DE202015009422U1 - Implantable heart pump - Google Patents

Abstract

An implantable heart pump (6) with a delivery channel and with a delivery device (6b, 6c, 34) arranged therein for blood, characterized by one on the heart pump, in particular on a wall of the delivery channel, in particular on a pump tube (6a, 105a) the delivery channel at least partially extends, fixed first sensor means (100, 101, 102) for measuring the oxygen saturation of the blood.

Description

This patent is in the field of medical technology and deals in particular with cardiac pumps and support systems for patients with insufficient or defective cardiac function.

Implantable and extra-body pumps for supporting and supplementing cardiac function in the delivery of blood have become widely used and developed in the art. This also includes control systems that, on the one hand, determine the need for support and adjust the degree of support of the patient's heart, with demanding tasks being, for example, determining and setting the actual volume flow through the pump.

Such pumps are often designed as rotor pumps with a rotating conveyor with conveying elements in the form of blades, whereby a radial pump or an axial pump can be formed. In such pumps, the actual volume flow is usually determined from technical operating parameters of the pump, such as the rotational speed of the rotor, the torque or an axial bearing stress of a thrust bearing, using characteristic fields. To control the support system, the consideration of another parameter, namely the oxygen saturation of the pumped blood or the volume flow of oxygen-saturated blood, helpful. Arterially measured (LVAD), this parameter depends on how well the pulmonary system works to absorb oxygen. In the case of z. As a pulmonary edema decreases the arterial saturation. In the case of a RVAD, the mixed / central venous oxygen saturation, measured in the right atrium or ventricle, can also be used to detect physiological stress states.

Measuring devices for determining the oxygen saturation in the blood have long been known from the prior art. Of particular note here is the process of optical pulse oximetry, in which a pulse oximeter in the tissue located blood (for example, in a finger or earlobe) with a light beam in two wavelength ranges. The effect is exploited that oxygenated and non-oxygenated hemoglobin have different absorption spectra. The quotient of two absorption values in the different wavelength ranges is formed and thus the ratio of the distribution density of the oxygenated and the non-oxygenated hemoglobin in the tissue and thus also in the blood is determined.

From the European patent EP 2 570 143 B1 For example, the use of an oxygen sensor in conjunction with an implantable cardiac therapy device is already known.

The present invention is based on the background of the prior art, the task of connecting a device for determining the oxygen saturation of the blood of a patient with a cardiac assist system such that an easy handling with a reliable measurement accuracy and good reproducibility of the measurement is connected.

The object is achieved according to protection claim 1 by an implantable heart pump. The protection claims 2 to 6 denote embodiments of the invention. The claims 7 and 8 relate to a pump device with an implantable heart pump.

Described is thus an implantable heart pump with a delivery channel and with a arranged in this conveyor for blood. The object is achieved by a first sensor device for measuring the oxygen saturation of the blood, which is attached to the heart pump, in particular on a wall of the delivery channel, more particularly on a pump tube in which the delivery channel runs at least partially.

One effect of this is that the oxygen saturation of the blood or, in other words, the proportion of oxygen-saturated hemoglobin molecules in the total number of hemoglobin molecules in the blood is detected directly at the pump. Such pumps are usually in the immediate vicinity of the heart and often suck the blood directly from a heart chamber. In this respect, it can be ensured that the detected oxygen saturation of the blood corresponds to the value in the corresponding heart chamber. In addition, the volume flow can be determined by the pump, so that together with the oxygen content of the total oxygen flow can be accurately determined by the pump. The components of the heart pump, to which the first sensor device can be attached, are also structurally invariable, so that the boundary conditions for oxygen measurement are reproducible. This would not be met with the same reproducibility, for example, in an arrangement of the first sensor device regardless of the heart pump in the patient's body.

Another effect is that the detected, in particular the venous oxygen content of the blood can be used directly for controlling and / or regulating the heart pump. By integrating the sensor device in the Heart pump is no subsequent adjustment or calibration of the measurement necessary, and also the connections to a control unit of the pump can be easily and reliably produced, in particular before implantation.

