Method for performing P / V maneuver to automatically avoid lung overexpansion and respiratory device configured to perform the method

Abstract

The invention relates to a respiratory device (10) for artificially respiring a patient (12), wherein a control device (18) is designed to control the flow changing device (16) to perform a P / V action, wherein in an inspiration phase, breathing gas is supplied to the patient (12) while increasing the breathing gas pressure, and in an expiration phase, after the pressure increase has ended, the breathing gas flows passively out of the patient, wherein during the inspiration phase and during the expiration phase, for a plurality of breathing gas pressures, an action-breathing gas volume associated with the currently prevailing breathing gas pressure, which is present in the patient due to the P / V action, is determined. According to the present invention, the control device (18) is configured to: - determine a sequence of compliance values ​​based on the signals of the flow sensor device (44) and the pressure sensor device (27) during the inhalation phase; - determine a reference compliance value based on the sequence of compliance values; - determine a termination compliance value as a criterion for terminating the inhalation phase, based on the reference compliance value, as a threshold value, which is different in magnitude from the reference compliance value; and - terminate the inhalation phase if the termination compliance value is reached or passed.

Description

Technical Field

[0001] The present invention relates to a respiratory device for performing artificial respiration on a patient, the respiratory device comprising:

[0002] a breathing gas source device which provides inspired breathing gas for artificially respiring a patient,

[0003] a flow changing device which is designed to generate an inspiratory breathing gas flow and changes it in magnitude,

[0004] a breathing gas line arrangement having a proximal longitudinal end portion located proximal to the patient in operation and a distal longitudinal end portion located distal to the patient in operation so as to facilitate a flow of breathing gas from the breathing gas source arrangement towards inspiration of the patient,

[0005] a flow sensor designed to detect the amount of an inspiratory breathing gas flow and an expiratory breathing gas flow,

[0006] a pressure sensor arrangement designed to detect the pressure of the inhaled breathing gas and the pressure of the expiratory breathing gas in the breathing gas line arrangement,

[0007] - A control device having a data memory, wherein the control device is connected to the data memory, the flow sensor and the pressure sensor device in terms of signal transmission, and the control device is configured to control the operating power of the flow changing device to change the breathing gas flow of inspiration, wherein the control device is configured to control the flow changing device to perform a P / V action, in which breathing gas is delivered to the patient during the inspiration phase under an increased breathing gas pressure, and the breathing gas pressure passively flows out of the patient after the pressure increase has ended during the expiration phase, wherein the action-breathing gas volume present in the patient body due to the P / V action is determined for a large number of breathing gas pressures during the inspiration phase and during the expiration phase in association with the currently prevailing breathing gas pressure.

[0008] The present invention further relates to a method for performing a P / V maneuver on a lung of a patient, preferably for the purpose of determining data for assessing the recruitability and distensibility of lung tissue of the lung of the patient. Background Art

[0009] A ventilator of the type mentioned above and a method for performing a P / V maneuver on a patient's lungs are known from EP 2 091 429 B1. This document teaches that for a specific patient, a positive end-expiratory pressure (PEEP) is determined in the patient or his lungs by a so-called P / V maneuver, hereinafter referred to as "PEEP" in accordance with academic standards.P ositive E nd-Expiratory P ressure).

[0010] In this P / V maneuver known from EP 2 091 429 B1, inspiratory breathing gas is supplied to the patient starting from a starting breathing gas pressure while the breathing gas pressure is continuously increased until a predetermined inspiratory breathing gas pressure is reached. An inspiratory PV curve is recorded, which indicates the inspiratory breathing gas volume supplied to the patient during the inspiratory phase of the P / V maneuver, in relation to the currently prevailing breathing gas pressure.

[0011] After reaching the predetermined breathing gas pressure, while the P / V maneuver is still ongoing, the previously delivered breathing gas is allowed to escape from the patient's lungs as exhaled breathing gas, again by measuring the breathing gas volume still present in the patient, associated with the pressure of the exhaled breathing gas prevailing during the respective test. For this purpose, a PV curve is also recorded, this time as an exhaled PV curve, which indicates the exhaled breathing gas volume present in the patient during the exhalation phase of the P / V maneuver, associated with the exhaled breathing gas pressure prevailing during the test. The P / V maneuver ends at the predetermined end pressure.

[0012] The inspiratory and expiratory PV curves pass through a common respiratory gas pressure range, wherein the two curves have hysteresis. The expiratory PV curve has higher volume values ​​over a wide average respiratory gas pressure range at the same respiratory gas pressure value.

[0013] EP 2 091 429 B1 teaches to automatically determine the PEEP adapted to the respective patient on whom the P / V maneuver is performed as the pressure at which the expiratory and inspiratory PV curves have a maximum difference in magnitude.

[0014] Since, due to the properties of the two PV curves (when the maximum volume difference in magnitude between the two PV curves has been detected), the volume difference between the expiratory and inspiratory PV curves decreases during the expiratory phase with a further decrease in the pressure of the exhaled respiratory gas, and a renewed increase in this volume difference is not to be expected, EP 2 091 429 B1 recommends interrupting the expiratory phase of the P / V maneuver when the maximum volume difference in magnitude between the expiratory and inspiratory PV curves can be detected during the expiratory phase.

[0015] A respiratory device is known from US Pat. No. 5,915,381, which teaches calculating the instantaneous compliance of the patient's lungs undergoing breathing from an inspiratory PV curve determined during the patient's normal machine-assisted breathing, and changing respiratory parameters such as pressure level, PEEP, inspiration duration, expiration duration, and respiratory rate when the instantaneous compliance of the lungs is less than a predetermined threshold value.

[0016] Here, "compliance" refers to the elastic resistance of the lungs to changes in volume in a manner common in the art. It is determined in a manner known in the art by the ratio of the change in lung volume to changes in the pressure of the respiratory gas. In contrast to the overall or average compliance determined over a complete inspiratory phase, "instantaneous compliance" refers to the compliance prevailing at a specific point in time or in a specific inspiratory state.

[0017] US Pat. No. 5,915,381 states that, depending on the pathological condition of the lung being inhaled, different amounts of breathing gas must be delivered to the lung in order to prevent complete or partial lung collapse. Diseased lungs typically have a smaller breathing area than healthy lungs. Therefore, according to US Pat. No. 5,915,381, a specific compliance threshold must be predetermined for each patient, with which the instantaneous compliance during the inhalation phase induced by the device is compared. US Pat. No. 5,915,381 mentions that, as an additional safety measure for some patients, the inhalation phase is terminated as soon as the instantaneous compliance determined during the inhalation phase falls below the predetermined threshold.

[0018] In this application, unless otherwise stated in individual cases, the term "compliance" refers to instantaneous compliance.

[0019] When artificial inspiration begins with the lungs in a state of maximum expiration, the increase in the inspired breathing gas pressure initially causes a relatively small increase in the lung's volume. Therefore, at the beginning of the inspiration phase of the P / V maneuver, the lung's compliance is relatively low in magnitude. After the lungs have been filled to a certain extent with the inspired breathing gas, as the inspired breathing gas pressure increases, the lung's volume increases to a greater extent than at the beginning of the P / V maneuver, resulting in a greater compliance in the temporal intermediate phase of the P / V maneuver than at the beginning of the maneuver. Near the end of the P / V maneuver, even if the inspired breathing gas pressure is further increased, the lungs, already largely filled with breathing gas, no longer increase in volume, resulting in a further decrease in compliance near the end of the P / V maneuver.

[0020] US Pat. No. 5,915,381 therefore mentions the following advantages: determining a suitable compliance threshold value for each patient to influence the pressure level, PEEP, inspiration duration, expiration duration, respiratory rate, etc. However, this determination of a predetermined compliance threshold value presupposes artificial respiration during which the compliance threshold value is applied. Precalculating such patient-specific compliance threshold values ​​based on the patient's medical history is complex and time-consuming. Furthermore, determining the patient-specific compliance threshold value and transmitting it to the respiratory system is prone to errors. Summary of the Invention

[0021] The object of the present invention is to improve the respiratory device known from EP 2 091 429 B1 so that the patient is well protected from the health-damaging effects of the P / V maneuver with the lowest possible effort when performing the P / V maneuver and so that the measurement data obtained from the P / V maneuver are influenced as little as possible by the effects of lung overexpansion.

