VENTILATOR FOR MECHANICAL VENTILATION OF A PATIENT

Description

[0001] The invention relates to a ventilator for the mechanical ventilation of a patient.

[0002] Ventilators with preset ventilation pressure profiles for the mechanical ventilation of patients are known. Depending on the patient's condition, ventilation parameters such as positive end-expiratory pressure (PEEP), mean airway pressure, tidal volume, respiratory rate, and the like can be adjusted.

[0003] To perform automated or semi-automated ventilation, it is known that at least one sensor must measure gas flow and / or a gas flow-dependent measurement at regular intervals. This allows the gas flow to be monitored during both inspiration and expiration of the corresponding respiratory cycle.

[0004] A ventilator is known from WO 2016 / 067 619 A1. The ventilator is configured to determine the occurrence of a dPEEP from a measured expiratory volume flow and to begin inspiration when the dPEEP is present.

[0005] A ventilator is known from EP 3 769 668 A1. The ventilator is configured to change a ventilation setting upon detection of inspiratory flow limitation and / or expiratory flow limitation and / or intrinsic PEEP and / or inefficient breathing effort and / or double breathing effort. The ventilation setting is selected from IPAP and / or EPAP and / or inspiratory time and / or expiratory time and / or trigger sensitivity.

[0006] From DE 696 23 400 T2 a ventilation system is known which is designed to find an optimal ratio between inspiratory time and expiratory time.

[0007] Further ventilators are known from EP 0 127 905 A2 and EP 1 961 378 A1.

[0008] The object of the present invention is to provide an improved ventilator, in particular a ventilator with particularly efficient and patient-friendly ventilation.

[0009] According to the invention, a ventilator for the mechanical ventilation of a patient is proposed to solve this problem, comprising at least one sensor unit, one storage unit and one processing unit.

[0010] The at least one sensor unit is designed to measure a course of gas flow-dependent measured values, in particular gas flows, in the ventilation circuit of the ventilator and to output a corresponding sensor signal.

[0011] The memory unit stores a multitude of ventilation parameters for the currently active ventilation mode. These stored ventilation parameters indicate at least the inspiratory time of the ventilation currently provided by the ventilator and the subsequent expiratory time for a corresponding respiratory cycle. A respiratory cycle is, as is well known, formed by a combination of inspiratory time and subsequent expiratory time.

[0012] The processing unit is configured to receive the sensor signal and, based on the course of the gas flow-dependent measured values, to determine at least a current end-expiratory gas flow, wherein the processing unit is further configured to adjust a ratio between inspirational time and expiratory time for the currently present ventilation mode for ventilating the patient, depending on a comparison between the determined current end-expiratory gas flow and a lower threshold and / or an upper threshold, wherein the duration of the corresponding respiratory cycle remains essentially constant.

[0013] Within the scope of the invention, it was recognized that a phase with no or low expiratory gas flow leads to unnecessarily rapid delivery of respiratory gas to the patient during inspiration. Therefore, the expiratory time can be shortened by this phase of low gas flow, thus lengthening the inspiration time and minimizing the inspiratory gas flow gradient. This is particularly advantageous because ventilation with a low inspiratory gas flow gradient is especially gentle on the patient.

[0014] Alternatively or additionally, according to the invention, the ratio between inspiratory and expiratory time, particularly in patients with chronic obstructive pulmonary disease, can be modified by prolonging the expiratory time if the end-expiratory gas flow is above the upper threshold. This allows for the most natural exhalation possible, and the subsequent pressure gradient during inspiratory time usually does not pose a problem for the corresponding patient group.

[0015] A further advantage of the ventilator according to the invention is its ease of implementation. Changing the ratio between inspiratory and expiratory time can be achieved as a purely software-based solution for adapting existing ventilators. This makes the implementation of the invention particularly cost-effective.

[0016] Given the large number of ventilation modes established on the market for ventilators, the invention can be advantageously applied to a variety of different ventilation modes, since ventilation by a ventilator usually involves an inspiratory time and an expiratory time. A ventilation mode is understood to be a mode of the ventilator that controls the patient's ventilation in a mode-specific manner by controlling or regulating corresponding ventilation parameters.

[0017] The course of the gas flow-dependent measured values ​​is a time-dependent course that describes a development of these gas flow-dependent measured values ​​over time, either continuously or in discrete time steps.

[0018] The ratio between inspiratory and expiratory time is, for example, a quotient of inspiratory and expiratory time, which is altered by a change in inspiratory time and / or by a change in expiratory time. Preferably, the sum of inspiratory and expiratory time, i.e., the duration of a respiratory cycle, is kept essentially constant according to a predetermined respiratory rate.

[0019] The units of the ventilator according to the invention are preferably arranged at least partially spatially separated from one another. For example, the sensor unit is arranged in the ventilation circuit of the ventilator. The ventilation circuit delivers the respiratory gas to the patient and back to the ventilator. The storage unit and the processing unit are preferably arranged in a central housing of the ventilator and are particularly preferably controlled by a common processor. The units are separated from one another at least at the software level.

[0020] The lower and upper thresholds can be predefined, stored values ​​for end-expiratory gas flow or a correlated system parameter. Alternatively or additionally, at least one of the thresholds can be continuously recalculated based on currently determined values, such as gas flow-dependent measurements.

