Monitoring the effectiveness of a support pulse in extracorporeal circulatory support

Abstract

The present invention relates to methods for monitoring cardiac cycle-synchronized extracorporeal circulatory support as well as corresponding devices and circulatory support devices, in particular for optimizing a provided support pulse.Accordingly, a method for monitoring a patient's cardiac cycle-synchronized extracorporeal circulatory support (12) is described, comprising the following steps: receiving pressure values ​​characteristic of the aortic pressure of the supported patient; determining a first minimum pressure value (40) of a cardiac cycle of the patient from the pressure values ​​and a first time point for the minimum pressure value (40); determining, from the pressure values, whether at a subsequent second time point there is a reduced pressure change rate (42) between an immediately preceding and a subsequent larger pressure change rate; and outputting a signal depending on whether a reduced pressure change rate (42) is present. The pressure values ​​are received by a pressure sensor (32) which is arranged upstream of an arterial cannula (30) and downstream of an oxygenator (38) of the extracorporeal circulatory support (12).

Description

Technical field

[0001] The present invention relates to methods for monitoring cardiac cycle-synchronized extracorporeal circulatory support as well as corresponding devices and circulatory support devices, in particular for optimizing a provided support pulse. State of the art

[0002] When the heart's pumping capacity or function fails, cardiogenic shock can occur. A reduction in cardiac output can lead to reduced perfusion or blood flow to end organs such as the brain, kidneys, and the vascular system in general. Acute heart failure can therefore cause acute blood deprivation in tissues and organs, accompanied by oxygen deprivation, also known as hypoxia, potentially resulting in end-organ damage.

[0003] To stabilize the patient's condition, circulatory support systems have been developed that provide mechanical support and can be quickly connected to the circulatory system. They can improve blood flow and perfusion to the organs, including the coronary arteries, and prevent hypoxia. For example, extracorporeal circulatory support systems are known to draw blood from, for example, the right atrium or the vena cava through a cannula inserted into the femoral vein and return it to the patient via a perfusion cannula inserted into the femoral artery using a membrane ventilator. The membrane ventilator removes CO2 and oxygenates the blood. Such systems are also known as extracorporeal membrane oxygenation (ECMO).

[0004] To largely prevent retrograde blood flow during the systolic phase of the heart, which is directed against the heart's natural ejection direction and thus undesirably increases afterload, circulatory support systems can be synchronized with the patient's heartbeat as an alternative to continuous blood return. In such cardiac cycle-synchronized circulatory support systems, the blood pump is triggered, for example, by a detected R-wave in the ECG signal with a manually entered, predefined delay time. This allows a support pulse to be delivered at a predetermined time, particularly during the diastolic phase of the cardiac cycle. Description of the invention

[0005] According to the invention, it was recognized that provided circulatory support does not necessarily lead to the desired increase in diastolic pressure in the aorta, and that a corresponding diastolic pressure effect may not be present despite a delivered support pulse. For example, despite a properly set delay time of a trigger signal for a support pulse, such a pressure effect may fail to occur, so that blood flow in the coronary arteries may not be sufficiently improved.

[0006] It was also recognized that no evidence of such a diastolic pressure effect is provided in the prior art. Without such evidence, optimization of the extracorporeal circulatory support pump speed and / or adjustment of the set delay time, for example, cannot be carried out efficiently. Accordingly, a predetermined speed is usually used, and a delay time, for example, is selected manually based solely on a received ECG signal.

[0007] To enable verification of aortic pressure, a pressure sensor can be inserted into the patient's aortic arch, allowing pressure measurements to be taken in close proximity to the coronary arteries and the delivered support pulse. However, this requires an additional invasive procedure during therapy to insert an arterial pressure sensor into the patient and position it at the level of the aortic arch, for example, using a catheter. Such an invasive procedure can not only be complex but also pose a risk to the patient.

[0008] Based on the known state of the art, it is therefore an object of the present invention to further improve the circulatory support to be provided and in particular to enable proof of a diastolic pressure effect and, if necessary, to optimize it.

[0009] The problem is solved by the subject matter of the independent claims. Advantageous developments arise from the dependent claims, the description, and the figures.

[0010] Accordingly, a procedure for monitoring a patient's cardiac cycle-synchronized extracorporeal circulatory support is proposed, comprising the following steps: - Receiving pressure values ​​that are characteristic of the aortic pressure of the supported patient; - Determining a first minimum pressure value of a cardiac cycle of the patient from the pressure values ​​and a first time point for the minimum pressure value; - Determine, from the pressure values, whether at a subsequent second time point there is a reduced pressure change rate between an immediately preceding and a subsequent larger pressure change rate; and - Outputting a signal depending on a given reduced pressure change rate, whereby the pressure values ​​are received from a pressure sensor which is located before an arterial cannula and after an oxygenator of the extracorporeal circulatory support.

[0011] The inventors have determined that a temporarily reduced pressure change rate, in the context of an otherwise increasing pressure, indicates the presence of a diastolic pressure effect in the patient's aorta. This reduced pressure change rate, which appears as a dip in the pressure curve, only occurs when the pressure generated by the circulatory support system and the patient's arterial pressure overlap, and the diastolic pressure signal is clearly and strongly pronounced. Accordingly, the characteristic signal pattern can be used to determine whether or not such a diastolic pressure effect is present.

