VENTILATION DEVICE

Description

[0001] The present invention relates to a ventilator for artificially respiration of a patient, comprising: a respiratory gas source arrangement which provides an inspiratory respiratory gas for artificial ventilation of the patient, a flow change device which is designed to generate an inspiratory respiratory gas flow and to change its amount, a respiratory gas line arrangement with a proximal longitudinal end which is closer to the patient during operation and with a distal longitudinal end which is further away from the patient during operation in order to promote the inspiratory respiratory gas flow from the respiratory gas source arrangement to the patient, a flow sensor arrangement which is designed to detect the amount of the inspiratory respiratory gas flow as well as the amount of the expiratory respiratory gas flow, a pressure sensor arrangement which is designed to detect a pressure of the inspiratory respiratory gas as well as the expiratory respiratory gas in the respiratory gas line arrangement, a control device with a data memory,wherein the control device is connected to the data memory, to the flow sensor arrangement and to the pressure sensor arrangement in terms of signal transmission and which is designed to control the operating power of the flow changing device for changing the inspiratory respiratory gas flow, , wherein the control device is designed to control the flow change device to carry out a P / V maneuver, in which respiratory gas is supplied to a patient in an inspiration phase while increasing the respiratory gas pressure, which in an expiration phase flows passively out of the patient after completion of the pressure increase, wherein both during the inspiration phase and during the expiration phase for a plurality of respiratory gas press the maneuver breathing gas volume present in the patient due to the P / V maneuver is determined in relation to the prevailing breathing gas pressure.

[0002] The present invention also relates to a method for performing a P / V maneuver on a patient's lung, preferably for the purpose of determining data for assessing a recruitability and extensibility of lung tissue of a patient's lung.

[0003] A ventilation device of the type mentioned above and a method for performing a P / V maneuver on a patient's lung are known from EP 2 091 429 B1. This document teaches a positive end-expiratory pressure, hereinafter referred to in agreement with the expert as "PEEP" (for Positive E nd- E xpiratical P ressure), for a specific patient by means of a so-called P / V maneuver on the patient or his lung.

[0004] In this P / V maneuver, known from EP 2 091 429 B1, inspiratory gas is delivered to the patient starting from a starting respiratory gas pressure while continuously increasing the respiratory gas pressure until a predetermined final inspiratory gas pressure is reached. An inspiratory PV curve is recorded, which indicates the inspiratory respiratory gas volume delivered to the patient during the inspiration phase of the P / V maneuver in relation to the prevailing respiratory gas pressure.

[0005] Once the predetermined end-of-breathing gas pressure is reached, the previously delivered breathing gas is allowed to escape from the patient's lungs as expiratory breathing gas during the ongoing P / V maneuver. The breathing gas volume still present in the patient is recorded in relation to the expiratory breathing gas pressure prevailing at the time of the recording. For this purpose, a PV curve is also recorded, this time as an expiratory PV curve, which indicates the breathing gas volume present in the patient during the expiratory phase of the P / V maneuver in relation to the expiratory breathing gas pressure prevailing during the recording. The P / V maneuver ends at a predetermined end-of-breathing gas pressure.

[0006] The inspiratory and expiratory PV curves pass through a common respiratory gas pressure range, with both curves exhibiting hysteresis. The expiratory PV curve exhibits higher volume values ​​over a wide mean respiratory gas pressure range at the same respiratory gas pressure values.

[0007] EP 2 091 429 B1 teaches how to automatically determine a PEEP suitable for the respective patient on whom the P / V maneuver is performed as the pressure at which the expiratory and inspiratory PV curves show the greatest difference in magnitude.

[0008] Since, due to the characteristics of the two PV curves, if a maximum volume difference between the two PV curves has been recorded, the volume difference between the expiratory and inspiratory PV curves decreases as the pressure of the expiratory respiratory gas continues to decrease during the expiratory phase and no further increase in this volume difference is to be expected, EP 2 091 429 B1 recommends aborting the expiratory phase of the P / V maneuver if a maximum volume difference between the expiratory and inspiratory PV curves has been detected during the expiratory phase.

[0009] From US 5,915,381 a ventilation device is known which teaches to calculate a current compliance of the ventilated patient's lung from an inspiratory PV curve which is determined during normal mechanical ventilation of a patient and to change ventilation parameters such as pressure levels, PEEP, inspiration time, expiratory time and respiratory rate when the current compliance of the lung is less than a predetermined threshold value.

[0010] "Compliance" is commonly used to describe the elastic resistance of the lungs to a change in volume. It is determined, as is well known, by the ratio of the change in lung volume caused by a change in the pressure of the respiratory gas. "Instantaneous compliance," in contrast to overall compliance or average compliance determined over a complete inspiration phase, refers to compliance prevailing at a specific point in time or at a specific inspiration state.

[0011] US 5,915,381 points out that, depending on the pathological condition of the ventilated lung, different amounts of respiratory gas must be delivered to the lung to prevent complete or partial lung collapse. A diseased lung generally has a smaller ventilation area than a healthy lung. Therefore, according to US 5,915,381, a specific compliance threshold must be predetermined for each patient, with which the current compliance during a device-induced inspiration phase is compared. US 5,915,381 mentions, as an additional possible safety measure for some patients, the termination of an inspiration phase as soon as the current compliance determined during the inspiration phase falls below a predetermined threshold.

[0012] In this application, the term "compliance" refers to current compliance, unless otherwise stated in individual cases.

[0013] At the beginning of an artificial inspiration of a lung in a largely exhaled state, an increase in the inspiratory gas pressure initially leads to a relatively small increase in lung volume. Lung compliance is therefore low in magnitude at the beginning of the inspiration phase of the P / V maneuver. After a certain amount of filling of the lung with inspiratory gas, the volume of the lung increases more sharply with an increase in the pressure of the inspiratory gas than at the beginning of the P / V maneuver, so that in this middle phase of the P / V maneuver, lung compliance is greater in magnitude than at the beginning of the maneuver. Towards the end of the P / V maneuver, the lung, which is already heavily filled with gas, can no longer be increased in volume even by further increasing the pressure of the inspiratory gas, so that towards the end of a P / V maneuver, lung compliance decreases again in magnitude.

[0014] US Pat. No. 5,915,381 therefore cites the advantage of determining a suitable compliance threshold for each patient to influence pressure level, PEEP, inspiratory duration, expiratory duration, respiratory rate, and the like. However, this determination of a predetermined compliance threshold precedes artificial ventilation, during which the compliance threshold is applied. Such a patient-specific precalculation of a compliance threshold based on the patient's medical history is complex and time-consuming. Furthermore, determining a patient-specific compliance threshold and transmitting it to the ventilator is error-prone.

[0015] DE 10 2017 101 645 A1 discloses several ventilation devices and ventilation methods intended to enable the ventilation of a patient with minimal energy input into their airway. According to one ventilation device known from DE 10 2017 101 645 A1, both the inspiration process and the expiration process are to be controlled by the ventilation device in such a way that, for at least 60% of the ventilation interval, the ratio of the compliances occurring once during inspiration and once during expiration in pressure-controlled ventilation at the same pressure value, or the compliances occurring once during inspiration and once during expiration in volume-controlled ventilation at the same volume value, has a value of between 0.5 and 2.