[0021] Preferred embodiments of the ventilator according to the invention are described below.

[0022] In a particularly preferred embodiment, the processing unit is configured to shorten the expiratory time if the current end-expiratory gas flow is below the lower threshold. In this case, the current end-expiratory gas flow is so low that, from a physiological perspective, the next inspirational phase could have started earlier. Therefore, according to the invention, in this embodiment, the ventilator shortens the expiratory time during the next respiratory cycle. It is particularly preferred that the predetermined respiratory rate is maintained, so that the shortening of the expiratory time leads to a corresponding lengthening of the inspirational time. It is also particularly preferred that the tidal volume is kept constant, so that during the now longer inspirational time a particularly low pressure gradient, and thus also a particularly low gas flow gradient, and consequently particularly gentle ventilation of the patient is possible.

[0023] In a particularly advantageous embodiment of the preceding design, the processing unit provides a time control system in which the current end-expiratory gas flow serves as the measured variable of the time control and the inspiratory time as the manipulated variable of the time control, with the lower threshold representing a setpoint for the measured variable. Such a control system can reliably ensure that the duration of the inspiratory time is adjusted according to the invention in such a way that the end-expiratory gas flow stabilizes within the range of the lower threshold. The end-expiratory gas flow directly leads to an intrinsic end-expiratory gas pressure (intrinsic PEEP), which is the target in this embodiment. Since the pressure is essentially quadratically dependent on the gas flow, a low lower threshold for the gas flow should result in a substantially negligible intrinsic PEEP.It is particularly preferred that the expiratory time is also changed along with the inspiratory time, so that the sum of inspiratory and expiratory time, i.e., the duration of a respiratory cycle, remains constant. The provision of such control elements within a control device is known to those skilled in the art and is therefore not explained in detail below. In particular, it is known how such control can be implemented without significant oscillation of the parameters and thus without impairing the patient's ventilation.

[0024] In an alternative or supplementary variant of the described embodiments, the processing unit is configured to extend the expiratory time if the current end-expiratory gas flow is above the upper threshold. In this variant, a gas flow range between the lower and upper thresholds is defined, within which the end-expiratory gas flow should lie. If the end-expiratory gas flow is outside this range, the expiratory time is extended or shortened until the end-expiratory gas flow falls within this range. If the end-expiratory gas flow is above the upper threshold, extending the expiratory time causes the end-expiratory gas flow to decrease, and thus, even with a sufficient extension of the expiratory time, it will fall below the upper threshold.Accordingly, the upper threshold value according to the invention is generally higher than the lower threshold value. Such an extension of the expiratory time can be advantageous, for example, in patients with chronic obstructive pulmonary disease who have to exhale for a comparatively long period before inhalation can begin again. In these patients, the resulting increased pressure gradient during inspiration is usually not detrimental to their well-being.

[0025] According to the invention, the processing unit of the ventilator is designed to continuously adjust the expiratory and inspiratory times such that the duration of the corresponding respiratory cycle remains essentially constant. This advantageously ensures that a preferably predetermined respiratory rate is kept essentially constant by the ventilator according to the invention. Since the respiratory rate is a particularly relevant predetermined ventilation parameter in almost every ventilation mode, maintaining a specific respiratory cycle duration is especially advantageous in this embodiment.

[0026] In a further embodiment of the ventilator according to the invention, the lower threshold and / or the upper threshold depend on the measured profile of the gas flow-dependent measured values. Due to this dependence on the measured profile, the two thresholds in this embodiment are particularly advantageously at least partially dependent on the ventilation characteristics of the specific patient. It is especially preferred that the lower threshold and / or the upper threshold depend on a maximum gas flow, in particular a maximum expiratory gas flow. For example, the lower threshold can be between 0.1% and 5%, preferably between 0.5% and 3%, and particularly at 2% of the maximum expiratory gas flow.Expiratory gas flow is essentially the flow rate of a respiratory gas that the patient exhales during expiratory time, whereas inspiratory gas flow is the flow rate of a respiratory gas that the patient inhales during inspiration. Therefore, the maximum expiratory gas flow is determined from at least one of the gas flow-dependent measurements in the recorded profile.

[0027] The processing unit is further designed to adjust, depending on the adjustment of the ratio between inspiration time and expiration time, an increase in the gas pressure of the respiratory gas at the beginning of the inspiration time and / or a maximum pressure of the respiratory gas during the inspiration time.

[0028] By adjusting the rise in gas pressure and / or the maximum pressure, the provided ventilation characteristics are advantageously adapted to the adjusted inspiratory time. For example, a longer expiratory time can lead to a reduction in the maximum pressure, making ventilation during inspiration gentler for the patient. Alternatively or additionally, a longer inspiratory time can lead to a reduction in the rise in gas pressure, particularly the rise in gas pressure at the beginning of inspiration. This reduces the gas pressure gradient and thus also the gas flow gradient, which is known to make ventilation by the ventilator more comfortable for the patient. Consequently, in this embodiment, ventilation parameters are particularly advantageously adapted to the patient's current state of ventilation in order to enable particularly effective and preferably particularly patient-friendly ventilation.

