Monitoring the effectiveness of a support pulse of an extracorporeal circulatory support

Abstract

The invention relates to a method for monitoring a cardiac cycle-synchronized extracorporeal circulatory support and to corresponding devices and circulatory support devices, in particular for optimizing a provided support pulse. According to the invention, a method is provided for monitoring a cardiac cycle-synchronized extracorporeal circulatory support (12) for a patient, having the steps of: receiving pressure values which characterize 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 point in time for the minimum pressure value (40); determining, from the pressure values, whether a reduced pressure change rate (42) exists between an immediately preceding and a successive greater pressure change rate at a subsequent second point in time; and outputting a signal on the basis of an existing reduced pressure change rate (42). In the process, the pressure values are received from 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

[0001] Monitoring the effectiveness of a support pulse of extracorporeal circulatory support

[0002] Technical area

[0003] 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.

[0004] State of the art

[0005] If the heart's pumping capacity or pumping function fails, cardiogenic shock can occur. A reduction in cardiac output or 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 deficiency in the tissues and organs, accompanied by a lack of oxygen, also known as hypoxia, resulting in potential end-organ damage.

[0006] 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 organs, including the coronary arteries, and prevent a hypoxic state. For example, extracorporeal circulatory support systems are known. These systems withdraw blood from, for example, the right atrium or vena cava through a cannula inserted into the femoral vein and return it to the patient via a membrane ventilator through a perfusion cannula inserted into the femoral artery. The membrane ventilator depletes CO2 and oxygenates the blood. Such systems are also known as "extracorporeal membrane oxygenation" (ECMO).

[0007] To largely prevent retrograde blood flow during the systolic phase of the heart, which runs counter to the heart's actual 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 controlled, for example, based on 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 predefined time, particularly during the diastolic phase of the cardiac cycle.

[0008] According to the invention, it was recognized that provided circulatory support does not necessarily lead to a desired increase in diastolic pressure in the aorta, and a corresponding diastolic pressure effect may not be present despite an output support pulse. For example, despite a properly adjusted delay time of a trigger signal for a support pulse, such a pressure effect may not occur, so that blood flow to the coronary vessels of the heart cannot be sufficiently improved.

[0009] It was also recognized that the prior art does not provide evidence of such a diastolic pressure effect. Without such evidence, optimization of the speed of the blood pump for extracorporeal circulatory support and / or adjustment of the set delay time cannot be performed efficiently. Accordingly, a predefined speed is typically used, and a delay time, for example, is manually selected based solely on a received ECG signal.

[0010] To provide evidence of aortic pressure, a pressure sensor can be inserted into the patient's aortic arch, allowing pressure measurements to be recorded in the immediate vicinity of the coronary arteries and the delivered support pulse. However, this requires an arterial pressure sensor to be inserted into the patient during therapy and placed at the level of the aortic arch using an additional invasive procedure, such as a catheter. Such an invasive procedure can not only be complex but also pose a risk to the patient.

[0011] Based on the known prior art, it is therefore an object of the present invention to further improve the circulatory support to be provided and, in particular, to enable detection of a diastolic pressure effect and, if necessary, to optimize it.

[0012] The problem is solved by the subject matter of the independent claims. Advantageous further developments emerge from the subclaims, the description, and the figures. Accordingly, a method for monitoring cardiac cycle-synchronized extracorporeal circulatory support of a patient is proposed, comprising the steps:

[0013] Receiving pressure values ​​indicative of the aortic pressure of the assisted patient;

[0014] 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;

[0015] Determining 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

[0016] Outputting a signal as a function of an existing reduced pressure change rate, wherein the pressure values ​​are received from a pressure sensor which is arranged upstream of an arterial cannula and downstream of an oxygenator of the extracorporeal circulatory support.

