VENTILATION DEVICE

Description

[0001] The present invention relates to a ventilation device for a ventilation operation for the mechanical administration of respiratory gas to a patient, wherein the ventilation device comprises: a respiratory gas source arrangement which provides an inspiratory respiratory gas for administration to the patient, a flow-modifying device which is configured to generate and / or quantify an inspiratory respiratory gas flow, a respiratory gas line arrangement for conveying the inspiratory respiratory gas flow from the respiratory gas source arrangement to the patient, a sensor arrangement which is configured to detect at least one state variable of the inspiratory respiratory gas flow and / or a quantity flow of the inspiratory respiratory gas flow and / or respiratory muscle activity of the patient, a control device with a data storage device, wherein the control device is connected to the data storage device and to the sensor arrangement by means of signal transmission, and wherein the control device is configured to control the flow-modifying device. wherein the control device is configured to control the flow-changing device in normal ventilation operation, starting from a previous breath with or after the expiry of a predetermined normal time interval, to generate an inspiratory respiratory gas flow in order to effect a machine-triggered subsequent breath immediately following the previous breath, wherein the control device is further configured to detect a spontaneous respiratory effort of the patient during ventilation operation of the ventilation device on the basis of data determined by the sensor arrangement.

[0002] The present invention also enables the performance of a ventilation method (not claimed) for the mechanical administration of respiratory gas to a patient, wherein the ventilation method comprises the following steps: Initiating a machine-triggered follow-up breath immediately after a previous breath by generating an inspiratory gas flow using a flow-changing device starting from the previous breath after a predetermined normal time interval; detecting at least one state variable of the inspiratory gas flow and / or a quantity flow of the inspiratory gas flow and / or respiratory muscle activity of the patient by a sensor arrangement; detecting a spontaneous respiratory effort of the patient during the ventilation operation of the ventilation device based on data determined by the sensor arrangement.

[0003] Spontaneous respiratory activity in a mechanically ventilated patient, especially when it is not detected or is ignored by the ventilator, poses a fundamental problem in mechanical ventilation. This is because spontaneous respiratory activity, or equivalently, the patient's spontaneous breathing efforts, disrupts the rhythmic flow of mechanical ventilation. Spontaneous respiratory activity typically results in more or less respiratory gas being delivered than the ventilator setting indicates, or in excessive strain or even damage to the respiratory muscles. Therefore, spontaneous respiratory efforts are often referred to as "asynchronies."US Patent 2011 / 0213215 A1 discloses that, as part of a weaning strategy for a patient on mechanical ventilation, conventional mechanical ventilation is interrupted by so-called spontaneous breathing trials (SBTs). These SBTs are initiated based on preset configurations, input commands, or by selecting a specific operating mode. During these SBTs, the ventilator's control unit monitors key ventilation parameters, such as the respiratory rate-to-tidal volume ratio, also known as the Rapid Shallow Breathing Index (RSE).

[0004] Other key parameters can be at least one parameter from: spontaneous tidal volume, spontaneous expiratory volume, CO2 elimination levels, blood oxygen saturation levels, heart rate and an estimated work of breathing of the patient.

[0005] The recording of volume values ​​of spontaneous breathing, such as spontaneous tidal volume and spontaneous expiratory volume, shows that during the known spontaneous breathing trial phase, no supportive ventilation of the patient takes place, but rather it is simply observed to what extent the patient is able to breathe spontaneously on his own.

[0006] The control device of the ventilation device known from US 2011 / 0213215 A1 terminates a spontaneous breathing trial phase when a predetermined time has elapsed or when one of the key parameters is detected outside, or at least for a predetermined period of time outside, a predetermined range of values.

[0007] US Patent 2013 / 0053717 A1 discloses an operating mode for a ventilator designed to induce spontaneous breathing in a patient who is not breathing spontaneously. This is achieved by reducing mechanical ventilation to raise the partial pressure of CO₂ in the patient's arteries above a certain threshold. US Patent 2013 / 0053717 A1 is based on the principle that exceeding an individual threshold value in the arterial partial pressure of CO₂ triggers spontaneous breathing in the patient.

[0008] From US 9078984 B2, a ventilation device and a ventilation method are known in which the ventilation rate of a mechanical ventilator is brought within a predetermined tolerance range to the natural respiratory rate of a patient in order to avoid the patient starting to fight against the mechanical ventilator due to excessive differences between the ventilation rate of the mechanical ventilator and his natural, i.e. neural, respiratory rate.

[0009] The "SERVO-U" ventilation system from Maquet GmbH (Rastatt, Germany) is known to feature a ventilation mode called "Automode," in which the ventilator automatically switches between controlled and assisted ventilation to improve patient-ventilator interaction. When the patient exhibits spontaneous breathing activity in this mode, the ventilator immediately switches to an assisted mode, in which it supports the breath triggered by the spontaneous breathing activity by mechanically supplying inspiratory gas. If the patient no longer exhibits spontaneous breathing activity, the ventilator switches back to controlled mode and mechanically triggers breaths until further notice. The known "Automode" thus allows the patient to trigger breaths and provides support during inspiration.Breaths triggered by spontaneous patient breathing activity take precedence over machine-triggered breaths. If the patient does not make spontaneous breathing efforts, the ventilator is triggered mechanically. US 5937853A relates to a ventilator for the respiratory treatment of a patient with a selectable operating mode, in particular a control mode such as pressure control, volume control, and pressure-regulated volume control, or a support mode such as pressure support and volume support, with gas delivery means for delivering gas to the patient, sensing means for sensing the patient's breathing efforts, and control means for controlling the gas delivery means to deliver gas according to a selected operating mode.

[0010] In contrast to the prior art described above, the present application is based on the following technical problem: even in a ventilation mode that allows triggering of breaths by the patient's spontaneous respiratory efforts and supports such patient-triggered breaths by mechanically supplying inspiratory breathing gas, such as the "ASV" ("Adaptive Support Ventilation") mode in the applicant's ventilators, virtually all spontaneous breathing by the patient is suppressed if their natural (neural) respiratory rate is slightly lower than the mechanical respiratory rate. The normal interval of the normal ventilation mode, as the inverse of the purely mechanical respiratory rate, is then slightly shorter than the interval of the patient's natural breathing pattern.Should the patient succeed in triggering a breath through spontaneous effort, the subsequent breath will be mechanically triggered. This is because the normal interval of the ventilator during normal ventilation is shorter than the patient's natural or neural interval between two spontaneous breaths. This results in the patient being predominantly mechanically ventilated, even though they could trigger spontaneously. Most of the patient's spontaneous breaths after a successful patient-triggered breath subsequently fall within the inspiratory phase of mechanically triggered breaths and are simply overridden by the control system.