[0012] In this way, the invention makes it possible to monitor the cardiac cycle-synchronized circulatory support, and in particular to determine the effect of the delivered support pulse. If a reduced pressure change rate could be determined after the first time point, the output signal can, for example, indicate that the desired diastolic pressure effect is present and that sufficient or optimized circulatory support is being provided for the patient. Conversely, the output signal can also indicate that such a pressure effect could not be determined or demonstrated and that, for example, an adjustment of the extracorporeal circulatory support is necessary or desired.

[0013] Both the immediately preceding pressure change rate between the first and second time points, and the subsequent pressure change rate after the second time point or after the temporarily reduced pressure change rate, exhibit a positive value with a steeper slope, indicating that the reduced pressure change rate occurs during a cardiac cycle phase with rising pressure. Accordingly, the reduced pressure change rate can be clearly identified in a graphical representation as a notch.

[0014] Consequently, a signature formed by the pressure curve can be used to determine in a clear and simple way whether a diastolic pressure effect is present and whether a corresponding increase in pressure in the aortic arch occurs, with a concomitant improvement in coronary blood flow during the diastolic phase.

[0015] This monitoring remains non-invasive, as the pressure sensor that records the pressure values ​​is located in the extracorporeal circuit. The pressure values, and in particular the reduced rate of pressure change, are characteristic of the patient's aortic pressure. Therefore, additional invasive pressure sensors, such as those provided by a pressure-measuring catheter, are completely unnecessary. This not only significantly reduces the risk to the patient but also keeps monitoring costs down. Only one pressure sensor needs to be installed in the extracorporeal circulatory support system, and only its measurements need to be analyzed. An additional arterial pressure sensor and corresponding catheter are therefore not required for monitoring the pressure effect.

[0016] The invention can therefore be easily implemented in existing extracorporeal circulatory support devices. The method according to the invention can also be provided essentially as a software extension in the form of a computer-implemented method or a computer program product. If necessary, and if one is not already present in the extracorporeal circulatory support device, only a pressure sensor should be provided in the extracorporeal circuit between the oxygenator and the arterial cannula. It should also be ensured that the pressure measurements or pressure values ​​are available in a console of the circulatory support device, for example, via an existing interface, such as a CAN bus.

[0017] Consequently, due to the proven effectiveness of extracorporeal circulatory support according to the invention, a complex approval process can be dispensed with. For example, the method requires no modifications to disposable devices such as tubing sets or pressure-measuring catheters to detect pressure characteristic of the patient's aortic pressure.

[0018] To enable immediate monitoring of the efficacy and effectiveness of the provided circulatory support, pressure values ​​are preferably received in real time for the current cardiac cycle of the supported patient. The signal is then preferably output for the current cardiac cycle.

[0019] This allows for real-time monitoring without the need for averaging the pressure curve. Monitoring and potential adjustment of extracorporeal circulatory support can thus be synchronized with therapy. Virtually immediate feedback can be provided to the operator of the extracorporeal circulatory support regarding the effectiveness of the currently set or adjusted parameters. The signal can also be output in real time, for example, as a visual and / or audible signal, indicating the presence of a reduced pressure change rate in the current cardiac cycle.

[0020] To prevent potential pressure fluctuations and / or measurement variations from being inadvertently interpreted as a reduced pressure change rate, the signal is preferably output depending on whether the second time point falls within a predefined time interval between 10 percent and 50 percent of the cardiac cycle duration after the first time point. This allows for the definition of a time window within which the pressure effect is expected, which can be based, for example, on evaluated historical data and / or settings of the extracorporeal circulatory support device, particularly its blood pump.

[0021] Accordingly, the signal can also be output depending on whether the reduced pressure change rate is present for a predetermined time interval between 1 percent and 10 percent of the cardiac cycle duration. Any short measurement fluctuations or longer pressure changes that do not correspond to a typical pressure effect can thus be filtered out when determining whether a reduced pressure change rate is present.

[0022] For example, the method according to the invention can be designed to determine a reduced pressure change rate only if it occurs within a time interval between 60 ms and 300 ms, preferably between 100 ms and 200 ms, after the first time point, or if the determination is only carried out within this time interval. It can also be designed to consider only reduced pressure change rates between, for example, 5 ms and 50 ms, preferably between 10 ms and 30 ms. Accordingly, the risk of erroneous readings can be reduced and the accuracy of the monitoring can be further improved.

[0023] Starting from the initial minimum pressure value, a further expected maximum pressure value can be specified, which, for example, can also be determined based on evaluated historical data and / or settings of the extracorporeal circulatory support device. Accordingly, the signal can be output depending on whether the reduced pressure change rate is positive and / or whether the pressure value at the second time point is increased by between 20 percent and 300 percent, preferably between 20 percent and 150 percent or 30 percent and 150 percent, of the initial minimum pressure value.

[0024] In the case of a positive pressure change rate, i.e., a flattening pressure change rate greater than or equal to zero, it can be assumed that a reduced pressure change rate will be determined at a second time point, which corresponds to an increasing pressure. This increases the probability that a reduced pressure change rate was determined before a maximum diastolic pressure and that this corresponds to an actual diastolic pressure effect.