[0017] The inventors have determined that a temporarily reduced pressure change rate in an otherwise increasing pressure indicates that a diastolic pressure effect is actually present in the patient's aorta. Such a reduced pressure change rate, which is expressed as a notch in a 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 developed. Accordingly, the characteristic signal curve can be used to determine whether such a diastolic pressure effect is present or not.

[0018] In this way, the invention makes it possible to monitor cardiac cycle-synchronized circulatory support, in particular determining the effect of the delivered support pulse. If a reduced pressure change rate was determined after the first time point, the output signal can indicate, for example, that the desired diastolic pressure effect is present and 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, for example, an adjustment of the extracorporeal circulatory support is necessary or desired.

[0019] Both the immediately preceding pressure change rate between the first time point and the second time point, as well as the subsequent pressure change rate after the second time point or after the temporarily reduced pressure change rate, exhibit a positive value with a greater gradient, so that the reduced pressure change rate occurs in a cardiac cycle phase with increasing pressure. Accordingly, the reduced pressure change rate can be clearly recorded in a graphic representation in the form of a notch.

[0020] Consequently, based on a signature formed by the pressure curve, it can be determined in a clear and simple manner whether a diastolic pressure effect is present and whether a corresponding increase in pressure in the aortic arch with a concomitant improvement in the blood flow to the coronary vessels occurs in the diastolic phase.

[0021] This detection is still non-invasive. The pressure sensor that records the pressure values ​​is located in the extracorporeal circuit. However, the pressure values, and in particular the reduced rate of pressure change, are characteristic of the patient's aortic pressure. This completely eliminates the need for additional invasive pressure sensors, which could be provided, for example, using a pressure measurement catheter. This not only significantly reduces the risk of harm to the patient, but also keeps monitoring costs low. Only one pressure sensor needs to be provided in the extracorporeal circulatory support system, and only its measurements need to be evaluated. An additional arterial pressure sensor and corresponding catheter are therefore not required to monitor the pressure effect.

[0022] The invention can thus 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 this is not already present in the extracorporeal circulatory support device, only one 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.

[0023] Consequently, the inventive demonstration of the effectiveness of extracorporeal circulatory support eliminates the need for a complex approval process. For example, the method does not require any adjustments to disposable devices such as a tubing set or a pressure measurement catheter for measuring a pressure that is representative of the patient's aortic pressure.

[0024] To enable immediate monitoring of the efficacy of the provided circulatory support, the pressure values ​​are preferably received in real time for the current cardiac cycle of the supported patient. The signal is preferably output for the current cardiac cycle.

[0025] This allows for real-time monitoring, with no averaging required for the pressure profile signature. Monitoring and potential adjustment of extracorporeal circulatory support can thus be synchronized with the therapy. Virtually immediate feedback can be provided to the operator of extracorporeal circulatory support regarding the effectiveness of the currently set or adjusted parameters. The signal can also be output in real time, for example, in the form of a visual and / or acoustic signal, indicating the presence of a reduced pressure change rate in the current cardiac cycle.

[0026] To prevent any pressure fluctuations and / or measurement fluctuations from being inadvertently determined 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. In this way, a time window can be specified within which the pressure effect is expected. The time window can be based, for example, on evaluated historical data and / or settings of the extracorporeal circulatory support device, in particular its blood pump.

[0027] Accordingly, it can also be provided that the signal is output depending on whether the reduced pressure change rate is present for a specified time interval between 1 percent and 10 percent of the cardiac cycle. Any short measurement fluctuations or longer pressure changes that do not correspond to a normal pressure effect can thus be masked out when determining any reduced pressure change rate that may be present.

[0028] For example, the method according to the invention can provide for a reduced pressure change rate to be determined only if it occurs in a time interval between 60 ms and 300 ms, preferably between 100 ms and 200 ms, after the first time point, or for the determination to be performed only in this time interval. It can also be provided that only reduced pressure change rates between, for example, 5 ms and 50 ms, preferably between 10 ms and 30 ms, are taken into account. Accordingly, the risk of erroneous detections can be reduced and the accuracy of the monitoring can be further improved.