A further embodiment provides that the first sensor device has at least one, in particular two radiation sources and at least one, in particular two, radiation sensors. The measurement is based, as well as the structure of the sensor, on the known principle of pulse oximetry, which describes the oxygen saturation via the measurement of a light absorption or light reflection or transmission. This is based on the finding that oxygenated and non-oxygenated hemoglobin have different light absorption spectra. Accordingly, by measuring the light absorption in at least two wavelength ranges (typically in the 660 nanometer and 940 nanometer range), it is possible to measure the light transmission of the blood at the first sensor device and to ratio the light intensities by forming quotients relative to each other Determine the proportion of oxygenated hemoglobin molecules in the number of non-oxygenated molecules or total (ie oxygenated and non-oxygenated) hemoglobin molecules. The total density of the hemoglobin molecules in the examined volume does not matter in this context.

The mentioned measurement method has been tested and is sufficiently reliable and accurate in order to be able to measure sufficiently adequately the corresponding typical physiological values in a healthy and diseased patient arterially (LVAD) and venously.

As radiation sources usually semiconductor diodes (infrared / red area) and as a radiation sensor, for example, a phototransistor are used.

A further embodiment can provide that the radiation sensor detects the radiation intensity in at least two different wave ranges independently of one another. In the case mentioned, the system can use two radiation sources in the form of different diodes, but only a single radiation sensor with known sensitivity in the wavelength ranges used. However, it is also conceivable to use different radiation sensors for detecting the radiation of the two radiation sources.

A further embodiment provides that the connection path between the radiation source (s) and the radiation sensor is transverse, in particular perpendicular, to the flow direction of the blood in the delivery channel. With such a construction, the radiation sources and the radiation sensors can be easily located outside the blood flow or at the edge of the blood flow.

An optimized coverage of the entire blood flow and the best possible use of the absorption are achieved according to one embodiment in that the radiation source and the radiation sensor are opposite one another at the circumference of the pump tube.

The implementation can also provide a second sensor device for the bearing voltage of a magnetic thrust bearing of a pump rotor and / or a sensor device for detecting the torque transmitted to the rotor and / or the rotational speed. The torque of the pump rotor, for example, from the pump current, d. H. the current strength of the pump rotor driving electric motor can be determined. In particular, by simultaneous measurement of the bearing voltage and / or the rotational speed and / or the torque, variables such as volume flow and pressure difference across the pump can be determined, which are also closely related to physiological parameters of the patient. Thus, the information obtained about the oxygen saturation can be further processed together with data on the bloodstream to further meaningful data.

If necessary, when calculating a sufficient number of parameters, a calculation of the blood viscosity and thus also of the hematocrit in the blood is possible.

The considerations also relate to a pump device with a pump of the type described above and a control device or an analysis device, which is connected both to the first sensor device and to a third sensor for detecting the rotational speed of a pump rotor.

In addition, it may be provided in such a pump device that the control device is connected to a sensor for the volume flow and / or the detection of the pump current and the rotational speed of a motor driving the pump rotor and / or to a sensor for detecting the bearing voltage of a magnetic thrust bearing bearing the pump rotor is.

If the control device transmits both the measurement data on the oxygen saturation of the blood and on the rotational speed of the pump and the thrust bearing voltage and / or torque of the pump rotor, then in the control device, the volume flow of the blood through the pump, the oxygen content and thus also the oxygen flow be calculated by the pump into the body of the patient, especially if at the aortic valve / pulmonary valve does not open to these patients and thus the pump flow corresponds to the cardiac output. In this case, in a BiVAD configuration both the cardiac output and the venous and arterial saturation can be measured and thus calculated back to the patient's oxygen consumption.

From the oxygen saturation, in particular the venous, various physiological conditions of the patient can be determined, such as the physical stress of the patient. Accordingly, the pump can be controlled according to the exercise load and a target optimized oxygen content.