[0025] Similarly, an absolute pressure value at a second time point can, based on a reference range, define the pressure range within which a reduced pressure change rate is expected. For example, the reference range can be selected based on the determined first minimum pressure value. The reference range preferably defines a pressure range within which a reduced pressure change rate is only expected during an increasing pressure, and which typically does not exhibit a reduced pressure change rate after reaching a maximum diastolic pressure. For example, the determined first minimum pressure value might be approximately 40 mmHg, so the reduced pressure change rate preferably lies between 56 mmHg and 100 mmHg.By using a reference range for the reduced pressure change rate in combination with the assumption of a positive reduced pressure change rate, it is advantageous to achieve an even more precise definition of the reduced pressure change rate and, accordingly, an even more precise monitoring of the diastolic pressure effect.

[0026] Alternatively or additionally, it can be provided that, following the first time point, a maximum pressure is determined from the pressure values ​​at a third time point. The signal can be output depending on whether the second time point lies between the first and third time points. In this way, it is reliably prevented that a reduced pressure change rate is inadvertently determined within a cardiac cycle phase that occurs after the maximum diastolic pressure has been reached. In the graphical pressure curve, the maximum diastolic pressure is clearly identifiable directly after a dip corresponding to the reduced pressure change rate.Accordingly, the accuracy that a particular reduced pressure change rate is indeed characteristic of a present diastolic pressure effect can be further increased by defining that the reduced pressure change rate should be determined before the maximum diastolic pressure.

[0027] Following the first time point, a second minimum pressure value can be determined at a fourth time point. A first pressure integral can be calculated between the first and second time points, and a second pressure integral can be calculated between the second and fourth time points. The signal can preferably be output depending on whether the first pressure integral is greater or less than the second pressure integral.

[0028] The second minimum pressure value preferably coincides with the end of the diastolic phase of the respective cardiac cycle. If a diastolic pressure effect is reached for the respective cardiac cycle, the second pressure integral is larger than the first. This is because, in such a case, it is assumed that the reduced pressure change rate was determined before the maximum diastolic pressure, and the first pressure integral is therefore lower.

[0029] Based on one or more of the aforementioned preferred criteria, the reduced pressure change rate and the pressure profile signature can be defined more precisely. This allows the pressure change rate to more accurately reflect an actual diastolic pressure effect and, advantageously, enables even more precise monitoring and / or optimization of the patient's extracorporeal circulatory support. Furthermore, any physiological or technical fluctuations detected by the pressure sensor can be largely disregarded or ignored.

[0030] However, it is also possible that a diastolic pressure effect does not occur, is insufficient, and / or could not be determined based on a reduced pressure change rate. In such a case, the pressure profile may deviate from the desired profile and, for example, be saddle-shaped or exhibit a double-squat pattern. Such a pressure profile may indicate, in particular, that a pressure effect is beginning to develop but is not yet complete.

[0031] Accordingly, it can be provided that a maximum pressure is subsequently determined from the pressure values ​​at a first and a third time point, with the signal being output depending on whether the pressure change rate before the maximum pressure value is less than or equal to zero. For example, a local pressure maximum may precede the maximum pressure value. The pressure value may flatten or decrease, at least temporarily, before reaching the maximum (diastolic) pressure value.

[0032] Since a reduced pressure change rate is more likely to occur when the pressure is otherwise increasing, a pressure change rate of less than or equal to zero should not be interpreted as indicating an onset of diastolic pressure. Instead, in such a case, the pressure can be assumed to follow a saddle-shaped or double-peaked profile, allowing the signal to indicate an emerging pressure effect. For example, the signal can be used as a visual check signal, prompting an operator to verify and, if necessary, adjust the extracorporeal circulatory support.

[0033] Alternatively, it can be provided that a maximum pressure is determined from the pressure values ​​at a third time point following the first. The signal can be output depending on whether the pressure change rate after the maximum pressure value is greater than or equal to zero. As explained above, if a diastolic pressure effect is present, it can be assumed that it is determined before a maximum pressure value. In such a case, if the pressure change rate following the maximum pressure value is reduced, it should not be assumed that a diastolic pressure effect is present.

[0034] For example, if the pressure change rate is greater than zero, a local pressure maximum may occur downstream of the maximum pressure value and at a lower height. The pressure is therefore initially reduced before reaching this local maximum and then increased. In other words, even in such a case, the pressure can be assumed to follow a saddle-shaped or double-peaked profile. The pressure decreases in an arc-like pattern after the maximum pressure value and then increases again after an inflection point with a positive pressure change rate. Such a signal can also indicate an incipient pressure effect.

[0035] However, if neither a reduced pressure change rate, which is characteristic of a present diastolic pressure effect, nor an incipient pressure effect and thus no pressure effect for the respective cardiac cycle is determined, the signal can be output accordingly as a (e.g., visual) warning signal.

[0036] To enable a more precise determination of the existing diastolic pressure effect and / or a more specific output signal, it can be further stipulated that flow measurements from a flow sensor positioned between the oxygenator and the arterial cannula be received for each cardiac cycle. An amplitude value can be calculated from a maximum and a minimum flow value. The signal can then be output as a function of this amplitude value. Thus, with a reduced pressure change rate and an amplitude between 1.6 L / min and 3.1 L / min, preferably between 1.8 L / min and 2.8 L / min, the signal can be characteristic of the presence of a diastolic pressure effect for the respective cardiac cycle. In other words, the amplitude can be used as an additional factor that confirms or reinforces a previously determined diastolic pressure effect and thus advantageously increases the validity of the signal. The output signal can accordingly serve as confirmation of the presence of a diastolic pressure effect, preferably in visual form.

