RU202952U1 - Blood flow control device for implantable circulatory support systems - Google Patents

Abstract

This utility model relates to medical technology and medical equipment, namely, circulatory assist devices (VCs) using non-pulsating flow pumps (NPPs) to bypass the left ventricle of the heart. The proposed device for generating a pulsating blood flow in an implantable auxiliary blood circulation system contains a hydraulic resistance installed with the possibility of being connected to the inlet line of a non-pulsating flow pump. The hydraulic resistance is made in the form of a cylinder with a tube installed inside it made of an elastic biocompatible material, hermetically fixed by its ends along the ends of the cylinder from its inner side. The cylinder is located inside the outer casing to form a sealed compensation chamber between the outer surface of the elastic tube and the outer casing. The outer casing has a fitting for filling the compensation chamber with gas. The walls of the cylinder are perforated to regulate the lumen of the said tube so as to ensure a cardiosynchronized pulsating blood flow. In a particular case, a tube made of an elastic biocompatible material has a narrowing from the periphery to the center. The technical result consists in creating a physiological pulsating flow and pressure in the aorta at a constant set speed of the impeller of the pump in conditions of bypassing the ventricle of the heart; in minimizing the zones of recirculation and stagnation of blood in the pump, potentially dangerous for thrombus formation; in the versatility of the proposed VC system; in the absence of external power supply to the control system and cardiosynchronization system; in simplicity and compactness of design. 1 wp f-crystals, 3 fig.

Description

This utility model relates to medical technology and medical equipment, namely to circulatory assist devices (VCs) using non-pulsating flow pumps (NPPs) to bypass the left ventricle of the heart and can be used to generate pulsating blood flow and pressure in order to create a physiological arterial pulse , which reduces the likelihood of thrombus formation in the pump, the development of vacuum in the left ventricular cavity, effective unloading of the heart in implantable VC systems.

LEVEL OF TECHNOLOGY

At the initial stage of the use of VC for the treatment of patients with end-stage heart failure (TSF), pulsating flow pumps (PPP) were developed and introduced into clinical practice. However, in recent decades, NPP began to be replaced (more than 94%) by non-pulsating flow pumps (NPP) (centrifugal, axial), which have a number of significant advantages over NPP - smaller dimensions, lower energy consumption, higher reliability and service life. At the same time, the management strategy of all commercial NNP is based on maintaining a constant speed of rotation of the impeller (SORK), set by the operator.

Despite the high survival rate of patients using these pumps (the first year - up to 85%), there are still a number of problems, the solution of which could significantly improve the results of their clinical use. These include:

reduced aortic pulsation leads to a deterioration of microcirculation in vital organs (kidneys, liver, etc.), the development of von Willlebrand syndrome and gastrointestinal angiodysplasia;

a decrease in the likelihood of developing a vacuum in the cavity of the left ventricle (LV), associated with a mismatch in the balance of inflow and outflow of blood, which can lead to tissue damage in the area of the entrance cannula, displacement of the interventricular septum, impairment of right ventricular function, arrhythmia, heart ischemia and hemolysis;

relatively low pulsation of the flow in the pump, which contributes to the appearance of zones of stagnation and recirculation, which increases the risk of thromboembolism;

relatively low unloading of the heart at work in comparison with NPP, which is one of the main factors in the restoration of the function of its own myocardium.

To solve these problems, many researchers began to develop systems using NNP in the SORK modulation mode, which ensures the pulsating operation of the pump synchronously with the work of its own LV (Pirbodaghi T., Asgari S., Cotter C. Physiologic and hematologic concerns of rotary blood pumps: what needs to be improved? // Heart Fail Rev 2014; 19: 259-266; Rotary pumps and diminished pulsatility: do we need a pulse? ASAIO J. 2013 Jul-Aug; 59 (4): 355-66; Kishimoto S., Date K., Arakawa M., Takewa Y., Nishimura T, Tsukiya T. et al. Influence of a novel electrocardiogram-synchronized rotational-speed-change system of an implantable continuous-flow left ventricular assist device (EVAHEART) on hemolytic performance. J Artif Organs. 2014; 17 (4): 373-377).