[0029] InIn an advantageous embodiment, the processing unit is further designed to determine the current end-inspiratory gas flow based on the course of the gas flow-dependent measured values ​​and to adjust the ramp duration of the increase in the gas pressure of the respiratory gas at the beginning of the inspiration period, depending on the current end-inspiratory gas flow. The ramp duration is the time interval at the beginning of the inspiration period during which the inspiratory gas flow to the patient is increased linearly over time, i.e., in a ramp-like manner, up to a maximum inspiratory gas flow. By evaluating the current end-inspiratory gas flow, an additional characteristic value from the measured course of the gas flow-dependent measured values ​​is advantageously used to improve ventilation by the ventilator according to the invention.The end-inspiratory gas flow can be used to determine whether there is a remaining period at the end of the expiratory phase during which no respiratory gas is supplied to the patient before the expiratory phase of the corresponding respiratory cycle begins. In a preferred embodiment, the processing unit is configured to extend the ramp duration if the current end-inspiratory gas flow is below a lower inspiratory threshold, and simultaneously shorten any remaining plateau duration of the inspiratory phase, so that the inspiratory phase, i.e., the total inspiratory phase, is independent of the end-inspiratory gas flow. This ensures that the respiratory gas to be supplied to the patient during the inspiratory phase, preferably with a predetermined respiratory gas volume, can be delivered in the most patient-friendly way possible. The lower inspiratory threshold can be a fixed, predetermined value.Alternatively or additionally, the inspiratory threshold can depend on the measured profile of the gas flow-dependent measurements. Due to this dependence on the measured profile, the threshold in this embodiment is particularly advantageously at least partially dependent on the ventilation characteristics of the specific patient. It is especially preferred that the lower inspiratory threshold depends on a maximum gas flow, in particular a maximum inspiratory gas flow. For example, the lower inspiratory threshold can be between 0.1% and 5%, preferably between 0.5% and 3%, and particularly at 2% of the maximum inspiratory gas flow.

[0030] In a particularly preferred embodiment of the preceding design, the processing unit provides a ramp control system in which the current end-inspiratory gas flow serves as the measured variable for the ramp control and the ramp duration as the manipulated variable for the ramp control, with the lower inspiratory threshold representing a setpoint for the measured variable. In this embodiment, the ramp duration advantageously ensures that the inspiratory gas flow stabilizes within the range of the lower inspiratory threshold. A decrease in the ramp duration reduces the end-inspiratory gas flow, whereas an increase in the ramp duration increases the end-inspiratory gas flow.

[0031] In an alternative or supplementary variant to the preceding variant, the processing unit is configured to shorten the ramp duration if the current end-inspiratory gas flow is above an upper inspiratory threshold, and simultaneously to lengthen the remaining plateau duration of the inspiratory time, so that the inspiratory time is independent of the end-inspiratory gas flow. In this variant, the ventilator according to the invention is configured to define a range for the inspiratory gas flow, within which the ventilator operates, by controlling the ramp duration based on the predetermined upper and lower inspiratory thresholds.

[0032] The predetermined upper inspiratory threshold and / or the predetermined lower inspiratory threshold are preferably dependent on the measured profile of the gas flow-dependent values. Particularly preferably, the lower inspiratory threshold and / or the upper inspiratory threshold are dependent on a maximum inspiratory gas flow determined from the gas flow-dependent values ​​during the inspiration period of the provided ventilation.

[0033] In a particularly preferred embodiment, the processing unit is further configured to extend the expiratory time and / or the ramp duration at constant maximum pressure only if this results in the mean airway pressure over the corresponding respiratory cycle not falling below a predetermined lower mean pressure threshold. This embodiment advantageously ensures that the predetermined lower mean pressure threshold is not undercut. This is particularly advantageous because the lower mean pressure threshold is a crucial parameter in patient ventilation, and the ventilator should therefore reliably ensure that the actual mean pressure at the patient's lungs, as determined by adjusting the expiratory time and / or the ramp duration, always remains above this threshold.In this embodiment, the ventilator according to the invention allows, in addition to patient-friendly ventilation, for adherence to the predetermined lower mean effective pressure (MEP) threshold by adjusting the expiratory time and / or the ramp duration, thus ensuring particularly gentle and successful ventilation. Determining the mean effective pressure is common practice in ventilators known to those skilled in the art and typically involves summing ventilation pressures over time.

[0034] In a further embodiment, the ventilator according to the invention also has a user interface configured to receive user input. The user input indicates, for example, a range adjustable by the ventilator for the ratio between inspiratory and expiratory time. The ratio between inspiratory and expiratory time preferably lies between a ratio of 1:1 and a ratio of 1:5, such as between a ratio of 1:1 and a ratio of 1:3. Alternatively or additionally, the user input can indicate the ventilation mode to be used.Alternatively or additionally, the user input can indicate a ventilation parameter to be stored, such as a respiratory rate, a digital volume, a maximum pressure of the respiratory gas during inspiration, a rise in gas pressure at the beginning of inspiration, the lower threshold for end-expiratory gas flow, the lower mean pressure threshold, or the like.

[0035] A procedure for operating a ventilator for the mechanical ventilation of a patient is further described, comprising the following steps: Measuring a course of gas flow-dependent measured values ​​in the ventilation circuit of the ventilator and outputting a corresponding sensor signal; storing a multitude of ventilation parameters of a currently active ventilation mode, wherein these stored ventilation parameters indicate at least one inspiratory time of the ventilation currently provided by the ventilator and a subsequent expiratory time for a corresponding respiratory cycle; receiving the sensor signal and determining at least one current end-expiratory gas flow based on the course of the gas flow-dependent measured values; and adjusting a ratio between inspiratory time and expiratory time for the currently active ventilation mode to ventilate the patient depending on a comparison between the determined current end-expiratory gas flow and a lower threshold and / or an upper threshold.