[0016] US 2019 / 0275276 A1 discloses a device for recording and displaying a pressure-volume curve during artificial respiration. The device is designed to determine and display a gradient of the pressure curve.

[0017] The object of the present invention is to further develop the ventilation device known from EP 2 091 429 B1 in such a way that patients are well protected from adverse health effects of the P / V maneuver with the least possible effort when performing a P / V maneuver and that measurement data obtained from the P / V maneuver are burdened to the least possible extent by the effects of lung overexpansion.

[0018] The invention achieves this object by a ventilation device of the type mentioned at the outset, the control device of which is designed to During the inspiration phase of the P / V maneuver, on the basis of signals from the flow sensor arrangement and the pressure sensor arrangement, to determine a sequence of compliance values, each of which represents a lung compliance of the patient's lungs, to determine a reference compliance value in accordance with the sequence of compliance values, to determine a termination compliance value as a threshold value, based on the reference compliance value, which is different in amount from the reference compliance value, as a termination criterion for the inspiration phase, and to terminate the inspiration phase when the termination compliance value is reached or exceeded.

[0019] Using the flow sensor array and the pressure sensor array, the control device can easily determine a sequence of compliance values, each representing the patient's lung compliance at different times during the P / V maneuver. The flow sensor array measures the flow, or volumetric flow, of inspiratory breathing gas during the inspiration phase and the expiratory breathing gas during the expiration phase. The flow, or volumetric flow, of breathing gas corresponds to a change in the volume of breathing gas in the patient's lungs per unit of time.

[0020] The P / V maneuver can be performed, for example, with a predetermined pressure increase rate of the respiratory gas pressure or with a predetermined inspiratory respiratory gas volume flow, for example with a constant respiratory gas volume flow.

[0021] The flow sensor arrangement can have multiple flow sensors, for example one each for the inspiratory and expiratory respiratory gas flow. Preferably, the flow sensor arrangement comprises only one flow sensor to detect both the inspiratory and expiratory respiratory gas flow. This is preferably arranged proximally between the respiratory gas line arrangement and the patient interface, but can also be accommodated distally in a housing of the ventilator, in which, for example, the flow modification device is also accommodated. To achieve greater process reliability, the ventilator can also have multiple flow sensors, each of which detects both the inspiratory and expiratory respiratory gas flow, for example a distal flow sensor in a housing of the ventilator and a proximal flow sensor close to the patient.The same applies to the pressure sensor arrangement, which can also have one or more pressure sensors to measure both the pressure of the inspiratory and expiratory respiratory gas.

[0022] By integrating the flow of respiratory gas over a period of time, the volume of respiratory gas that flowed through the respiratory gas line arrangement during that period can be determined. This also includes the volume of respiratory gas that was either delivered to the lungs as inspiratory gas or flowed out of the lungs as expiratory gas during that period.

[0023] To distinguish it from any other breathing gas volumes that may occur during artificial ventilation or during a P / V maneuver, the breathing gas volume present in the patient's lungs during a P / V maneuver due to the supply of inspiratory breathing gas to the patient's lungs and the outflow of expiratory breathing gas from the patient's lungs is referred to in this application as the "maneuver breathing gas volume." In case of doubt, the maneuver breathing gas volume during the inspiration phase is the integral of the inspiratory breathing gas flow over time during the inspiration phase, and the maneuver breathing gas volume during the expiration phase is the value of the integral of the inspiratory breathing gas flow at the end of the inspiration phase minus the integral of the expiratory breathing gas flow over time during the expiration phase. The maneuver breathing gas volume can therefore be represented as a function of time from the beginning of the inspiration phase to the end of the expiration phase.Since the breathing gas pressure in the breathing gas line arrangement can also be represented as a function of time, the maneuver breathing gas volume can also be represented as a function of the breathing gas pressure in the breathing gas line arrangement during the inspiration phase and during the expiration phase.

[0024] In the present application, the PV curve or PV relationship refers to the functional relationship between the maneuver breathing gas volume present at the time and the breathing gas pressure prevailing during the maneuver.

[0025] The ventilation device preferably also comprises a time-measuring device in order to be able to determine the durations of processes and sub-processes during the P / V maneuver and the points in time during the P / V maneuver. With the aid of the time-measuring device, a change in the respiratory gas pressure, be it the pressure of an inspiratory or an expiratory respiratory gas, can also be precisely determined. However, a time-measuring device is not absolutely necessary. For example, the control device can be designed to query sensor signals at predetermined, known time intervals, so that a known period of time always elapses between the individually queried detection values ​​of the sensor arrangements. In this way, a temporal change in relevant parameters, such as respiratory gas pressure or respiratory gas volume, can also be determined with sufficient accuracy.

[0026] The compliance values ​​determined in this way are directly a patient-specific characteristic of the lungs of the specific ventilated patient. Therefore, a reference compliance value can be easily derived from the sequence of compliance values, which is also specific to the respective ventilated patient.

[0027] If, based on the reference compliance value thus determined, a termination compliance value is then determined. Upon reaching or exceeding this compliance value, the inspiration phase is terminated. This can prevent the patient from being "overinspired" during the P / V maneuver, i.e., their lungs from being overexpanded, generally stressed, or even damaged by an excessive amount of respiratory gas and / or excessive respiratory gas pressure. Furthermore, due to the limited volume of the thoracic cavity containing the lungs, which is limited by the rib cage, overexpanding the lungs often places a detrimental strain on the ventilated patient's cardiovascular system. This is because the overexpanded lungs require space at the expense of compressible tissue, such as blood vessels and the like.

[0028] Thus, the control device can automatically determine and use a suitable, individual termination compliance value for each patient as a threshold for termination of the inspiratory phase from the sensory data obtained during the inspiratory phase of the P / V maneuver. A time-consuming patient history to determine a predetermined termination compliance value and a potential error in its transmission to the ventilator can thus be avoided.

[0029] The control device can therefore be designed to abort the inspiration phase of each P / V maneuver in a patient-friendly manner based on the abort criterion determined during the respective P / V maneuver itself. Consequently, the control device can further be designed to apply abort compliance values ​​of different magnitudes as a threshold value and abort criterion during uninterrupted artificial ventilation of one and the same patient, depending on the respective state of health of the patient's lungs. In particular, the control device can be designed to determine a abort compliance value during each breath, during every second breath, or during every nth breath, where n is an integer, during uninterrupted artificial ventilation of one and the same patient and to apply it for the breath in which the determination occurs, preferably until a subsequent abort compliance value is determined.

[0030] In principle, there are different ways in which the control device can determine the sequence of compliance values ​​online, i.e., during an ongoing P / V maneuver, from the aforementioned sensor signals. For example, the control device can be configured to calculate the sequence of compliance values ​​based on a quotient of a volume change value associated with a breathing gas pressure and a pressure change value associated with the same breathing gas pressure, wherein the volume change value represents a temporal change in the maneuver breathing gas volume, and wherein the pressure change value represents a temporal change in the breathing gas pressure.To do this, it is sufficient to record two volume values ​​at different times, from which the volume change value can be determined, as well as to record two respiratory gas pressure values ​​at different times, preferably at the same time as the two volume values ​​are recorded, so that a pressure change value can be determined. This is a method based on difference quotients.