[0029] Based on the first minimum pressure value, an expected maximum pressure value can also be provided, which can also be specified, for example, 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 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 between 30 percent and 150 percent of the first minimum pressure value.

[0030] In the case of a positive pressure change rate, i.e., a flattening pressure change rate that is greater than or equal to zero, it can be assumed that a reduced pressure change rate is determined at a second time point, which corresponds to a rising pressure. It can therefore be assumed with increased probability that a reduced pressure change rate was determined before a maximum diastolic pressure and that this corresponds to an actual diastolic pressure effect.

[0031] Likewise, an absolute pressure value at the second time point can specify the pressure range within which a reduced pressure change rate is to be expected based on a reference range. 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 to be expected only with increasing pressure, and this range typically does not exhibit a reduced pressure change rate after reaching a maximum diastolic pressure. For example, the determined first minimum pressure value can be approximately 40 mmHg, so that the reduced pressure change rate is preferably between 56 mmHg and 100 mmHg.By using a reference range for the reduced pressure change rate in combination with the requirement of a positive reduced pressure change rate, an even more precise definition of the reduced pressure change rate and accordingly an even more precise monitoring of the diastolic pressure effect can advantageously be achieved.

[0032] 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 time point and the third time point. This correctly prevents a reduced pressure change rate from being 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 visible directly after a notch corresponding to the reduced pressure change rate.Accordingly, the accuracy that a certain reduced pressure change rate is actually indicative of an existing diastolic pressure effect can be further increased by defining that the reduced pressure change rate should be determined before the maximum diastolic pressure.

[0033] Following the first time, a second minimum pressure value can be determined at a fourth time. A first pressure integral value can be calculated between the first time and the second time, and a second pressure integral value can be calculated between the second time and the fourth time. The signal can preferably be output depending on whether the first pressure integral value is greater or less than the second pressure integral value.

[0034] 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 value is greater than the first pressure integral value. 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 value is therefore lower.

[0035] Using one or more of the aforementioned preferred criteria, the reduced pressure change rate and the signature of the pressure curve can be defined more precisely. This increases the probability that the pressure change rate indicates an actual diastolic pressure effect, advantageously providing even more precise monitoring and / or optimization of the patient's extracorporeal circulatory support. Likewise, any physiological or technical measurement fluctuations detected by the pressure sensor can be largely masked or ignored.

[0036] However, it may also be the case that a diastolic pressure effect does not occur or is insufficient, and / or cannot be determined based on a reduced pressure change rate. In such a case, the pressure curve may deviate from the desired pressure curve and, for example, be saddle-shaped or have a double-cushioned shape. Such a pressure curve may indicate, in particular, that a pressure effect is beginning to develop but is not yet fully developed.

[0037] Accordingly, it can be provided that a maximum pressure is determined from the pressure values ​​at a third time following the first time, wherein the signal is output depending on whether a pressure change rate less than or equal to zero exists before the maximum pressure value. For example, a local pressure maximum can precede the maximum pressure value. The pressure value can flatten out or be reduced at least temporarily before the maximum (diastolic) pressure value is reached. Because an existing reduced pressure change rate is to be expected preferably with an otherwise increasing pressure, a reduced pressure change rate, which characterizes an occurring diastolic pressure effect, cannot be assumed with such a pressure change rate in the range less than or equal to zero.Rather, in such a case, it can be assumed that the pressure is saddle-shaped or double-humped, so the signal can indicate an onset of pressure. For example, the signal can be output as a visual check signal, prompting an operator to check the extracorporeal circulatory support and adjust it if necessary.

[0038] Alternatively, it can also 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 a pressure change rate greater than or equal to zero exists after the maximum pressure value. As explained above, if a diastolic pressure effect is present, it can be assumed that this is determined before a maximum pressure value. In this case, a pressure change rate following the maximum pressure value cannot be assumed to be a reduced pressure change rate, which characterizes an existing diastolic pressure effect.