[0037] Conversely, if there is no reduced pressure change rate and the signal has an amplitude between 0.5 L / min and 2.0 L / min, preferably between 0.7 L / min and 1.6 L / min for the respective cardiac cycle, it can be indicative of an emerging diastolic pressure effect. If the amplitude is less than 1.1 L / min, preferably less than 0.9 L / min, for the respective cardiac cycle, the signal can still be indicative of an absent diastolic pressure effect, even if there is no reduced pressure change rate.

[0038] The flow rate and the resulting amplitude can thus further confirm or specify the operating state of the extracorporeal circulatory support. The corresponding signal can indicate either optimized circulatory support, circulatory support starting or establishing itself, or inefficient circulatory support.

[0039] Furthermore, a rotational speed value of a blood pump for extracorporeal circulatory support can be received for each cardiac cycle. The signal, preferably when a reduced pressure change rate is present and the rotational speed is greater than 3200 rpm, preferably greater than 3400 rpm, is indicative of the presence of a diastolic pressure effect. However, if a reduced pressure change rate cannot be determined or is absent, and the rotational speed is below 3400 rpm, preferably between 2500 rpm and 3200 rpm, the signal is preferably indicative of an incipient diastolic pressure effect.

[0040] The rotational speed can therefore be a further indicator of whether the extracorporeal circulatory support is already operating within its optimized range, or whether an increase in speed is possible or advisable to achieve the desired diastolic pressure effect. Because the rotational speed is linked to both the flow rate and the pressure of the extracorporeal circulatory support, any corresponding increase in speed may be limited, either patient-specifically or generally.

[0041] Preferably, the signal includes a control signal, whereby the rotational speed of a blood pump for extracorporeal circulatory support can be set or adjusted depending on the signal and user input. As explained above, in particular, if a diastolic pressure effect is developing and / or if the current rotational speed is between 2500 rpm and 3200 rpm, the rotational speed can be increased, preferably iteratively, to increase the corresponding flow rate and diastolic pressure and achieve the desired diastolic pressure effect. If a reduced pressure change rate has been determined for a particular cardiac cycle, the rotational speed can be set based on the output control signal and / or remain unchanged. Optionally, however, it can be provided that the rotational speed is also increased in the case of a specific reduced pressure change rate, for example, if it is below 3400 rpm.

[0042] User input ensures that the rotational speed is preferably set or adjusted only when specifically requested. For example, this could be triggered by user confirmation that circulatory support should be optimized based on the rotational speed. Such user input also serves to detect any deviation from the set value. In this way, (semi-)automatic optimization of extracorporeal circulatory support can be achieved.

[0043] Alternatively or additionally, a delay time of a trigger signal for extracorporeal circulatory support can also be set or adjusted depending on the control and / or regulation signal and a user input.

[0044] For example, at a heart rate of 90 BPM, a delay time of 400 ms for the trigger signal after a detected R-wave in an ECG signal can be preset. However, it may turn out that a diastolic pressure effect is not achieved. The delay time can be adjusted iteratively, for example in steps of 10 ms to 50 ms, so that a support pulse is delivered not only during the diastolic phase but also achieves a diastolic pressure effect. As explained above, the delay time is also adjusted based on user input, so that optimization of extracorporeal circulatory support only occurs when confirmed or requested by the user.

[0045] To prevent adjustments to one or more circulatory support parameters from inadvertently endangering the patient, the control signal can be output based on a comparison of a maximum pressure value determined for the respective cardiac cycle with a predefined threshold. This allows for a comparison of the maximum pressure value with a tolerance threshold, so that the control signal, for example, only indicates an increase in rotational speed if the maximum pressure value does not exceed the threshold. In this way, for instance, damage to blood cells and / or heart valves can be prevented, thereby reducing the risk of patient harm.

[0046] According to a further aspect of the invention, a computer program product is also proposed. This product comprises instructions which, when executed by a processor, cause the processor to execute the method described above. The computer program product can, for example, be stored in a non-volatile storage medium.

[0047] The problem underlying the invention is further solved by a device for monitoring cardiac cycle-synchronized extracorporeal circulatory support of a patient. The device comprises an interface for receiving pressure values ​​characteristic of the aortic pressure of the supported patient and an evaluation unit configured to determine a first minimum pressure value of a cardiac cycle of the patient and a first time point for the minimum pressure value from the pressure values. It is further configured to determine a reduced pressure change rate between an immediately preceding and a subsequent larger pressure change rate at a subsequent second time point from the pressure values. The device is configured to output a signal depending on a specific reduced pressure change rate.The pressure values ​​can be derived from a pressure sensor located before an arterial cannula and after an oxygenator for extracorporeal circulatory support.