[0036] The method is carried out by the ventilator according to the invention and therefore includes all the advantages mentioned in connection with the ventilator. Furthermore, the method can be supplemented by features corresponding to the described embodiments of the ventilator according to the invention.

[0037] A particularly advantageous aspect of this method is the dynamic adjustment of the ratio between inspirational and expiratory time. This allows for consideration of situations where the current end-expiratory gas flow is particularly high or low, enabling the inspirational and / or expiratory time to be adjusted accordingly. This ensures particularly gentle ventilation for the patient during inspiration while simultaneously avoiding periods without inspiratory or expiratory gas flow.

[0038] The steps of the procedure can be performed in a different order than shown. In particular, entering the numerous ventilation parameters can also be done before measuring the course of gas flow-dependent measurements.

[0039] Preferably, less than 20 seconds, particularly less than 10 seconds, and most preferably less than 2 seconds, elapse between measuring the course of the gas flow-dependent measured values ​​and adjusting the ratio between inspiratory and expiratory time accordingly. This allows for essentially real-time adjustment of inspiratory and expiratory time, enabling particularly rapid adaptation of the patient's ventilation to the current state of their specific respiration.

[0040] In one embodiment of the described method, an average is calculated over a number of past end-expiratory gas flows, for example, over the last two end-expiratory gas flows, in order to compare the average value with the lower threshold and / or the upper threshold. In this embodiment, the comparison is made dependent on the current end-expiratory gas flow by making the determined average value dependent on the current end-expiratory gas flow. In an alternative embodiment, the ratio between inspirational time and expiratory time is adjusted solely based on the last determined current end-expiratory gas flow.

[0041] The invention will now be explained in more detail with reference to advantageous embodiments schematically illustrated in the figures. These show, in detail: Fig. 1 a schematic representation of an embodiment of a ventilator according to the invention; Figs. 2, 3 a respective diagram of the course of gas flow-dependent measured values, before ( Fig. 2 ) and after ( Fig. 3 ) an adjustment of the ratio between inspiration time and expiration time in an embodiment according to the invention; Figs. 4, 5 a respective diagram of the course of gas flow-dependent measured values, before ( Fig. 4 ) and according to (5) an adjustment of a ramp duration of an increase in the gas pressure of a breathing gas in an embodiment according to the invention; Fig. 6 a flow diagram of a control of ventilation parameters in an embodiment according to the invention; and Fig. 7 a flow diagram of an embodiment of a method.

[0042] Fig. 1 shows a schematic representation of an embodiment of a ventilator 100 according to the invention.

[0043] The ventilator 100 is designed for the mechanical ventilation of a patient 102. The ventilator 100 comprises at least one sensor unit 110, one storage unit 120, and one processing unit 130.

[0044] The at least one sensor unit 110 is configured to measure a profile 114 of gas flow-dependent measured values ​​115 in the ventilation circuit 105 of the ventilator 100. For this purpose, the sensor unit 110, in the illustrated embodiment, has a sensor head 112 which is arranged within the ventilation circuit 105, in particular near a tube located on the patient 102. Furthermore, the sensor unit 110 is configured to output a corresponding sensor signal 116. The gas flow-dependent measured values ​​115 in this case represent a measured gas flow.

[0045] Alternatively or additionally, in an embodiment not shown, the gas pressure is measured as a gas flow-dependent measured value.

[0046] The storage unit 120 comprises a memory in which a multitude of ventilation parameters 122 of a currently active ventilation mode of the ventilator 100 are stored. The multitude of stored ventilation parameters 122 indicates at least an inspiratory time 124 of the ventilation currently provided by the ventilator 100 and a subsequent expiratory time 126 for a corresponding respiratory cycle. In the illustrated embodiment, the storage unit 120 contains at least the inspiratory time 124, the subsequent expiratory time 126, a vital volume to be provided, a respiratory rate, and a maximum pressure during inspiration.The storage unit 120 can be connected to a user interface for entering ventilation parameters and / or to a control unit 140 of the ventilator 100 for specifying the current ventilation parameters and / or to a network, in particular a hospital network, for providing the ventilation parameters to be applied. For the sake of clarity, such a connection according to one of these variants is not shown in [reference]. Fig. 1 depicted.

[0047] The processing unit 130 is configured to receive the sensor signal 116 and, based on the course 114 of the gas flow-dependent measured values ​​115, to determine at least one current end-expiratory (EE) gas flow 132. In the illustrated embodiment, the determination of the current end-expiratory gas flow 132 takes place within a first module 131. A related second module 133 of the processing unit 130 is further configured to adjust a ratio 136 between inspirational time 124 and expiratory time 126 for the currently active ventilation mode for ventilating the patient 102, depending on a comparison between the determined current end-expiratory gas flow 132 and a lower threshold 134 and / or an upper threshold 135. The determination of the newly provided ratio 136 takes place in a third module 137 of the processing unit 130.The three modules 131, 133 and 137 are separated at least at the software level in such a way that different processing steps of an executable program represent different modules.