[0039] For example, with a pressure change rate greater than zero, a local pressure maximum may be present that is downstream of the maximum pressure value and has a lower height. The pressure value is thus initially reduced before reaching this local pressure maximum and then increased. In other words, in such a case, it can also be assumed that the pressure is saddle-shaped or double-humped. The pressure is reduced in an arc after the maximum pressure value and, after a turning point, increased with a positive pressure change rate. Such a signal can also indicate an incipient pressure effect.

[0040] However, if neither a reduced pressure change rate, which is characteristic of an existing diastolic pressure effect, nor an onset pressure effect and thus no pressure effect for the respective cardiac cycle is determined, the signal can be output accordingly as a (e.g. optical) warning signal.

[0041] In order to enable an even more precise determination of an existing diastolic pressure effect and / or an even more specific signal to be output, it can further be provided that flow measurements are received for the respective cardiac cycle from a flow sensor arranged between the oxygenator and the arterial cannula. An amplitude value can be calculated from a maximum flow value and a minimum flow value. The signal can furthermore be output as a function of the amplitude value. Thus, with a present 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 indicative of the presence of a diastolic pressure effect for the respective cardiac cycle. In other words, based on the amplitude, a further factor can be taken into account which confirms or contradicts an already determined diastolic pressure effect.This advantageously increases the validity of the signal. The output signal can therefore be a confirmation of the presence of a diastolic pressure effect, preferably in visual form.

[0042] Conversely, if there is no reduced pressure change rate and 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, the signal may be indicative of an incipient 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 may still be indicative of a non-existent diastolic pressure effect even if there is no reduced pressure change rate.

[0043] The flow value and the resulting amplitude can thus further confirm or more precisely specify the operating status of extracorporeal circulatory support. The corresponding signal can indicate either optimized circulatory support, incipient or established circulatory support, or inefficient circulatory support.

[0044] Furthermore, a speed value of a blood pump providing extracorporeal circulatory support can be received for the respective cardiac cycle. The signal can preferably be indicative of the presence of a diastolic pressure effect if a reduced pressure change rate is present and a speed value greater than 3200 rpm, preferably greater than 3400 rpm. However, if a reduced pressure change rate cannot be determined or is not present and the speed value is below 3400 rpm, preferably between 2500 rpm and 3200 rpm, the signal is preferably indicative of an onset of a diastolic pressure effect.

[0045] The speed value can therefore be a further indicator of whether extracorporeal circulatory support is already operating within the optimized range or whether the speed can or should be increased to achieve the diastolic pressure effect. Because the speed is linked to both the flow value and the pressure value of the extracorporeal circulatory support, a corresponding increase in the speed may be patient-specific or generally limited.

[0046] The signal preferably comprises a control and / or regulating signal, wherein the speed of a blood pump for extracorporeal circulatory support can be set or adjusted depending on the signal and a user input. As explained above, in particular when a diastolic pressure effect is starting and / or when a current speed value is between 2500 rpm and 3200 rpm, a speed increase can be carried out, preferably iteratively, in order to increase the corresponding flow value and the diastolic pressure and achieve the diastolic pressure effect. If a reduced pressure change rate was determined for a respective cardiac cycle, the speed value can be set and remain unchanged based on the output control and / or regulating signal. Optionally, however, it can be provided that a speed is increased even in the case of a certain reduced pressure change rate, for example if this is below 3400 rpm.

[0047] The user input also serves to ensure that the setting or adjustment of the speed occurs only when there is a corresponding reason. For example, this can be done based on user confirmation that circulatory support should be optimized based on the speed. Such a user input also serves to acknowledge any deviation from the set value. In this way, a (semi-)automatic optimization of extracorporeal circulatory support can be achieved.

[0048] Alternatively or additionally, a delay time of a trigger signal of the extracorporeal circulatory support can also be set or adjusted depending on the control and / or regulation signal and on a user input.