[0011] The patient is therefore sufficiently active, but cannot self-trigger breaths through spontaneous respiratory effort. This can lead to several disadvantages, such as large transpulmonary pressure fluctuations and diaphragmatic fatigue due to eccentric contractions, as the muscle is stretched under tension. It can also lead to the administration of excessive tidal volumes, double-triggering events, large fluctuations in the delivered inspiratory gas volume, and consequently, shortened expiratory phases and, more generally, asynchrony. As a result, sensor-detected parameters, such as tidal volume or the lung time constant (the product of lung resistance and compliance), can be unreliable with respect to the measured values ​​and lead to unstable ventilation control based solely on these sensor-detected parameters.

[0012] It is therefore an object of the present invention to provide a technical teaching which allows an artificially ventilated but sufficiently spontaneously active patient to take over the trigger control of his ventilation and not have his spontaneous breathing efforts ignored and overridden by the control device of the ventilation device.

[0013] This problem is solved according to the present invention in a ventilation device described above by the fact that the control device is configured to switch to a challenge ventilation mode when it has detected at least a predetermined plurality of spontaneous respiratory efforts of the patient within a predetermined monitoring period, in which a challenge interval that is longer in time than the normal interval is used instead of the normal interval, wherein the control device in the challenge ventilation mode does not cause a machine-triggered subsequent respiratory stroke immediately following a previous respiratory stroke before the challenge interval has elapsed.

[0014] The present invention also enables the further development of the ventilation method described above in such a way that the ventilation method comprises the following additional steps: Then, if at least a predetermined majority of spontaneous respiratory efforts by the patient are detected within a predetermined monitoring period, switch to a challenge ventilation mode in which a longer challenge interval is used instead of the normal interval, and trigger a machine-triggered follow-up breath immediately after the challenge interval has elapsed.

[0015] The ventilation device according to the invention is preferably designed to carry out this ventilation method, which is why the following description of the ventilation device, which also contains detailed aspects of the ventilation method, is also a description of the ventilation method and its advantageous further developments.

[0016] The basic idea of ​​the present invention is to first determine that the artificially ventilated patient is sufficiently active, i.e., exhibits sufficient spontaneous respiratory activity, to enable them to trigger breaths through their spontaneous breathing efforts. For this purpose, a single spontaneous respiratory effort by the patient is not sufficient; rather, the patient must exhibit a predetermined number of spontaneous respiratory efforts within a predetermined monitoring period, such that sufficient spontaneous respiratory activity can be assumed.

[0017] Once sufficient spontaneous respiratory activity of the patient is recognized, the normal interval is extended in time, so that on the one hand the patient's natural or neural interval may be shorter than the extended interval, which is referred to as the "challenge interval" to distinguish it from the normal interval, and so that on the other hand an interval is still applied to continue ventilating the patient even if, contrary to expectations, he permanently does not show sufficient spontaneous respiratory activity.

[0018] The challenge ventilation mode described above differs from normal ventilation mode preferably only in the extended interval between a breath and a machine-triggered subsequent breath. The other ventilation settings, such as minute volume, are preferably retained to ensure an adequate supply of inspiratory gas to the patient even in the absence of spontaneous breathing.

[0019] In this application, the term "interval" refers to the time interval between a preceding breath and a subsequent machine-triggered breath. After the interval has elapsed without any intervening spontaneous triggering, the control device forcibly triggers a subsequent breath. With a spontaneously or patient-triggered breath, the interval period begins anew as the waiting time until the next machine-triggered breath. Thus, the fact that the subsequent breath immediately follows the preceding breath means that no further breath occurred between the preceding and subsequent breaths.

[0020] Breaths triggered by the control device are referred to in the present application as "machine-triggered". Breaths triggered by a spontaneous respiratory effort of the patient are referred to in the present application as "patient-triggered".

[0021] In the relevant professional field, "triggering" refers to initiating an inspirational process. Initiating an expiration process, or the change from inspiration to expiration, is referred to as "cycling" in the professional field.

[0022] "Spontaneous respiratory activity" or "spontaneous respiratory effort" refers to a patient's attempt to initiate a breath, particularly an inspiration. This requires muscular exertion, typically to increase the volume of the thoracic cavity (which houses the lungs) or the throat and pharynx. Such activity initially only concerns the initiation of a breath, not its complete, automatic execution. Therefore, the control device for ensuring an adequate supply of inspiratory gas to the patient is preferably designed, in challenge ventilation mode, to deliver inspiratory gas to the patient through the ventilator under predetermined ventilation conditions in response to a spontaneous trigger from the patient.Challenge ventilation is therefore a supportive ventilation mode that ensures the patient receives sufficient inspiratory gas in response to their spontaneous trigger. The patient's ability to breathe completely independently is therefore not a prerequisite. However, it should not be ruled out that the patient can breathe independently. This scenario, however, is extremely rare in the phase of mechanical ventilation relevant to this application.

[0023] Since, as described above, normal ventilation mode and challenge ventilation mode preferably differ only in the longer challenge interval compared to the shorter normal interval, normal ventilation mode is preferably also a ventilation mode that both mechanically triggers breaths and allows spontaneous triggering of breaths by the patient, and also delivers a quantity of inspiratory breathing gas to the patient in the case of spontaneously triggered breaths by the patient through appropriate control of the flow-modifying device. However, it should not be excluded that normal ventilation mode is an exclusively controlled ventilation mode in which breaths are triggered exclusively mechanically.

[0024] The flow-modifying device can include a blower or a pump whose speed or delivery rate can be varied by the control device. Additionally or alternatively, the flow-modifying device can include a valve whose flow cross-section can be varied by the control device.

[0025] The breathing gas source assembly can be or include an intake opening for ambient air as the breathing gas. Additionally or alternatively, the breathing gas source assembly can include a reservoir containing inspiratory breathing gas, which can be selectively emptied by means of the flow-changing device. Also additionally or alternatively, the breathing gas source assembly can include or be a coupling device, such as a quick-release coupling or a coupling for gas lines, with which the ventilator can be connected to a breathing gas supply installed in a building, as is the case in numerous hospitals.

[0026] In principle, the same minute volume is preferably used as a target parameter for ventilation in both challenge and normal ventilation modes. However, it should not be excluded that, in challenge ventilation mode, due to the reduced challenge ventilation rate compared to normal ventilation, a challenge minute volume reduced by 20%, preferably 15%, or more preferably 10%, compared to normal ventilation is used in order to prevent the administration of excessively large tidal volumes due to the extended challenge interval.