[0048] The processing unit 130 is configured to output the ratio via a corresponding internal output 138 from the third module 137 to the control unit 140 of the ventilator 100. The control unit 140 applies the newly determined ratio 136 by overwriting the previously used ratio 136' between inspirational time 124 and expiratory time 126 when ventilating the patient 102.

[0049] In the illustrated embodiment, the processing unit 130 is configured to shorten the expiratory time 126 if the current end-inspiratory gas flow 132 is below the lower threshold value 134. This advantageously ensures that the inspiratory time 124 is as long as possible, so that during ventilation there is the lowest possible pressure gradient with constant tidal volume and constant respiratory rate. This allows for particularly gentle ventilation for the patient.

[0050] Excessive end-expiratory gas flow correlates with high intrinsic end-expiratory pressure (intrinsic PEEP), which is also known to be undesirable. For this purpose, the processing unit is preferably designed to prolong the expiratory time 126 if the current end-expiratory gas flow 132 is above the upper threshold 136.

[0051] The ratio between inspiratory time 124 and expiratory time 126 is always changed in such a way that the duration of the corresponding respiratory cycle, i.e., the sum of inspiratory and expiratory time, always remains constant. This ensures that a preferably predetermined respiratory rate remains essentially unchanged during the adjustment of the ratio.

[0052] In the illustrated embodiment, the lower threshold and / or the upper threshold depend on the measured profile 114 of the gas flow-dependent measured values ​​115. These two thresholds are determined based on the maximum expiratory gas flow during the expiratory time 126. Preferably, the lower threshold is between 0.5% and 5% of the maximum inspiratory gas flow, particularly between 1% and 3% of the maximum expiratory gas flow, and most preferably about 2% of the maximum expiratory gas flow.

[0053] Finally, the processing unit 130 is further designed to extend the expiratory time 126 only if this results in a mean respiratory pressure over the corresponding respiratory cycle not being within a predetermined lower mean pressure threshold.

[0054] The processing unit is also designed to adjust the course of the gas flow during the inspiration time 124, for example by changing the increase of the gas flow and / or by changing a maximum gas flow during the inspiration time 124.

[0055] The various units of the ventilator 100 according to the invention can be arranged, at least partially, in a common housing. The various units are separated from each other, at least at the software level. Communication between these units is wired or wireless. Various ways of implementing such wired or wireless communication are known to those skilled in the art, so these will not be discussed in detail below.

[0056] The Figures 2 and 3 show a respective diagram 200, 300 of the course 214, 314 of gas flow-dependent measured values ​​115, before ( Fig. 2 ) and after ( Fig. 3 ) an adjustment of the ratio between inspiration time 124 and expiration time 126 in an embodiment according to the invention.

[0057] Diagrams 200 and 300 show, above their respective x-axes 202 and 302, the time represented by slightly more than one respiratory cycle. The duration of a respiratory cycle is between 3 and 12 seconds, particularly between 5 and 10 seconds. The beginning of each depicted respiratory cycle is located at the origin of the coordinate system of diagrams 200 and 300.

[0058] The gas flow-dependent measured value, in this case the gas flow, is displayed on the respective Y-axis 204 and 304. One marker indicates a value of 25 L / min.

[0059] The gas flow is positive during inspiration 124 and negative during expiratory time 126. During inspiration 124, the gas flow increases essentially linearly over a ramp period 250 before decreasing again after a maximum inspiratory gas flow 252. Ideally, the end of inspiration 254 of inspiration 124 has a positive gas flow close to 0 L / min. After inspiration 254 ends, expiratory time 126 begins, during which the gas flow increases in the negative direction of the Y-axis up to a maximum expiratory gas flow 255 before decreasing again to a value close to 0 L / min. Before the adjustment of expiratory time 126 according to the invention, there is a positive gas flow close to 0 L / min in the Fig. 2The illustrated example sequence 214 shows an extensive period 256 in which there is essentially no gas flow until the next inspirational period 124 begins after the end of expiratory flow 258. If ventilation were to continue in this way, there would be an extended expiratory period 256 in every respiratory cycle, which does not effectively contribute to the ventilation of the patient.

[0060] According to the invention, when the curve 214 is present, it is determined that a lower threshold value 134 is undershot at the end of expiratory flow 258, thus altering the ratio between inspiratory time 124 and expiratory time 126. In the illustrated embodiment, the lower threshold value 134 is approximately 2% of the maximum expiratory gas flow 255.

[0061] Falling below this lower threshold value 134 shortens the expiratory time 126 and simultaneously lengthens the inspiratory time 124, as in Fig. 3The entire respiratory cycle retains its duration, so that the end of expiration 358 is essentially at the same time as the end of expiration 258. Fig. 2 The course of expiration is described in the Figures 2 and 3 identical, except that the shortening of the expiratory time 126 eliminates the extended period 256 with little or no gas flow. The course of expiration is essentially dependent on the tidal volume provided and the patient's physiology, and is therefore independent of any change in the course 214 of the gas flow during the inspiratory time 124.

[0062] Given the extended inspiration time 124, the gas volume to be supplied is delivered over a longer period, so that the gradient of the gas flow, i.e., the change per unit of time, is lower and therefore more comfortable for the patient. Furthermore, in the illustrated embodiment, the maximum inspiratory gas flow 352 is lower than the maximum inspiratory gas flow 252 from Fig. 2 According to the invention, depending on the adjustment of the ratio between inspiration time and expiration time, an increase in the gas pressure of the respiratory gas at the beginning of the inspiration time and / or a maximum pressure of the respiratory gas during the inspiration time is adjusted.