[0049] For example, at a heart rate of 90 BPM, a trigger signal delay of 400 ms 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 accordingly iteratively, for example, in steps of 10 ms to 50 ms, so that a support pulse is not only delivered in the diastolic phase, but a diastolic pressure effect is also achieved. As explained above, the delay time is also adjusted based on user input, so that optimization of extracorporeal circulatory support is only performed if confirmed or requested by the user.

[0050] To prevent an adjustment of one or more circulatory support parameters from accidentally endangering the patient, it can further be provided that the control and / or regulation signal is output depending on a comparison of a maximum pressure value determined for the respective cardiac cycle with a predetermined threshold value. Consequently, a comparison of the maximum pressure value with a tolerance threshold can be made, so that the control and / or regulation signal only indicates an increase in speed, for example, if the maximum pressure value does not exceed the threshold value. In this way, for example, blood cell damage and / or heart valve damage can be prevented, thereby correspondingly reducing the risk of patient endangerment.

[0051] According to a further aspect of the invention, a computer program product is also proposed. This includes instructions which, when executed by a processor, cause the processor to execute the method described above. The computer program product can be stored, for example, on a non-volatile storage medium.

[0052] The object underlying the invention is further achieved by a device for monitoring cardiac cycle-synchronized extracorporeal circulatory support of a patient. The device comprises an interface for receiving pressure values ​​that are characteristic of the aortic pressure of the assisted patient, and an evaluation unit that is configured to determine a first minimum pressure value of a cardiac cycle of the patient and a first time 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 greater pressure change rate at a subsequent second time 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 upstream of an arterial cannula and downstream of an oxygenator for extracorporeal circulatory support.

[0053] The device can, for example, control or regulate one or more pump drives or pump heads for (particularly non-occlusive) blood pumps present in an extracorporeal circulatory support system and, if necessary, be fluidically connected to other modules. For example, the blood pump can be fluidically connected to an oxygenator or membrane ventilator provided in the extracorporeal circulatory support system. In this way, the oxygen enrichment and CO2 depletion of the blood can occur. The fluidic connection can, for example, be established with a venous access via a venous cannula and an arterial access via an arterial cannula for aspirating or pumping the blood. This provides blood flow from a side with low pressure to a side with higher pressure.Thus, extracorporeal oxygen enrichment of the blood and improved oxygen supply can be ensured for the patient using the blood pump.

[0054] By activating the motor or pump drive and the rotor blade, and by triggering the pulse at this time, a (pulsatile) blood flow can be delivered via the arterial cannula into the area (directly) downstream of the left ventricle and into the aorta. The positioning and countercurrent orientation of the cannula tip ultimately result in increased pulsatile blood flow in the coronary arteries. This provides a correspondingly improved perfusion of the myocardial tissue without compromising the systemic circulation.

[0055] The monitoring of extracorporeal circulatory support according to the invention makes it possible to determine whether a diastolic pressure effect is actually being achieved through the blood flow. For this purpose, the interface can be communicatively connected to a pressure sensor of the extracorporeal circulatory support, which is arranged upstream of an arterial cannula and downstream of an oxygenator of the extracorporeal circulatory support. 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 using non-invasive pressure sensors (without direct blood contact).

[0056] The interface can, for example, be designed as a sensor box, which can be connected via connectors to various sensors, such as pressure sensors integrated into the tubing system, and an ECG device. Flow values ​​from a flow sensor for extracorporeal circulatory support, which is also arranged upstream of an arterial cannula and downstream of an oxygenator for extracorporeal circulatory support, can also preferably be received via the interface.

[0057] Preferably, the interface is also configured to receive the patient's ECG signals as cardiac measurements. This allows measurements representative of cardiac activity to be determined easily and clearly. For example, an R-wave from a QRS complex and the time of the onset of diastole can be determined from the ECG to control the blood pump.

[0058] The device may further be configured to carry out the preferred method steps described above.

