RU210252U1 - Blood flow control device in extracorporeal circulatory assist systems - Google Patents

Abstract

The utility model relates to medical technology and medical equipment, namely to circulatory assist devices using non-pulsating flow pumps to bypass the left ventricle of the heart. The device for generating a pulsating blood flow in extracorporeal circulatory support systems contains a hydraulic resistance 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. The hydraulic resistance is made with the possibility of connection with the input NNP line connected to the left ventricle. At the same time, the wall of the cylinder has openings connecting the space between the tube of elastic biocompatible material and the inner surface of the cylinder with the atmosphere for the passage of air to provide a cardiosynchronized pulsating blood flow. Parallel to the hydraulic resistance with the help of tees, a shunt is installed in the form of a tube of constant cross section made of a biocompatible material, the inner diameter of which is three times smaller than the inner diameter of the hydraulic resistance cylinder. The technical result provided by the proposed utility model is to create a physiological pulsating flow and pressure in the aorta at a constant given LOR HNP under conditions of bypassing the left ventricle of the heart with the elimination of the pulsating element bounce to reduce the injury of blood cells. 1 ex., 1 tab., 3 figs.

Description

The utility model relates to medical technology and medical equipment, namely to circulatory assist devices (VC) using non-pulsatile flow pumps (NPF) to bypass the left ventricle of the heart and can be used to generate a pulsating blood flow and pressure in order to create a physiological arterial pulse, reducing the likelihood of thrombus formation in the pump, the development of rarefaction in the cavity of the left ventricle, effective unloading of the heart in extracorporeal VC systems.

BACKGROUND OF THE INVENTION

In recent decades, for the treatment of adult patients with end-stage heart failure (TSF), in world clinical practice, along with heart transplantation, which is limited by the shortage of organs used, implantable HNP pumps have been widely used, which have practically replaced (96%) pulsatile flow pumps (PHP) by virtue of significantly better weight and size characteristics, energy consumption, reliability and service life.

At the same time, the main strategy for controlling all commercial NNPs is to maintain a constant impeller speed (IRR) set by the operator.

Despite the high survival rate of patients with the use of 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 deterioration of microcirculation in vital organs (kidneys, liver, etc.), development of von Willlebrand syndrome and gastrointestinal angiodysplasia;

- reducing the likelihood of rarefaction in the cavity of the left ventricle (LV), associated with a mismatch in the balance of blood inflow and outflow of blood, which can lead to tissue damage in the area of the inlet cannula, displacement of the interventricular septum, deterioration of right ventricular function, arrhythmia, cardiac ischemia and hemolysis;

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

- relatively low unloading of the heart for work compared to NLP, which is one of the main factors in restoring the function of one's own myocardium.

To solve these problems, many researchers began to develop systems using NNP in the SORK modulation mode, which provides pulsating operation of the pump synchronously with the operation 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; Soucy K. G. et al. Rotary pumps and diminished pulsatility: do we need a pulse // ASAIO J. 2013 Jul-Aug; 59:355-66; Kishimoto S. p. 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;17:373-377.

A device is known (US 7850594, B2), which contains 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 pulsation index based on the measurement of the back EMF of the drive non-contact DC motor.

A device is known (WO 2009150893, A1), which consists of a detector of the reference signals of the cardiac cycle and a NNP control unit that synchronizes its operation with the phases of the cardiac cycle.

Other VC systems are also described (US 2017080138, A1; US 20110178361, A1; US 9579435, B2; US 9345824, B2; US 8864644 B2) SORK using ECG signals. provides cardio-synchronized pulsating mode of the pump.

The main disadvantage of the devices described above is the periodic change in the IOR, synchronized with the heart rate, which can lead to an increase in shear stresses in the pump and, accordingly, to blood injury. (Tayama E, Nakazawa T, Takami Y, et al: The hemolysis test of Gyro C1E3 pump in pulsatile mode. Artif Organs. 1997; 21:675-679).