[0048] The device can, for example, control or regulate one or more pump drives or pump heads for (especially non-occlusive) blood pumps within an extracorporeal circulatory support system and may be fluidically connected to other modules. For instance, the blood pump can be fluidically connected to an oxygenator or diaphragm ventilator provided in the extracorporeal circulatory support system. This allows for oxygenation and CO2 removal from the blood. The fluidic connection can be established, for example, via a venous access using a venous cannula and an arterial access using an arterial cannula for aspiration and delivery of the blood, respectively. This provides blood flow from a low-pressure side to a higher-pressure side.Thus, extracorporeal oxygenation of the blood and improved oxygen supply can be ensured for the patient by means of the blood pump.

[0049] By activating the motor or pump drive and the rotor blade, and by triggering the pulse at that precise moment, a (pulsatile) blood flow can be delivered via the arterial cannula to the area directly downstream of the left ventricle and into the aorta. The positioning and counterflow orientation of the cannula tip ultimately result in increased pulsatile blood flow in the coronary arteries. This provides correspondingly improved blood flow to the heart muscle tissue without affecting the systemic circulation.

[0050] The monitoring of extracorporeal circulatory support according to the invention makes it possible to determine whether the blood flow actually produces a diastolic pressure effect. For this purpose, the interface can be connected to a pressure sensor of the extracorporeal circulatory support system, which is located upstream of an arterial cannula and downstream of an oxygenator of the extracorporeal circulatory support system. Corresponding measured values ​​can be received via the interface and forwarded to the evaluation unit. The pressure values ​​can be measured, for example, on the tubing set of the extracorporeal circulatory support system using non-invasive pressure sensors (without direct blood contact).

[0051] The interface can, for example, be designed as a sensor box which can be connected via ports to various sensors, such as pressure sensors integrated into the tubing system, and to an ECG device. The interface can also preferably receive flow values ​​from a flow sensor of the extracorporeal circulatory support system, which is also located upstream of an arterial cannula and downstream of an oxygenator of the extracorporeal circulatory support system.

[0052] The interface is preferably also configured to receive the patient's ECG signals as cardiac measurements. This allows for the simple and unambiguous determination of measurements characteristic of cardiac activity. For example, an R wave from a QRS complex and the time of diastole onset can be determined from the ECG to control the heart pump.

[0053] The device can further be configured to perform the preferred process steps described above.

[0054] Furthermore, a circulatory support device is proposed which comprises the device according to the invention described above.

[0055] In addition to the interface and evaluation unit, the circulatory support device can also include an ECG device that is communicatively connected to the interface. This allows the circulatory support device to be used completely independently, in particular without the need for additional components. The ECG device can also be attached to the device, enabling a compact arrangement. Preferably, the ECG device is implemented, for example, in a sensor box in the form of an ECG card or an ECG module.

[0056] One or more components of the circulatory support device can be integrated into a single housing. This housing can, for example, take the form of a console with a user interface for entering and reading system settings, particularly parameters of the blood pump and / or the trigger signal being provided or already provided. Such a user interface can also display an optical or visual component of the output signal. For instance, the console can include a touchscreen and / or a display with a keypad for user operation. Short description of the characters

[0057] Preferred further embodiments of the invention are explained in more detail by the following description of the figures. They show: Fig. 1 A schematic representation of a laboratory model of a cardiovascular system with cardiac cycle-synchronized extracorporeal circulatory support; Fig. 2 a schematic representation of measured arterial pressure values ​​in the cardiovascular system without cardiac cycle-synchronized extracorporeal circulatory support; Fig. 3 a schematic representation of measured arterial pressure values ​​in the cardiovascular system and flow values ​​in extracorporeal circulatory support during cardiac cycle-synchronized extracorporeal circulatory support; Fig. 4 a schematic representation of measured arterial pressure and flow values ​​in extracorporeal circulatory support during cardiac cycle-synchronized extracorporeal circulatory support in the case of a diastolic pressure effect; Fig. 5 a schematic representation of measured arterial pressure and flow values ​​such as Fig. 4 in the case of an incipient diastolic pressure effect; and Fig. 6. A schematic representation of measured arterial pressure and flow values ​​such as Fig. 5 in the case of an alternative incipient diastolic pressure effect. Detailed description of preferred embodiments

[0058] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the different figures are designated with identical reference numerals. Repeated descriptions of these elements are sometimes omitted to avoid repetition.

[0059] According to Fig. Figure 1 schematically shows a laboratory model of a cardiovascular system 10 with a cardiac cycle-synchronized extracorporeal circulatory support 12. The cardiovascular system 10 simulates a patient's circulatory system and accordingly includes a pulsatile blood pump 14, which provides arterial blood flow, as indicated by the arrows. The arterial blood flow is directed to a limiting valve 16 and then enters a venous system. The pumped blood is subsequently collected in a reservoir 20 via a check valve 18 and returned to the blood pump 14 via the venous system.

[0060] The present simplified cardiovascular model was established for the present invention to compare characteristics of the extracorporeal circulatory support 12 with the simulated conditions in the cardiovascular system 10, in particular with the arterial pressure of the cardiovascular system, which was detected by means of an arterial pressure sensor 22. The arterial pressure sensor 22, which detects a simulated aortic pressure immediately after the heart or blood pump 14, is shown with a dashed line. It was used for the invention only as a reference value and was not included to determine whether a diastolic pressure effect was actually achieved by the extracorporeal circulatory support 12.