[0059] Furthermore, a circulatory support device is proposed which comprises the device according to the invention described above.

[0060] In addition to the interface and the evaluation unit, the circulatory support device can also have an ECG device which is communicatively connected to the interface. This allows the circulatory support device to be used functionally completely independently, in particular without the need to provide further components. The ECG device can also be attached to the device, thereby enabling a compact arrangement. The ECG device is preferably implemented, for example, in a sensor box in the form of an ECG card or an ECG module. One or more components of the circulatory support device can also be integrated in one (e.g. single) housing. In this case, the device can be implemented, for example, in the form of a console which has a user interface for entering and reading out system settings, in particular parameters of the blood pump and / or the blood to be provided orprovided trigger signal. Such a user interface can also be used to display, in particular, an optical or visual part of the output signal. For example, the console can include a touchscreen and / or a display with a keyboard for user operation.

[0061] Short description of the characters

[0062] Preferred further embodiments of the invention are explained in more detail in the following description of the figures. They show:

[0063] Figure 1 is a schematic representation of a laboratory model of a cardiac circuit with cardiac cycle-synchronized extracorporeal circulatory support;

[0064] Figure 2 shows a schematic representation of measured arterial pressure values ​​in the cardiac circulation without cardiac cycle-synchronized extracorporeal circulatory support;

[0065] Figure 3 shows a schematic representation of measured arterial pressure values ​​in the cardiac circulation and flow values ​​in the extracorporeal circulatory support during cardiac cycle-synchronized extracorporeal circulatory support;

[0066] Figure 4 shows a schematic representation of measured arterial pressure values ​​and flow values ​​in extracorporeal circulatory support during cardiac cycle-synchronized extracorporeal circulatory support in the case of an existing diastolic pressure effect;

[0067] Figure 5 is a schematic representation of measured arterial pressure values ​​and flow values ​​as in Figure 4 in the case of an onset of diastolic pressure effect; and

[0068] Figure 6 is a schematic representation of measured arterial pressure values ​​and flow values ​​as in Figure 5 in the case of an alternative onset diastolic pressure effect.

[0069] Detailed description of preferred embodiments

[0070] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements are provided with identical reference numerals in the different figures. A repeated description of some of these elements is omitted to avoid repetition. Figure 1 shows a schematic of a laboratory model of a cardiac circuit 10 with cardiac cycle-synchronized extracorporeal circulatory support 12. The cardiac circuit 10 simulates a patient's circulation and accordingly comprises a pulsatile blood pump 14, which provides an arterial blood flow, as shown by the arrows. The arterial blood flow is accordingly guided to a limiting valve 16 and then passes into a venous system. The pumped blood is then collected in a reservoir 20 via a check valve 18 and further returned to the blood pump 14 via the venous system.

[0071] The present simplified cardiovascular model was established for the present invention to compare characteristics from 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 measured by an arterial pressure sensor 22. The arterial pressure sensor 22, which measures a simulated aortic pressure immediately after the heart or blood pump 14, is shown in dashed lines. It was used for the invention merely as a reference value and was not included in determining whether a diastolic pressure effect was actually achieved by the extracorporeal circulatory support 12.

[0072] The extracorporeal circulatory support 12 accordingly 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 accordingly pumped via the venous cannula 24 into the extracorporeal circuit by means of a pulsatile blood pump 26 of the extracorporeal circulatory support and is guided to an oxygenator 28, which is, for example, membrane-based. The pulsatile blood flow is guided from the oxygenator 28 to an arterial cannula 30, which is fluidically connected to the arterial system of the cardiovascular system 10 and provides a retrograde blood flow in the arterial system of the cardiovascular system 10. A 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 countercurrently orienting the cannula tip, increased pulsatile blood flow in the coronary arteries can be achieved. This ensures improved perfusion of the myocardial tissue without compromising the systemic cardiovascular system.