[0063] Adjusting the ratio between inspiratory time (124) and expiratory time (126) can be achieved via a predetermined time control, where the current end-expiratory gas flow acts as the measured variable of the time control and the inspiratory time as the manipulated variable of the time control, with the lower threshold representing a setpoint for the measured variable. This ensures, for example, that a reduction in expiratory time (126) does not result in intrinsic end-expiratory pressure (intrinsic PEEP).

[0064] The other ventilation parameters to be considered during ventilation are known to those skilled in the art, depending on the ventilation mode used. Preferably, at least the respiratory rate is predetermined.

[0065] Preferably, at least one of the following pressures is also predefined: positive end-expiratory pressure (PEEP), maximum inspiratory pressure, mean airway pressure. If only one of these pressures is predefined, the tidal volume of ventilation is preferably also a predetermined ventilation parameter of the current ventilation mode.

[0066] Figures 4 and 5 show a respective diagram 400, 500 of the course 414, 514 of gas flow-dependent measured values ​​115, before ( Fig. 4 ) and after ( Fig. 5 ) an adjustment of a ramp duration 450, 550 of an increase in the gas pressure of a breathing gas in an embodiment according to the invention.

[0067] The axes of diagrams 400 and 500 are identical to the axes of diagrams 200 and 300.

[0068] In Fig. 4 The course of 414 of the gas flow-dependent measured values ​​115 differs from the courses from Figs. 2 and 3by the fact that the end-inspiratory gas flow 465 is essentially 0 l / min over an extended inspirational period 467. In addition to the end of inspiration 454 and the end of expiration 458, the time of maximum inspiratory gas flow 452 is characterized, which represents the end of the ramp duration 450.

[0069] The ventilator according to the invention detects that the end-inspiratory gas flow 465 is above a lower inspiratory threshold 468 and therefore the ramp duration 450 must be extended while the inspiratory time 124 remains constant. This shortens the plateau duration 470, which represents the remaining time of the inspiratory time 124. The term "plateau duration" is used for this time interval because the pressure within the Y-piece remains constant during this period, while the remaining positive gas flow reaches the patient's lungs directly. As is known, this results in a pressure plateau for a pressure sensor typically located in the region of the Y-piece.

[0070] The resulting course 514 is in Fig. 5 The ramp duration of 550 is approximately twice as long as the ramp duration of 450. Fig. 4, whereas the course 514 during expiratory time 126 remained essentially unchanged. The longer ramp duration 550 is used to reduce the increase in gas flow and thus to provide gentler ventilation for the patient.

[0071] In this embodiment, the ventilator would also shorten the ramp duration accordingly if the end-inspiratory gas flow exceeds an upper inspiratory threshold.

[0072] The appropriate adjustment of the ramp duration and / or the inspiratory time and / or the expiratory time is achieved by iterative adjustments of predetermined time increments. After each adjustment, the effect on the corresponding measured values ​​is considered to guide further adjustments. Such a procedure is well-known in control engineering, so the possibilities for its implementation will not be discussed in detail here.

[0073] Fig. 6 shows a flowchart of a control 600 of ventilation parameters in an embodiment according to the invention.

[0074] Regulation 600 illustrates an embodiment of the inventive work steps of the ventilator when adjusting the inspiration time and the ramp duration.

[0075] After the initiation of step 605 of the inventive control, the input and storage of the multitude of ventilation parameters takes place in step 610. Then the ventilation of the patient is started in step 615.

[0076] During ventilation, in this embodiment, it is advantageously always checked in step 620 whether the mean airway pressure over the corresponding respiratory cycle is above a predetermined lower mean airway pressure threshold. The mean airway pressure is calculated, for example, by summing the measured gas flow-dependent values, i.e., the measured gas pressures, using an appropriate scale. Alternatively or additionally, the mean airway pressure (MAP) can be approximated using the following calculation method: MAP = PEEP + T I − 1 2 * T Ramp * RR * P

[0077] Here, TI is the inspiratory time, which is calculated, for example, from the ratio between inspiratory and expiratory time and the predetermined respiratory rate (RR). TRamp is the ramp duration, and P is the inspiratory pressure jump, which is calculated as the quotient of tidal volume and lung capacity.

[0078] If, in step 620, it is determined that the mean airway pressure is above the lower mean pressure threshold, control 600 continues with step 630. If the mean airway pressure is below the lower mean pressure threshold, step 625 checks whether the current ramp duration is greater than a predetermined minimum ramp duration. If the ramp duration is greater than the predetermined minimum ramp duration, step 627 incrementally reduces the ramp duration and repeats step 620. If the ramp duration is less than or equal to the minimum ramp duration, step 629 increases the inspiratory time to raise the mean airway pressure and continues with step 630.