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 output relative to operation, which significantly reduces the effect of generating a pulsating flow (S Bozkurt, van de Vosse F.N., Rutten M.C.M Enhancement of Arterial Pressure Pulsatility by Controlling Continuous-Flow Left Ventricular Assist Device Flow Rate in Mock Circulatory System J. Med. Biol. Eng. 2016; 36:308-331).

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 cardiosynchronous modulation of SORK is inefficient operation associated with cardiac arrhythmias in THF (arrhythmia, asystole, etc.).

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

The proposed system for generating a pulsating flow includes one NNP pump with a control unit that maintains a constant pump SOP, as well as a shunt connected in parallel to the inlet and outlet lines of the pump with a controlled valve. The device generates a pulsating flow by partially or fully opening/closing the shunt with a solenoid valve in synchronism with the cycles of the heart. The operation of the solenoid valve in closing requires a relatively large amount of power to actuate and maintain a predetermined gap in the systolic phase. The solenoid valve has rather large weight and size characteristics, which, together with high energy consumption, makes the system unsuitable for use in portable small-sized VC systems.

A device and method for controlling the blood flow of rotary pumps is known, presented in patent RU 2725083, C1, which includes a rotary pump with a pump control unit, while the inlet line of the pump contains hydraulic resistance, ensuring complete opening of the lumen of the inlet line in the systolic phase of the cardiac cycle and decrease in the lumen of the inlet line in the diastolic phase of the cardiac cycle. For the operation of variable hydraulic resistance, an external electromechanical, electrohydraulic or electropneumatic drive with a cardiosynchronization unit is used to receive ECG signals. The use of a 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 small-sized VC systems, especially for young children.

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

Closest to the claimed technical solution is a blood flow control device in extracorporeal circulatory support systems, presented in patent RU 201911 U1. The device for generating a pulsating blood flow in extracorporeal VC systems includes a hydraulic resistance configured to be connected to the NNP inlet line.

The disadvantage of this device is the unstable operation (bounce) of the working element (elastic tube) in the suction phase, which is potentially dangerous for blood cells.

The task to be solved by the claimed utility model is the optimization of the operating mode of an autonomous self-regulating device, based on the stabilization of the operation of the working element.

The technical result provided by the proposed utility model is to create a physiological pulsating flow and pressure in the aorta at a constant given LOR HNP under conditions of bypassing the left ventricle of the heart with the elimination of the pulsating element bounce to reduce the injury of blood cells.

The essence of the utility model is as follows.

The device for generating a pulsating blood flow in extracorporeal circulatory support systems contains a hydraulic resistance in the form of a cylinder with a tube made of an elastic biocompatible material installed inside it, hermetically fixed by the ends along the ends of the cylinder from its inner side. The hydraulic resistance is made with the possibility of connection with the input NNP line connected to the left ventricle. At the same time, the wall of the cylinder has openings connecting the space between the tube of elastic biocompatible material and the inner surface of the cylinder with the atmosphere for the passage of air to provide a cardiosynchronized pulsating blood flow. Parallel to the hydraulic resistance with the help of tees, a shunt is installed in the form of a tube of constant cross section made of a biocompatible material, the inner diameter of which is three times smaller than the inner diameter of the hydraulic resistance cylinder.

Thus, for the stable operation of the main working element of the hydraulic resistance (elastic tube), a shunt is installed in parallel with it using tees. At the same time, the parameters of the shunt (its inner diameter) are chosen in such a way as to minimize the unstable operation of the elastic element in the diastolic phase, without changing the LOR of the NNP.

BRIEF DESCRIPTION OF THE DRAWINGS

The essence of the utility model is illustrated in the figures, which show:

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

In FIG. 2 shows a schematic diagram of a system for generating a pulsating flow for extracorporeal VC systems;

In FIG. Figure 3 shows the diagram of pressures and flow rates obtained on a hydrodynamic stand (HS) when simulating heart failure and operating the NNP without generating a pulsating flow (a), with generating a pulsating flow (b) and with the system of the proposed utility model (c).