[0027] In this application, the terms "frequency" and "rate" are used synonymously to mean frequency per unit of time.

[0028] When the challenge ventilation mode starts, the mechanical ventilation rate is preferably reduced to a challenge rate of 40% to 60% of the normal ventilation rate set during normal ventilation. In absolute terms, the reduced challenge ventilation rate can be, for example, approximately 6 to 8 breaths per minute, with the exact rate depending on the patient's physical and clinical condition.

[0029] Frequency and interval are reciprocals of each other.

[0030] The starting condition for initiating a challenge ventilation mode, namely the detection of multiple spontaneous respiratory efforts occurring during the predetermined monitoring period, can be implemented in various ways. According to a first possible embodiment, the control device can detect patient-triggered breaths during the predetermined monitoring period. The number of patient-triggered breaths detected during the predetermined monitoring period can then be used as the number of spontaneous respiratory efforts occurring during that period. The number of patient-triggered breaths detected during the predetermined monitoring period is equivalent to a detected spontaneous respiratory rate, expressed as patient-triggered breaths per minute or, more generally, per unit of time.

[0031] A patient-triggered breath can be identified, for example, by the temporal profile of the respiratory gas pressure. If the patient triggers a breath, the respiratory gas pressure drops briefly at the end of the expiratory phase due to the patient's spontaneous respiratory effort, which occurs before the next scheduled machine trigger. This pressure drop does not typically occur with machine-triggered breaths.

[0032] Additionally or alternatively, a patient-triggered breath can be detected by the temporal profile of the respiratory gas flow, for example, if the magnitude of the inspiratory respiratory gas flow exceeds a predetermined threshold before the next scheduled machine trigger. This threshold can be set relatively low. It simply needs to be chosen to reliably distinguish a spontaneous respiratory effort from another short-term cause, such as swallowing or a change in the patient's position.

[0033] A trigger value of patient-triggered breaths detected during the monitoring period, upon reaching which the challenge ventilation mode begins, can be, for example, 4 to 6 patient-triggered breaths per minute. In trials, a value of 5 patient-triggered breaths per minute has proven to be particularly advantageous as a trigger value.

[0034] The number of patient-triggered breaths per monitoring period is typically smaller, often significantly smaller, than the number of spontaneous breathing efforts that actually occurred during the monitoring period. This is because, as described above, many spontaneous breathing efforts can occur during the inspiratory phase of an already machine-triggered breath and are simply overridden by the control device. While the detected number of patient-triggered breaths per unit of time is lower than the number of actual spontaneous breathing efforts, patient-triggered breaths can be detected with a very high degree of accuracy and very little error. The overall lower number of detection events can be compensated for by using a correspondingly lower trigger threshold.

[0035] Additionally or alternatively, the control device can detect spontaneous respiratory efforts occurring during the predetermined monitoring period by recording and analyzing the pressure and / or flow rates of the inspiratory gas during the predetermined monitoring period. An additional or alternative analysis of the expiratory gas pressure and / or flow rate to detect spontaneous respiratory efforts is also conceivable.Thus, only the inspiratory phase or a part thereof, or only the expiratory phase or a part thereof, or the entire respiratory cycle with inspiratory and expiratory phases, or a part of the entire respiratory cycle with sections of both the inspiratory and expiratory phases, including the pressure profile and / or flow profile occurring therein, can be used to detect spontaneous respiratory efforts occurring during the predetermined monitoring period.

[0036] In cases where the device attempts to detect spontaneous respiratory efforts instead of actual patient-triggered breaths, the value detected by the control unit is closer to the true value of the actual spontaneous respiratory efforts. However, accurately detecting these is more complex than detecting only patient-triggered breaths or their rate. Typically, a spontaneous respiratory effort during an inspiratory phase of an already machine-triggered breath leads to characteristic changes in the inspiratory gas pressure as a function of time and / or the inspiratory gas flow rate as a function of time, compared to an undisturbed inspiratory process.By analyzing the temporal profiles of the pressure of the inspiratory respiratory gas and / or the flow of the inspiratory respiratory gas, spontaneous respiratory efforts can be detected even during an ongoing respiratory stroke.

[0037] Spontaneous respiratory efforts detected in this way can also trigger the initiation of challenge ventilation if they quantitatively reach a predetermined trigger value during the monitoring period. The predetermined trigger value for spontaneous respiratory efforts detected based on the aforementioned temporal profiles of inspiratory gas values ​​is preferably a different magnitude than the trigger value for the detected, actually patient-triggered breaths.

[0038] Additionally or alternatively, the sensor array can include a sensor that detects the patient's respiratory muscle activity, thus enabling the detection of spontaneous respiratory efforts by recording the necessary activity of the respiratory muscles. This could involve measuring esophageal pressure or performing electromyography on a muscle involved in the patient's respiratory system. The number of respiratory muscle activities recorded during the monitoring period can also be used by the control device as the number of detected spontaneous respiratory efforts, in order to decide whether to initiate challenge ventilation. A trigger value related to respiratory muscle activity, upon reaching which challenge ventilation is initiated, can have a different magnitude than the aforementioned trigger values.

[0039] In particular, methods for detecting spontaneous respiratory efforts in patients based on temporal value profiles can be used on the ventilator without additional sensors. For example, the control unit can be configured to infer spontaneous respiratory effort from the patient when the pressure of the inspiratory gas drops and then rises again during an inspirational phase, and / or when the flow rate of the inspiratory gas drops and then rises again during an inspirational phase. The temporal profile of the flow rate of inspiratory gas during spontaneous respiratory effort by the ventilated patient typically exhibits a bimodal pattern, meaning a pattern with two local extreme values.The pressure profile of inspiratory respiratory gas shows a characteristic, brief pressure drop when spontaneous respiratory effort occurs during the inspiration phase. The control device can search for such characteristic profile segments when detecting spontaneous respiratory activity.

[0040] In this application, the term "flow" refers to both a volume of respiratory gas or a respiratory gas volume flow rate moved per unit of time and a mass of respiratory gas or a respiratory gas mass flow rate moved per unit of time.

[0041] The aim of the present invention is not to stimulate the patient's spontaneous breathing, but rather to minimize any potential interference with the spontaneous breathing of a mechanically ventilated patient. The existing interval, after which a breath is triggered by the control device, ensures an adequate supply of respiratory gas to the patient even during challenge ventilation. However, it is possible that the patient's respiratory gas supply may be quantitatively lower during challenge ventilation than during normal ventilation. This can have the positive side effect of encouraging the patient to maintain spontaneous breathing.