It can also be provided in a pump device with a pump of the type mentioned above, a sensor for detecting the flow rate through the pump.

In addition, an acceleration sensor in the area of the heart pump can be provided in order to approximate the corresponding oxygen saturation data with a potential physical movement and the associated physiological load of the patient approximately for plausibility.

The present embodiments relate to better understanding except for an implantable heart pump and a pump device of the type described above also to a method for operating an implantable heart pump, wherein the volume flow and oxygen saturation are determined by sensor devices directly to the pump and from the oxygen flow through the pump is determined continuously.

By simultaneously determining the oxygen content of the blood and the volume flow of the pump under the same boundary conditions, the values determined can be linked with high accuracy and reliability and, for example, the oxygen flow through the pump can be determined. The energy supply for the first sensor, which measures the oxygen content of the blood, can be derived directly from the energy supply of the heart pump, for example the power supply of the motor or the other sensors. The cables for the connection of the sensors to a control unit can bundle all the lines of the sensors arranged on the pump with one another, such that all lines are connected to one another and enveloped by a common cable sheath. As a result, interference and interactions of individual lines with the tissue can be minimized.

The method described for a better understanding of the device can be advantageously designed so that the determined oxygen saturation or the determined oxygen flow through the pump is based on the control of the rotational speed or the volume flow through the pump. For example, in the case where a low flow of oxygen is measured by the pump, the delivered volume may be attempted by increasing the speed to provide the body of the patient with as much oxygen as possible.

It can also be provided that an indicator is determined from the oxygen saturation of the blood and / or the degree of support of the patient's heart.

Exemplary embodiments are shown below with reference to figures of a drawing and explained below. It shows

1 1 is a schematic view of a patient's body with the patient's heart and a VAD (ventricular assist device) pump;

2 in a three-dimensional view schematically an axial rotor pump,

3 in a schematic side view of the housing of an axial pump with a rotor, a drive and a magnetic thrust bearing,

4 a typical characteristic field of a pump with characteristics that allow an assignment of a speed and a pressure difference to a volume flow,

5 a diagram according to 4 by which a determination of the pressure difference across the pump will be explained by means of two different methods and the comparison of the results,

6 schematically the structure of a pump, in the pump tube, a pulse oximetry device is integrated, and

7 schematically the structure of a pump device for the application of the method, which is described for a better understanding of the devices according to the invention.

1 shows the upper body of a patient 1 wth the heart 2 of the patient and part of the aorta 3 , On a ventricle 4 of the heart is an inlet nozzle 5 an implanted VAD pump (ventricular assist device) 6 connected to the ventricle 4 in the direction of the arrow 7 Draws blood to the inlet of the pump and this from the outlet of the pump Pump via the outlet cannula 8th directly into the aorta 3 promotes.

Such pumps can substantially support the pumping function of a sick or not fully performing heart. This can be designed as a temporary therapy or as a long-term therapy. Particularly advantageous is the use of axial rotor pumps has been found that by means of a rapidly rotating rotor in the pump housing in the axial direction 7 Promote blood. Such pumps are usually driven by an electric motor drive in the region of the pump housing, which can be fed by a battery or a stationary power supply entrained.

In order to be able to control physiological parameters of the patient as well as the operating state of the pump with sufficient accuracy, it is necessary to determine and track the volume throughput through the pump. For this purpose, fundamentally different methods are known in which, for example, the rotational speed of the rotor and the pressure difference across the rotor are detected. Also by means of the speed of the pump, the determination of the volume flow is possible. Finally, the volumetric flow rate may also be determined taking into account the rotational speed of the pump rotor and the torque acting on the rotor or the rotational speed of the pump rotor and the bearing stress in a thrust bearing of the rotor.

