to adjust the breathing support, a breathing assistance can be realized, which prevents weakening of the respiratory drive by an excessive pressure support. However, a breath flow that exceeds the limit is still possible, but requires your own breathing effort. Thus, the patient himself controls the transition between within and out-of-bound support levels without the need for a respiratory phase detector or breath trigger.

The invention is also suitable for controlling breathing work. With high pressure support for shallow breathing and little to no support for heavy breathing, normalization of the respiratory activity can be achieved. This task arises in particular in the therapy of patients with Cheyne-Stokes respiration.

For this purpose, it is particularly advantageous according to claim 3, instead of

Amplitudenbegrenzers use computational elements that evaluate the alternating proportion of the momentarily measured at the reference resistance pressure loss, and to use this as an additional pressure signal. In this case, the weighting factor is determined as the difference between a reference value and that of a computing element from the alternating portion of the pressure loss currently measured at the reference resistance. In this case, the reference value may be one specified from the outside or one dynamic, for example act value determined by the last breaths. In this case, the computing element may, for example, continuously determine the amplitude maximum or the time integral from the amount of the alternating component or an average value of the amount of the alternating component of the pressure loss currently measured at the reference resistor.

By such a device of the ventilator according to the invention, it is for example possible to perform the respiratory support antiproportional to the breathing depth.

To determine the alternating proportion of the currently

Reference resistance measured pressure loss, a computing element for eliminating the spectral components with a frequency of zero from the signal of the instantaneous pressure loss can be used.

Preferably, the ventilator is set up according to claim 4 so that external accessories, which are arranged between the gas outlet and the patient connection point, have a working on the basis of transponders or contact codes identifier and that the control part of the ventilator is set up so that he decodes the respective identifier and takes into account the respectively connected flow resistance of the external breathing system. Such a device of the device makes a manual input of additional flow resistance or recalibration superfluous. This makes upgrading the external accessories safer, easier and faster.

Preferably, an internal reference resistor is used as a reference resistor according to claim 5, which is placed between breathing gas generator and gas outlet and as flow resistance has a certain resistance characteristic, which preferably coincides with the resistance characteristic of the externally flowed through resistors.

By using an internal, lying in the gas flow from the generator to the gas outlet reference resistance, it is possible to use the gas flow necessary anyway for measuring the reference resistance. As a result, the generated gas stream can be used efficiently become. If a reference resistor is used, the characteristic of which corresponds to that of the externally flowed resistors, a particularly precise control of the breathing assistance is possible without complicated calculation steps.

Particularly advantageous and energy, component and space saving is to use an already necessary component as a reference resistor according to claim 6.

Preferably, according to claim 7, a parameter of the respiratory gas generator, preferably its instantaneous speed or its current operating current consumption, is used to determine the loss pressure at the flow resistance of the inner respiratory system. This is particularly advantageous since these parameters can be detected comparatively easily and can be used simultaneously with the operational control of the respiratory gas generator.

Brief description of the figures of the drawings

The invention will be explained below with reference to an embodiment to which the invention is by no means limited. On the other hand, further advantages and execution options become clear. The accompanying drawings show:

FIG. 1 shows a block diagram of a ventilator according to the invention

FIG. 2 shows a schematic signal course of the block diagram in FIG. 1

FIG. 3 shows an example of regulated respiratory support in Cheyne-Stokes respiration

The drawings are purely schematic and do not limit the invention.

Way (s) for carrying out the invention

The example device in FIG. 1 has an internal breathing system 1, which has a respiratory gas generator 2, a reference resistor 3, a gas outlet 4, a breathing tube 5, a patient connection point 6, which is preferably a face mask, and an exhalation valve 7. The respiratory gas generator 2 is preferably a fan which is operated in a pressure control device and the introduced breathing air on the prescribed ventilation pressure. This is supplied to the patient via the reference resistor 3 and possible further flow resistance of the inner respiratory system 1 and the breathing tube 5. The patient has a physiological airway resistance 8 and a physiological breathing pump 9. The exhalation valve 7 serves to vent the entire system and is preferably only an opening with a cross section of slightly more than 10 mm ² . From a systemic point of view, this exhalation valve 7 is a flow resistance to the atmospheric pressure and causes an artificial leakage.

The pressure control device for the breathing gas generator 2 consists of a control device 12 which controls the fan via an actuator 13, whereby the ventilation pressure is adjusted so that at the difference point 11, the difference between the measured with a pressure sensor 10 actual value of the base pressure pθ and the Setpoint supplied by adder 21 is a minimum. This goal is achieved the better the greater the dynamics of the respiratory gas generator 2 in particular.

The reference resistor 3, the differential pressure sensor 14 and consisting of the resistors 23 and 24 dividers for the size of the signal V1 form a system for compensating the loss pressure on the breathing tube 5. Provided that the reference resistance 3 is greater than the flow resistance of the breathing tube 5, the dimensioning rule applies

Δp (5) ₌ R (24)

Ap (3) R (24) + R {23)

If the reference resistance 3 should be smaller than the flow resistance of the breathing tube 5, then measured by the differential pressure sensor 14 signal V1 must not be shared but amplified.