[0042] To avoid an undersupply of respiratory gas to the patient during challenge ventilation, the control device is designed to terminate challenge ventilation under defined conditions and return to normal ventilation.

[0043] To prevent under-supply of the patient, the control device may be configured to terminate the challenge ventilation operation and return to normal ventilation operation using the normal interval instead of the challenge interval if at least one of the following conditions is met: a) the number of breaths spontaneously triggered by the patient during a trigger observation period is less than a predetermined trigger threshold, b) the amount of inspiratory respiratory gas administered to the patient during a quantity observation period is less than a predetermined quantity threshold.

[0044] Condition a) indicates that although the patient initially showed sufficient spontaneous respiratory activity to initiate the challenge ventilation operation, they do not consistently exhibit sufficient spontaneous respiratory effort to trigger breaths based on their natural or neural breathing at a predetermined minimum rate. For example, the patient may temporarily show sufficient spontaneous respiratory activity, but this is not stable.

[0045] The number of spontaneously patient-triggered breaths during a trigger observation period corresponds to a specific rate or frequency of patient-triggered breaths. The latter is also expressed in breaths per unit of time.

[0046] Condition b) simply indicates that the patient received less respiratory gas during the challenge ventilation than the predetermined volume threshold would indicate. This can occur, for example, because the patient spontaneously triggers breaths, but their natural or neural interval is only slightly shorter than, or has become shorter than, the challenge interval. Although the patient receives a preset tidal volume with each spontaneously triggered breath, supported by the ventilator, the administered tidal volumes can lead to lower minute volumes than intended for the patient if the interval is too long.An excessively long neural interval or challenge interval cannot be compensated for, or can only be compensated for to a limited extent, by higher tidal volumes, since only a certain amount of respiratory gas can be administered to the patient per breath without causing medium- or long-term harm.

[0047] Often, if condition a) is met, sooner or later, depending on the choice of the trigger threshold on the one hand and the quantity threshold on the other, condition b) will also be met, and vice versa.

[0048] In further specifying the termination conditions, according to an advantageous embodiment of the present invention, condition a) can be fulfilled if at least one of the following sub-conditions is fulfilled: ai) after the start of challenge ventilation, the patient does not trigger a breath within the challenge interval as a first trigger observation period, a-ii) at least a predetermined number of breaths during a second trigger observation period or at least a predetermined percentage of breaths during a third trigger observation period is machine-triggered, a-iii) a difference between a total breath rate recorded during a fourth trigger observation period as the total number of breaths recorded in the fourth trigger observation period, divided by the duration of the fourth trigger observation period, and a target breath rate set in the previous normal ventilation operation is greater than a predetermined limit breath rate difference.

[0049] Condition ai) applies to the case where the patient initiates the challenge ventilation mode based on spontaneous respiratory efforts detected by the control device, but the fulfillment of the necessary conditions is due either to a faulty detection of spontaneous respiratory efforts or to a single episode of spontaneous respiratory effort. If the patient does not even trigger the first breath after the challenge ventilation mode has started, the challenge ventilation mode is terminated. The challenge interval then becomes the first trigger observation period, since after its expiration the control device triggers the first breath following the start of the challenge ventilation mode, and the patient no longer has the opportunity to trigger the first breath through spontaneous respiratory activity.

[0050] Condition a-ii) is a less stringent version of condition ai) for cases where the patient self-triggers the first breath after the start of the challenge ventilation, but exhibits insufficient spontaneous respiratory activity overall to allow for meaningful control of their ventilation based on their neural respiratory rate. Both the second and third trigger observation periods are longer than the first. For example, the second and / or third trigger observation period may cover the duration of a predetermined number of breaths, such as five breaths. The second and third trigger observation periods may have the same or different durations.For example, the control device can return from challenge ventilation mode to normal ventilation mode if two or more out of five breaths during challenge ventilation mode are machine-triggered, or if 20% or more of the breaths during challenge ventilation mode are machine-triggered.

[0051] Condition a-iii) aims to assess the natural or neural respiratory rate, also known as the "breathing rate." If this is too low, the challenge ventilation operation is also terminated. A total breathing rate is calculated by adding up the total number of breaths triggered during the fourth trigger observation period, regardless of whether they are machine-triggered or patient-triggered. This total number can then be divided by the duration of the fourth trigger observation period to determine the total breathing rate.

[0052] The target respiratory rate or target breathing rate of the previous normal ventilation operation is generally the normal respiratory rate or normal breathing rate as the inverse of the normal interval. It is therefore a measure of the quantity of ventilation being performed correctly on the patient.

[0053] The difference between the total respiratory rate (RR) and the target RR of the preceding normal ventilation mode is therefore a measure of whether the patient is receiving adequate ventilation. Since ventilation in challenge ventilation mode is primarily patient-triggered, this difference also serves as a measure of whether the patient's spontaneous breathing activity is sufficient. If the total respiratory rate deviates by more than the predetermined threshold difference between the RR and the target RR of the preceding normal ventilation mode, the challenge ventilation mode is terminated due to insufficient spontaneous breathing activity. The fourth trigger observation period can last in the single-digit minute range, for example, 3 minutes, 2 minutes, or 1 minute.The limiting difference in breath rate can be, for example, 2 to 4, preferably 3, breaths per minute.

[0054] In contrast to condition a), which targets spontaneous respiratory activity, condition b) targets the amount of administered inspiratory respiratory gas. According to an advantageous embodiment of the present invention, condition b) can be fulfilled if at least one of the following subconditions is met: (b) the minute volume administered to the patient is less than a first limit fraction of the set minute volume for a first volume observation period, (b)-ii) the minute volume administered to the patient is less than a second limit fraction of the set minute volume for a second volume observation period, wherein the second volume observation period is longer than the first volume observation period and wherein the second limit fraction value is greater than the first limit fraction value.

[0055] Subconditions bi) and b-ii) refer to different durations of quantity observation periods. Subcondition bi) allows for a greater shortfall in the set minute volume to be administered over a shorter period. Subcondition b-ii), which is designed for a longer quantity observation period, ensures that the minute volume to be administered is only slightly undershot over a longer period.

[0056] The first limiting fraction can be, for example, 70% to 80%, preferably 75%. The first quantity observation period can preferably be in the range of 25 seconds to 1 minute, particularly preferably 30 seconds.

[0057] The second limit fraction can be 85% to 95%, preferably 90%. The second quantity observation period can be, for example, 3 to 6 minutes, preferably 5 minutes.