[0022] According to an apparatus-related aspect, the object of the invention is achieved by a respiratory apparatus of the type mentioned at the outset, the control device of which is designed to:

[0023] - based on the signals of the flow sensor and the pressure sensor arrangement, determining a sequence of compliance values ​​during the inspiratory phase of the P / V maneuver, said compliance values ​​each representing the lung compliance of the patient's lungs,

[0024] - obtaining a reference compliance value based on the sequence of compliance values,

[0025] - as a termination criterion for the inspiratory phase, based on the reference compliance value, determining a termination compliance value which differs in magnitude from the reference compliance value as a threshold value, and

[0026] - When the stop compliance value is reached or passed, the inspiration phase is stopped.

[0027] Using a flow sensor and a pressure sensor arrangement, the control device can easily determine a series of compliance values ​​representing the lung compliance of the patient's lungs at different points in time during a P / V maneuver. The flow sensor measures the flow rate, i.e., the volume flow, of the respiratory gas inhaled during the inspiration phase, and the flow rate, i.e., the volume flow, of the respiratory gas exhaled during the expiration phase. The flow rate or volume flow of the respiratory gas corresponds to the change in volume of the respiratory gas in the patient's lungs per unit time.

[0028] The P / V maneuver can be performed, for example, with a predefined rate of increase in the breathing gas pressure or with a predefined inspiratory breathing gas volume flow, for example with a constant breathing gas volume flow.

[0029] The flow sensor can have multiple flow sensors, for example, one each for the inhaled and expiratory respiratory gas flow. Preferably, the flow sensor arrangement includes only one flow sensor to detect the inhaled and expiratory respiratory gas flows. The flow sensor is preferably arranged proximally between the respiratory gas line arrangement and the patient interface, but can also be accommodated distally in the housing of the respiratory device, in which, for example, a flow changing device is also accommodated. To achieve higher process safety, the respiratory device can also have multiple flow sensors, each of which detects the inhaled and expiratory respiratory gas flows, for example, a distal flow sensor in the housing of the respiratory device and a proximal flow sensor close to the patient. This applies accordingly to the pressure sensor arrangement, which can also have one or more pressure sensors to measure the pressure of the inhaled and expiratory respiratory gas.

[0030] By integrating the flow of breathing gas over a time period, the volume of breathing gas flowing in the breathing gas line arrangement during this time period can be determined. This is also the volume of breathing gas delivered to the lungs as inhaled breathing gas or flowing out of the lungs as exhaled breathing gas during this time period.

[0031] To distinguish it from any other respiratory gas volume that may occur during artificial respiration or during a P / V maneuver, the volume of respiratory gas present in the patient's lungs during a P / V maneuver due to the delivery of inspiratory respiratory gas to the patient's lungs and the outflow of expiratory respiratory gas from the patient's lungs is referred to herein as the "action-breathing gas volume." In case of doubt, the action-breathing gas volume during the inspiratory phase is the time-integrated flow of inspiratory respiratory gas during the inspiratory phase, while the action-breathing gas volume during the expiratory phase is the time-integrated flow of inspiratory respiratory gas at the end of the inspiratory phase minus the time-integrated flow of expiratory respiratory gas during the expiratory phase. Therefore, the action-breathing gas volume can be expressed as a function of the time from the start of the inspiratory phase to the end of the expiratory phase. Because the respiratory gas pressure in the respiratory gas circuit assembly can also be expressed as a function of time, the action-breathing gas volume can also be expressed as a function of the respiratory gas pressure in the respiratory gas circuit assembly during the inspiratory and expiratory phases.

[0032] In the present application, a PV curve or a PV relationship denotes the functional relationship between the currently present action breathing gas volume and the breathing gas pressure prevailing during this period.

[0033] Preferably, the respiratory system also includes a time measurement device to determine the duration of processes and subprocesses during the P / V maneuver, as well as the time points during the P / V maneuver. The time measurement device also allows for precise determination of changes in the breathing gas pressure, whether the pressure is currently inhaled or exhaled. However, a time measurement device is not absolutely necessary. For example, the control device can be configured to query the sensor signal at predetermined, known time intervals, so that a known duration always elapses between the individual queried detection values ​​of the sensor device. This also allows for sufficiently precise determination of the temporal changes in relevant parameters, such as the temporal changes in the breathing gas pressure or volume.

[0034] The compliance value thus determined is a direct patient-specific characteristic of the lungs of the particular breathing patient. Thus, without great effort, reference compliance values ​​can be used from the sequence of compliance values, which are also specific to the respective breathing patient.

[0035] If a termination compliance value is then determined based on the reference compliance value thus determined, and the inspiration phase is terminated upon reaching or passing the termination compliance value, it is possible to prevent the patient from "overinhaling" during the P / V maneuver, i.e., overexpanding or generally stressing or even damaging their lungs due to excessive amounts of respiratory gas and / or excessive respiratory gas pressure. Furthermore, due to the thoracic cavity's limited volume, which houses the lungs, overexpanding the lungs often results in adverse stress on the cardiovascular system of the patient undergoing the breathing. This is because the overexpanded lungs require space at the expense of compressible tissue, such as blood vessels.

[0036] The control device can thus automatically determine an individually adapted termination compliance value for each patient from the data acquired by sensory means during the inspiratory phase of the P / V maneuver and use it as a threshold value for terminating the inspiratory phase. This avoids the need for complex patient history acquisition to determine a predetermined termination compliance value and possible errors in transmitting this termination compliance value to the respiratory device.

[0037] The control device can thus be configured to terminate the inspiratory phase of each P / V maneuver in a patient-friendly manner, already using the termination criterion determined during the corresponding P / V maneuver itself. The control device can also be configured to use termination compliance values ​​of varying magnitude as threshold values ​​and termination criterion for the same patient during uninterrupted artificial respiration, depending on the respective state of health of the patient's lungs. In particular, the control device can be configured to determine a termination compliance value for the same patient during uninterrupted artificial respiration during each breathing event, every two breathing events, or every n breathing events, and to use this termination compliance value for the breathing event in which the determination is made, preferably until a subsequent termination compliance value is determined, where n is an integer.

[0038] In principle, there are various possibilities, such as enabling the control device to determine a sequence of compliance values ​​from the aforementioned sensor signals online, i.e., during an ongoing P / V maneuver. For example, the control device can configure a sequence for calculating compliance values ​​based on the 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 the temporal change of the maneuver breathing gas volume, and wherein the pressure change value represents the temporal change of the breathing gas pressure. In other words, for this purpose, it is sufficient to detect two volume values ​​at different points in time (from which the volume change value can be determined) and two breathing gas pressure values ​​at different points in time, preferably at the same point in time as the two volume values, so that the pressure change value can be determined from this. This is a method based on a difference quotient.

[0039] Alternatively, or in addition to providing redundancy, the control device can be configured to calculate a sequence of compliance values ​​based on the quotient of a flow value associated with a breathing gas pressure and a pressure change value associated with the same breathing gas pressure, wherein the flow value represents the breathing gas flow during inspiration. As described above, the flow value is a measure of the change in the volume of breathing gas delivered to or removed from the lungs per unit time. This is also a method of determining the compliance value based on a difference quotient.

[0040] It should be noted that the volume change values ​​and the pressure change values ​​apply to identical time periods, preferably identical points in time, so that the volume change values ​​and the pressure change values ​​are temporally correlated. If the breathing gas pressure changes over time and the breathing gas volume present in the patient's lungs changes over time, then the exhaust volume present in the patient's lungs changes with the breathing gas pressure due to the change in breathing gas pressure. This also applies, mutatis mutandis, to the flow values ​​and the pressure change values.

[0041] A certain temporal inaccuracy in the consistency of the detection times of the respective required sensor values ​​can be accepted. However, the more consistent the detection times of the required sensor values ​​are, the more accurate the compliance calculated therefrom will be.