[0073] 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, in particular during the diastolic phase of the cardiac cycle. In the present laboratory model, such synchronization can be achieved by controlling the blood pump 14. Corresponding control during actual patient support can, for example, be based on 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 not shown in Figure 1.

[0074] Furthermore, a pressure sensor 32 is provided in the extracorporeal circulatory support 12, which is arranged between the oxygenator 28 and the arterial cannula 30. This makes it possible to record the behavior or the course of the pressure values ​​of the pulsatile blood flow in the extracorporeal circuit and, for example, to compare them with the pressure values ​​in the arterial system of the cardiovascular system 10. Furthermore, in the present example, a flow sensor 34 is provided, which is also arranged between the oxygenator 28 and the arterial cannula 30. It allows, for example, the determination of a relationship between the pressure value detected by the pressure sensor 32 and the flow value detected by the flow sensor 34.

[0075] Figure 2 shows a curve of the arterial pressure value 36, which was recorded by the pressure sensor 22 from the cardiac circuit 10 according to Figure 1. In this example, the cardiac circuit 10 was operated without cardiac cycle-synchronized extracorporeal circulatory support 12. A characteristic, simulated cardiac cycle curve can be seen with a pressure increase, which simulates the systolic cardiac cycle phase, and a corresponding pressure drop, which simulates the diastolic cardiac cycle phase. The cardiac cycle curve shown was provided at a simulated heart rate of 90 BPM, so that the cardiac cycle duration is approximately 660 ms. The pump volume was set to 2.4 L / min. In the laboratory model, a minimum pulsatile pressure value of approximately 40 mmHg and a maximum pulsatile pressure value of approximately 120 mmHg were achieved.

[0076] In Figure 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, with the circulatory support 12 providing 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 value 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 pulsatile pressure value and the maximum pulsatile pressure value were not significantly changed.

[0077] Furthermore, Figure 3 clearly shows that the pulsatile blood flow 38 provided by the extracorporeal circulatory support 12 is increased in the diastolic phase. Accordingly, an optimized blood and oxygen supply to the heart's coronary vessels can be provided in this way.

[0078] The present results were obtained with 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.

[0079] An evaluation of the pressure values ​​recorded by pressure sensor 32 in the extracorporeal circuit is shown in Figure 4. Here, too, it can be seen that the pressure and flow values ​​in the extracorporeal circuit increase primarily 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 measured in the cardiac circuit 10.

[0080] As explained above, it was recognized according to the invention that, when a diastolic pressure effect is present, after a first minimum pressure value 40, a notch in the rising 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 shown in Figure 4, after an immediately preceding, larger pressure change rate. The pressure change rate after the notch is also larger. It was recognized that this characteristic, which is expressed as a notch in the pressure curve, only exists when a diastolic pressure effect is present.

[0081] Furthermore, such a reduced pressure change rate 42 occurs in the present Figure 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 further lower than a second pressure integral value between the second time point and a time point for a subsequent second minimum pressure value 46.

[0082] From the pressure curve of the extracorporeal circuit, further criteria or characteristics can be determined - in addition to the reduced pressure change rate - which enable a more precise determination of a reduced pressure change rate and / or improved detection of the presence of a diastolic pressure effect.

[0083] Additionally, the flow value 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 the dashed line, was within the intended range between 1.4 L / min and 2.8 L / min.

[0084] Examples of pump settings in which no existing diastolic pressure effect, but rather an incipient diastolic pressure effect, could be determined are shown in Figures 5 and 6. In these examples, the blood pump 14 of the cardiovascular system 10 was also operated at a simulated heart rate of 90 BPM and a pump volume of 2.4 L / min. However, unlike in the example shown in Figure 4, the blood pump 26 of the extracorporeal circulatory support system 12 was set to a flow of 1 L / min.