[0061] The extracorporeal circulatory support 12 comprises a venous cannula 24, which is fluidically connected to the venous system of the cardiovascular system 10 and directs a portion of the venous blood into the extracorporeal circulatory support 12. The venous blood is then pumped via the venous cannula 24 into the extracorporeal circuit by means of a pulsatile blood pump 26 of the extracorporeal circulatory support and directed to an oxygenator 28, which is, for example, membrane-based. From the oxygenator 28, the pulsatile blood flow is directed to an arterial cannula 30, which is fluidically connected to the arterial system of the cardiovascular system 10 and provides a retrograde blood flow within the arterial system of the cardiovascular system 10. The cannula tip of the arterial cannula 30 is preferably located in the simulated aortic region of the cardiovascular system 10, preferably directly below the arterial pressure sensor 22 of the cardiovascular system 10.By positioning and orienting the cannula tip in a counterflow direction, an increased pulsatile blood flow in the coronary arteries can be achieved. This ensures improved blood flow to the heart muscle tissue without impairing the systemic cardiovascular system.

[0062] To prevent an undesirable increase in afterload, the delivery of the support pulse provided by the extracorporeal circulatory support 12 is synchronized with the simulated heartbeat of the patient. The support pulse can be administered at a predetermined time, particularly during the diastolic phase of the cardiac cycle. In the present laboratory model, such synchronization can be achieved by controlling the blood pump 14. For example, when actually supporting a patient, this control can be triggered by a detected R-wave in the ECG signal with a manually entered, predetermined delay time. For the sake of simplicity, a corresponding interface, an evaluation unit, and an ECG device are included in the Fig. 1 not shown.

[0063] Furthermore, the extracorporeal circulatory support system 12 includes a pressure sensor 32, which is positioned between the oxygenator 28 and the arterial cannula 30. This allows the behavior or progression of the pressure values ​​of the pulsatile blood flow in the extracorporeal circuit to be recorded and, for example, compared with the pressure values ​​in the arterial system of the cardiovascular system 10. In addition, a flow sensor 34 is provided in this example, which is also positioned between the oxygenator 28 and the arterial cannula 30. It allows, for example, the determination of a ratio between the pressure value recorded by the pressure sensor 32 and the flow value recorded by the flow sensor 34.

[0064] In Fig. 2 is a curve of the arterial pressure value 36, which is taken from the pressure sensor 22 from the cardiovascular system 10 according to Fig. The cardiac cycle was recorded and is shown. In this example, the cardiovascular system 10 was operated without cardiac cycle-synchronized extracorporeal circulatory support 12. A characteristic, simulated cardiac cycle profile is shown, with a pressure increase simulating the systolic phase and a corresponding pressure decrease simulating the diastolic phase. The depicted cardiac cycle profile was provided at a simulated heart rate of 90 BPM, resulting in a cardiac cycle duration of approximately 660 ms. The pump volume was set to 2.4 L / min. In the laboratory model, a minimum pulsatile pressure of approximately 40 mmHg and a maximum pulsatile pressure of approximately 120 mmHg were achieved.

[0065] In Fig. In step 3, the blood pump 14 was also operated at a simulated heart rate of 90 BPM and a pump volume of 2.4 L / min. In this example, however, the cardiovascular system 10 was supported by the cardiac cycle-synchronized extracorporeal circulatory support 12, which provided a (retrograde) pulsatile blood flow 38. The blood pump 26 of the circulatory support 12 was operated with a pump volume of 3 L / min. It can be seen that the arterial pressure 36 in the arterial system of the cardiovascular system 10, which was detected by the pressure sensor 22, is increased in the diastolic phase, while the minimum and maximum pulsatile pressure values ​​were not significantly changed.

[0066] Furthermore, the Fig. Figure 3 clearly shows that the pulsatile blood flow 38 provided by the extracorporeal circulatory support 12 is increased during the diastolic phase. Accordingly, this allows for an optimized blood and oxygen supply to the coronary arteries.

[0067] The results presented here were obtained using a 17Fr-140 mm arterial cannula. However, depending on the therapeutic application, an alternative, suitable cannula can be used, preferably between 15Fr-90 mm and 21Fr-380 mm.

[0068] An evaluation of the pressure values ​​recorded by pressure sensor 32 in the extracorporeal circuit is in Fig. Figure 4 illustrates this. It can also be seen here that the pressure and flow rate in the extracorporeal circuit increase predominantly during the diastolic phase, as can be seen, for example, from a comparison with the course of the arterial pressure value 36. The pressure value within the extracorporeal circuit is significantly higher than the arterial pressure value 36, which is measured in the cardiac circulation 10.

[0069] As explained above, it was discovered according to the invention that, in the presence of a diastolic pressure effect, after a first minimum pressure value 40, a notch in the increasing pressure can be detected, which is characterized by a reduced pressure change rate 42. The reduced pressure change rate 42, which is preferably positive, occurs as described in Fig. Figure 4 shows the pressure change rate immediately following a larger, preceding pressure change. The pressure change rate after the indentation is also larger. It was found that this property, which manifests as an indentation in the pressure curve, only occurs in the presence of a diastolic pressure effect.

[0070] Furthermore, such a reduced pressure change rate 42 occurs in the present Fig. 4 before reaching a maximum pressure value 44. A first pressure integral value between a first time point for the first minimum pressure value and a second time point for the reduced pressure change rate 42 is still less than a second pressure integral value between the second time point and a time point for a subsequent second minimum pressure value 46.