In 2 is schematically an axial pump 6 with one in a housing 6a stored hub 6b shown on the one or more conveying elements 6c , For example, in the form of a rotating helical conveyor blade, are attached. By rotation of the rotor is in the housing 6a the liquid to be pumped or the blood in the direction of the arrow 7 promoted. A hub need not necessarily be provided when the rotor is mounted in a magnetic thrust bearing. In this case, it is only necessary to properly shape, arrange and hold the conveying elements of the rotor.

In 3 is more detailed, but still schematic, the bearing and the drive of the rotor of the pump 6 shown. First, in the area of the hub 6b a first radial bearing shown symbolically and with the reference numeral 10 while a second radial bearing is also shown symbolically and with 11 is designated. The second radial bearing 11 For example, with a magnetic thrust bearing 12 combined, but also be constructed separately from this.

The thrust bearing 12 is designed as a controllable magnetic thrust bearing, wherein a first annular magnet 12a with the hub 6b or, when the rotor is hullless, connected to and rotating with the rotor.

A second annular magnet or an annular array of individual magnets 12b is stationary in the housing 6a the pump 6 arranged and surrounds the hub 6b or part of the rotor. By repulsion of the stationary magnet 12b or the stationary magnet arrangement 12b on the one hand and the rotating magnet 12a on the hub 6b an axial force acting on the rotor is recorded, that of the flow direction 7 the liquid is opposed by the pump as reaction force.

The thrust bearing 12 has a second sensor for detecting the axial position of the magnet mounted on the hub 12a , For example, with eddy current sensors, wherein the information about the axial position to a control device 13 is determined, for example, in the form of a voltage measured by the sensors. This allows the control loop of the magnetic bearing 12 be closed, and the controller 13 can be the axial position of the magnet 12a and thus the rotor or the hub 6b to a constant size. The force that is absorbed by the thrust bearing is determined by the control device 13 applied current or the voltage measured in eddy current sensors determined.

The force absorbed by the thrust bearing can be determined in an unregulated bearing, for example, by measuring the axial deflection of the hub against the magnetic force of the thrust bearing.

In 3 is schematically an electric motor 14 represented, for example, the permanent magnets 14a , which are firmly connected to the rotor, and a stator 14b that with the pump housing 6a is connected, can provide. By appropriate control of stator windings thus a brushless electric motor is realized. The current with which the stator 14b is applied by means of a measuring device 15 measurable, and from this current strength can be determined in a simple manner, the torque generated on the rotor.

3 also shows in the area of the pump housing to a pump inlet nozzle, a first sensor device 100 . 101 . 102 , which is a first radiation source in the form of a diode 100 and a second radiating diode 101 and a phototransistor 102 as a radiation sensor, which can detect radiation of both diodes has. The first diode 100 For example, at a wavelength of 660 Nanometers radiate while the second diode 101 at 940 Nanometers shines. The radiation sources are diametrically on the radiation sensor Circumference of the pump inlet nozzle opposite. At least parts of the pump inlet nozzle are either provided with apertures covered by the sensors and radiation sources, or made of a transparent material. From the absorption coefficients of the blood in the individual wavelength ranges, it is possible to determine the absorption and thus the concentration ratio of the molecules which preferentially absorb the respective wavelength (oxygenated and non-oxygenated hemoglobin molecules in the oxygen saturation measurement).

By the quotient of the concentration values, which results in the oxygen saturation, a normalization takes place at the same time. Nevertheless, a calibration of the sensor device is useful, especially if during the measurement, a transparent part of the pump inlet nozzle or a pump tube is irradiated.

The saturation is given by the equation:

Here, S _p O _{2 is} the oxygen saturation, Hb is the concentration of non-oxygenated hemoglobin and HbO _{2 is} the concentration of oxygenated hemoglobin. The concentrations can be determined by the respective radiation absorption.

Coming back to 2 should be mentioned that there is a hydrostatic pressure sensor 16 at the pump inlet 5 is shown, with a corresponding processing device 17 connected is. Also at the pump outlet, a pressure sensor may be provided. Thus, a pressure difference across the pump can be determined directly. Moreover, in 2 a temperature sensor 18 inside the pump housing 6a shown with a processing device 19 connected is. The temperature sensor 18 can also be arranged outside of the pump in a flow-through by the funded liquid area.