[0042] There are also different possibilities for determining the reference compliance value.

[0043] According to a first preferred embodiment, the control unit can be configured to select the largest compliance value as a reference compliance value from a sequence of compliance values ​​that first increase in magnitude and then decrease in magnitude starting from the inspiratory phase of the P / V maneuver. The selected reference compliance value is advantageously temporarily stored in a data memory of the control unit.

[0044] If we consider the observable, one-to-one relationship between the breathing gas volume present in the patient's lungs during the P / V maneuver and the breathing gas pressure prevailing in the breathing gas circuit arrangement, then compliance is the first derivative of the breathing gas volume with respect to the breathing gas pressure as it changes. This can be determined in a substantially known manner using discrete measurement points via a difference quotient, or by interpolating the discrete measurement points using a differentiable function and determining it via its derivative, to name just two methods.

[0045] Simply put, compliance as a function of respiratory gas pressure is the slope of the graph of effort versus respiratory gas volume during inspiration. Due to the initially described change in compliance during the inspiratory phase of the P / V maneuver, the graph of effort versus respiratory gas volume as a function of respiratory gas pressure has a concave curve segment closer to the initial respiratory gas pressure of the P / V maneuver and a convex curve segment closer to the final pressure of the P / V maneuver. Typically, the inflection point at the transition between these two segments with different curvature directions represents a very high or even maximum compliance in the inspiratory PV curve. The initial and final respiratory gas pressures of the PV maneuver can be the same pressure. However, they can also be different, in which case the final pressure is preferably an absolute pressure of the respiratory gas that is lower than the initial respiratory gas pressure. In principle, the initial respiratory gas pressure can be freely selected within a medically relevant range. Preferably, a pressure is selected as the starting breathing gas pressure which lies within a pressure range from the PEEP ascertained for the respective patient up to approximately 1.6 times the PEEP, inclusive of the range limits.

[0046] Additionally or alternatively, the control device can be configured to determine, from a sequence of value pairs consisting of breathing gas pressure and the inspiratory effort-breathing gas volume associated with the respective breathing gas pressure, an inflection point between segments of a graph representing the sequence of value pairs that curve in different directions, and to select the compliance value associated with the breathing gas pressure at the inflection point as a reference compliance value. To determine the inflection point, the control device can be configured to form the second derivative of the volume value with respect to the pressure as a function of the pressure value in a manner known per se. According to one alternative, this can be performed, as with the determination of the first derivative, by interpolating the obtained measured values ​​using a quadratically differentiable function and using its derivative. The reference compliance then lies at the breathing gas pressure value at which the sequence of second derivatives of the value pairs has the value zero or the value that is closest to zero in magnitude. According to another alternative, forming the second derivative can be performed, as with the determination of the first derivative, using a difference quotient.

[0047] Preferably, the sequence of the mentioned value pairs forms a PV curve.

[0048] The two aforementioned methods for selecting or determining a reference compliance value allow, on the one hand, a reference compliance value to be selected that, based on experience, lies within the temporal middle range of the inspiratory phase of the P / V maneuver, within which it is virtually certain that the lungs will not be overloaded by manual inspiration. Furthermore, based on the thus selected reference compliance value, compliance values ​​occurring during other inspiratory phases are smaller in magnitude than the reference compliance value, making it possible to very reliably determine a meaningful termination compliance value based on this reference compliance value.

[0049] To determine the termination compliance value, the control device can be configured to calculate the termination 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 termination compliance value is generally smaller in magnitude than the maximum compliance value, which preferably serves as the reference compliance value, during the inhalation phase due to the aforementioned properties of the compliance value profile. For this reason, the predetermined factor is preferably less than 1.

[0050] In a preferred embodiment, the stop compliance value can be 75% to 95% of the reference compliance value, preferably 80% to 92.5%, and particularly preferably 85% to 91%. Particularly preferably, if a compliance value close to the maximum occurring value is selected, i.e., approximately in the range of 40% to 60% of the maximum occurring value, the stop compliance value is approximately 90% of the reference compliance value. This is independent of the method of calculating the stop compliance value based on the reference compliance value. Consequently, excessive loading of the patient's lungs, in particular overexpansion, during the inspiration phase can be reliably avoided.

[0051] In principle, it is conceivable to carry out a P / V maneuver as known from the prior art in order to determine a PEEP that is particularly suitable for the respective patient undergoing respiration.

[0052] However, it has been shown that reliable and dependable conclusions can be drawn about the expected success of a recruitment method for recruiting a functional lung volume using the P / V maneuver.

[0053] The above-mentioned termination criterion using a termination compliance value is particularly advantageous here, since it is thereby possible to avoid using values ​​for evaluating the expected success of a recruitment maneuver that could have been detected during lung overload and would therefore disadvantageously falsify the evaluation result if incorporated into the evaluation.

[0054] In addition to and in addition to the previously described approach of avoiding the detection of values ​​during lung overload, in particular during lung overdistension, by automatically determining the cut-off compliance value, it is also possible, according to a less preferred embodiment, to achieve undesired detection of values ​​during lung overdistension as follows:

[0055] According to a first alternative, a predetermined negative value of the second derivative of the P / V curve can be used as a 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 a previously detected positive value of the second derivative.

[0056] According to a second alternative, a first P / V maneuver can be performed without determining an inhalation termination criterion, as is known from the prior art. If lung overdistension 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 lung overdistension is not detected during the first P / V maneuver, the values ​​and / or the PV curve obtained during the first P / V maneuver are used to assess lung recruitability; otherwise, the values ​​and / or the PV curve obtained during the second P / V maneuver are used.

[0057] According to a third alternative, the control device is configured to reduce the end pressure obtained from the operator or from a callable data source for the P / V action by a predetermined amount by subtracting a predetermined safety margin value or by multiplying by a value less than 1, preferably by a value between 0.78 and 0.92, for example by a value of 0.8.

[0058] The control device can be designed to carry out one of the three mentioned alternatives.

[0059] Reliably assessing the success potential of a recruitment maneuver directly from the data of the P / V maneuver is therefore highly advantageous, as it can replace the need for a computed tomography scan. Thus, in the case of an at least partially collapsed lung, the success potential of a recruitment maneuver can be assessed directly on the patient's bed while they are being ventilated. The recruitment maneuver can be any known recruitment maneuver in the medical field.

[0060] In order to provide the data required for assessing the prospects for success of a recruitment maneuver for a patient undergoing respiration, the control device can be designed to calculate a volume quotient from:

[0061] the maximum difference in magnitude between the expiratory maneuver—the breathing gas volume—and the inspiratory maneuver—the breathing gas volume—occurring during the P / V maneuver for the breathing gas pressure, and

[0062] the difference between the maneuver-breathing gas volume value in the upper end range and the maneuver-breathing gas volume value in the lower end range of the breathing gas pressure range passed through during the P / V maneuver,

[0063] The lower end range includes the starting breathing gas pressure and extends to 1.05 times the starting breathing gas pressure, at which the P / V action begins, and the upper end range includes the termination breathing gas pressure and begins at 95% of the termination breathing gas pressure, to which the termination compliance value is associated.

[0064] For a final assessment of the potential success of a subsequent recruitment maneuver, the control device can, but need not necessarily, be configured to generate an output indicating a high potential success of the recruitment maneuver for recruiting the patient's lung when the volume quotient exceeds a predetermined first threshold. This predetermined first threshold is preferably between 38% and 46%, with 42% having been shown in previous studies to be the most suitable first threshold for distinguishing between patient lungs that are likely to be successfully recruited and those that are likely to be unsuccessful.

