DE2558921B2 - DRIVE FOR A PNEUMATIC OR HYDRAULIC PULSE PUMP - Google Patents

Description

25th

JO

The invention relates to a drive for a pneumatic or hydraulic pulse pump, in particular Blood pump in the artificial heart or intra-aortic balloon pump for circulatory support, for Generation of preselected pump cycles consisting of a surge phase and a suction phase with a vacuum accumulator for a pump drive medium and a medium feed pump, each during the Shock phase via line connections on the input side with the vacuum accumulator and on the output side with the Pulse pump is connected, and with a controllable switching device for the medium need pump.

In biomedical technology there is the problem of providing drives for pumps operating in pulse mode to develop. It is important that such drives are on the one hand so small in terms of volume that they are implantable especially when used for blood pumps in the artificial heart, but that on the other hand a sufficiently large output power is produced "on the blood" so that the heart or the circulatory system bo is effectively relieved. Since the core sizes mentioned influence each other, i. H. the to The higher performance that provides a correspondingly large construction volume or a predeterminable smaller one Building volume is only able to provide a limited service, compromise solutions must be found for individual problems to be searched for. Furthermore, the efficiency of such drives, i. H. the ratio of Output power to the power consumed should be as large as possible, because not for conveying the medium The power consumed is released as heat in the body and, moreover, the energy source is unnecessarily burdened.

Through the article “Development of an Electrohydraulic Energy Source to Power and Control Circulatory Assist Devices «by N. Griffith and W. Burne, reprinted in the reports on the Artifical Heart Program Conference Proceedings, Washington D.C. June 9-13, 1969, US Department of Health Education and Welfare, pp. 953 to 967, particularly 964 and 966, a drive of the type mentioned for a blood pump in the artificial heart is previously known in which a centrifugal pump is used as the medium feed pump. This well-known drive works in the way that during the "systole", i.e. H. during the surge phase of the blood pump, through the centrifugal pump that Drive medium is pumped from the vacuum reservoir into the blood pump. With the beginning of the "diastole" d. H. the suction phase of the blood pump is switched off from the centrifugal pump outlet through the line switching device (switching valve) and connecting the blood pump to a separate storage line the drive medium located in the blood pump through the negative pressure vacuum accumulator located is sucked back into the accumulator.

A modification of that of Griffith and Burne The proposed solution consists in the suction phase, i. H. after switching off the centrifugal pump, the To let drive medium from the blood pump suck through the centrifugal pump. This will make that The structural volume of such a drive is significantly reduced.

The disadvantage of the two mentioned drives is that the hydraulic output power, d. H. the Pumping power in the blood, which decreases rapidly with increasing pumping frequency. This is due to the proportionate large flow resistances caused during the Suagphase, which a correspondingly large suction capacity the vacuum accumulator.

From the DT-OS 23 22 103 is now a drive for a Blood pump known, in which the container for the drive medium with its internal pressure External pressure during an entire pumping cycle is not falling below the volume storage, with the Volume storage a line switching device for switching the container from the feed pump inlet to the feed pump output and the pulse pump from the feed pump output to the feed pump input assigned. In addition, it has already been proposed (DT-OS 23 22 104), in addition to the vacuum accumulator to provide an overpressure accumulator which is connected to the output of the feed pump during the entire pumping cycle, and the Line switching device for connecting the feed pump input to the pulse pump through a To train clock generator at the beginning and for the duration of a suction phase. The latter two Drives deliver a sufficiently high output power, but they are comparatively complex in structure and accordingly have a large construction volume.

The invention is based on the object of building a drive of the type mentioned at the outset, which is in Even with the smallest construction volume, it still provides a sufficiently large performance.

This object is achieved according to the invention by what is stated in the characterizing part of claim 1

Features solved. The invention was preceded by extensive research and considerations as to why it Up until now it was impossible to realize small volume drives with a high output line. It has Surprisingly shown that the absolute power output is not the measure of the avertability of a Drive, but an evaluation factor weighted with power, efficiency and mass volume. This is defined as follows:

E = A ^ - [W / kg],

where Ph is the mean hydraulic power delivered "on the blood", μ the efficiency and G the ιϊ volume weight of the entire drive. Such an evaluation factor takes into account, in particular, the mutual dependence of performance and construction volume, which is to be optimized. Practical experiments have now confirmed that in comparison with the drives of the prior art described above, the drive according to the present invention delivers the best results.

In the context of the invention, it is advantageous to choose a flap valve as the valve which enables high switching frequencies and a large flow rate with the lowest power consumption. Furthermore, passive, self-regulating valves can also be used. Since in the drive according to the invention the total flow resistance of the system, in particular in the back suction phase, is minimized, the restoring force in the vacuum accumulator can be very small, which in turn allows a correspondingly lower power consumption of the pump drive motor. v-,

Further details of the invention emerge from the following description of an exemplary embodiment based on the drawing in conjunction with the subclaims.