[0071] From the pressure profile of the extracorporeal circulation, further criteria or characteristics can be determined – in addition to the reduced pressure change rate – which allow for a more precise determination of a reduced pressure change rate and / or improved proof of the presence of a diastolic pressure effect.

[0072] Additionally, the flow rate of the flow sensor 34 can be taken into account when determining the reduced pressure change rate 42 or when outputting a signal. In the present example, a pump volume of 2 L / min was set for the blood pump 26 at a speed of 3500 RPM. An amplitude 48 of the blood flow 38, i.e., the difference between the maximum blood flow value and the minimum blood flow value, as indicated by the arrows. - and marked by the dashed line, was within the intended range between 1.4 L / min and 2.8 L / min.

[0073] Examples of pump settings where no existing diastolic pressure effect, but rather an incipient diastolic pressure effect, could be determined are found in the Fig. 5 and Fig. Figure 6 shows that in these examples, the blood pump 14 of the cardiac circulation 10 was also operated at a simulated heart rate of 90 BPM and a pump volume of 2.4 L / min. However, the blood pump 26 of the extracorporeal circulatory support 12 was operated differently than in the example shown in Figure 6. Fig. 4, set with a flow rate of 1 L / min.

[0074] Neither in Fig. 5 still in Fig. Figure 6 shows the characteristic indentation in the rising pressure signal, which would be indicative of a reduced pressure change rate 42. Instead, the pressure curve is saddle-shaped, so that the graphical representation essentially forms a double hump. According to Fig. 5. A local pressure maximum is located upstream of the maximum pressure value 44. The pressure value before reaching the maximum (diastolic) pressure value is reduced. Accordingly, there is a negative pressure change rate 50, which is less than zero. According to Fig. 6 is such a local pressure maximum downstream. After the maximum pressure value 44, a negative pressure change rate initially occurs, followed by a positive pressure change rate 52. In both cases, such a saddle shape, which can be identified based on the aforementioned characteristics, indicates an incipient diastolic pressure effect.

[0075] An emerging diastolic pressure effect can still be verified using the blood flow amplitude 48 explained above. In the examples according to the Fig. 5 and Fig. The amplitude 48 was in the range between 0.9 L / min and 1.6 L / min, which is characteristic of the initial pressure effect. Therefore, the initial pressure effect can be confirmed based on the amplitude 48.

[0076] Accordingly, this can be done according to the Fig. 5 and Fig. The signal to be output indicates an initiating pressure effect. This signal can, for example, be a visual check signal prompting an operator to check and, if necessary, adjust the extracorporeal circulatory support. In this case, the signal can, for instance, indicate an increase in rotational speed if it falls below 3500 RPM, for example, in the range between 2500 RPM and 3200 RPM. In this way, both the blood flow value (38) and the pressure value can be adjusted.

[0077] Additionally or alternatively, an adjustment of the delay time can also be suggested based on the signal. Furthermore, an adjustment of the rotational speed and / or delay time can also be initiated based on a control signal included in the signal, preferably based on user input or confirmation from an operator of the extracorporeal circulatory support 12.

[0078] The absence of a diastolic pressure effect or a developing pressure effect may also depend on which arterial cannula 30 was used. For example, in the present, non-restrictive examples, a 17Fr-200 mm arterial cannula 30 was used for the laboratory model according to Fig. 4 used. In the laboratory models according to the Fig. 5 and Fig.In 6, a 19Fr-380 mm arterial cannula 30 or a 21Fr-380 mm arterial cannula 30 were used. If an adjustment of the rotational speed and / or the delay time based on the signal, for example iteratively, does not lead to the desired diastolic pressure effect, or if such an adjustment would lead to exceeding a tolerance value for the maximum pressure, the signal can accordingly also include a recommendation regarding which arterial cannula 30 should be used.

[0079] Where applicable, all individual features shown in the exemplary embodiments can be combined and / or exchanged without leaving the scope of the invention. Reference symbol list 10 Cardiovascular system 12 Extracorporeal circulatory support 14 Blood pump 16 Limiting valve 18 Check valve 20 Reservoir 22 Pressure sensor 24 Venous cannula 26 Blood pump 28 Oxygenator 30 Arterial cannula 32 Pressure sensor 34 Flow sensor 36 Arterial pressure 38 Blood flow 40 First minimum pressure value 42 Reduced pressure change rate 44 Maximum pressure value 46 Second minimum pressure value 48 Amplitude 50 Negative pressure change rate 52 Positive pressure change rate