[0058] Finally, the control device can be configured to terminate the challenge ventilation mode and return to normal ventilation mode using the normal interval instead of the challenge interval if, for a predetermined challenge duration, the rate or frequency of spontaneously triggered breaths by the patient is greater than the target breath rate or target respiratory rate of the preceding normal ventilation mode. This target breath rate is typically the normal breath rate, i.e., the reciprocal of the normal interval.Alternatively, the control device can be configured to terminate the challenge ventilation mode and return to normal ventilation mode using the normal interval instead of the challenge interval if, for a predetermined challenge duration, the patient's neural interval is shorter than the normal interval of the preceding normal ventilation mode. In this case, the challenge ventilation mode is successfully terminated because the problematic initial situation, in which the neural interval (the inverse of the rate or frequency of spontaneously triggered breaths by the patient) is longer than the normal interval of normal ventilation mode, no longer exists. The predetermined challenge duration can be, for example, 20 to 45 minutes, preferably 30 minutes.

[0059] To prevent a challenge ventilation cycle from being initiated too soon after the previous one has ended, the control device can be configured to initiate a subsequent challenge ventilation cycle only after a predetermined waiting period has elapsed. This predetermined waiting period can range from 5 to 20 minutes, preferably 10 minutes. This ensures that the patient does not have to re-establish control of their artificial ventilation through their neural respiratory rate if they have recently demonstrated an inability to do so.

[0060] Furthermore, it can be considered that the predetermined waiting time increases with the number of completed challenge ventilation phases in order to give the patient sufficient time to stabilize their spontaneous breathing activity in order to finally be able to trigger breaths with their neural respiratory rate in a further challenge ventilation phase.

[0061] The term "interval time," as preferably used in the present application as the inverse of a respiratory rate, extends from the trigger time of a preceding breath to the trigger time of the immediately following breath. However, it should not be excluded that intervals are used which are not the inverse of a respiratory rate, but which, for example, extend from the end time of an inspiratory phase of the preceding breath to the start time of the inspiratory phase of the following breath.

[0062] The ventilator can include a CO₂ sensor for detecting CO₂ in the breathing gas, particularly in the expiratory breathing gas, which is connected to the control device via signal transmission. Preferably, the control device is configured to determine a value for the CO₂ content, especially the end-tidal CO₂ content, in the patient's expiratory breathing gas from the data of the CO₂ sensor. Such a value, measured approximately in the last 20%, preferably in the last 10%, and most preferably in the last 5% of the duration of the expiratory phase between cycling and triggering, is particularly informative because the breathing gas then detected by the sensor is no longer, or only to a negligible extent, mixed with CO₂-free breathing gas from a dead space volume of the breathing gas line assembly.If the CO₂ concentration measured in the respiratory gas, particularly in the expiratory gas, exceeds a predetermined threshold, this may indicate that the patient's ventilation is too dependent on the ventilator and that the patient is unable to breathe independently. Therefore, if the measured CO₂ concentration does not exceed the predetermined threshold, the control device may be configured to refrain from switching to challenge ventilation mode, even if other conditions for switching to challenge ventilation mode are met.

[0063] The present invention will be explained in more detail below with reference to the accompanying drawings. It illustrates: Figure 1 is a schematic representation of a ventilation device according to the invention, prepared for the artificial ventilation of a patient; Figure 2 is a rough schematic representation of the problem underlying the present invention; Figure 3 is a representation of ventilation parameter profiles of a successful switch from normal ventilation operation to challenge ventilation operation; and Figure 4 is a representation of ventilation parameter profiles of a switch from normal ventilation operation to a challenge ventilation operation that was subsequently aborted.

[0064] In Figure 1 An embodiment of a ventilation device according to the invention is generally designated by 10. In the illustrated example, the ventilation device 10 serves for the artificial ventilation of a human patient 12.

[0065] 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-modifying device 16 and a control device 18 are accommodated. The intake opening 15 allows the flow-modifying device 16 to draw in ambient air from the external environment U of the ventilation device and, after purification by at least one filter (a process known per se), supply it to the patient 12 as breathing gas. The intake opening 15 is therefore a breathing gas source arrangement within the meaning of the present application.

[0066] 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.

[0067] The flow-modifying 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 ventilation device 10 comprises an inspiratory valve 20 and an expiratory valve 22 in a manner known per se.

[0068] The control device 18 is typically implemented as a computer or microprocessor. It comprises a Figure 1The data storage device 19, designated by the numeral , is used to store and, if necessary, retrieve data required for the operation of the ventilation device 10. In network operation, the data storage device 19 can also be located outside the housing 14 and connected to the control device 18 via a data transmission link. This data transmission link can be wired or wireless. However, to prevent interference with the data transmission link from affecting the operation of the ventilation device 10, the data storage device 19 is preferably integrated into the control device 18 or at least housed in the same housing 14.

[0069] For inputting data into the ventilation device 10, or more precisely into the control device 18, the ventilation device 10 can have an input device 24, which is located in the Figure 1The example shown 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 as an alternative to the keyboard, for example via a network cable, a radio link, or via sensor connections 26.

[0070] For the purpose of outputting data to the treating therapist, the ventilation device 10 can have an output device 28, in the example shown a screen.

[0071] For mechanical ventilation, patient 12 is connected to the ventilation device 10, specifically to the flow-modifying device 16 in the housing 14, via a breathing gas line assembly 30. Patient 12 is intubated for this purpose using an endotracheal tube as a patient interface 31. The patient interface can, in contrast to the example shown, be formed by a mask. A proximal longitudinal end 31a of the patient interface 31 delivers the inspiratory gas flow AF into the lungs of patient 12. The expiratory gas flow EF also enters the breathing gas line assembly 30 through the proximal longitudinal end 31a.

[0072] A distal longitudinal end 31b of the patient interface 31 is designed for connection to the respiratory gas line assembly 30. From point 31c downstream in the direction of inspiration 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, from its distal longitudinal end 31b to point 31c, is exposed to the external environment U and is in a predominantly convective heat transfer connection with it.

[0073] The breathing gas line assembly 30 has an inspiratory tube 32 through which fresh breathing gas can be supplied from the flow-modifying device 16 to the lungs of the patient 12. The inspiratory tube 32 may be interrupted and have a first inspiratory tube 34 and a second inspiratory tube 36, between which a humidification device 38 may be provided for targeted humidification and, if necessary, also temperature control of the inspiratory breathing gas supplied to the patient 12. The humidification device 38 may be connected to an external fluid reservoir 40, through which water for humidification or a medication, such as an anti-inflammatory agent or an airway dilator, can be supplied to the humidification device 38.When the present ventilation device 10 is used as an anesthesia ventilation device, volatile anesthetics can be delivered to the patient 12 in a controlled manner via the ventilation device 10. The humidification device 38 ensures that the fresh breathing gas is supplied to the patient 12 at a predetermined humidity, optionally with the addition of a drug aerosol, and at a predetermined temperature.