[0031] Alternatively, or additionally to provide redundancy, the control device can be configured to calculate the sequence of compliance values ​​based on a quotient of a flow value associated with a respiratory gas pressure and the pressure change value associated with the same respiratory gas pressure, wherein the flow value represents the inspiratory respiratory gas flow. As already explained above, the flow value is a measure of the change in the respiratory gas volume supplied to or escaped from the lungs per unit of time. This, too, is a determination method based on difference quotients.

[0032] It is important to ensure that the volume change value and the pressure change value apply to a consistent period of time, preferably to a consistent point in time, so that the volume change value and the pressure change value are temporally related to each other. If the respiratory gas pressure changes over time and the respiratory gas volume present in the patient's lungs changes over time, the exhaust gas volume present in the patient's lungs will change with the respiratory gas pressure due to the change in respiratory gas pressure. The same applies to the flow value and the pressure change value, mutatis mutandis.

[0033] A certain temporal uncertainty in the correspondence between the acquisition times of the respective required sensor values ​​can be tolerated. However, the better the acquisition times of the required sensor values ​​correspond, the more accurate the resulting compliance will be.

[0034] There are also different options for determining the reference compliance value.

[0035] According to a first preferred embodiment, the control device can be configured to select the largest compliance value as the reference compliance value from a sequence of compliance values ​​that initially increase in magnitude and then decrease in magnitude from the start of the inspiration phase of the P / V maneuver. The selected reference compliance value is advantageously temporarily stored in the data memory of the control device.

[0036] Considering the clear relationship between the respiratory gas volume present in the patient's lungs and the respiratory gas pressure prevailing in the respiratory gas line arrangement during a P / V maneuver, compliance is the first derivative of the respiratory gas volume, which changes with the respiratory gas pressure, with respect to the respiratory gas pressure. This can be determined using discrete measurement points in a conventional manner using difference quotients or by interpolating discrete measurement points with a differentiable function and deriving it, to name just two methods.

[0037] Put more simply: compliance is the slope of the graph of inspiratory maneuver breathing gas volume as a function of breathing gas pressure. Due to the change in compliance during the inspiration phase of a P / V maneuver described above, the graph of maneuver breathing gas volume as a function of breathing gas pressure has a section with a concave curvature closer to the starting breathing gas pressure of the P / V maneuver and a section with a convex curvature closer to the end pressure of the P / V maneuver. Typically, the inflection point at the transition between these two sections with different curvatures exhibits a very large or even the largest compliance of the inspiratory PV curve. The starting breathing gas pressure and the end pressure of the PV maneuver can be the same pressures. However, they can also be different, in which case the final pressure is preferably a lower absolute pressure of the breathing gas than the starting breathing gas pressure.In principle, the starting respiratory gas pressure can be freely selected within the scope of what is medically reasonable. Preferably, the starting respiratory gas pressure is selected within a pressure range that extends from the PEEP determined for the respective patient to approximately 1.6 times the PEEP, including range limits.

[0038] Therefore, additionally or alternatively, the control device can be designed to determine an inflection point between sections of a graph representing the sequence of value pairs curved with different senses of curvature from a sequence of value pairs of respiratory gas pressure and the inspiratory maneuver respiratory gas volume associated with the respective respiratory gas pressure, and to select the compliance value associated with the respiratory gas pressure at the inflection point as the reference compliance value. To determine the inflection point, the control device can be designed to form the second derivative of the volume values ​​as a function of the pressure values ​​with respect to the pressure in a manner known per se. According to an alternative, this can be done, like the determination of the first derivative, by interpolating obtained measured values ​​with a doubly differentiable function and by deriving the same.The reference compliance then lies at the breathing gas pressure value at which the second derivative of a sequence of pairs of values ​​has the value zero or a value closest to zero. According to another alternative, the second derivative can be calculated using difference quotients, just like the first derivative.

[0039] Preferably, the sequence of the mentioned pairs of values ​​forms a PV curve.

[0040] The two preferred methods for selecting or determining a reference compliance value mentioned above enable, firstly, a reference compliance value to be selected which, based on experience, is located in the mid-temporal range of the inspiration phase of the P / V maneuver, during which, with near certainty, lung overload due to artificial inspiration is not present. Furthermore, based on the reference compliance value selected in this way, the compliance values ​​occurring during the subsequent inspiration phase are smaller in magnitude than the reference compliance value, so that, based on the reference compliance value, a meaningful termination compliance value can be obtained with a high degree of certainty.

[0041] To determine the abort compliance value, the control device can be configured to calculate the abort compliance value by multiplying the reference compliance value by a predetermined factor or by adding the reference compliance value to a predetermined addend. The predetermined addend is preferably negative, since the abort compliance value, due to the above-described nature of the compliance value curve during the inspiration phase, is generally smaller in magnitude than the maximum compliance value preferred as the reference compliance value. For the same reason, the predetermined factor is preferably less than 1.

[0042] In a preferred embodiment, the termination compliance value can be 75% to 95%, preferably 80% to 92.5%, particularly preferably 85% to 91% of the reference compliance value. The termination compliance value is particularly preferably approximately 90% of the reference compliance value if it is selected close to the maximum compliance value, i.e., approximately in a range of 40% to 60% of the maximum compliance value. This applies regardless of the method of calculating the termination compliance value based on the reference compliance value. In this way, overloading, in particular overexpansion, of the patient's lungs during the inspiration phase can be reliably avoided.

[0043] In principle, it can be considered to perform the P / V maneuver, as known from the state of the art, to determine a PEEP that is particularly suitable for the respective ventilated patient.

[0044] However, it has been shown that the P / V maneuver can provide a robust and reliable statement about the expected success of a recruitment procedure for recruiting functional lung volume.

[0045] The use of the above-mentioned termination criterion of the termination compliance value is particularly advantageous because it avoids the use of values ​​to assess the expected success of a recruitment procedure that would have been recorded during lung overload and which would therefore adversely distort the assessment result if included in the assessment.

[0046] Deviating from and alternatively to the previously described manner of avoiding the recording of values ​​during lung overload, in particular lung overexpansion, by the automated determination of a termination compliance value, the undesired recording of values ​​during lung overexpansion can also be achieved according to less preferred embodiments as follows: According to a first alternative, a predetermined negative value of the second derivative of the P / V curve can serve as the termination criterion. The second derivative can be determined by the control device as described above. As at least one further additional criterion, the termination criterion can be activated by the control device only after a zero crossing of the second derivative or after previously detected positive values ​​of the second derivative.

[0047] According to a second alternative, a first P / V maneuver can initially be performed without determining an inspiratory termination criterion, as is known from the prior art. If lung overexpansion is detected during this first P / V maneuver, the control device can be configured to perform a second P / V maneuver with a reduced end pressure. If no lung overexpansion is detected during the first P / V maneuver, the values ​​obtained during the first P / V maneuver and / or the obtained PV curve are used to assess lung recruitability; otherwise, the values ​​obtained during the second P / V maneuver and / or the obtained PV curve are used.