A device (US 7850594, B2) is known, which contains an NNP with a drive that provides a pulsating pump mode synchronously with the work of the heart. Moreover, the cardiac cycle is determined from the ripple index based on the measurement of the back EMF of the driving contactless DC motor.

Known device (WO 2009150893, A1), which consists of a detector of the reference signals of the cardiac cycle and the control unit NNP, synchronizing its work with the phases of the cardiac cycle.

Other IPC systems are also described (US 2017080138 A1, US 20110178361 A1, US 9579435 B2, US 9345824 B2, US 8864644 B2), in which the NNP is connected according to the "ventricle-aorta" scheme with a control unit, which, due to the modulation of SORK, using signals ECG. provides a cardiosynchronized pulsating pump mode.

The main disadvantage of the devices described above is the periodic change in SORK, synchronized with the heart rate, which can lead to an increase in shear stresses in the pump and, accordingly, to blood trauma. (Tayama E., Nakazawa T., Takami Y., et al: The hemolysis test of Gyro C1E3 pump in pulsatile mode. Artif Organs. 1997; 21: 675-79).

Another disadvantage of these devices is the inertia of the motor-pump system, which limits the receipt of a given amplitude of flow and pressure in the systolic phase and leads to a phase shift of the pump ejection relative to operation, which significantly reduces the effect of generating a pulsating flow (Bozkurt S., van de Vosse FN, Rutten MC Enhancement of Arterial Pressure Pulsatility by Controlling Continuous-Flow Left Ventricular Assist Device Flow Rate in Mock Circulatory System. J. Med. Biol. Eng. 2016; 36: 308-31). In addition, these devices require significant material and technical costs for the improvement of pumps and control units.

The disadvantage of most systems based on cardiosynchronized SORK modulation is ineffective work associated with heart rhythm disturbances in TSN (arrhythmia, asystole, etc.).

A device and method for controlling the blood flow of rotary blood pumps is known, involving the use of a recirculation channel connected in parallel to the input-output of the NNP (RU 2665178, C1).

The disadvantage of this device is the introduction into the pump circuit of an additional surface in the form of a recirculation channel (elastic shunt), which increases the contact area of blood with a foreign surface.

In addition, to generate a pulsating flow, the recirculation channel synchronously with the heart cycles (systole / diastole) is partially or completely opened / closed by an electromagnetic valve. Closing the solenoid valve requires relatively high power to operate and maintain a predetermined gap in the systolic phase. The solenoid valve has sufficiently large weight and size characteristics, which, together with high energy consumption, makes the system unsuitable for use in VC implantable systems.

The closest to the claimed technical solution is a device and method for controlling the blood flow of rotary pumps, presented in patent RU 2725083, C1. The device includes a rotary pump with a pump control unit, while the input line of the pump contains hydraulic resistance, which ensures full opening of the lumen of the input line in the systolic phase of the cardiac cycle and a decrease in the lumen of the input line in the diastolic phase of the cardiac cycle.

For the functioning of the variable hydraulic resistance, an external electromechanical, electrohydraulic or electro-pneumatic drive with a cardiosynchronization unit is used to receive ECG signals. The use of the drive complicates the design of the system, requires additional energy for its operation, and the weight and size characteristics of the drive and control circuits complicate the possibility of using the system in implanted IPC devices.

In addition, the disadvantage of this device is the need to use ECG signals for its functioning, which makes the system ineffective in conditions of cardiac arrhythmias (arrhythmia, asystole), which often accompany TSN.

The task to be solved by the claimed utility model is the creation of an autonomous self-regulating device that provides cardiosynchronized generation of a pulsating flow in implantable VC systems using NNP, without the use of additional drive devices and cardiac contraction sensor systems (ECG, etc.).