The adder 21 obtains the sum of a predetermined base pressure pθ, which can be adjusted by means of the adjusting element 22, and the calculated loss pressure, which is available as a signal across the resistor R24. The resulting sum signal V5 is supplied to the pressure control device as a setpoint continuously.

In the function, a gas flow through the breathing tube 5 causes a Pressure loss. Since the pressure generator provides its desired pressure at the gas outlet 4, the pressure in the patient connection point 6 would always be too low by the pressure loss at the breathing tube 5. The figure shows, however, that the loss pressure at the reference resistor 3 is measured with the differential pressure sensor 14 and a part (or multiple) of this signal is added by the adder 21 to the predetermined signal of the base pressure pθ. This ensures that the pressure control device in the gas outlet 4 permanently generates the base pressure pθ and plus the expected pressure loss over the breathing tube 5. This is namely proportional to a portion of the pressure drop across the reference resistor and this part is made in the example by the consisting of the resistors 23 and 24 divider. As a result, the base pressure pθ in the patient connection point 6 is constant independently of the flow and independent of the pressure loss in the breathing tube 5.

For a pressure support of the breathing in the example figure are the

Elements 15 to 20 arranged. Respiratory support may only be used on the breathed flow, not on the leakage that escapes through the exhalation valve 7 or through other parasitic leaks. For this purpose, the signal processor 15 removes the spectral component with the frequency zero from the spectrum of the signal V1 delivered by the differential pressure sensor 14. Thus, an alternating signal V2 is available at its output.

With the amplifier 16, whose gain can be changed with the adjusting member 17 from zero to a certain size, the degree of pressure support can be adjusted. Conveniently, the adjustment member 17 could directly obtain a scale in resistance values, for example, from 0 mbar / (l / s) to -20 mbar / (l / s). The effect manifests itself in a different rate of change of the assisting additional pressure.

The limiter 18 cuts the amplitudes of the signal V3 supplied by the amplifier 16. With the adjustment element 19, a value for limiting the positive signal amplitude can be set. The Adjustment element 20 is used to set a limit for the negative signal amplitude. The resulting signal V4 is supplied to the adder 21.

When a patient breathes with his breathing pump 9, then arise

Pressure losses at the flow resistance 8. Without pressure support, the patient has to work to overcome this resistance. The pressure assistance would be optimal if the negative internal resistance of the ventilator, measured into the patient interface 6, is exactly the same as the positive airway resistance 8 of the patient.

The resulting at breathing at the reference resistance 3 loss pressure is mapped by the differential pressure sensor 14 to the signal V1. The signal processor 15 eliminates from this signal the spectral component with the frequency zero, whereby the signal V2 is formed. This signal is amplified by the amplifier 16 in its amplitude, wherein the gain can be specified with the setting 17. The amplified signal V3 is clipped by the limiter 18 in amplitude, provided that the amplitudes exceed the value set by the setting elements 19 and 20.

First, assume that the signal magnitude and the

Gain are set so that the cropping limits are not reached. In this case, the signal V4 at the output of the limiter 18 is identical to the signal V3 at its input. The pressure losses at the respiratory resistance 8 and at the reference resistance 3 are similar in their course, but different in size. After measuring the loss pressure at the reference resistor 3 and amplifying the signal, a pressure is generated by the addition of this signal V4 to the base pressure pθ from the pressure generator in the patient interface 6, which is ideally greater by exactly the loss pressure at the respiratory resistance than the predetermined base pressure pθ. Thus, the ventilator provides an additional pressure to overcome the airway resistance 8 or a portion thereof and relieves the respiratory muscles of the patient. The advantage here is that the pressure support is not flow proportional, but proportional to the pressure loss that generates the same flow at a flow resistance. One application would be a CPAP ventilator that compensates for the pressure loss at the nasal passages. This not only makes breathing easier, but also achieves the same therapeutic effect with lower treatment pressure.

Excessive pressure support can be the respiratory drive of a

Weaken patients. By limiting the amplitudes of signal V3, the pressure support is suspended during the limiting phase. Although the patient can still force his breath, he has to do so by his own efforts. Pressure support occurs only in the transitions until the onset of a limit. If a large gain has been specified with the setting element 17 and the limits are set accordingly, then the device works much like a bi-level device, but avoids its disadvantages. The difference lies in the fact that not the device but the patient himself controls the pressure transfer from one limiter level to the other. In addition, separate settings of the delimiter can be made for inspiration and expiration. Thus, the expiration can be facilitated because the base pressure pθ at the end of an inspiration does not fall immediately to the lower pressure level, but first to the base pressure pθ, and a further pressure reduction is controlled by the expiratory strength. Another advantage is that a respiratory phase detector or breath trigger is not necessary.

In the figure 2, the signal waveforms V1 to VO of the example arrangement are shown for better understanding once for a deep breathing with limiting effect and once for a shallow breathing.