[0074] In the present example, the second inspiration tube 36 can be electrically heated by a line heating device 37. The line heating device 37 can be controlled for operation by the control device 18. Contrary to the above, the first inspiration tube 34 can also be heated, and / or at least one tube 34 and / or 36 can be heated by a device other than an electric line heating device 37, for example, by being flushed with a heat exchange medium.

[0075] The respiratory gas line arrangement 30 has, in addition to the already mentioned inspiratory valve 20 and expiratory valve 22, an expiratory tube 42 through which metabolized respiratory gas flows as expiratory respiratory gas flow. EC is blown from the lungs of patient 12 into the outside environment U.

[0076] 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 to the expiratory valve 22. Preferably, only one of the two valves is open at any given time to allow a gas flow. The actuation control of the valves 20 and 22 is also carried out by the control device 18.

[0077] During a ventilation cycle, the expiratory valve 22 is initially closed and the inspiratory valve 20 is open for the duration of the inspiratory phase, allowing fresh inspiratory breathing gas to flow from the housing 14 to the patient 12. The flow of this fresh breathing gas is initiated by a controlled increase in the pressure of the breathing gas via the flow-modifying device 16. Due to this pressure increase, the fresh breathing gas flows into the lungs of the patient 12 and expands the area near the lungs, particularly the rib cage, against the individual elasticity of these tissues. This also increases the gas pressure inside the lungs of the patient 12.

[0078] At the end of the inspiratory phase, the inspiratory valve 20 closes and the expiratory valve 22 opens. The expiratory phase begins. Due to the increased gas pressure of the respiratory gas in the patient's lungs 12 until the end of the inspiratory phase, this gas flows into the external environment U after the expiratory valve 22 opens. As the flow continues, the gas pressure in the patient's lungs 12 decreases. When the gas pressure in the lungs 12 reaches a positive end-expiratory pressure (PEEP) set on the ventilator 10, i.e., a pressure slightly higher than atmospheric pressure, the expiratory phase is terminated by closing the expiratory valve 22, and another ventilation cycle begins.

[0079] During the inspiration phase, the patient receives the so-called tidal volume, i.e., the volume of respiratory gas per breath. Multiplying the tidal volume by the number of ventilation cycles per minute, i.e., by the respiratory rate, yields the minute volume of the mechanical ventilation being performed.

[0080] Preferably, the ventilator 10, and in particular the control device 18, is configured to repeatedly update or determine ventilation operating parameters that characterize the ventilation operation of the ventilator 10 during ventilation operation, in order to ensure that the ventilation operation is optimally adapted to the patient 12 being ventilated at all times. It is particularly advantageous to determine one or more ventilation operating parameters in conjunction with the ventilation rate, so that current ventilation operating parameters, optimally adapted to the patient 12, can be provided for each ventilation cycle.

[0081] For this purpose, the ventilator 10 can be connected to one or more sensors via data transmission, which monitor the patient's condition and / or the operation of the ventilator 10. The following are merely examples of a number of possible sensors: Figure 1A proximal flow sensor 44 is used to measure the magnitude of the breathing gas flow in the breathing gas line assembly 30, specifically both the inspiratory and expiratory breathing 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 assembly 46. The sensor line assembly 46 may, but need not, include electrical signal transmission lines. It may also include hoses that transmit the gas pressure on both sides of the flow sensor 44 in the direction of flow to the data inputs 26, where it is quantified by pressure sensors 27.

[0082] More precisely, 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 inspiratory tube 36 and the expiratory tube 42 and which is connected at its proximal end region to the proximal flow sensor 44.

[0083] 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 respiratory gas line arrangement 30.

[0084] The second inspiratory tube 36 can have a proximal temperature sensor 48 at its proximal longitudinal end, which measures the temperature of the respiratory gas flow AF in the second inspiratory tube 36 as close as possible to the patient 12 and transmits it to the control device 18.

[0085] The sensor arrangement cooperating with the control device 18 can also include a diaphragm sensor 50, which is connected to the control device 18 via a data line 52. The diaphragm sensor 50 can detect the activity of the patient's respiratory muscles 12 and transmit corresponding information to the control device 18. From the signals of the diaphragm sensor 50 and / or from the signals of the pressure sensors 27, the control device 18 can determine the patient's spontaneous respiratory efforts. In the case of the differential pressure flow sensor 44 used here, flow signals are determined from the signals of the pressure sensors 27, which quantify the inspiratory airflow AF and the expiratory airflow EF, respectively.

[0086] For the sake of completeness, it should be noted that the ventilation device 10 according to the invention can be mounted as a mobile ventilation device 10 on a rolling frame 54.

[0087] In Figure 2 The problem underlying the present invention is shown in a rough schematic. The abscissa of Figure 2 The graph represents a time axis. Figure 56 roughly schematically depicts a spontaneously patient-triggered inspiratory event with dashed lines. This spontaneous, or patient-triggered, inspiratory event (56) begins at time t0 and ends at time t1.

[0088] A solid line indicates that in Figure 2An arrow 58 is shown, representing the applicable normal interval. After the normal interval 58 has elapsed, the control device 18 triggers a subsequent breath with a subsequent inspiration 60. As a machine-triggered inspiration 60, this, like the normal interval 58, is shown as part of the control of the ventilation device 10 with a solid line.

[0089] The natural or neural interval 62 is shown with a dashed line. Figure 2The diagram shows a sequence of events after which patient 12 would trigger a subsequent inspirational event due to his physical and health condition. Since the neural interval 62 is slightly longer than the normal interval 58 of the control device 18, patient 12 initially has no chance to trigger breaths himself, as the end of his respective neural interval 62 always lies within an already ongoing machine-triggered inspirational event, at least for the following three depicted subsequent inspirational events 60, 64, and 66. Thus, any spontaneous respiratory effort by patient 12 is simply overridden by the control device 18.

[0090] To mitigate or avoid the described situation in which a patient capable of triggering is overridden by the control device 18 or the ventilator 10 due to an unfavorable combination of machine and personal circumstances, the control device 18 initiates a challenge ventilation mode under predetermined conditions, such as a detected predetermined majority or rate of spontaneous respiratory activity from the patient 12. In this challenge ventilation mode, the challenge interval is reduced by approximately 40% to 60% compared to the normal interval in normal ventilation mode.