[0065] Alternatively or additionally, in order to provide the data required for assessing the prospects for success of a recruitment maneuver for a patient undergoing respiration, the control device can be designed to calculate a hysteresis quotient value from,

[0066] - the area of ​​a hysteresis region, which is a graph of the expiratory action-breathing gas volume and the inspiratory action-breathing gas volume as a function of the breathing gas pressure between a starting breathing gas pressure and a stopping breathing gas pressure at which the P / V action begins, and to which the stopping compliance value is associated, and

[0067] a rectangle bounding the area of ​​the hysteresis portion, one corner of which is determined by the lower breathing gas pressure value in the lower end range of the breathing gas pressure range passed through during the P / V maneuver and by the breathing gas volume value associated with the lower breathing gas pressure value,

[0068] The lower end range includes the starting breathing gas pressure and extends to 1.05 times the starting breathing gas pressure, and its diagonally opposite corner is determined by the upper breathing gas pressure value in the upper end range and by the breathing gas volume value associated with the upper breathing gas pressure value, wherein the upper end range includes the termination breathing gas pressure and starts at 95% of the termination breathing gas pressure, and the termination breathing gas pressure is associated with a termination compliance value.

[0069] To assess the success potential of the recruitment maneuver from the aforementioned data, the control device is capable of, but not configured to, generate an output indicating a high probability of success for the recruitment maneuver to recruit the patient's lungs when the hysteresis quotient exceeds a predetermined second threshold value. Preferably, the second threshold value differs from the first threshold value in magnitude. For hysteresis quotient values, a second threshold value in the range of 28% to 36% has been shown to be more convincing. Preferably, based on previous research, the second threshold value is 32%.

[0070] It should be added that the breathing gas source device of the respiratory apparatus can have a suction opening as a breathing gas source, through which ambient air or gas can be sucked from a predetermined gas reservoir. The breathing gas source device can additionally or alternatively have a gas reservoir as a breathing gas source, for example as a reservoir container or as a connection structure for connecting a supply line that connects the respiratory apparatus to a locally installed gas reservoir, as is often the case in clinics. In order to provide the possibility of mixing different gases into one breathing gas, the breathing gas source device can have a plurality of separate breathing gas sources, as mentioned above. In this case, the different gases to be mixed have different temperatures and / or different humidity levels due to the supply and pressure reduction. In order to ensure that the inhaled breathing gas actually reaches the patient at the humidity set once, it is particularly preferred that no breathing gas components are added to the breathing gas flow flowing out of the humidifier downstream of the humidifier, which is preferably present, in the inhalation direction.

[0071] The object mentioned at the outset is also achieved by a method for performing a P / V maneuver on the lungs of a patient, in particular for determining data for assessing the recruitability of lung tissue, comprising the following steps:

[0072] - performing a P / V action and, in this process, delivering inspired breathing gas to the patient during the inspiration phase at an increased breathing gas pressure,

[0073] During the inspiratory phase: the inspiratory work breathing gas volume delivered during the inspiratory phase or the inspiratory work volume flow of the inspiratory breathing gas is ascertained, and the breathing gas pressure is ascertained,

[0074] - determining a sequence of compliance values, each of which represents a lung compliance of a patient's lungs, - determining a reference compliance value from the sequence of compliance values ​​based on the sequence of compliance values,

[0075] - based on the reference compliance value, determining a termination compliance value that is different in magnitude from the reference compliance value as a termination threshold, and

[0076] - If the stop compliance value is reached or passed, the inspiration phase is stopped.

[0077] Preferably, the present invention also relates to an apparatus configured to carry out the aforementioned method. This is preferably a breathing apparatus as described and improved above.

[0078] The method aspects described in the description of the respiratory device are developments of the method according to the invention, and the device aspects described in the description of the method according to the invention are developments of the respiratory device according to the invention.

[0079] As already described, the method can prevent the patient's lungs from being overloaded due to excessively high respiratory gas pressures. By preventing overloading, in particular overexpansion of the lungs, it is also possible to prevent measured values ​​or measured value pairs from being detected in an overloaded lung state. Compared to value pairs detected in a normal lung load state, a sequence of measured value pairs detected in an overloaded state has only limited validity or may even falsify the associated measurement results.

[0080] In order to be able to obtain data for further treatment of the patient undergoing breathing from the P / V action, the inhalation phase is preferably followed in time by an exhalation phase, in which the respiratory gas flows passively out of the patient's body, wherein the expiratory respiratory gas pressure and the expiratory action-respiratory gas volume value are determined during the exhalation phase, wherein the expiratory action-respiratory gas volume value represents the expiratory action-respiratory gas volume present in the patient's body during the exhalation phase due to the P / V action.

[0081] In the method according to the invention and in the device according to the invention, in particular a respiratory device, a maneuver-breathing gas volume value associated with the breathing gas is detected during a P / V maneuver and stored as a value pair or as a value relationship. The maneuver-breathing gas volume value is associated with the breathing gas pressure prevailing during its detection.

[0082] While determining the inspiratory motion value (breathing gas quantity) is relatively simple, for example by integrating the flow value since the start of the inspiratory phase, determining the expiratory motion value (breathing gas volume) requires a higher computational effort. Determining the expiratory motion value (breathing gas volume) within the scope of the method according to the invention can, for example, include:

[0083] - determining the exhaled volume of the respiratory gas exhaled during the exhalation phase, and / or

[0084] - Determine the exhalation motion volume flow of the exhaled breathing gas.

[0085] The expiratory action-breathing gas volume value can then be determined from the inspiratory action-breathing gas volume value at the end of the inspiratory phase minus the determined expiratory volume or the action-volume flow integrated over the previous duration of the expiratory phase.

[0086] Furthermore, the method for determining data for later evaluating the success prospects of a recruitment maneuver in the lungs of the respective patient can include calculating a volume quotient from the maximum difference in magnitude between the expiratory maneuver breathing gas volume and the inspiratory maneuver breathing gas volume occurring for the breathing gas pressure during the P / V maneuver and from the reference maneuver breathing gas volume in the upper end range of the breathing gas pressure range passed through during the P / V maneuver, wherein the upper end range includes the stop breathing gas pressure and begins at 95% of the stop breathing gas pressure to which the stop compliance value is assigned. The above statements regarding the volume quotient in conjunction with the respiratory device according to the invention apply in particular.

[0087] Alternatively or additionally, the method for ascertaining data for later evaluating the prospects for success of a recruitment method in the lung of the respective patient can include calculating a hysteresis quotient from:

[0088] - the area of ​​the hysteresis region, which is a graph of the expiratory action-breathing gas volume and the inspiratory action-breathing gas volume as a function of the breathing gas pressure between the starting breathing gas pressure at which the P / V action begins and the ending breathing gas pressure associated with the ending compliance value, and

[0089] a rectangle bounding the area of ​​the hysteresis portion, one corner of which is determined by the lower breathing gas pressure value in the lower end range of the breathing gas pressure range passed through during the P / V maneuver and by the breathing gas volume value associated with the lower breathing gas pressure value,

[0090] The lower end range includes the starting breathing gas pressure and extends to 1.05 times the starting breathing gas pressure, and its diagonally opposite corner is determined by the upper breathing gas pressure value in the upper end range and by the breathing gas volume value associated with the upper breathing gas pressure value, wherein the upper end range includes the termination breathing gas pressure and starts at 95% of the termination breathing gas pressure, and the termination breathing gas pressure is associated with a termination compliance value.

[0091] Furthermore, as described above in conjunction with the respiratory apparatus, the method can include, after the data acquisition, a step of evaluating the data in order to assess the prospects for success of the recruitment method. To this end, the method can include a step of comparing the volume quotient with a predetermined first threshold value, wherein an output is generated as a function of the comparison result, the output indicating whether the recruitment method for recruiting the patient's lungs has a prospect of success in most cases. The above statement applies to the predetermined first threshold value. Preferably, if the volume quotient has a value that exceeds the first threshold value, an output is generated, the output indicating that the recruitment method has a prospect of success in most cases. Preferably, in other cases, no display is output or a display with the opposite content is output.