[0079] In step 630, it is checked whether the end-expiratory gas flow is greater than 2% of the maximum expiratory gas flow. If the end-expiratory gas flow is greater than 2% of the maximum expiratory gas flow, the expiratory time is prolonged in step 634 while the sum of inspiration and expiratory time is kept constant until the end-expiratory gas flow is essentially 2% of the maximum expiratory gas flow and / or the mean airway pressure is equal to the lower mean pressure threshold. If the end-expiratory gas flow is greater than 2% of the maximum expiratory gas flow, the expiratory time is shortened in step 638 until the end-expiratory gas flow is essentially 2% of the maximum expiratory gas flow.

[0080] Step 640 is then executed, in which it is checked whether the end-inspiratory gas flow is greater than 2% of the maximum inspiratory gas flow. If the end-inspiratory gas flow is greater than 2% of the maximum inspiratory gas flow, the ramp duration in step 644 is reduced until the end-inspiratory gas flow is substantially 2% of the maximum inspiratory gas flow or the ramp duration is substantially equal to the minimum ramp duration. If the end-inspiratory gas flow is less than 2% of the maximum inspiratory gas flow, the ramp duration in step 648 is increased until the end-inspiratory gas flow is substantially 2% of the maximum inspiratory gas flow or the mean airway pressure is substantially equal to the lower mean pressure threshold.

[0081] After performing step 644 or step 648, the steps are repeated starting with performing ventilation 615.

[0082] In this embodiment, all aspects of the control of the ventilator according to the invention are explained. In alternative embodiments, only the inspiratory time is controlled, or only a combination of inspiratory time and ramp control, or only a combination of inspiratory time and mean airway pressure control.

[0083] The structure of control 600 essentially visualizes the iterative nature of the control according to the invention. The incremental change of a value occurs with each iteration of a corresponding step of this control 600. Suitable starting conditions for ventilation are known from medical practice and are therefore not described here.

[0084] Fig. 7shows a flowchart of an example of a Procedure 700. Compared to the one in Fig. 6 The described arrangement represents a higher-level sequence of process steps according to the invention in process 700. It is clearly understandable to the person skilled in the art from the following explanation that individual process steps of process 700 comprise several stages of the process within the framework of Fig. 6 The explained regulation 600 may include.

[0085] Procedure 700 is designed to operate a ventilator for the mechanical ventilation of a patient. For this purpose, Procedure 700 comprises the steps described below. A first step, 710, involves measuring the course of gas flow-dependent measured values ​​in the ventilation circuit of the ventilator and outputting a corresponding sensor signal.

[0086] A subsequent step 720 involves storing a variety of ventilation parameters of a currently existing ventilation mode, whereby these stored ventilation parameters indicate at least an inspiration time of the ventilation currently provided by the ventilator and a subsequent expiratory time for a corresponding respiratory cycle.

[0087] A further step 730 involves receiving the sensor signal and determining at least one current end-expiratory gas flow based on the course of the gas flow-dependent measurements.

[0088] A final step 740 involves adjusting a ratio between inspirational time and expiratory time for the currently active ventilation mode to ventilate the patient, depending on a comparison between the determined current end-expiratory gas flow and a lower threshold and / or an upper threshold.

[0089] The sequence of procedure steps 710 and 720 can change. For example, the input of the numerous ventilation parameters can occur when the ventilator is provided, but it can also be done again during the execution of the procedure by changing ventilation parameters.

[0090] Steps 730 and 740 are performed after the two initial steps 710 and 720. The determination of the current end-expiratory gas flow, as in step 730, always takes place before adjusting the ratio between inspirational and expiratory time, also as in step 730.

[0091] Preferably, steps 730 and 740 are executed at least nearly in real time, so that the measured values ​​for one respiratory cycle can be taken into account when changing the ratio between inspiratory and expiratory time of the following respiratory cycle. In an alternative or supplementary embodiment, the adjustment of the ratio between inspiratory and expiratory time is based on a number of measured values ​​from previous respiratory cycles, in particular on the last two respiratory cycles. Taking previous respiratory cycles into account can improve the reliability of the ventilator according to the invention, since, for example, a comparison between the current respiratory cycle and the previous respiratory cycle can reveal measurement errors if there is a particularly large deviation.For example, a deviation above a deviation threshold value can lead to the current measured values ​​not being used to adjust the ratio between inspiration time and expiration time.

[0092] The steps of the described procedure 700 can be performed multiple times within the procedure. For example, several current end-expiratory gas flows can be determined according to step 730 before the ratio between inspiratory time and expiratory time is adjusted according to step 740.

[0093] Preferably, at least parts of the procedure, such as the measurement according to step 710, the determination of the current end-expiratory gas flow according to step 730, and the adjustment according to 740, are repeated for each respiratory cycle. According to the invention, the adjustment according to step 740 is only performed if the comparison between the determined current end-expiratory gas flow and the corresponding threshold value according to a stored rule indicates this.