[0085] Neither in Figure 5 nor in Figure 6 can the characteristic notch in the rising pressure signal be seen, which would be indicative of a reduced pressure change rate 42. Instead, the pressure curve is saddle-shaped, so that the graphic curve essentially forms a double hump. According to Figure 5, a local pressure maximum precedes the maximum pressure value 44. The pressure value before the maximum (diastolic) pressure value is reached is reduced. Accordingly, a negative pressure change rate 50, which is less than zero, exists. According to Figure 6, such a local pressure maximum exists downstream. After the maximum pressure value 44, there is initially a negative pressure change rate followed by a positive pressure change rate 52. In both cases, such a saddle shape, which can be determined based on the above characteristics, indicates an onset of a diastolic pressure effect.

[0086] An onset of a diastolic pressure effect can also be verified using the blood flow amplitude 48 explained above. In the examples shown in Figures 5 and 6, the amplitude 48 was in the range between 0.9 L / min and 1.6 L / min, which is characteristic of the onset of a pressure effect. Therefore, the onset of a pressure effect can be confirmed using the amplitude 48.

[0087] Accordingly, the signal output according to Figures 5 and 6 can indicate an onset of pressure. The signal can, for example, be output as a visual check signal, prompting an operator to check the extracorporeal circulatory support and adjust it if necessary. In this case, the signal can, for example, specify an increase in the speed if it is 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.

[0088] Additionally or alternatively, an adjustment of the delay time can also be suggested based on the signal. An adjustment of the speed and / or the delay time can also be initiated based on a control and / or regulation signal included in the signal, preferably based on a user input or confirmation from an operator of the extracorporeal circulatory support system 12.

[0089] The absence of a diastolic pressure effect or an onset of a pressure effect may also depend on which arterial cannula 30 was used. For example, in the present non-limiting examples, a 17Fr-200 mm arterial

[0090] Cannula 30 was used for the laboratory model shown in Figure 4. In the laboratory models shown in Figures 5 and 6, a 19 Fr-380 mm arterial cannula 30 and a 21 Fr-380 mm arterial cannula 30 were used, respectively. Should an iterative adjustment of the speed and / or the delay time based on the signal, for example, not result in the desired diastolic pressure effect, or should such an adjustment result in exceeding a tolerance value for the maximum pressure, the signal may also include a recommendation regarding an arterial cannula 30 to be used.

[0091] Where applicable, all individual features presented in the embodiments may be combined and / or exchanged without departing from the scope of the invention.

[0092] ichenl iste

[0093] 10 Cardiovascular system

[0094] 12 Extracorporeal circulatory support

[0095] 14 Blood pump

[0096] 16 Limit valve

[0097] 18 Check valve

[0098] 20 reservoirs

[0099] 22 Pressure sensor

[0100] 24 Venous cannula

[0101] 26 Blood pump

[0102] 28 Oxygenator

[0103] 30 Arterial cannula

[0104] 32 pressure sensor

[0105] 34 Flow sensor

[0106] 36 Arterial pressure

[0107] 38 Blood flow

[0108] 40 First minimum pressure value

[0109] 42 Reduced pressure change rate

[0110] 44 Maximum pressure value

[0111] 46 Second minimum pressure value

[0112] 48 amplitude

[0113] 50 Negative pressure change rate

[0114] 52 Positive pressure change rate

Claims

Claims 1 . A method for monitoring cardiac cycle-synchronized extracorporeal circulatory support (12) of a patient, comprising the steps: 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 according to 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. The 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 point 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 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 depending on whether the second time point lies between the first time point and the third time point.

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 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 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 in the case of 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 generated at a non-existent 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 is characteristic of an onset diastolic pressure effect.

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. The 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. A device for monitoring cardiac cycle-synchronized extracorporeal circulatory support (12) of a patient, comprising an interface for receiving pressure values ​​that are characteristic of the aortic pressure of the assisted patient, and an evaluation unit that 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 ​​of a pressure sensor (32) are,which is arranged in front of an arterial cannula (30) and after an oxygenator (28) of the extracorporeal circulatory support (12).

21. Device according to claim 20, which is arranged to carry out the method according to 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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