4 shows a diagram in which is plotted on the horizontal axis, the volume flow through the pump in volume per time against the pressure difference across the pump for different speeds of the pump. This results in a characteristic field in which, for example, three characteristics 20 . 21 . 22 are shown for different speeds. The arrow 23 thus indicates the direction of transition between curves of different speeds.

Thus, operating points of the pump (pressure difference between the inlet and outlet of the pump as well as the volume flow delivered by the pump) for different rotational speeds of the pump are represented in the form of the characteristic curves. In each case, the speed and the axial bearing position of the rotor are recorded as a representative variable for the pressure difference across the rotor for characteristic determination. Alternatively, the speed and torque of the pump rotor, measured by the motor current, can be detected. By means of corresponding regression curves, measuring points can be interpolated into characteristic curves. During operation of the pump can thus be determined from the detected operating parameters, in particular from the speed and the axial bearing position of the rotor, for example, the flow rate through the pump in each case in certain areas of the characteristic field.

Since it was recognized that for certain types of pump areas in the characteristic field exist, in which the assignment between the storage position / pressure difference and the flow at a known speed is not clear or at least blurred, for certain areas of the family curve another method can be selected to the flow to determine. Depending on the range of the characteristic field in which the operating point of the pump is located, that is, for example, depending on the rotational speed and / or the pressure difference across the pump, the corresponding determination method can thus be selected. Also during operation of the pump on the basis of the stored characteristic field then depending on the operating parameters, the appropriate selection of operating parameters is used for control.

In 4 is for example between the two dashed lines 24 and 25 formed a subfield of the characteristic field in which the volume flow is not determined from the speed and the pressure difference across the rotor or at least not from these parameters alone. In the field between the lines 24 and 25 For example, the torque of the rotor, determined by the current of the electric drive motor of the rotor, and / or the absolute pressure at the inlet and / or outlet of the pump can be taken into account. These variables can be evaluated alone or in combination with the speed, but it can also be included in the bearing position as an indicator of the pressure difference across the rotor in the determination of the flow rate.

In addition, the fluid temperature can be detected by a sensor, since, especially in blood pumps, the temperature of the blood has a strong influence on the viscosity and thus on the operating conditions or parameters of the pump.

5 shows the use of several measurement methods in a particular, predetermined Area that represents a boundary area / transition area of the characteristic fields and that through the dashed circle 26 should be indicated. This area is in the neighborhood of the dividing line 24 between the two ranges of the characteristic field, which require and enable different measuring methods for determining the volume flow. In a predetermined area around the dividing line 24 around several determination methods for the flow rate and / or the pressure difference across the pump can be reliably used, for example, the flow or the pressure difference across the pump can be determined using different detected operating parameters. By comparing the thus determined values for the volume flow and / or the pressure difference across the pump, the viscosity of the pumped liquid, for example the patient's blood, can be determined. In principle, the viscosity can be determined even without a specific determination of the volume flow and / or the pressure difference across the pump from the detected redundant operating parameters.

6 shows a blood pump 103 with a rotor 104 , one of the pump housing 105 lying stator 106 is driven by an electric motor. The rotor has not shown conveying elements, the blood, in the inflow direction 107 into the pump tube 105a flows in, axially convey. The pump tube 105a is part of the pump housing 105 , In the flow direction in front of the rotor 104 is the first sensor device on the pump tube 100 . 101 . 102 attached to measure the oxygen saturation of the blood, for example screwed, glued or clamped. The first sensor device has a first radiation source in the form of a diode 100 on, as well as a second diode 101 and a phototransistor 102 as a radiation sensor that detects radiation from both diodes. The diodes 100 and 101 can be operated separately at the same time or alternately to the irradiation of the blood.

The radiation sensor is operated in such a way that it separately detects the transmitted light in two separate wavelength ranges, so that the quotient formation explained above is made possible.