It shows

F i g. 1 the embodiment in principle structure,
2 shows a graphic representation of evaluation factors of drives as a function of the pump frequency.

In Fig. 1, 1 denotes a blood pump according to the membrane type, which is driven by a movable membrane 2, for. B. made of plastic, in a space 3 for the blood and a space 4 for the drive medium, z. B. water, is divided. It has an arterial connection 5 and a venous connection 6. The valves which simulate the heart valves are designated ^{with 7 and 8 r> o.} The direction of the. The valve tip shows the direction of movement of the blood to be pumped. With a vacuum reservoir for the Αηίΐ iebsmedium is designated. The vacuum accumulator 9 is fixed at its lower end, for. B. attached to the implanted housing for the drive, and freely movable at its upper end. The vacuum accumulator 9 consists of a plastic bellows 10 which is prestressed in the emptied or partially emptied state with a compression spring 11. A centrifugal pump for conveying the drive medium for the blood pump 1 is designated by 12. This is connected to the vacuum reservoir 9 through the line 13 and to the blood pump through the line 14. A bypass with the controllable switching valve 17 is paralleled to the centrifugal pump 12 via the lines 15 and 1b. The motor 18 serves to drive the centrifugal pump 12. A control element 19 with an upstream actuator 20 controls the motor 18 and valve 17 in alternation.

The mode of operation of the exemplary embodiment of the invention shown in the figure results as follows follows:

In the systolic phase, valve 17 is closed, and the centrifugal pump 12 pumps the drive medium from the vacuum reservoir 9 into the space 4 of the Blood pump 1. The vacuum reservoir 9 is charged. In the diastolic phase, the valve 17 opened. The vacuum reservoir 9 then sucks in the drive medium located in the space 4 of the blood pump 1 via the lines 13 to 16 back into the vacuum accumulator. The drive medium is in the main flow through the open valve 17, but also partly sucked back into the memory by the centrifugal pump 12. The total flow resistance created by the lines is minimized. In the performance diagram the power consumed is shown as a function of time. This goes on in the systolic phase peaks and drops to a very small value in the diastolic phase. The relation between The pump output to the output absorbed by the switching valve is approx. 10: 1.

Tests with the drive according to the invention have shown that the frequency dependence of the output power is low. Despite the small volume of construction in "in vitro" tests a sufficient output is achieved that at least relieves the load on the Enough from the heart.

The F i g. 2 shows the superiority of the invention Drive. The results of “in vitro” tests on the “Kolffs Mock” model are shown in comparison to the values measured with known concepts. The curve 21 mean the through Equation (I) defined evaluation factor of the drive according to the invention as a function of the Pump drive to be provided pump frequency, the curves 22 and 23 the corresponding size of a according to DT-OS 23 22! 04 designed or a modified drive according to N. Griffith and W. B u r η e. Of the The frequency range of interest is between 60 and 120 per minute, the delivery pressure is 120 mm Hg in each case. Curves 21 and 23 have a falling pumping frequency, while curve 22 has a falling frequency upward trend. Up to a frequency of about 90 per minute, the drive according to the invention is far on cheapest. At higher frequencies, the weighting factor for the drive according to DT-OS 23 22 104 cheaper, which is essentially due to the much greater output power. However have the "in vivo" experiments on the calf showed that this higher output due to the blood pump was not exploited can be and therefore brings no advantages compared to the drive according to the invention.

Of course, such drive systems are not only used in biomedical technology, but also in technical equipment that requires a pulsed medium and a high degree of efficiency is required, can be used.

For this purpose 2 sheets of drawings

Claims (4)

Patent claims: 1. Drive for a pneumatic or hydraulic pulse pump, especially a blood pump when artificial heart or intra-aortic balloon pump for circulatory support, to generate preselected, Pump cycles made up of surge and suction phases with a vacuum accumulator for a pump drive medium as well as a medium feed pump between the storage tank and Pulse pump is, and a controllable switching device for the medium pump, thereby characterized in that a centrifugal pump (12) as a medium pump, a bypass (15, 16) for the Medium is connected in parallel with a controllable switching valve (17) for switching the bypass (15,16) in the sense that it is closed in the suction phase of the centrifugal pump (12), in the pump back suction phase however, is open. 2. Drive according to claim 1, characterized in that the valve (17) is a rapidly switchable Flap valve with minimized flow resistance is. 3. Drive according to claim 1 or 2, characterized in that for controlling the drive motor (18) a clock generator (19) is provided for the centrifugal pump (12) and the switching valve (17), which alternately controls the pump motor (18) and valve (17). 4. Drive according to one of claims 1 to 3, characterized in that the controllable switching valve (17) in the pump back suction phase with switching off the centrifugal pump (12) from the pulse pump (1) the bypass (15, 16) to the pulse pump (1) turns on. 20th