[0092] To assess the success potential of a recruitment maneuver based on the aforementioned hysteresis quotient value, the method can include a step of comparing the hysteresis quotient value with a predetermined second threshold value, wherein, based on the comparison result, an output is generated indicating whether the recruitment maneuver for recruiting the patient's lung has a high probability of success in most cases. The above statements also apply to the second threshold value. Preferably, based on current research, the second threshold value is 32%. Preferably, if the hysteresis quotient value exceeds the predetermined second threshold value, an output is generated indicating that the recruitment maneuver for recruiting the patient's lung has a high probability of success in most cases. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] The present invention is described in detail below with reference to the accompanying drawings. The accompanying drawings show:

[0094] Figure 1 A schematic diagram of a respiratory apparatus according to the invention configured for artificial respiration of a patient is shown, and

[0095] Figure 2 A schematic diagram shows a PV curve determined by a P / V operation of a respiratory device according to the invention and its evaluation. DETAILED DESCRIPTION

[0096] exist Figure 1 In FIG, an embodiment of a respiration device according to the invention is generally designated by 10. In the example shown, the respiration device 10 is used for artificial respiration of a human patient 12.

[0097] The respiratory device 10 has a housing 14, in which a suction opening 15 is formed and (not visible from the outside due to the opaque housing material) accommodates a flow-modifying device 16 and a control device 18. The suction opening 15 allows the flow-modifying device 16 to draw in ambient air from the external environment U of the respiratory device and, after a per se known cleaning process using a filter, deliver it as breathing gas to the patient 12. Therefore, the suction opening 15 is a breathing gas source for the purposes of this application.

[0098] An ambient temperature sensor 17 can be located in the intake opening 15 , which measures the temperature of the air of the environment U and transmits it to a control device 18 .

[0099] The flow-modifying device 16 is constructed in a manner known per se and can comprise a pump, a compressor, a blower, a pressure vessel, a pressure-reducing valve, etc. Furthermore, the respiratory device 10 comprises an inhalation valve 20 and an exhalation valve 22 in a manner known per se.

[0100] The control device 18 is usually implemented as a computer or a microprocessor. Figure 1 A data memory, denoted by 19 in the figure, is provided to store and, when necessary, retrieve data required for operating the respiratory device 10. 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 connection. The data transmission connection can be formed via a cable or a radio link. However, to prevent interference with the data transmission connection from affecting the operation of the respiratory device 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.

[0101] In order to input data into the respiratory device 10 or more precisely into the control device 18 , the respiratory device 10 can have an input device 24 , which is used to input data into the respiratory device 10 . Figure 1 In the example shown in FIG, the keyboard is represented. As will be explained below, the keyboard is not necessarily the only data entry point for the control device 18. In fact, in addition to or as an alternative to the keyboard, the control device 18 can obtain data via different data entry points, for example via a network line, a radio link or via the sensor interface 26.

[0102] In order to output data to a treating therapist, the respiratory device 10 can have an output device 28 , in the example shown a screen.

[0103] For artificial respiration, the patient 12 is connected to the respiratory device 10, more precisely to the flow-changing device 16 in the housing 14, via a breathing gas line arrangement 30. To this end, the patient 12 is intubated by means of an endotracheal tube serving as a patient interface 31. The proximal longitudinal end 31a of the patient interface 31 outputs an inspired 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 via the proximal longitudinal end 31a.

[0104] The distal longitudinal end 31b of the patient interface 31 is designed for connection to the respiratory gas line arrangement 30. From a point 31c located downstream in the inhalation direction to the proximal longitudinal end 31a, the patient interface is surrounded by the body of the patient 12. This means, on the other hand, that the patient interface 31 is exposed to the external environment U from its distal longitudinal end 31b to the point 31c and is in a predominantly convective heat transfer connection with the external environment.

[0105] The breathing gas line arrangement 30 includes an inhalation hose 32, through which fresh breathing gas can be conveyed from the flow-modifying device 16 into the lungs of the patient 12. The inhalation hose 32 can be interrupted and includes a first inhalation hose 34 and a second inhalation hose 36, between which a humidifier 38 can be located for targeted humidification and, if necessary, temperature control of the inhaled breathing gas supplied to the patient 12. The humidifier 38 can be connected to an external liquid reservoir 40, through which water for humidification or also medication, for example, to reduce inflammation or dilate the airways, can be supplied to the humidifier 38. In this manner, when the respirator 10 is used as an anesthetic respirator, a volatile anesthetic agent can be delivered to the patient 12 via the respirator 10 in a controlled manner. The humidifier 38 ensures that the fresh breathing gas is supplied to the patient 12 at a predetermined humidity, if necessary with the addition of a medication aerosol, and at a predetermined temperature.

[0106] In this example, the second suction hose 36 can be electrically heated by a line heater 37. The line heater 37 can be controlled for operation by the control device 18. Alternatively, the first suction hose 34 can also be heatable, and / or at least one hose 34 and / or 36 can be heated by a device other than the electrical line heater 37, for example, by surrounding it with a heat exchange medium.

[0107] In addition to the already mentioned inhalation valve 20 and exhalation valve 22 , the breathing gas line arrangement 30 also has an exhalation hose 42 , via which metabolized breathing gas is blown out of the lungs of the patient 12 into the external environment U as an exhaled breathing gas flow EF.

[0108] At the distal longitudinal end 30b of the breathing gas line arrangement 30, the inhalation hose 32 is coupled to the inhalation valve 20, while the exhalation hose 42 is coupled to the exhalation valve 22. Preferably, only one of these valves is open at a time to allow gas to flow through. The operation of valves 20 and 22 is also controlled by the control device 18.

[0109] During the breathing cycle, exhalation valve 22 is initially closed for the duration of the inhalation phase, while inhalation valve 20 is open, allowing fresh inhaled breathing gas to be directed from housing 14 to patient 12. The flow of fresh breathing gas is achieved by deliberately increasing the pressure of the breathing gas passing through flow-modifying device 16. Due to the increased pressure, the fresh breathing gas flows into the lungs of patient 12, where it causes the body regions adjacent to the lungs, particularly the thorax, to expand, overcoming the individual elasticity of the body parts adjacent to the lungs. Consequently, the gas pressure inside the lungs of patient 12 also increases.

[0110] At the end of the inhalation phase, inhalation valve 20 closes and exhalation valve 22 opens. The exhalation phase begins. Due to the increased gas pressure of the respiratory gas present in the lungs of patient 12 until the end of the inhalation phase, after the opening of exhalation valve 22, the respiratory gas flows into the external environment U, wherein the gas pressure in the lungs of patient 12 decreases as the flow duration progresses. When the gas pressure in lungs 12 reaches the positive end-expiratory pressure (PEEP) set on respiratory device 10, i.e., a pressure slightly above atmospheric pressure, the exhalation phase ends with the closing of exhalation valve 22, and another breathing cycle immediately follows.

[0111] During the inspiration phase, the so-called tidal volume, ie the volume of breathing gas per breathing process, is delivered to the patient 12. The minute volume of the currently performed artificial respiration is obtained by multiplying the tidal volume by the number of breathing cycles per minute, ie by the respiratory rate.

[0112] Preferably, the respiratory device 10, in particular the control device 18, is designed to repeatedly update or determine respiratory operation parameters that characterize the respiratory operation of the respiratory device 10 during the respiratory operation in order to ensure that the respiratory operation is optimally adapted to the respective patient 12 to be ventilated at any given time. Particularly advantageously, one or more respiratory operation parameters are determined via the respiratory frequency, so that current and therefore optimally adapted respiratory operation parameters can be provided for each respiratory cycle.

[0113] For this purpose, the respiratory device 10 can be connected to one or more sensors in a data-transmitting manner, which monitor the patient's condition and / or the operation of the respiratory device 10. A list of possible sensors is shown only as an example. Figure 1, a proximal flow sensor 44 is mentioned, which measures the respiratory gas flow prevailing in the respiratory gas line arrangement 30, specifically, the inspiratory respiratory gas flow AF and the expiratory respiratory gas flow EF. The proximal flow sensor 44, which is preferably designed as a differential pressure sensor, can be coupled to the data input 26 of the control device 18 by means of a sensor circuit arrangement 46. The sensor circuit arrangement 46 can, but need not, include electrical signal transmission lines. The sensor circuit arrangement can also include a hose line that transmits the gas pressure prevailing in the flow direction on both sides of the flow sensor 44 to the data input 26, where it is quantified by a pressure sensor 27.