[0094] The various process steps of Procedure 700 can be executed at a common location, for example, by a shared device. In this case, the execution of the individual steps is separated from one another, for example, by a shared processor, at least at the software level. Alternatively, Procedure 700 can be executed, at least partially, at different locations. Reference symbol list

[0095] 100 Ventilator 102 Patient 105 Ventilation circuit 110 Sensor unit 112 Sensor head 114, 214, 314, 414, 514 Measurement data progression 115 Gas flow-dependent measurement value 116 Sensor signal 120 Storage unit 122 Ventilation parameters 124 Inspiratory time 126 Expiratory time 130 Processing unit 131 First module 132 End-expiratory gas flow 133 Second module 134 Lower threshold 135 Upper threshold 136 Inspiratory-to-expiratory time ratio 136 Past ratio 137 Third module 138 Internal output 140 Control unit 200, 300, 400, 500 Graph 202, 302 X-axis 204, 304 Y-axis 250, 450, 550 Ramp duration 252, 352, 452 Maximum inspiratory gas flow 254, 454 End of inspiration 255 Maximum expiratory gas flow 256 Extended expiratory range 258, 358, 458 End of expiratory range 465 End-inspiratory gas flow 467 Extended inspiratory range 468 Lower inspiratory threshold 470 Plateau duration 600 Regulation 605, 610, 615, 620,625, 627, 629, 630, 634, 638, 640, 644, 648 Regulatory steps 700 Procedures 710, 720, 730, 740 Procedural steps,

Claims

1. Ventilator (100) for mechanical ventilation of a patient (102), comprising - at least one sensor unit (110), which is designed to measure a profile (114) of gas flow-dependent measured values (115) in the ventilation circuit (105) of the ventilator (100) and to output a corresponding sensor signal (116), - a storage unit (120), in which a plurality of ventilation parameters (122) of a currently present ventilation mode are stored, these stored ventilation parameters (122) indicating at least one inspiratory time (124) of the ventilation currently provided by the ventilator (100) and a subsequent expiratory time (126) for a corresponding respiratory cycle, - a processing unit (130), which is designed to receive the sensor signal (116) and to determine at least one current end-expiratory gas flow (132) based on the profile (114) of the gas flow-dependent measured values (115), the processing unit (130) being further designed to adjust, depending on a comparison between the determined current end-expiratory gas flow (132) and a lower threshold value (134) and / or an upper threshold value (135), a ratio (136) between inspiratory time (124) and expiratory time (126) for the currently present ventilation mode for ventilating the patient (102), the duration of the corresponding respiratory cycle remaining substantially constant, characterized in that the processing unit (130) is designed to adjust, depending on the adjustment of the ratio (136) between inspiratory time (124) and expiratory time (126), an increase in a gas pressure of the respiratory gas at the beginning of the inspiratory time (124) and / or a maximum pressure of the respiratory gas during the inspiratory time (124).

2. Ventilator (100) according to claim 1, wherein the processing unit (130) is designed to shorten the expiratory time (126) if the current end-expiratory gas flow (132) is below the lower threshold value (134).

3. Ventilator (100) according to claim 1 and claim 2, wherein the processing unit (130) provides a time control in which the current end-expiratory gas flow (132) acts as a measured variable of the time control and the inspiratory time (124) acts as a manipulated variable of the time control, and wherein the lower threshold value (134) represents a target value of the measured variable.

4. Ventilator (100) according to claim 1 and claim 2, wherein the processing unit (130) is designed to extend the expiratory time (126) if the current end-expiratory gas flow (132) is above the upper threshold value (135).

5. Ventilator (100) according to at least one of the preceding claims, wherein the lower threshold value (134) and / or the upper threshold value (135) are dependent on the measured profile (114) of the gas flow-dependent measured values (115).

6. Ventilator (100) according to claim 5, wherein the lower threshold value (134) and / or the upper threshold value (135) are dependent on a maximum expiratory gas flow (255) determined from the gas flow-dependent measured values (115) during the expiratory time (126) of the provided ventilation.

7. Ventilator (100) according to at least one of the preceding claims, wherein the processing unit (130) is further designed to reduce the increase in the gas pressure at the beginning of the inspiratory time (124) and / or to reduce the maximum pressure of the respiratory gas if the inspiratory time (124) is extended.

8. Ventilator (100) according to at least one of the preceding claims, wherein the processing unit (130) is further designed to determine, via the profile (114) of the gas flow-dependent measured values (115), a current end-inspiratory gas flow (465) and to adjust, depending on the current end-inspiratory gas flow (465), a ramp duration (450) of the increase in the gas pressure of the respiratory gas at the beginning of the inspiratory time (124).

9. Ventilator (100) according to claim 8, wherein the processing unit (130) is designed to extend the ramp duration (450) if the current end-inspiratory gas flow (465) is below a lower inspiratory threshold value (468), and at the same time to shorten a remaining plateau duration (470) of the inspiratory time (124) so that the inspiratory time (124) is independent of the end-inspiratory gas flow (465).

10. Ventilator (100) according to claim 8 and claim 9, wherein the processing unit (130) provides a ramp control in which the current end-inspiratory gas flow (465) acts as a measured variable of the ramp control, and the ramp duration (450) acts as a manipulated variable of the ramp control, and wherein the lower inspiratory threshold value (468) represents a target value of the measured variable.

11. Ventilator (100) according to claim 8 and claim 9, wherein the processing unit (130) is designed to shorten the ramp duration (450) if the current end-inspiratory gas flow (465) is above an upper inspiratory threshold value, and at the same time to extend a remaining plateau duration (470) of the inspiratory time (124) so that the inspiratory time (124) is independent of the end-inspiratory gas flow (465).

12. Ventilator (100) according to at least one of the preceding claims, wherein the processing unit (130) is further designed to extend the expiratory time (126) and / or to extend the ramp duration (450) at constant maximum pressure only if, as a result, a mean ventilation pressure over the corresponding respiratory cycle is not below a predetermined lower mean pressure threshold value.