Claims

[1] A method for monitoring cardiac cycle-synchronized extracorporeal circulatory support (12) of a patient, comprising the steps of: - Receiving pressure values ​​indicative of the aortic pressure of the assisted patient; - determining a first minimum pressure value (40) of a cardiac cycle of the patient from the pressure values ​​and a first time point for the minimum pressure value (40); - determining, from the pressure values, whether at a subsequent second time point there is a reduced pressure change rate (42) between an immediately preceding and a subsequent larger pressure change rate; and - Outputting a signal as a function of an existing reduced pressure change rate (42), wherein the pressure values ​​are received by a pressure sensor (32) which is arranged upstream of an arterial cannula (30) and downstream of an oxygenator (38) of the extracorporeal circulatory support (12). [2] The method of claim 1, wherein the pressure values ​​are received in real time for a current cardiac cycle of the assisted patient and the signal is output for the current cardiac cycle. [3] Method according to claim 1 or 2, wherein the signal is output depending on whether the second time point is within a predetermined time interval between 10 percent and 50 percent of the cardiac cycle duration after the first time point. [4] Method according to one of the preceding claims, wherein the signal is output depending on whether the reduced pressure change rate (42) is present for a predetermined time interval between 1 percent and 10 percent of the cardiac cycle duration. [5] Method according to one of the preceding claims, wherein the signal is output depending on whether the reduced pressure change rate (42) is positive and / or the pressure value at the second time is increased by between 20 percent and 300 percent of the first minimum pressure value (40). [6] Method according to one of the preceding claims, wherein a maximum pressure (44) is determined from the pressure values ​​following the first time at a third time, wherein the signal is output depending on whether the second time is between the first time and the third time. [7] Method according to one of the preceding claims, wherein a second minimum pressure value (46) is determined following the first time at a fourth time, wherein a first pressure integral value is calculated between the first time and the second time and a second pressure integral value is calculated between the second time and the fourth time, and wherein the signal is output depending on whether the first pressure integral value is greater or less than the second pressure integral value. [8] Method according to one of the preceding claims, wherein a maximum pressure (44) is determined from the pressure values ​​following the first time at a third time, wherein the signal is output depending on whether a pressure change rate less than (50) or equal to zero is present before the maximum pressure value (44). [9] Method according to one of claims 1 to 7, wherein following the first time point at a third time point, a maximum pressure (44) is determined from the pressure values, wherein the signal is output as a function of whether a pressure change rate greater than (52) or equal to zero is present after the maximum pressure value (44). [10] Method according to one of the preceding claims, wherein for the respective cardiac cycle, flow measurements are further received from a flow sensor (34) arranged between the oxygenator (28) and the arterial cannula (30) and an amplitude value (48) is calculated from a maximum flow value and a minimum flow value, wherein the signal is further output as a function of the amplitude value (48). [11] Method according to claim 10, wherein the signal is indicative of the presence of a diastolic pressure effect at a present reduced pressure change rate (42) and an amplitude (48) between 1.6 L / min and 3.1 L / min, preferably between 1.8 L / min and 2.8 L / min for the respective cardiac cycle. [12] Method according to claim 10 or 11, wherein the signal is indicative of an onset diastolic pressure effect in the absence of a reduced pressure change rate (42) and an amplitude (48) between 0.5 L / min and 2.0 L / min, preferably between 0.7 L / min and 1.6 L / min for the respective cardiac cycle. [13] Method according to one of claims 10 to 12, wherein the signal is indicative of a non-existent diastolic pressure effect in the case of a non-existent reduced pressure change rate (42) and an amplitude (48) of less than 1.1 L / min, preferably less than 0.9 L / min for the respective cardiac cycle. [14] Method according to one of the preceding claims, wherein for the respective cardiac cycle, a speed value of a blood pump (26) of the extracorporeal circulatory support (12) is further received, wherein the signal is indicative of the presence of a diastolic pressure effect in the case of a present reduced pressure change rate (42) and a speed value greater than 3200 rpm, preferably greater than 3400 rpm. [15] Method according to one of the preceding claims, wherein for the respective cardiac cycle a speed value of a blood pump (26) of the extracorporeal circulatory support (12) is further received, wherein the signal is indicative of an onset of diastolic pressure effect in the absence of a reduced pressure change rate (42) and a speed value of less than 3400 rpm, preferably between 2500 rpm and 3200 rpm. [16] Method according to one of the preceding claims, wherein the signal comprises a control and / or regulating signal and the speed of a blood pump (26) of the extracorporeal circulatory support (12) is set or adjusted depending on the signal and a user input. [17] Method according to one of the preceding claims, wherein the signal comprises a control and / or regulating signal and a delay time of a trigger signal of the extracorporeal circulatory support (12) is set or adjusted depending on the signal and a user input. [18] Method according to claim 16 or 17, wherein the control and / or regulating signal is output as a function of a comparison of a maximum pressure value (44) determined for the respective cardiac cycle with a predetermined threshold value. [19] A computer program product comprising instructions which, when the program is executed by a processor, cause the processor to carry out the method according to any one of the preceding claims. [20] Device for monitoring a cardiac cycle-synchronized extracorporeal circulatory support (12) of a patient, comprising an interface for receiving pressure values ​​indicative of the aortic pressure of the assisted patient, and an evaluation unit which is configured to determine a first minimum pressure value (40) of a cardiac cycle of the patient and a first time for the first minimum pressure value (40) from the pressure values ​​and is configured to determine a reduced pressure change rate (42) between an immediately preceding and a subsequent greater pressure change rate at a subsequent second time from the pressure values, wherein the device is configured to output a signal as a function of a specific reduced pressure change rate (42) and wherein the pressure values ​​are from a pressure sensor (32) which is arranged upstream of an arterial cannula (30) and downstream of an oxygenator (28) of the extracorporeal circulatory support (12). [21] Apparatus according to claim 20, which is arranged to carry out the method according to any one of claims 1 to 18. [22] A circulatory support device comprising a device according to any one of claims 20 or 21.

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