[0048] According to a third alternative, the control device is designed to reduce a final pressure obtained from an operator or from a retrievable data source for a P / V maneuver by a predetermined amount, either by subtracting a predetermined safety margin value or by multiplying it by a value less than 1, preferably by a value between 0.78 and 0.92, for example by 0.8.

[0049] The control device can be designed to carry out one of the three alternatives mentioned.

[0050] The reliable assessment of the prospects of success of a recruitment procedure directly from data from a P / V maneuver is particularly advantageous because it can replace the need for a CT scan. The ventilated patient can therefore be examined directly in their hospital bed regarding the prospects of success of a recruitment procedure in the case of an at least partially collapsed lung. The recruitment procedure can be any known recruitment procedure in the medical community.

[0051] In order to provide the data necessary for assessing the prospects of success of a recruitment procedure for the respective ventilated patient, the control device can be designed to calculate a volume quotient value from the greatest difference in magnitude between the expiratory and inspiratory maneuver breathing gas volume occurring during the P / V maneuver for a breathing gas pressure and a difference value between a maneuver breathing gas volume value in an upper end range and a maneuver breathing gas volume value in a lower end range of the breathing gas pressure range traversed during the P / V maneuver, wherein the lower end range includes a starting breathing gas pressure at which the P / V maneuver begins and extends up to 1.05 times the starting breathing gas pressure, and wherein the upper end range includes an aborting breathing gas pressure to which the abort compliance value is assigned and begins at 95% of the aborting breathing gas pressure.

[0052] For the final assessment of the prospects of success of a subsequent recruitment procedure, the control device can, but need not, be configured to generate an output when the volume quotient value exceeds a predetermined first threshold value, indicating that a recruitment procedure for recruiting the patient's lung has a predominantly good chance of success. This predetermined first threshold value is preferably between 38% and 46%, with 42% having proven to be the most suitable first threshold value in previous studies to distinguish a patient lung that is likely to be successfully recruited from a patient lung that is likely to be unsuccessfully recruited.

[0053] Alternatively or additionally, the control device can be designed to provide the data necessary for assessing the prospects of success of a recruitment procedure for the respective ventilated patient, by calculating a hysteresis quotient value from the area of ​​the hysteresis surface, which represents the graphs of the expiratory and inspiratory maneuver breathing gas volumes as functions of the breathing gas pressure between a starting breathing gas pressure at which the P / V maneuver begins and a termination breathing gas pressure to which the termination compliance value is assigned, and the area of ​​a rectangle circumscribing the hysteresis surface, one corner of which is determined by a lower breathing gas pressure value in a lower end range of the breathing gas pressure range traversed during the P / V maneuver and by the breathing gas volume value assigned to the lower breathing gas pressure value, wherein the lower end range contains the starting breathing gas pressure and extends up to 1.05 times the starting breathing gas pressure, and whose diagonally opposite corner is determined by an upper breathing gas pressure value in an upper end range and by the breathing gas volume value associated with the upper breathing gas pressure value, wherein the upper end range contains a termination breathing gas pressure to which the termination compliance value is associated and begins at 95% of the termination breathing gas pressure.

[0054] To assess the prospects of success of a recruitment process from the aforementioned data, the control device can, but does not have to, be configured to generate an output when the hysteresis quotient value exceeds a predetermined second threshold value, indicating that a recruitment process for recruiting the patient's lung has a predominantly good chance of success. The second threshold value is preferably different in magnitude from the first threshold value. For the hysteresis quotient value, a second threshold value in a range of 28% to 36% has proven to be meaningful. Based on previous studies, the second threshold value is preferably 32%.

[0055] It should be added that the breathing gas source arrangement of the ventilator can have an intake opening as a breathing gas source, through which ambient air or gas from a predetermined gas supply can be sucked in. The breathing gas source arrangement can additionally or alternatively have a gas supply as a breathing gas source, for example as a storage container or as a connection formation for connecting a supply line that connects the ventilator to a locally installed gas supply, as is often the case in hospitals. In order to provide the option of mixing different gases to form a breathing gas, the breathing gas source arrangement can have a plurality of individual breathing gas sources, such as those mentioned above. The different gases to be mixed can have different temperatures and / or different humidities due to supply and expansion.In order to ensure that the inspiratory breathing gas actually reaches the patient with a humidity that has been set once, it is particularly preferred that no more breathing gas component is added to the breathing gas flow exiting from the humidification device downstream of a preferably present humidification device in the inspiration direction.

[0056] The following describes a method for performing a P / V maneuver on a patient's lung, in particular for obtaining data for assessing the recruitability of lung tissue, the method comprising the following steps: Performing a P / V maneuver and supplying inspiratory breathing gas to a patient in an inspiration phase while increasing the breathing gas pressure, during the inspiration phase: determining an inspiratory maneuver breathing gas volume or an inspiratory maneuver volume flow of inspiratory breathing gas supplied during the inspiration phase and determining the breathing gas pressure, determining a sequence of compliance values, each representing a lung compliance of the patient's lungs, determining a reference compliance value from the sequence of compliance values ​​in accordance with the sequence of compliance values, determining, based on the reference compliance value, a termination compliance value which is different in amount from the reference compliance value as a termination threshold, and terminating the inspiration phase when the termination compliance value is reached or exceeded.

[0057] The present invention preferably also relates to a device designed to carry out the aforementioned method. This is preferably the previously described and further developed ventilation device.

[0058] Method aspects presented in the description of the ventilation device are further developments of the method and device aspects presented in the description of the method are further developments of the ventilation device according to the invention.

[0059] As previously described, this method can prevent overloading of the patient's lungs due to excessively high respiratory gas pressure. By preventing overload, particularly lung overexpansion, the recording of measured values ​​or pairs of measured values ​​in a state of lung overload is also avoided. Compared to pairs of values ​​recorded in a state of normal lung load, sequences of measured value pairs recorded in an overload state have only limited significance or may even falsify the measurement result to which they belong.

[0060] In order to be able to obtain data from the P / V maneuver for the further treatment of a ventilated patient, the inspiration phase is preferably followed by an expiratory phase in which respiratory gas flows passively out of the patient, whereby during the expiratory phase both the expiratory respiratory gas pressure and an expiratory maneuver respiratory gas volume value are determined, whereby the expiratory maneuver respiratory gas volume value represents an expiratory maneuver respiratory gas volume present in the patient due to the P / V maneuver during the expiratory phase.

[0061] In both the described method and the device according to the invention, in particular the ventilation device, maneuver respiratory gas volume values ​​are recorded and stored during the P / V maneuver in association with a respiratory gas pressure as value pairs or as value relationships. The respiratory gas pressure prevailing during the recording is assigned to a maneuver respiratory gas volume value.

[0062] While determining the inspiratory maneuver breathing gas volume value is comparatively simple, for example, by integrating the flow values ​​since the beginning of the inspiration phase, determining the expiratory maneuver breathing gas volume value requires more computational effort. Determining the expiratory maneuver breathing gas volume value as part of the procedure may, for example, include: determining a volume of expiratory breathing gas exhaled during the expiratory phase and / or determining an expiratory maneuver volume flow of expiratory breathing gas.

[0063] The expiratory maneuver breathing gas volume value can then be determined from the inspiratory maneuver breathing gas volume value at the end of the inspiration phase minus either the determined exhaled volume or the maneuver volume flow integrated over the previous duration of the expiration phase.