[0091] Figure 3 This parametrically illustrates such a case of challenge ventilation following normal ventilation. The abscissa of the graphs of Figure 3 This is the time axis. Graph 68 in the top row of Figure 3This shows the pressure curve of the breathing gas in cm of water column. The unit of pressure is not important here; what matters is the qualitative shape of the pressure curve 68.

[0092] In the row below, graph 70 shows the flow of respiratory gas in milliliters per second, i.e., as a volume flow. Positive flow values ​​indicate an inspiratory respiratory gas flow (RR), negative flow values ​​an expiratory respiratory gas flow (EF).

[0093] In the third row, graph 72 shows the volume of respiratory gas supplied to patient 12. The respiratory gas volume is the breath-by-breath integral of the respiratory gas flow over time.

[0094] Pressure curve 68 shows spontaneous respiratory efforts of patient 12 at various points, for example at A1 during the third depicted inspiratory phase, or at A2 during the seventh depicted inspiratory phase. In both cases, the pressure value initially decreases due to the spontaneous respiratory effort of patient 12 and then rises again.

[0095] Since the pressure of the respiratory gas is the driving force behind the respiratory gas flow, the spontaneous pressure drop resulting from spontaneous breathing is also reflected in flow curve 70, for example at B1 during the third depicted inspiratory phase, or at B2 during the seventh depicted inspiratory phase. At B2, flow curve 70 shows a pronounced bimodal pattern, which is typical for spontaneous respiratory activity in a mechanically ventilated patient during an inspiratory phase.

[0096] In the present example, however, the control device 18 does not perform an analysis of the pressure curve 68 or the flow curve 70 to determine spontaneous respiratory efforts of the patient 12. Instead, the control device 18 determines spontaneous breaths triggered by the patient 12. These are recognizable by a characteristic pressure drop at the end of the expiratory phase or at the beginning of the subsequent inspiratory phase triggered by this pressure drop, and thus before a subsequent breath would be machine-triggered. Such a characteristic pressure drop is in Figure 3 This can be seen, for example, in pressure curve 68 at A3, A4 and each breath following A4, see for example at A5.

[0097] In Figure 3The first vertical line 74, running across all horizontal rows, indicates a trigger point, and the second vertical line 76, running across all horizontal rows, indicates a cycling point. The vertical lines, running from left to right, alternate between trigger and cycling points. Machine-triggered breaths indicate... Figure 3 The upper edge of the vertical trigger time lines is marked with "MT". In contrast, the triangles on the abscissa of curves 68, 70 and 72 each indicate a patient-triggered breath.

[0098] At the spontaneous trigger event A4, a predetermined majority of spontaneously triggered breaths is reached for a predetermined monitoring period, such as 1 minute or 3 minutes. In the example shown, the predetermined majority of spontaneously triggered breaths reached within the predetermined monitoring period corresponds to a spontaneous respiratory rate of four breaths per minute, which in this example is the trigger threshold to switch from normal ventilation mode to challenge ventilation mode. Graph 78 in the bottom row of Figure 3The display shows the patient's (12) spontaneous respiratory rate as determined by the control device (18) at the current time. Line 80 indicates the limit or trigger threshold for initiating challenge ventilation. In this example, the spontaneous respiratory rate is determined over a predetermined number of consecutive breaths, for example, over 8 breaths. The spontaneous respiratory rate is calculated by multiplying the number of spontaneously triggered breaths by the quotient of 60 seconds divided by the duration of eight breaths in seconds.

[0099] Graph 82 in Figure 3The bottom row shows the normal respiratory rate at which patient 12 continues to receive mechanical ventilation during the challenge ventilation phase, triggered by the machine, if they were to exhibit no spontaneous respiratory activity. When patient 12's spontaneous respiratory rate reaches the trigger threshold according to graph 78, the control device 18 reduces the normal respiratory rate in the illustrated example by 50%, from 14 breaths per minute to a challenge respiratory rate of 7 breaths per minute. Other patients may receive different values ​​depending on their physical and health condition.

[0100] The normal respiratory rate is the inverse of the previously discussed normal interval. By lowering the normal respiratory rate, which corresponds to increasing the interval by the inverse factor applied to the normal respiratory rate, patient 12 now has the opportunity to trigger breaths based on their neural respiratory rate and thus take over the control of the ventilator 10 with regard to triggering breaths. In the event of a successful challenge ventilation operation, the artificial ventilation of patient 12 then occurs in better accordance with their natural breathing pattern than if normal ventilation operation were continued.

[0101] Graph 84 shows the total respiratory rate determined by the control device 18, i.e., the sum of machine-triggered and patient-triggered breaths per unit of time. The control device 18 determines graph 84, as well as the spontaneous respiratory rate of graph 78, as a sliding frequency or rate value. The relative timing of the recorded breaths in relation to the sliding, predetermined monitoring period can cause a slight change in the calculated total respiratory rate without significantly altering the patient's breathing pattern.

[0102] Graph 86 shows the normal respiratory rate set in normal ventilation mode as the target respiratory rate for adaptive support ventilation mode. In this adaptive support ventilation mode, the patient is ventilated at the normal respiratory rate as the target respiratory rate. However, the patient can also trigger this through spontaneous respiratory activity.

[0103] The control device 18 regulates the ventilation operation in the example shown on the basis of periods of 5 breaths each and thus on the basis of a different periodicity than the periodicity for determining the spontaneous respiratory rate.

[0104] The challenge ventilation mode remains a supportive ventilation mode, however, by decreasing the normal ventilation rate to the challenge ventilation rate, the number of machine-triggered breaths is reduced.

[0105] Following the start of the challenge ventilation operation in Figure 3 The patient triggers each individual breath 12 himself, with a sufficient spontaneous respiratory rate for a predetermined trigger observation period, such that the difference between the total respiratory rate according to Graph 84 and the normal or target respiratory rate set in the previous normal ventilation operation according to Graph 86 is less than a predetermined limit rate difference 88. The limit rate difference that is just tolerated can, for example, be 3 breaths per minute.

[0106] In Figure 4 The same graphs 68 to 86 and the same limit frequency difference 88 are shown in a different ventilation process.

[0107] The predetermined trigger threshold according to line 80 in Figure 4is reached shortly before 7:55:00, whereupon the challenge ventilation operation is started by reducing the normal ventilation rate according to Graph 82 in the example shown by slightly more than 50% from 15 breaths per minute to a challenge ventilation rate of 7 breaths per minute.