The first sensor device can be designed as a ring, to which the radiation sources / diodes and the radiation sensor / phototransistor are attached and which can be placed as a whole on the pump tube and latched there.

In 7 schematically a pump device is shown, which has corresponding means for detecting the operating parameters and a first sensor device for determining the oxygen saturation of the blood. Such a pump device comprises a pump 6 with a rotor 34 , a magnetic thrust bearing 12 , a sensor 29 for the bearing voltage and a motor 27 with an outside stator, the pump 6 drives. There is also a speed sensor 33 and a current sensor 28 intended for the motor current. The measured operating parameters become an analysis device 30 transmitted, which is a control device 31 having a characteristic data storage device. In addition, the analyzer has 30 An institution 32 for determining the viscosity. This exchanges data with the control device 31 so that each optimized characteristic data can be used in the pump control. By determining a volume flow in connection with the oxygen saturation of the blood, the supply of the patient's body with oxygen can be monitored, evaluated and controlled or regulated.

It is also an acceleration sensor 108 in the body of the patient, in particular also on the pump, so that a physical activity of the patient and thus a physiological load can be detected and related to the measured oxygen saturation of the blood. The acceleration sensor 108 For example, it can be designed as a semiconductor component which can also be combined with one of the diodes serving as radiation sources or a phototransistor serving as a radiation sensor.

The measured values of oxygen saturation and volume flow can also be used as a basis for the control of a cardiac pacemaker and, for this purpose, directed to the control unit of a cardiac pacemaker.

By the measures shown, the determination of the volume flow by a pump, for example, using a currently determined viscosity is significantly improved, especially for those pumps for which a sufficient number of operating parameters in certain areas of the family of characteristics can be detected. By measuring the oxygen saturation, various measurement options on the blood of a patient are made possible. The integration of the first sensor device in the pump makes the handling, even during implantation, easy and the measurement of oxygen saturation reliable. The first sensor device can not only be designed as an optical measuring device as described, but also use any other known measuring method.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2570143 B1 [0005]

Claims (8)

Implantable heart pump ( 6 ) with a conveyor channel and with a conveyor arranged in this ( 6b . 6c . 34 ) for blood, characterized by a on the heart pump, in particular on a wall of the conveying channel, in particular on a pump tube ( 6a . 105a ), in which the delivery channel extends at least partially, attached first sensor device ( 100 . 101 . 102 ) for measuring the oxygen saturation of the blood. Heart pump according to claim 1, characterized in that the first sensor device ( 100 . 101 . 102 ) at least one, in particular two radiation sources ( 100 . 101 ) and at least one, in particular two radiation sensors ( 102 ) having. Heart pump according to claim 2, characterized in that the radiation sensor ( 102 ) detects the radiation intensity in at least two different wavelength ranges independently. Heart pump according to claim 2 or 3, characterized in that the connection path between the radiation source ( 100 . 101 ) and the radiation sensor ( 102 ) transversely, in particular perpendicular, to the flow direction of the blood in the conveying channel. Heart pump according to Claim 2 or one of the following, characterized in that the radiation source ( 100 . 101 ) and the radiation sensor ( 102 ) each other at the periphery of the pump tube ( 6a . 105a ) are opposite. Heart pump according to Claim 1 or one of the following, characterized by a second sensor device for the bearing voltage of a magnetic thrust bearing of a pump rotor, and / or with a sensor device ( 15 . 28 ) to detect the torque transmitted to the rotor and / or the speed to estimate the volume flow through the pump. Pump device with a pump according to one of claims 1 to 6 with a sensor for detecting the volume flow through the pump. Pumping device according to claim 7, characterized in that the control device ( 31 ) with a sensor ( 15 . 28 ) for the volume flow and / or for the detection of the pump current and rotational speed of the pump rotor ( 34 ) driving engine ( 27 ) and / or with a sensor for detecting the bearing voltage of a bearing the pump rotor magnetic thrust bearing ( 12 ) connected is.

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