[0114] More precisely, in a preferred embodiment, the breathing gas line device 30 has a separately designed Y-shaped line section 47 at its proximal longitudinal end region 30 a, which is connected to the second inspiratory hose 36 and the expiratory hose 42 at its distal end region, and is connected to the proximal flow sensor 44 at its proximal end region.

[0115] The proximal flow sensor 44 has a coupling structure 44a at its proximal end region, by means of which the patient interface 31 can also be coupled to the proximal flow sensor 44 and thus to the respiratory gas line device 30 . The patient interface can also be a mask instead of a tube.

[0116] The second inspiratory hose 36 can have a proximal temperature sensor 48 at its proximal longitudinal end region, which measures the temperature of the breathing gas flow AF in the second inspiratory hose 36 as close as possible to the patient 12 and transmits it to the control device 18 .

[0117] Merely for the sake of completeness, it should be pointed out that the respiratory device 10 according to the invention can be accommodated as a mobile respiratory device 10 on a rollable stand 50 .

[0118] exist Figure 2 In the diagram, the PV curve is roughly schematically shown and is indicated by 52, which is obtained by the P / V action, which is obtained by the P / V action Figure 1 The P / V maneuver of the present application can be a one-time maneuver that is distinct from the rest of the breathing operation. However, the sequence of P / V maneuvers of the present application can also be a series of breathing processes for delivering an expiratory tidal volume, and thus part of a regular artificial respiration ordered by the patient 12.

[0119] The abscissa of the coordinate system represents the pressure of the breathing gas, which increases in the direction of the arrow, and the ordinate of the coordinate system represents the action-breathing gas volume, which increases in the direction of the arrow. The representation of the PV curve in the coordinate system is merely an example and is roughly schematic. The intersection of the coordinate system does not necessarily correspond to the coordinate origin at a pressure of 0 mbar and an action-breathing gas volume of 0 ml.

[0120] P / V action at the initial breathing gas pressure P Start The inspiratory phase begins, that is, the initial breathing gas pressure P Start High enough to direct inspired breathing gases into the lungs of patient 12 .

[0121] Starting from the inspiration phase, the control device 18 quantitatively detects the inspiratory breathing gas flow rate AF and its pressure in the breathing gas line arrangement 30 via the flow sensor 44 and the associated pressure sensor 27, thereby forming a value pair consisting of the inspiratory breathing gas and the pressure-associated action-breathing gas volume delivered to the patient 12. The delivered action-breathing gas volume corresponds to the integral of the inspiratory breathing gas flow rate from the start of the inspiration phase to the detection time point. Therefore, the control device 18 determines the value of Figure 2 First, the inspiratory branch 54 of the PV curve 52 is determined. After the inspiratory phase, the expiratory branch 56 is determined in such a way that the respiratory gas initially supplied to the patient 12 is passive, i.e., can escape from the patient 12 into the environment U only at the pressure of the respiratory gas present in the patient 12.

[0122] Starting from the inspiration phase, the control device 18 determines the inspiratory breathing gas pressure from the difference between the breathing gas pressures of successive inspirations and the difference between the action-breathing gas volumes associated with these breathing gas pressures, wherein the inspiratory breathing gas pressures lie in the range of inspiratory breathing gas pressures for determining the breathing gas pressure difference in terms of magnitude (including the range limits), the associated lung compliance C i Also as a function of the breathing gas pressure. Figure 2 In the example, the breathing gas pressure P i The gradient triangle ΔV / ΔP in is represented by . Figure 2 The PV curve represents the lung compliance C during the inspiration phase. i It is the first derivative of the PV curve with respect to the breathing gas pressure. Therefore, it is used to obtain the lung compliance C associated with the corresponding breathing gas pressure. i In principle, different methods are available and usable.

[0123] The control device 18 calculates the lung compliance C thus determined. iThe value pair consisting of the associated breathing gas pressure Pi is stored in the data memory 19 and the maximum occurring value C of the lung compliance is determined from the stored values. max In this context, use can be made of the fact that at the beginning and at the end of the inspiratory phase the lungs each have a lower lung compliance value C at the beginning and at the end of the inspiratory phase than in the middle region of the inspiratory phase. i Therefore, if lung compliance C is achieved i The maximum value C max And the lung compliance C obtained later when the breathing gas pressure is high i The maximum value is also considered to be the absolute maximum value of lung compliance during the entire inspiratory phase. max .

[0124] The PV curve can be smoothed with the aid of conventional smoothing methods in order to eliminate noise components and thus achieve a more stable determination of the lung compliance.

[0125] Maximum lung compliance C max exist Figure 2 The maximum slope at this point is shown by the tangent line 59 at the suction branch 54 of the PV curve 52 at point 58 .

[0126] The maximum lung compliance value C obtained in this way is max Selected by the control device 18 as the reference compliance value C ref When choosing the reference compliance value C ref Afterwards, the control device 18 automatically calculates the termination compliance value C term , the inspiratory phase of the P / V action is terminated at this termination compliance value. In this embodiment, the control device 18 will refer to the compliance value C ref Multiply by a predetermined factor less than 1, for example by 0.9, to thereby calculate the cut-off compliance value C term .

[0127] From now on, for an increased breathing gas pressure, the control device 18 will calculate the correspondingly determined lung compliance C i and the termination compliance value C term Compare and when it is identified: instantaneous lung compliance C i The abort compliance value C has been reached or exceeded term The inhalation phase ends when Figure 2 This is the case at point 60, where the lung compliance C is again taken into account at point 60 by the tangent line 61 at the inspiratory branch 54 of the PV curve 52. term visible.

[0128] Alternatively or additionally, the control device 18 can determine the point 58 from the curve of the movement-breathing gas volume as a function of the breathing gas pressure as the inflection point between the concave section 54a at low breathing gas pressure and the convex section at high breathing gas pressure, as the maximum lung compliance C max The location is then used as the reference compliance value C ref .

[0129] By terminating the inspiration phase at point 60, the lungs of the patient 12 can be automatically protected from barotrauma or other damage caused by a breathing gas pressure in the lungs that is too high for the respective patient 12. term The formal abort criterion is determined during the P / V action thus aborted and is immediately applied.

[0130] In the subsequent expiration phase represented by the branch 56 of the PV curve 52, the exhaled respiratory gas is Figure 1 The flow of φ from the patient's lungs into the environment U occurs here between the expiratory branch 56 and the inspiratory branch 54 , which is known for the P / V action.

[0131] Although the lung tissue can already be recruited within a short time during the P / V maneuver itself, this can be achieved, for example, during the expiration phase at the initial breathing gas pressure P Start There is a higher movement of the maneuver-breathing gas volume in patient 12 during the P / V maneuver than during the inspiratory phase, but the delayed performance of patient 12's lungs during the P / V maneuver is a reliable indicator for concluding about the prospects for success of the medically known recruitment methods at the patient's lungs for recruiting lung tissue for gas exchange.

[0132] Here, timely and automatic termination of the P / V maneuver before reaching an excessively high inspired breathing gas pressure also contributes to increasing the confidence of the obtained PV curve with respect to the success prospects of the upcoming recruitment method for recruiting the lung tissue of the patient 12. A less convincing PV curve would result from advancing the P / V maneuver to a predetermined high end pressure, at which the patient's lungs are already more or less strongly expanded.

[0133] The control device 18 can be designed, for example, to quantify the area of ​​the hysteresis region 62 which is enclosed at the starting breathing gas pressure P Start and the stop breathing gas pressure P present at the stop point 60 term Furthermore, the control device 18 can be configured to calculate the area of ​​a rectangle 64, one corner of which is located at the area defined by the initial breathing gas pressure P Startand the initial breathing gas pressure P Start The values ​​of the associated inspiratory effort-breathing gas volume are centered and their diagonally opposite corners are located at the end breathing gas pressure P term and the cessation of breathing gas pressure P term The associated action - breathing gas volume. Because there is a stop breathing gas pressure P term At point 60, the inspiratory motion-breathing gas volume and the expiratory motion-breathing gas volume are usually of the same size, so it is not important to select the motion-breathing gas volume value from the inspiratory and expiratory motion-breathing gas volumes here.