[0108] Although patient 12 was on challenge ventilation from the start of the challenge operation Figure 4 If the device triggers each subsequent breath itself, the challenge ventilation operation is terminated because the patient's neural respiratory rate is too low and thus the total respiratory rate determined by the control device 18 according to graph 84 differs by more than the maximum permissible limit frequency difference 88 for the duration of a predetermined trigger observation period.

[0109] With the end of the challenge ventilation operation in Figure 4The challenge ventilation rate is reset to its original value as the normal ventilation rate according to graph 82.

[0110] A challenge ventilation operation can only be restarted after a predetermined waiting period, preferably at least 10 minutes, has elapsed following its termination.

Claims

1. Ventilation device (10) for a ventilation operation for mechanical administration of respiratory gas to a patient (12), where the ventilation device (10) comprises: - A respiratory gas source arrangement (15) which provides an inhalatory respiratory gas for administration to the patient (12), - A flow-modification device (16) which is configured to generate and / or quantitatively modify an inhalatory respiratory gas flow (AF), - A respiratory gas line arrangement (30) in order to convey the inhalatory respiratory gas flow (AF) from the respiratory gas source arrangement (15, 62) towards the patient (12), - A sensor arrangement (27, 44, 52) which is configured to capture at least one state variable (68) of the inhalatory respiratory gas flow (AF) and / or a mass flow (70) of the inhalatory respiratory gas flow (AF) and / or a respiratory musculature activity of the patient (12), - A control device (18) with a data store (19), where the control device (18) is connected with the data store (19) and with the sensor arrangement (27, 44, 50) for signal transmission, and where the control device (18) is configured for controlling the flow-modification device (16), Characterized in that the control device (18) is configured to actuate, in a normal ventilation operation, the flow-modification device (16) for initiating a machine-triggered breath starting from a preceding breath not before expiration of a predetermined temporal normal gap interval (58) for generating an inhalatory respiratory gas flow (AF), in order to effect a machine-triggered following breath which immediately follows the preceding breath, Where the control device (18) is further configured to recognize, on the basis of data ascertained by the sensor arrangement (27, 44, 50), a spontaneous respiratory effort of the patient (12) during the ventilation operation of the ventilation device (10), Where the control device (18) is further configured, when in a predetermined monitoring time period it has recognized at least one predetermined plurality of spontaneous respiratory efforts of the patient (12), to change over into a challenge ventilation operation in which instead of the normal gap interval (58) a challenge gap interval is used which is temporally longer compared with the normal gap interval (58), where in the challenge ventilation operation the control device (18) not before expiration of the challenge gap interval effects a machine-triggered following breath which immediately follows a preceding breath.

2. Ventilation device (10) according to Claim 1, Characterized in that the control device (18) is configured to supply to the patient (12) at least in the challenge ventilation operation, upon a spontaneous trigger of the patient (12), under predetermined ventilation conditions, inhalatory respiratory gas.

3. Ventilation device (10) according to Claim 1 or 2, Characterized in that in the challenge ventilation operation and in the normal ventilation operation the same minute volume is used as a target variable of the ventilation.

4. Ventilation device (10) according to one of the preceding Claims, Characterized in that the control device (18) for recognizing spontaneous respiratory efforts occurring during the predetermined monitoring time period captures breaths (78) actually triggered by the patient (12) during the predetermined monitoring time period.

5. Ventilation device (10) according to one of the preceding Claims, Characterized in that the control device (18) for recognizing spontaneous respiratory efforts occurring during the predetermined monitoring time period captures courses (68) of the pressure of the inhalatory and / or of the exhalatory respiratory gas during the predetermined monitoring time period and / or courses (70) of the flow of the inhalatory respiratory gas during the predetermined monitoring time period.

6. Ventilation device (10) according to Claim 5, Characterized in that the control device (18) infers a spontaneous respiratory effort of the patient (12) if the pressure of the inhalatory respiratory gas drops during an inhalation phase and rises again and / or if the flow of the inhalatory respiratory gas drops during an inhalation phase and rises again.

7. Ventilation device (10) according to one of the preceding Claims, Characterized in that the control device (18) ends the challenge ventilation operation and returns to the normal ventilation operation, using the normal gap interval (58) instead of the challenge gap interval, if at least one of the following conditions is met: a) A number of breaths triggered spontaneously by the patient (12) in a trigger observation period is smaller than a predetermined triggering threshold value, b) A quantity of inhalatory respiratory gas administered to the patient (12) in a quantity observation period is smaller than a predetermined quantity threshold value.

8. Ventilation device (10) according to Claim 7, Characterized in that condition a) is met if at least one of the following sub-conditions is met: a-i) After the beginning of the challenge ventilation operation the patient (12) does not trigger a breath within the challenge gap interval as a first trigger observation period, a-ii) At least one predetermined number of breaths during a second trigger observation period or at least one predetermined quota of breaths during a third trigger observation period is machine-triggered, a-iii) A difference between a total breathing frequency (84) captured during a fourth trigger observation period as the number of breaths captured overall in the fourth trigger observation period overall, divided by the duration of the fourth trigger observation period, and a target breathing frequency (86) set in the preceding normal ventilation operation, is greater than a predetermined boundary frequency difference (88).

9. Ventilation device (10) according to Claim 7 or 8, Characterized in that condition b) is met if at least one of the following sub-conditions is met: b-i) The minute volume administered to the patient (12) is, for a first quantity observation period, smaller than a first boundary fraction of the minute volume set, b-ii) The minute volume administered to the patient (12) is, for a second quantity observation period, smaller than a second boundary fraction of the minute volume set, where the second quantity observation period is greater than the first quantity observation period and where the second boundary fraction value is greater than the first boundary fraction value.

10. Ventilation device (10) according to one of the preceding Claims, Characterized in that the control device (18) ends the challenge ventilation operation and returns to the normal ventilation operation, using the normal gap interval (58) instead of the challenge gap interval, if for a predetermined challenge duration the frequency of breaths (78) triggered spontaneously by the patient (12) is greater than the target breathing frequency (86) set in the preceding normal ventilation operation.

11. Ventilation device (10) according to one of the preceding Claims, Characterized in that the control device (18) is configured to begin, after the end of a preceding challenge ventilation operation, a following further challenge ventilation operation at the earliest after expiration of a predetermined waiting time.

12. Ventilation device (10) according to Claim 11, Characterized in that the predetermined waiting time increases with the number of ended challenge ventilation operation phases.