[0064] Furthermore, the method for determining data for a later assessment of the prospects of success of a recruitment procedure on the respective patient's lung can comprise: calculating a volume quotient value from the greatest difference in magnitude occurring during the P / V maneuver for a respiratory gas pressure between the expiratory and inspiratory maneuver respiratory gas volume and a reference maneuver respiratory gas volume in an upper end range of the respiratory gas pressure range traversed during the P / V maneuver, wherein the upper end range contains a termination respiratory gas pressure to which the termination compliance value is assigned and begins at 95% of the termination respiratory gas pressure. In particular, what was stated above in connection with the ventilation device according to the invention regarding the volume quotient value applies here.

[0065] Alternatively or additionally, the method for determining data for a later assessment of the prospects of success of a recruitment procedure on the respective patient lung may include: calculating a hysteresis quotient value from the area of ​​the hysteresis surface, which represents the graphs of the expiratory and inspiratory maneuver breathing gas volumes as functions of the breathing gas pressure between the starting breathing gas pressure at which the P / V maneuver begins and a termination breathing gas pressure to which the termination compliance value is assigned, and the area of ​​a rectangle circumscribing the hysteresis surface, one corner of which is determined by a lower breathing gas pressure value in a lower end range of the breathing gas pressure range traversed during the P / V maneuver and by the breathing gas volume value assigned to the lower breathing gas pressure value, wherein the lower end range contains the starting breathing gas pressure and extends up to 1.05 times the starting breathing gas pressure, and whose diagonally opposite corner is determined by an upper breathing gas pressure value in an upper end range and by the breathing gas volume value associated with the upper breathing gas pressure value, wherein the upper end range contains a termination breathing gas pressure to which the termination compliance value is associated and begins at 95% of the termination breathing gas pressure.

[0066] Furthermore, as described above in connection with the ventilation device, the method can comprise a data evaluation step after data acquisition to assess the prospects of success of a recruitment process. For this purpose, the method can comprise a step of comparing the volume quotient value with a predetermined first threshold value, wherein, depending on the comparison result, an output is generated which indicates whether a recruitment process for recruiting the patient's lungs has a predominantly prospect of success or not. The above applies to the predetermined first threshold value. Preferably, if the volume quotient value has an amount exceeding the first threshold value, an output is generated which indicates that the recruitment process has a predominantly prospect of success. Preferably, otherwise, no display or a display with contrary content is output.

[0067] To assess the prospects of success of a recruitment process from the aforementioned hysteresis quotient value, the method can comprise the step of comparing the hysteresis quotient value with a predetermined second threshold value, wherein, depending on the comparison result, an output is generated which indicates whether a recruitment process for recruiting the patient's lung has a predominantly chance of success or not. The above again applies to the second threshold value. Based on previous studies, the second threshold value is preferably 32%. Preferably, if the hysteresis quotient value exceeds the predetermined second threshold value, an output is generated which indicates that a recruitment process for recruiting the patient's lung has a predominantly chance of success.

[0068] The present invention is described in more detail below with reference to the accompanying drawings. It shows: Figure 1 is a schematic representation of a ventilation device according to the invention, adapted for artificial ventilation of a patient, and Figure 2 is a schematic representation of a PV curve determined by a P / V maneuver of the ventilation device according to the invention and its evaluation.

[0069] In Figure 1 An embodiment of a ventilation device according to the invention is generally designated 10. In the example shown, the ventilation device 10 serves for the artificial ventilation of a human patient 12.

[0070] The ventilation device 10 has a housing 14 in which an intake opening 15 is formed and—not visible from the outside due to the opaque housing material—a flow-changing device 16 and a control device 18 are accommodated. The intake opening 15 allows the flow-changing device 16 to draw in ambient air from the external environment U of the ventilation device and, after conventional purification by filters, to supply it as breathing gas to the patient 12. The intake opening 15 is therefore a breathing gas source arrangement within the meaning of the present application.

[0071] An ambient temperature sensor 17 can be located in the intake opening 15, which measures the temperature of the ambient air U and transmits it to the control device 18.

[0072] The flow-changing device 16 is constructed in a manner known per se and may include a pump, a compressor, a blower, a pressure vessel, a reducing valve, and the like. Furthermore, the ventilator 10 includes an inspiratory valve 20 and an expiratory valve 22 in a manner known per se.

[0073] The control device 18 is usually implemented as a computer or microprocessor. It comprises a Figure 1The data memory, designated 19, is used to store data necessary for operating the ventilator 10 and to retrieve it if necessary. In network operation, the data memory 19 can also be located outside the housing 14 and connected to the control device 18 via a data transmission link. The data transmission link can be formed by a cable or a radio link. However, to prevent disruptions in the data transmission link from affecting the operation of the ventilator 10, the data memory 19 is preferably integrated into the control device 18 or at least accommodated in the same housing 14 as the control device.

[0074] For entering data into the ventilator 10 or more precisely into the control device 18, the ventilator 10 can have an input device 24, which in the Figure 1In the example shown, this is represented by a keyboard. As will be explained further below, the keyboard is not necessarily the only data input of the control device 18. In fact, the control device 18 can receive data via various data inputs in addition to or alternatively to the keyboard, for example via a network line, a radio link, or via sensor connections 26.

[0075] To output data to the treating therapist, the ventilator 10 may have an output device 28, in the example shown a screen.

[0076] For artificial ventilation, the patient 12 is connected to the ventilation device 10, more precisely to the flow-modifying device 16 in the housing 14, via a breathing gas line arrangement 30. For this purpose, the patient 12 is intubated using an endotracheal tube as a patient interface 31. A proximal longitudinal end 31a of the patient interface 31 delivers the inspiratory breathing gas flow AF into the lungs of the patient 12. The expiratory breathing gas flow EF also flows into the breathing gas line arrangement 30 through the proximal longitudinal end 31a.

[0077] A distal longitudinal end 31b of the patient interface 31 is configured for connection to the breathing gas line assembly 30. From the location 31c downstream in the inspiration direction to the proximal longitudinal end 31a, the patient interface is surrounded by the body of the patient 12. Conversely, this means that the patient interface 31 is exposed to the external environment U from its distal longitudinal end 31b to the location 31c and is in predominantly convective heat transfer connection with it.

[0078] The breathing gas line arrangement 30 has an inspiration tube 32, via which fresh breathing gas can be directed from the flow-modifying device 16 into the lungs of the patient 12. The inspiration tube 32 can be interrupted and have a first inspiration tube 34 and a second inspiration tube 36, between which a humidification device 38 can be provided for the targeted humidification and, if necessary, also the temperature control of the inspiratory breathing gas supplied to the patient 12. The humidification device 38 can be connected to an external liquid supply 40, via which water for humidification or a medication, for example for anti-inflammatory purposes or to dilate the airways, can be supplied to the humidification device 38.When the present ventilator 10 is used as an anesthesia ventilator, volatile anesthetics can be delivered to the patient 12 in a controlled manner via the ventilator 10. The humidification device 38 ensures that the fresh respiratory gas is supplied to the patient 12 at a predetermined humidity, optionally with the addition of a medication aerosol, and at a predetermined temperature.