[0134] The control device 18 can also be configured to calculate a hysteresis quotient from the area of ​​the hysteresis area and the area of ​​the rectangular area and compare it to a predetermined first threshold value. If the hysteresis quotient is greater than the predetermined first threshold value, the control device 18 outputs an output via the output device 28 indicating that the recruitment method for the currently breathing lung has a promising prospect of successful recruitment in most cases.

[0135] Initial breathing gas pressure P Start It can be the PEEP set for the patient or can be up to about 1.6 times the set PEEP. Preferably, the starting breathing gas pressure of the P / V maneuver (irrespective of the embodiment currently described) is in the pressure range of 5 to 8 mbar, preferably in the pressure range of 7 to 8 mbar.

[0136] Alternatively or additionally, the control device 18 can be designed to determine the maximum difference in magnitude between the expiratory branch 56 and the inspiratory branch 54. Figure 2 Indicated as ΔV hyst-max .

[0137] Furthermore, the control device 18 can be designed to determine the maximum volume difference between the inspiratory action and the breathing gas volume, which is typically the maximum volume difference between the inspiratory branch 54 at the end of the breathing gas pressure P term At the initial breathing gas pressure P Start The difference in volume coordinates at . Figure 2 is called ΔV insp-max .

[0138] The control device 18 can also be configured to calculate the maximum volume difference ΔV between the expiratory branch 56 and the inspiratory branch 54 and the maximum volume difference ΔV between the inspiratory effort and the breathing gas volume. insp-maxThe volume quotient is calculated and compared with a predetermined second threshold value. If the volume quotient is greater than the predetermined second threshold value, the control device 18 again outputs an output via the output device 28 indicating that the recruitment maneuver performed on the lungs of the currently breathing patient has a promising future in most cases.

[0139] exist Figure 2 The right vertical side of the middle rectangle 64 and the maximum volume difference ΔV of the inhaled air insp-max Only particularly preferably at the stop breathing gas pressure P term If the right vertical side of rectangle 64 and / or the maximum inhaled volume difference ΔV insp-max The upper end range 66 of the breathing gas pressure range passed during the P / V maneuver is located from the stop breathing gas pressure P term If the 95% of the total number of patients who underwent the intervention was extended to 100%, the previously described criteria for assessing the prospects for success of a recruitment maneuver in the patient's lungs would always be sufficiently reliable.

[0140] Likewise, the left vertical side of the rectangle 64 can be located in a lower end range 68 of the breathing gas pressure range passed through during the P / V maneuver, the lower end range being from the starting breathing gas pressure P Start Therefore, the left vertical side of rectangle 64 does not need to be directly at the starting breathing gas pressure P Start although this is preferred.

[0141] In this way, the success prospects of a recruitment method for expanding lung tissue carried out on the patient's body can be assessed directly at the point of his breathing without requiring complex computed tomography methods.

Claims

1. A respiratory device (10) for artificially respiring a patient (12), the respiratory device comprising: a breathing gas source device (15) which provides inspired breathing gas for artificially respiring the patient (12), a flow changing device (16) configured to generate an inspiratory breathing gas flow (AF) and to change the same in terms of its magnitude, a breathing gas circuit arrangement (30) having a proximal longitudinal end (30a) positioned proximal to the patient (12) in operation and a distal longitudinal end (30b) positioned distal to the patient in operation, so as to facilitate an inspiratory breathing gas flow (AF) from the breathing gas source arrangement (15, 62) towards the patient (12), - a flow sensor device (44) designed to detect the magnitude of the inspiratory breathing gas flow (AF) and the expiratory breathing gas flow (EF), a pressure sensor device (27) designed to detect the pressure of the inhaled breathing gas and the pressure of the exhaled breathing gas in the breathing gas line device (30), a control device (18) having a data memory (19), wherein the control device (18) is connected to the data memory (19), the flow sensor device (44) and the pressure sensor device (27) in terms of signal transmission, and is designed to control the operating power of the flow changing device (16) in order to change the inspiratory breathing gas flow (AF), wherein the control device (18) is designed to actuate the flow changing device (16) to perform a P / V maneuver, wherein breathing gas is supplied to the patient (12) during an inhalation phase while increasing the breathing gas pressure, and wherein the breathing gas flows passively out of the patient during an exhalation phase after the pressure increase has ended, wherein during the inhalation phase and during the exhalation phase for a plurality of breathing gas pressures, an action breathing gas volume associated with the currently prevailing breathing gas pressure, which is respectively present in the patient as a result of the P / V maneuver, is ascertained, It is characterized by: The control device (18) is configured to: - determining a sequence of compliance values ​​during the inspiration phase from the signals of the flow sensor device (44) and the pressure sensor device (27), each of which represents the lung compliance of the lungs of the patient (12), -According to the compliance value (C i ) sequence to obtain the reference compliance value (C ref ), - As the termination criterion of the inspiratory phase, based on the reference compliance value (C ref ), determine the compliance value (C ref ) Different stop compliance values ​​(C term ) as the threshold, and - If the abort compliance value (C term ), then the inhalation phase is terminated.

2. The breathing apparatus (10) according to claim 1, characterized in that The control device (18) is configured to calculate a compliance value (C i ) sequence: i) a quotient of a volume change value (ΔV) associated with a breathing gas pressure and a pressure change value (ΔP) associated with the same breathing gas pressure, wherein the volume change value (ΔV) represents a change in the action-breathing gas volume over time, and wherein the pressure change value (ΔV) represents a change in the breathing gas pressure over time, and / or ii) the quotient of a flow value associated with a breathing gas pressure and a pressure change value (ΔP) associated with the same breathing gas pressure, wherein the flow value represents an inspiratory breathing gas flow (AF).

3. The breathing apparatus (10) according to claim 1, characterized in that The control device (18) is designed to start with a compliance value (C i ) in the sequence and select the compliance value with the largest value (C max ) as the reference compliance value (C ref ).

4. The breathing apparatus (10) according to claim 2, characterized in that The control device (18) is designed to start with a compliance value (C i ) in the sequence and select the compliance value with the largest value (C max ) as the reference compliance value (C ref ).

5. The breathing apparatus (10) according to claim 1, characterized in that The control device (18) is configured to determine, from a sequence of value pairs consisting of an inspiratory breathing gas pressure and an action-breathing gas volume associated with the respective inspiratory breathing gas pressure, an inflection point (58) between sections (54a, 54b) of a graph (54) representing the sequence of value pairs that are curved in different curvature directions, and to select a compliance value associated with the breathing gas pressure at the inflection point (58) as a reference compliance value (C ref ).

6. The breathing apparatus (10) according to any one of claims 2, 3 and 4, characterized in that The control device (18) is configured to determine, from a sequence of value pairs consisting of an inspiratory breathing gas pressure and an action-breathing gas volume associated with the respective inspiratory breathing gas pressure, an inflection point (58) between sections (54a, 54b) of a graph (54) representing the sequence of value pairs that are curved in different curvature directions, and to select a compliance value associated with the breathing gas pressure at the inflection point (58) as a reference compliance value (C ref ).

7. The breathing apparatus (10) according to claim 1, characterized in that The control device (18) is configured to adjust the reference compliance value (C ref ) by a predetermined factor or by multiplying the reference compliance value (C ref ) is added to a predetermined addend to calculate the termination compliance value (C term ).

8. The breathing apparatus (10) according to any one of claims 2, 3, 4 and 5, characterized in that The control device (18) is configured to adjust the reference compliance value (C ref ) by a predetermined factor or by multiplying the reference compliance value (C ref ) is added to a predetermined addend to calculate the termination compliance value (C term ).

9. The breathing apparatus (10) according to claim 7, characterized in that The suspension compliance value (C term ) is the reference compliance value (C ref ) of 75% to 95%.

10. The breathing apparatus (10) according to claim 7, characterized in that The suspension compliance value (C term ) is the reference compliance value (C ref ) from 80% to 92.5%.