The technical result provided by the proposed utility model consists of:

in creating a physiological pulsating flow and pressure in the aorta at a constant set speed of the pump impeller in conditions of bypassing the heart ventricle;

in minimizing the zones of recirculation and stagnation of blood in the pump, potentially dangerous for thrombus formation, due to the generation of a pulsating flow in it without changing the rotor speed;

in the versatility of the proposed VC system, in which an NNP of any design can be used as a base pump;

in the absence of external power supply to the control system and cardiosynchronization system with receiving control signals from external sensors (ECG);

in the simplicity and compactness of the design, allowing it to be placed inside the pump inlet cannula, which makes it possible to use it both in extracorporeal and implanted VC systems with a minimum of parts used.

The essence of the utility model is as follows.

The proposed device for generating a pulsating blood flow in an implantable auxiliary blood circulation system contains a hydraulic resistance installed with the possibility of connecting to the inlet line of the non-pulsating flow pump. The hydraulic resistance is made in the form of a cylinder with a tube made of an elastic biocompatible material installed inside it, hermetically fixed by its ends along the ends of the cylinder from its inner side. The cylinder is located inside the outer casing to form a sealed compensation chamber between the outer surface of the elastic tube and the outer casing. The outer casing has a fitting for filling the compensation chamber with gas. The walls of the cylinder are perforated to regulate the lumen of the said tube so as to provide a cardiosynchronized pulsating blood flow.

In a particular case, a tube made of an elastic biocompatible material has a narrowing from the periphery to the center.

BRIEF DESCRIPTION OF DRAWINGS

The essence of the utility model is illustrated in the following figures.

FIG. 1 shows a diagram of the generation of a pulsating flow in VC systems using NNP using the example of connection to the left ventricle of the heart.

FIG. 2 shows a diagram of the proposed device for implantable VC systems.

FIG. 3 shows a diagram of pressures and flow rates obtained on a hydrodynamic stand, when simulating heart failure and operating the system without generation and with the generation of a pulsating flow.

The following positions are indicated in the figures:

1 - pump (ННП) with a control unit,

2 - pump inlet line,

3 - left ventricle,

4 - pump outlet line,

5 - aorta,

6 - a device for generating a pulsating blood flow,

7 - elastic tube,

8 - cylinder (cylindrical body),

9 - space (between the cylinder and the elastic tube),

10 - perforations (holes),

11 - compensation chamber,

12 - outer case,

13 - fitting.

The pulsating flow generation circuit shown in FIG. 1, includes a pump 1 with a control unit, an input line 2 NPP for connection to the left ventricle 3, an output line 4 NNP for connection to the aorta 5; at the same time, a device for generating a pulsating flow 6 is installed in the input line 2 of the NPP, which is a variable hydraulic resistance, which ensures full opening of the lumen of the input line 2 in the systolic phase of the cardiac cycle and a decrease in the lumen of the input line 2 in the diastolic phase of the cardiac cycle.

The device works as follows (Fig. 2): when the ventricle of the heart 4 (systole) contracts, the intraventricular pressure tends to fully open the elastic tube 7, pressing it against the body of the cylinder 8. In this case, the gas filling the space 9 (between the elastic tube 7 and the cylinder 8) through the holes 10 it enters the compensation chamber 11 formed by the outer surface of the elastic tube 7 and the outer casing 12, providing free movement of the elastic tube 7 at a relatively low intraventricular pressure (30-60 mm Hg), usually associated with heart failure. In this case, the hydraulic resistance to blood flow from the left ventricle 3 to pump 1 decreases, forming the maximum amplitude of blood flow through pump 1.