[0079] In the present example, the second inspiratory tube 36 is electrically heated by a line heating device 37. The line heating device 37 can be activated by the control device 18. Deviating from the above, the first inspiratory tube 34 can also be heated and / or the at least one tube 34 and / or 36 can be heated by a line heating device other than an electrical one, for example, by flushing with a heat exchange medium.

[0080] In addition to the already mentioned inspiration valve 20 and expiration valve 22, the breathing gas line arrangement 30 further comprises an expiration tube 42, via which metabolized breathing gas is blown off as expiratory breathing gas flow EF from the lungs of the patient 12 into the external environment U.

[0081] At the distal longitudinal end 30b of the breathing gas line assembly 30, the inspiratory tube 32 is coupled to the inspiratory valve 20, and the expiratory tube 42 is coupled to the expiratory valve 22. Preferably, only one of the two valves is open at a time to allow the passage of a gas flow. The actuation of the valves 20 and 22 is also controlled by the control device 18.

[0082] During a ventilation cycle, the expiration valve 22 is initially closed and the inspiration valve 20 is opened for the duration of the inspiration phase, allowing fresh inspiratory gas to be directed from the housing 14 to the patient 12. A flow of fresh respiratory gas is achieved by a targeted increase in the pressure of the respiratory gas by the flow-modifying device 16. Due to the pressure increase, the fresh respiratory gas flows into the lungs of the patient 12 and expands the body area near the lungs, in particular the rib cage, against the individual elasticity of the body parts near the lungs. This also increases the gas pressure inside the lungs of the patient 12.

[0083] At the end of the inspiration phase, the inspiration valve 20 is closed and the expiration valve 22 is opened. The expiration phase begins. Due to the increased gas pressure of the breathing gas in the lungs of the patient 12 until the end of the inspiration phase, this gas flows into the outside environment U after the expiration valve 22 opens, with the gas pressure in the lungs of the patient 12 decreasing as the flow duration progresses. If the gas pressure in the lungs 12 reaches a positive end-expiratory pressure (PEEP) set on the ventilation device 10, i.e., a pressure slightly higher than atmospheric pressure, the expiration phase is ended with the closing of the expiration valve 22, and another ventilation cycle follows.

[0084] During the inspiration phase, the patient 12 is supplied with the so-called ventilation tidal volume, i.e., the volume of respiratory gas per breath. The ventilation tidal volume multiplied by the number of ventilation cycles per minute, i.e., multiplied by the ventilation rate, results in the minute volume of the artificial ventilation being performed.

[0085] Preferably, the ventilation device 10, in particular the control device 18, is designed to repeatedly update or determine ventilation operating parameters that characterize the ventilation operation of the ventilation device 10 during ventilation operation in order to ensure that the ventilation operation is optimally tailored to the patient 12 being ventilated at all times. Particularly advantageously, one or more ventilation operating parameters are determined using the ventilation frequency, so that current ventilation operating parameters that are thus optimally adapted to the patient 12 can be provided for each ventilation cycle.

[0086] For this purpose, the ventilator 10 can be connected to one or more sensors for data transmission, which monitor the condition of the patient and / or the operation of the ventilator 10. Merely as an example of a series of possible sensors, Figure 1a proximal flow sensor 44, which measures the magnitude of the respiratory gas flow prevailing in the respiratory gas line arrangement 30, namely both the inspiratory respiratory gas flow AF and the expiratory respiratory gas flow EF. The proximal flow sensor 44, preferably designed as a differential pressure sensor, can be coupled to the data inputs 26 of the control device 18 by means of a sensor line arrangement 46. The sensor line arrangement 46 can, but does not have to, include electrical signal transmission lines. It can also have hose lines that transmit the gas pressure prevailing in the flow direction on both sides of the flow sensor 44 to the data inputs 26, where this pressure is quantified by pressure sensors 27.

[0087] More specifically, in the preferred embodiment, the breathing gas line arrangement 30 has a separately formed Y-line section 47 at its proximal longitudinal end region 30a, which is connected at its distal end region to the second inspiration tube 36 and the expiration tube 42 and which is connected at its proximal end region to the proximal flow sensor 44.

[0088] The proximal flow sensor 44 has a coupling formation 44a at its proximal end region, with which the patient interface 31, which could also be a mask instead of a tube, can be coupled to the proximal flow sensor 44 and consequently to the breathing gas line arrangement 30.

[0089] The second inspiration tube 36 may have a proximal temperature sensor 48 at its proximal longitudinal end region, which measures the temperature of the respiratory gas flow AF in the second inspiration tube 36 as close as possible to the patient 12 and transmits it to the control device 18.

[0090] For the sake of completeness, it should be noted that the ventilation device 10 according to the invention can be accommodated as a mobile ventilation device 10 on a rollable frame 50.

[0091] In Figure 2 A PV curve is shown schematically and designated 52, obtained by a P / V maneuver that was carried out with the ventilator 10 of Figure 1was performed. The P / V maneuver of the present application may be a one-time maneuver distinct from the rest of the ventilation operation. However, a sequence of P / V maneuvers of the present application may also be a sequence of breaths for administering the ventilator tidal volume and thus part of the medically indicated regular artificial ventilation of the patient 12.

[0092] The abscissa of the coordinate system indicates increasing breathing gas pressures in the direction of the arrow, while the ordinate of the coordinate system indicates increasing maneuver breathing gas volumes in the direction of the arrow. The representation of the PV curve in the coordinate system is merely exemplary and roughly schematic. The intersection point of the coordinate system is not necessarily the coordinate origin at a pressure of 0 mbar and a maneuver breathing gas volume of 0 ml.

[0093] The P / V maneuver begins at a starting respiratory gas pressure P Start with an inspiration phase, ie the starting respiratory gas pressure P Start is high enough to introduce inspiratory respiratory gas into the lungs of the patient 12.

[0094] From the beginning of the inspiration phase, the control device 18 quantitatively records the inspiratory respiratory gas flow AF and its pressure in the respiratory gas line arrangement 30 via the flow sensor 44 and the associated pressure sensors 27, thus forming value pairs from an inspiratory respiratory gas pressure and a maneuver respiratory gas volume assigned to the pressure and administered to the patient 12. The administered maneuver respiratory gas volume corresponds to the integral of the inspiratory respiratory gas flow from the time of the beginning of the inspiration phase to the recording time. In this way, the control device 18 determines the Figure 2PV curve shown. First, the inspiratory branch 54 of the PV curve 52 is determined. After completion of the inspiration phase, the expiratory branch 56 is determined by allowing the respiratory gas initially supplied to the patient 12 to escape passively from the patient 12 into the environment U, ie, solely under the pressure of the respiratory gas present in the patient 12.

[0095] From the beginning of the inspiration phase, the control device 18 determines, from the difference between successive inspiratory gas pressures and the difference between the maneuver gas volumes associated with these gas pressures, the lung compliance Ci associated with an inspiratory gas pressure, which in terms of magnitude - including the range limits - lies within the range of inspiratory gas pressures used to determine the gas pressure difference, as a function of the gas pressure. This is Figure 2exemplified by the gradient triangle ΔV / ΔP at the breathing gas pressure P i. Related to the PV curve of Figure 2 This means that lung compliance Ci during the inspiration phase is the first derivative of the PV curve with respect to the respiratory gas pressure. Thus, fundamentally different methods are available and usable for determining the lung compliance Ci associated with a particular respiratory gas pressure.