11. The breathing apparatus (10) according to claim 7, characterized in that The suspension compliance value (C term ) is the reference compliance value (C ref ) of 85% to 91%.

12. The breathing apparatus (10) according to claim 1, characterized in that The control device (18) is configured to calculate a volume quotient from the following: the maximum difference in magnitude (ΔV) between the exhalation maneuver-breathing gas volume (56) and the inspiration maneuver-breathing gas volume (54) occurring during the P / V maneuver for the breathing gas pressure hyst-max ); and the difference (ΔV between the action-breathing gas volume value in the upper end range (66) and the action-breathing gas volume value in the lower end range (68) of the breathing gas pressure range passed during the P / V action. insp-max ), wherein the lower end range (68) includes the starting breathing gas pressure (P Start ) and extends to the starting breathing gas pressure (P Start ) times, and wherein the upper end range (66) includes the stop breathing gas pressure (P term ) and at 95% of the cessation breathing gas pressure (P term ), the stop breathing gas pressure is associated with the stop compliance value (C term ).

13. The breathing apparatus (10) according to any one of claims 2, 3, 4, 5 and 7, characterized in that The control device (18) is configured to calculate a volume quotient from the following: the maximum difference in magnitude (ΔV) between the exhalation maneuver-breathing gas volume (56) and the inspiration maneuver-breathing gas volume (54) occurring during the P / V maneuver for the breathing gas pressure hyst-max ); and the difference (ΔV between the action-breathing gas volume value in the upper end range (66) and the action-breathing gas volume value in the lower end range (68) of the breathing gas pressure range passed during the P / V action. insp-max ), wherein the lower end range (68) includes the starting breathing gas pressure (P Start ) and extends to the starting breathing gas pressure (P Start ) times, and wherein the upper end range (66) includes the stop breathing gas pressure (P term ) and at 95% of the cessation breathing gas pressure (P term ), the stop breathing gas pressure is associated with the stop compliance value (C term ).

14. The breathing apparatus (10) according to claim 12, characterized in that The control device (18) is designed to generate an output indicating that a recruitment method for recruiting the patient's lungs has a promising prospect of success in most cases if the volume quotient exceeds a predetermined first threshold value.

15. The breathing apparatus (10) according to any one of claims 1, 2, 3, 4 and 5, characterized in that The control device (18) is configured to calculate the hysteresis quotient from the following: the area of ​​the hysteresis region (62) as the area of ​​the hysteresis region at the initial breathing gas pressure (P Start ) and the breathing gas pressure (P term ), wherein the P / V action starts at the starting breathing gas pressure, and the stopping breathing gas pressure is associated with the stopping compliance value (C term ); and a rectangle (64) bounding the area of ​​the hysteresis part, one corner of the rectangle being determined by a lower breathing gas pressure value in a lower end range (68) of the breathing gas pressure range passed during the P / V maneuver and by a breathing gas volume value associated with the lower breathing gas pressure value, wherein the lower end range (68) contains the starting breathing gas pressure (P Start ) and extends to the starting breathing gas pressure (P Start ), and the diagonally opposite corners of the rectangle are determined by the upper breathing gas pressure value in the upper end range (66) and by the breathing gas volume value associated with the upper breathing gas pressure value, wherein the upper end range (66) contains the stop breathing gas pressure (P term ) and at 95% of the cessation breathing gas pressure (P term ), the stop breathing gas pressure is associated with the stop compliance value (C term ).

16. The breathing apparatus (10) according to claim 15, characterized in that The control device (18) is designed to generate an output indicating that a recruitment method for recruiting the patient's lungs has a promising prospect of success in most cases if the hysteresis quotient exceeds a predetermined second threshold value.

17. A method for performing a P / V maneuver on a patient's lung to obtain data for evaluating the recruitability of lung tissue, the method comprising the steps of: - performing a P / V action and, in this process, delivering inspiratory breathing gas to the patient (12) during the inspiration phase while increasing the breathing gas pressure, during the inspiratory phase: determining the inspiratory work breathing gas volume or the inspiratory work volume flow of the inspiratory breathing gas delivered during the inspiratory phase, and determining the breathing gas pressure, - Obtain the compliance value (C i ), the compliance values ​​respectively represent the lung compliance of the lungs of the patient (12), -According to the compliance value (C i ) sequence to obtain the reference compliance value (C ref ), - Based on the reference compliance value (C ref ), determine the reference compliance value (C ref ) The different stop compliance values ​​(C term ) as the termination threshold, and - If the abort compliance value (C tern ), the inhalation phase is terminated.

18. The method according to claim 17, characterized in that An expiration phase is provided which temporally follows the inspiratory phase, in which respiratory gas flows passively out of the patient (12), wherein an expiration respiratory gas pressure and an expiration action-respiratory gas volume value are determined during the expiration phase, wherein the expiration action-respiratory gas volume value represents the expiration action-respiratory gas volume present in the patient during the expiration phase due to the P / V action.

19. The method according to claim 18, characterized in that Determining the exhaled action-breathing gas volume value includes: - determining the exhaled volume of respiratory gas exhaled during said exhalation phase, and / or - Determine the exhalation motion volume flow of the exhaled breathing gas.

20. The method according to claim 18, wherein Calculate the volume quotient from: - The pressure of the breathing gas during the P / V maneuver that occurs during the exhalation maneuver - the maximum difference in magnitude (ΔV) between the respiratory gas volume (56) and the inspiratory effort - the respiratory gas volume (54) hyst-max );and - the difference (ΔV) between the action-breathing gas volume value in the upper end range (66) and the action-breathing gas volume value in the lower end range (68) of the breathing gas pressure range passed during the P / V action insp-max ), wherein the lower end range (68) includes the initial breathing gas pressure (P Start ) and extends to the starting breathing gas pressure (P Start ) times, and wherein the upper end range (66) includes the stop breathing gas pressure (P term ) and at 95% of the cessation breathing gas pressure (P term ), the stop breathing gas pressure is associated with the stop compliance value (C term ).

21. The method according to claim 19, wherein Calculate the volume quotient from: - the maximum difference in magnitude (ΔV) between the exhalation action-breathing gas volume (56) and the inspiration action-breathing gas volume (54) occurring during the P / V action for the breathing gas pressure hyst-max );and - the difference (ΔV) between the action-breathing gas volume value in the upper end range (66) and the action-breathing gas volume value in the lower end range (68) of the breathing gas pressure range passed during the P / V action insp-max ), wherein the lower end range (68) includes the initial breathing gas pressure (P Start ) and extends to the starting breathing gas pressure (P Start ) times, and wherein the upper end range (66) includes the stop breathing gas pressure (P term ) and at 95% of the cessation breathing gas pressure (P term ), the stop breathing gas pressure is associated with the stop compliance value (C term ).

22. The method according to any one of claims 18 to 21, characterized in that Calculate the hysteresis quotient from: - the area of ​​the hysteresis part (62), which is the area of ​​the hysteresis part at the initial breathing gas pressure (P Start ) and the breathing gas pressure (P term ) between the breathing gas pressure and the exhalation action-breathing gas volume (56) and the inhalation action-breathing gas volume (54), when the P / V action starts at the starting breathing gas pressure, the stopping breathing gas pressure (P term ) is associated with the termination compliance value (C term );and a rectangle (64) bounding the area of ​​the hysteresis portion, one corner of the rectangle being determined by a lower breathing gas pressure value in a lower end range (68) of the breathing gas pressure range passed through during the P / V maneuver and by a breathing gas volume value associated with the lower breathing gas pressure value, wherein the lower end range (68) includes the initial breathing gas pressure (P Start ) and extends to the starting breathing gas pressure (P Start ), and the diagonally opposite corners of the rectangle are determined by the upper breathing gas pressure value in the upper end range (66) and by the breathing gas volume value associated with the upper breathing gas pressure value, wherein the upper end range (66) contains the stop breathing gas pressure (P term ) and at 95% of the cessation breathing gas pressure (P term ), the stop breathing gas pressure is associated with the stop compliance value (C term ).

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