FIG. 3 shows what an application for stabilizing the breathing depth could look like. Such stabilization is required in Cheyne-Stokes respiration, which is remarkable in that the patient has an increasing and decreasing depth of breathing.

In place of the amplifier 16 and the limiter 18, the two average processors 25 and 25, whose output signals in a The mean value processor 26 calculates the signal mean over an extended period of time and the mean value processor 25 calculates the signal mean over a much shorter period of time, for example only during a single period of respiration. Preferably, the output values of both processors are normalized to a uniform maximum before being supplied to the difference point 27. This then results in a control signal V6. The multiplier 28 forms the product of the control signal V6 and the original breath signal V2. The result is the signal V4, which is a measure of the pressure support of the respiration. As the time courses show, the pressure support is small when the breathing depth is large. On the other hand, breathing support is great when breathing is only shallow. This behavior causes the breathing depth of a patient with Cheyne-Stokes breathing to become even, as any decrease in the depth of breath would immediately result in pressure support.

For the example arrangements, electrical switching elements and

Elements of block representations are used because they are well suited to convey common functions. In practice, of course, it is much more advantageous to have the entire signal processing performed by digital computers with a corresponding program.

List of reference symbols used

[0064] 1 inner breathing system of the ventilator

[0065] 2 respiratory gas generators

3 reference resistance

[0067] 4 Breathing gas evacuation

[0068] 5 breathing tube

[0069] 6 Patient connection point

7 exhalation valve

[0071] 8 airway resistance

9 respiratory pump

10 pressure sensor

[0074] 11 difference point [0075] 12 control device

[0076] 13 actuator

[0077] 14 differential pressure sensor

15 signal processor

16 amplifiers

[0080] 17 setting element

(Setting a gain> 0)

18 limiters

19 setting element (positive signal amplitude)

[0083] 20 setting element (negative signal amplitude)

21 adders

[0085] 22 adjustment element (base pressure)

[0086] 23 Signal Divider Resistor

24 Signal divider resistor

25 Mean value processor (short-term average

26 mean value processor (long term average)

Pθ base pressure

[0091] V1 signal (loss pressure at the reference resistor)

V2 signal

(alternating part of the loss pressure)

V3 signal

(Factor - weighted alternating portion of the

[0094] loss pressure)

[0095] V4 signal (signal for an additional pressure)

[0096] V5 signal (signal of the controlled variable)

V6 signal

(Evaluation factor for pressure support)

Claims

claims

A variable pressure assist ventilator including an inner breathing system (1) with a breathing gas generator (2) in a pressure control device (11, 12, 13) comprising a gas exhaust (4) for providing breathing gas under a predetermined pressure and any one of external accessories, preferably only a breathing tube (5) for guiding the respiratory gas via a patient connection point (6), preferably a face mask, are provided in the respiratory tract of a patient, characterized in that a differential pressure sensor (14) for determining the instantaneous pressure loss (V1) at a reference resistor (3), at least one computing element for calculating at least one additional pressure signal (V4) from the instantaneous pressure loss (V1) and an adder (21) for adding the at least one additional pressure signal (V4) to a signal for a base pressure (pθ) a control variable (V5) of the pressure control device (11, 12, 13) are provided.

A variable pressure ventilator as claimed in claim 1, characterized in that a calculating member (15) for removing zero frequency spectral components from the instantaneous pressure loss signal (V1) and an amplitude limiter (18) for limiting the remaining signal to one are any adjustable amount, in negative and positive amplitude in the same or different heights, preferably after prior amplification by an amplifier (16) are provided.

3. ventilator with variable pressure support according to claim 1, characterized in that the control part of the ventilator is set up so that the alternating portion (V2) of the currently at the reference resistor (3) measured pressure loss (V1) with an amplifier or a potentiometer or a multiplier (28) and used as an additional pressure signal (V4), wherein the weighting factor (V6) is the difference between a specific reference value and one of a computing element (25) continuously from the alternating portion (V2) of the pressure loss currently measured at the reference resistor (3) (V1) determined value, preferably the amplitude envelope, is.

4. ventilator with variable pressure support, according to any one of claims 1 to 3, characterized in that external auxiliary devices, which are arranged between the gas outlet (4) and the patient connection point (6), have an identifier that operates on the basis of transponders or contact codes and that the control part of the ventilator is set up so that it decodes the respective identifier and takes into account the respectively connected flow resistance of the external breathing system.

5. ventilator with variable pressure support, according to one of claims 1 to 4, characterized in that between breathing gas generator (2) and gas outlet (4) an internal reference resistor (3) is arranged, which has a certain resistance characteristic as a flow resistance, preferably with the Resistance characteristic of the externally flowed resistors matches.

6. ventilator with variable pressure support, according to one of claims 1 to 5, characterized in that the internal reference resistor (3) is the flow resistance of a component located there anyway.

7. ventilator with variable pressure support, according to one of claims 1 to 6, characterized in that the control part of the ventilator is set up so that to determine the loss pressure (V1) at the flow resistance of the inner respiratory system (1) a parameter of the breathing gas generator (2) , Preferably its instantaneous speed or its current operating current consumption is used.