[0096] The control device 18 stores the thus determined value pairs of lung compliance Ci and associated respiratory gas pressure P i in the data memory 19 and determines the largest occurring value C max of the lung compliance from the stored values. In doing so, one can take advantage of the fact that lungs at the beginning and at the end of an inspiration phase each have lower lung compliance values ​​Ci in terms of magnitude than in a middle region of the inspiration phase. Consequently, if a largest value C max of lung compliance Ci is reached in terms of magnitude and lung compliances Ci subsequently determined at higher inspiratory respiratory gas pressures have lower values ​​in terms of magnitude, the largest value in terms of magnitude also represents the absolute highest value of lung compliance C max for the entire inspiration phase.

[0097] The PV curve can be smoothed using standard smoothing methods to detect noise components and thus obtain a more stable determination of lung compliance.

[0098] The highest lung compliance C max prevails in Figure 2 at point 58. The greatest gradient there is indicated by the tangent 59 to the inspiratory branch 54 of the PV curve 52 at point 58.

[0099] The value of the greatest lung compliance C max thus determined is selected by the control device 18 as the reference compliance value C ref . After selecting the reference compliance value C ref , the control device 18 automatically calculates a termination compliance value C term , at which the inspiration phase of the P / V maneuver is terminated. In the present embodiment, the control device 18 multiplies the reference compliance value C ref by a predetermined factor less than 1, for example, by 0.9, in order to calculate the termination compliance value C term .

[0100] From then on, the control device 18 for increasing respiratory gas pressures compares the respectively determined lung compliance Ci with the termination compliance value C term and ends the inspiration phase when it detects that the current lung compliance Ci has reached or exceeded the termination compliance value C term.

[0101] This is in Figure 2This is the case at point 60, where the lung compliance C term is again made visible by the tangent 61 to the inspiratory branch 54 of the PV curve 52 at point 60.

[0102] Alternatively or additionally, the control device 18 can determine from the course of the maneuver breathing gas volumes as a function of the breathing gas pressure the point 58 as the inflection point between a concave section 54a at lower breathing gas pressures and a convex section 54b at higher breathing gas pressures as the location of the greatest lung compliance C max and thus as the reference compliance value C ref.

[0103] By terminating the inspiration phase at point 60, the lungs of patient 12 can be automatically protected from barotrauma or other damage caused by excessive respiratory gas pressure in the lungs for the respective patient 12. The termination criterion, in the form of the termination compliance value C term, is determined during the P / V maneuver that is thereby terminated and applied immediately.

[0104] In the subsequent expiratory phase, represented by branch 56 of the PV curve 52, expiratory breathing gas flows from the patient’s lungs according to the above explanations to Figure 1 into the environment U. The hysteresis known for P / V maneuvers occurs between the expiratory branch 56 and the inspiratory branch 54.

[0105] Although lung tissue can already be recruited for a short time during the P / V maneuver itself, which can, for example, be the reason why a higher maneuver breathing gas volume is present in patient 12 during the expiratory phase at the start breathing gas pressure P Start than during the inspiration phase, the hysteresis behavior of patient 12's lungs during the P / V maneuver is a reliable indicator for making a statement about the prospects of success of medically known recruitment procedures on the patient's lungs to recruit lung tissue for gas exchange.

[0106] The timely, automated termination of the P / V maneuver before excessive inspiratory gas pressures are reached is also advantageous for increasing the informative value of the obtained PV curve regarding the prospects of success of future recruitment procedures for recruiting lung tissue from patient 12. Advancing the P / V maneuver to predetermined high final pressures, at which the patient's lungs are already more or less over-expanded, would yield less informative PV curves.

[0107] For example, the control device 18 can be designed to quantify the surface area of ​​the hysteresis surface 62, which encloses the two branches 54 and 56 between the start respiratory gas pressure P start and the termination respiratory gas pressure P term prevailing at the termination point 60. Furthermore, the control device 18 can be designed to calculate the surface area of ​​a rectangle 64, one corner of which is located at the value pair of start respiratory gas pressure P start and the inspiratory maneuver respiratory gas volume assigned to the start respiratory gas pressure P start and the diagonally opposite corner of which is located at the termination respiratory gas pressure P term and the maneuver respiratory gas volume assigned to the termination respiratory gas pressure P term.Since at point 60, where the termination breathing gas pressure P term prevails, the inspiratory and expiratory maneuver breathing gas volumes are usually equal, the choice of the maneuver breathing gas volume value from the inspiratory and expiratory maneuver breathing gas volumes is not important here.

[0108] The control device 18 can be further configured to calculate a hysteresis quotient value from the surface area of ​​the hysteresis surface and the surface area of ​​the rectangular area and to compare it with a predetermined first threshold value. If the hysteresis quotient value is greater than the predetermined first threshold value, the control device 18 outputs an output via the output device 28 indicating that a recruitment procedure on the currently ventilating lung has a high probability of recruitment success.

[0109] The starting respiratory gas pressure Pstart can be the PEEP set for the patient or can be up to approximately 1.6 times the set PEEP. The starting respiratory gas pressure of the P / V maneuver—regardless of the embodiment described here—is preferably in a pressure range of 5 to 8 mbar, preferably 7 to 8 mbar.

[0110] Alternatively or additionally, the control device 18 can be designed to determine the greatest difference in magnitude between the expiratory branch 56 and the inspiratory branch 54. This is shown in Figure 2 referred to as ΔV hyst-max.

[0111] Furthermore, the control device 18 can be designed to determine the largest volume difference of the inspiratory maneuver breathing gas volume, which is usually the difference between the volume coordinates of the inspiratory branch 54 at the termination breathing gas pressure P term on the one hand and the start breathing gas pressure P start on the other hand. This difference is in Figure 2 referred to as ΔV insp-max.

[0112] The control device 18 can be further configured to calculate a volume quotient value from the determined greatest volume difference between the expiratory branch 56 and the inspiratory branch 54 and the greatest volume difference ΔV insp-max in inspiratory maneuver breathing gas volume and to compare it with a predetermined second threshold value. If the volume quotient value is greater than the predetermined second threshold value, the control device 18 again outputs an output via the output device 28 indicating that a recruitment procedure performed on the currently ventilated patient lung has a high probability of success.

[0113] The Figure 2right vertical side of the rectangle 64, as well as the largest inspiratory volume difference ΔV insp-max are only particularly preferably located at the pressure value of the termination respiratory gas pressure P term . The significance of the previously described criteria for assessing the prospects of success of a recruitment procedure on the patient's lung is still sufficiently reliable if the right vertical side of the rectangle 64 and / or the largest inspiratory volume difference ΔV insp-max are in an upper end range 66 of the respiratory gas pressure range traversed during the P / V maneuver, which ranges from 95% to 100% of the termination respiratory gas pressure P term.