In the diastolic phase, due to a decrease in intraventricular pressure and the suction action of pump 1, the pressure in the elastic tube 7 decreases, which leads to the closure of its walls and an increase in the hydraulic resistance to blood flow on the way from the left ventricle 3 to pump 1 and, accordingly, to a decrease in the blood flow rate through pump 1.

Thus, a cardiosynchronized pulsating flow is formed at the output of pump 1.

For the free movement of gas from space 9 (between the cylinder 8 and the elastic tube 7) into the compensation chamber 11, the total section (total perforation area) of the holes 10 must be at least 2% of the inner surface of the cylinder 8, and the volume of the compensation chamber 11 must be at least two volumes of space 9 when filling the compensation chamber through the nozzle 13 with air.

Due to the fact that this design does not have a free outlet of gas into the atmosphere for effective operation, this device for generating a pulsating flow can only be used in implanted VC systems using NNP.

Comparative tests of two modes of operation of pump 1 (centrifugal pump (CP) (Rotaflow, Maquet inc., Germany) on a hydrodynamic stand (HS) were carried out under conditions of simulating heart failure using a model of device 6. A medical adapter (cylinder 8), equipped with two fittings (holes 9) with 3-way valves.An elastic tube 7 made by dipping from medical polyurethane was mounted inside the adapter at the ends.A compensation chamber was connected to the fitting 13 through 3-way valves.

In this case, the mode of operation without a pulsator was carried out by supplying a small vacuum to the space between the adapter and the elastic tube and blocking the gas outlet to the outer chamber with 3-way valves.

During operation of the central pump with a device for generating a pulsating flow, the space between the adapter with the elastic tube and the compensation chamber was filled with gas (air) at zero pressure through the fitting and 3-way valves.

In the systole mode of the left ventricular simulator (LVL), air from the space (between the outer surface of the elastic tube and the inner surface of the adapter through the fittings and 3-way tees enters the compensation chamber and the elastic tube is fully opened without creating hydraulic resistance to the blood flow from the left ventricle to the central nervous system ...

In the diastole mode, due to the suction action of the CN, air through the choke and 3-way valves moved from the compensation chamber into the space between the adapter and the elastic tube, which collapses at the same time, creating a hydraulic resistance to the flow from the LV IL to the CN.

FIG. 3 shows a comparative diagram of pressures and flow rates obtained at the HS, where a) when simulating heart failure when the pump is operating without a pulsator, b) when the pump is operating with the claimed utility model, where P _ao is the pressure in the aorta P _lp is the pressure in the left atrium, R _lzh - pressure in the left ventricle, Q _n - flow rate in the pump, Q _ao - flow rate in the aorta.

The results of the comparison of the pump operation in the standard non-pulsating mode and in the pump operation mode with the claimed utility model when simulating heart failure, obtained on the HS are summarized in the table.

As can be seen from the table, the pulse pressure in the aorta P _ao during the operation of the central pump with the claimed utility model is 2.5 times higher, and the pulse flow is higher by 2.0, due to which conditions are created in the cavities of the central pump to minimize stagnation and recirculation zones that are dangerous for blood clots.

Claims (2)

1. A device for generating a pulsating blood flow in an implantable auxiliary blood circulation system, containing a hydraulic resistance installed with the possibility of connecting to the inlet line of a non-pulsating flow pump, characterized in that the hydraulic resistance is made in the form of a cylinder with a tube installed inside it made of an elastic biocompatible material, hermetically fixed by the ends along the ends of the cylinder from its inner side, and the cylinder is located inside the outer casing to form a sealed compensation chamber between the outer surface of the elastic tube and the outer casing, while the outer casing has a fitting for filling the compensation chamber with gas, and the cylinder walls are perforated with the possibility of gas passage from the space of the compensation chamber between the tube and the cylinder to the space of the compensation chamber between the cylinder and the outer casing to regulate the lumen of the tube and provide cardiosynchronized pulsating blood flow. 2. The device of claim. 1, characterized in that the tube is tapered from the periphery to the center.

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