[0114] Likewise, the left vertical side of rectangle 64 can lie in a lower end region 68 of the breathing gas pressure range traversed during the P / V maneuver, which ranges from the starting breathing gas pressure P start to 1.05 times the starting breathing gas pressure P start . Therefore, the left vertical side of rectangle 64 does not have to be located directly at the starting breathing gas pressure P start , although this is preferred.

[0115] In this way, patients can be assessed directly at the site of their ventilation with regard to the prospects of success of recruitment procedures performed on them to recruit lung tissue without the need for complex computed tomography procedures.

Claims

1. Ventilation device (10) for artificial ventilation of a patient (12), comprising: - A respiratory gas source arrangement (15) which provides an inspiratory respiratory gas for artificial ventilation the patient (12), - A flow modification device (16) which is configured to produce and quantitatively modify an inspiratory respiratory gas flow (AF), - A respiratory gas line arrangement (30) with a proximal longitudinal end (30a) which during operation lies nearer to the patient (12) and with a distal longitudinal end (30b) which during operation lies further away from the patient, in order to convey the inspiratory respiratory gas flow (AF) from the respiratory gas source arrangement (15, 62) towards the patient (12), - A flow sensor arrangement (44) which is configured to acquire quantitatively both the inspiratory respiratory gas flow (AF) and an expiratory respiratory gas flow (EF), - A pressure sensor arrangement (27) which is configured to acquire a pressure both of the inspiratory respiratory gas and of the expiratory respiratory gas in the respiratory gas line arrangement (30), - A control device (18) with a data memory (19), where the control device (18) is connected for signal transmission with the data memory (19), with the flow sensor arrangement (44), and with the pressure sensor arrangement (27) and which is configured to control the operational output of the flow modification device (16) for modifying the inspiratory respiratory gas flow (AF), Where the control device (18) is configured to actuate the flow modification device (16) for performing a P / V maneuver in which in an inspiration phase, respiratory gas is supplied to a patient (12) under elevated respiratory gas pressure which in an expiration phase after completion of the pressure elevation flows passively out of the patient, where both during the inspiration phase and during the expiration phase, for a plurality of respiratory gas pressures, the respective maneuver respiratory gas volume present in the patient due to the P / V maneuver is determined in correlation with the prevailing respiratory gas pressure, Characterized in that the control device (18) is configured - To determine during the inspiration phase, on the basis of signals of the flow sensor arrangement (44) and of the pressure sensor arrangement (27), a sequence of compliance values each of which represents a pulmonary compliance of the lung of the patient (12), - To determine a reference compliance value (Cref) in accordance with the sequence of compliance values (Ci), - To determine as termination criterion for the inspiration phase, starting from the reference compliance value (Cref), a termination compliance value (Cterm) quantitatively different from the reference compliance value (Cref) as threshold value, and - To terminate the inspiration phase when the termination compliance value (Cterm) is reached or crossed.

2. Ventilation device (10) according to Claim 1, Characterized in that the control device (18) is configured to calculate the sequence of compliance values (Ci) from i) A ratio of a volume change value (ΔV) associated with a respiratory gas pressure and a pressure change value (ΔP) associated with the same respiratory gas pressure, where the volume change value (ΔV) represents a temporal change in the maneuver respiratory gas volume and where the pressure change value (ΔV) represents a temporal change in the respiratory gas pressure, and / or ii) A ratio of a flow value associated with a respiratory gas pressure and the pressure change value (ΔP) associated with the same respiratory gas pressure, where the flow value represents the inspiratory respiratory gas flow (AF).

3. Ventilation device (10) according to Claim 1 or 2, Characterized in that the control device (18) is configured to select, from a sequence of compliance values (Ci) which first become quantitatively larger and subsequently smaller, the quantitatively largest compliance value (Cmax) as reference compliance value (Cref).

4. Ventilation device (10) according to one of the preceding Claims, Characterized in that the control device (18) is configured to determine, from a sequence of value-pairs of an inspiratory respiratory gas pressure and the maneuver respiratory gas volume associated with the respective inspiratory respiratory gas pressure, an inflection point (58) between sections (54a, 54b) curved in different directions of curvature of a graph (54) representing the sequence of value-pairs, and to select the compliance value associated with the respiratory gas pressure at the inflection point (58) as reference compliance value (Cref).

5. Ventilation device (10) according to one of the preceding Claims, Characterized in that the control device (18) is configured to calculate the termination compliance value (Cterm) through multiplying the reference compliance value (Cref) by a predetermined factor or through adding the reference compliance value (Cref) to a predetermined summand.

6. Ventilation device (10) according to Claim 5, Characterized in that the termination compliance value (Cterm) equals 75% to 95%, preferably 80% to 92.5%, especially preferably 85% to 91% of the reference compliance values (Cref).

7. Ventilation device (10) according to one of the preceding Claims, Characterized in that the control device (18) is configured to calculate a volume ratio value from the quantitatively greatest difference (ΔVhyst-max) occurring during the P / V maneuver for a respiratory gas pressure between the expiratory (56) and the inspiratory maneuver respiratory gas volume (54) and a difference (ΔVinsp-max) between a maneuver respiratory gas volume value in an upper end-region (66) and a maneuver respiratory gas volume value in a lower end-region (68) of the respiratory gas pressure range traversed during the P / V maneuver, where the lower end-region (68) contains a start respiratory gas pressure (PStart) and extends up to 1.05 times the start respiratory gas pressure (PStart), and where the upper end-region (66) contains a termination respiratory gas pressure (Pterm) with which the termination compliance value (Cterm) is associated and begins at 95% of the termination respiratory gas pressure (Pterm).

8. Ventilation device (10) according to Claim 7, Characterized in that the control device (18) is configured to generate, when the volume ratio value exceeds a predetermined first threshold value, an output which indicates that a recruitment procedure for recruiting the patient's lung has overwhelming prospects of success.

9. Ventilation device (10) according to one of the preceding Claims, Characterized in that the control device (18) is configured to calculate a hysteresis ratio value from the size of the hysteresis area (62) which the graphs of the expiratory (56) and of the inspiratory maneuver respiratory gas volumes (54) as functions of the respiratory gas pressure between a start respiratory gas pressure (PStart) at which the P / V maneuver begins and a termination respiratory gas pressure (Pterm) with which the termination compliance value (Cterm) is associated, and the size of a rectangle (64) enclosing the hysteresis area whose one corner is determined by a lower respiratory gas pressure value in a lower end-region (68) of the respiratory gas pressure range traversed during the P / V maneuver and by the respiratory gas volume value associated with the lower respiratory gas pressure value, where the lower end-region (68) contains the start respiratory gas pressure (PStart) and extends up to 1.05 times the start respiratory gas pressure (PStart), and whose diagonally opposite corner is determined by an upper respiratory gas pressure value in an upper end-region (66) and by the respiratory gas volume value associated with the upper respiratory gas pressure value, where the upper end-region (66) contains a termination respiratory gas pressure (Pterm) with which the termination compliance value (Cterm) is associated and begins at 95% of the termination respiratory gas pressure (Pterm).

10. Ventilation device (10) according to Claim 9, Characterized in that the control device (18) is configured to generate, when the hysteresis ratio value exceeds a predetermined second threshold value, an output which indicates that a recruitment procedure for recruiting the patient's lung has overwhelming prospects of success.