The figures show the following positions:

1 - pump (NNP) with control unit,

2 - inlet line of the pump,

3 - left ventricle of the heart,

4 - output line of the pump,

5 - aorta,

6 - pulsating flow generation system,

7 - elastic tube,

8 - cylinder (cylindrical body) of hydraulic resistance,

9 - perforations (holes),

10 - recirculation line (shunt),

11 - input tee,

12 - output tee.

The pulsating flow generation scheme shown in Fig. 1, includes a pump 1 with a control unit, an input line 2 NNP for connection to the left ventricle 3 of the heart, 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 NNP, which is a variable hydraulic resistance with a shunt 10, which ensures complete 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 for generating a pulsating flow consists of: hydraulic resistance, made in the form of a cylinder 8 with a tube 7 installed inside it, made of an elastic biocompatible material, hermetically fixed by the ends along the ends of the cylinder from its inner side, equipped with perforations (holes) 9 for switching off and on hydraulic resistance, and shunt 10, made in the form of a tube of biocompatible material. Shunt 10 and hydraulic resistance are connected in parallel with input (11) and output (12) tees. Tees - 1/2 × 1/2 × 3/16 can be used. The inner diameter of the shunt 10 is three times smaller than the inner diameter of the cylinder 8.

The blood flow control device works as follows (Fig. 2): when the left ventricle 3 of the heart contracts (systole), intraventricular pressure tends to fully open the elastic tube 7 located inside the cylinder 8, pressing it against its body. At the same time, the air filling the space between the elastic tube 7 and the inner surface of the cylinder 8 through the holes 9 freely enters the atmosphere, ensuring the free movement of the elastic tube 7 at a relatively low intraventricular pressure (30-60 mm Hg), usually associated with heart failure. The hydraulic resistance to blood flow from the left ventricle 3 to NNP 1 decreases, forming the maximum amplitude of blood flow through NNP 1.

In the diastolic phase, due to a decrease in intraventricular pressure and the suction action of NNP 1, the pressure in the elastic tube 7 decreases, which leads to closure of its walls and an increase in hydraulic resistance to blood flow on the way from the left ventricle 3 to NNP 1 and, accordingly, to a decrease in blood flow velocity through NNP 1. Thus, at the output of NNP 1, a cardiosynchronized pulsating flow is formed. For free movement of air from the space between the cylinder 8 and the elastic tube 7 into the atmosphere, the total cross section (total perforation area) of the holes 9 should not be less than 2% of the inner surface of the cylinder 8.

Connecting the shunt 10, fixed with its ends to the tees at the inlet 11 and outlet 12 of the pulsating flow generation system parallel to the hydraulic resistance, stabilizes the operation of the elastic tube 7, dumping part of the flow from the left ventricle 3, thereby preventing complete clamping of the elastic tube 7. Thus, connecting the shunt 10 when the pulsating flow generation system 6 is operating in the diastole mode of the left ventricle 3 of the heart, it allows to exclude the vibration of the elastic tube 7, and therefore to exclude the high-frequency flow pulsation at the outlet to the NNP 1.

Due to the fact that this design must have a free air outlet to the atmosphere in order to function effectively, this device for generating a pulsating flow can only be used in extracorporeal VC systems using NNP.

Comparative tests of three operating modes of the pump 1 on the HS were carried out in the conditions of modeling heart failure using the model of the proposed system.

A medical tube (shunt) 10 with an inner diameter of 4 mm, inlet 11 and outlet 12 tees, and a medical adapter - a cylinder 8 with an inner diameter of 12 mm, equipped with two holes 9, were used to make a model of system 6. Inside the adapter, a thin-walled elastic tube 7 made by dipping from medical grade polyurethane.

Carrying out comparative tests of NNP 1 on HS without a pulsating flow generation system 6 is carried out by clamping the shunt 10, and the space between the inner surface of the cylinder 8 and the elastic tube 7 is blocked by applying a small vacuum through the holes 9 associated with the atmosphere.

In the contraction mode of the left ventricle 3 of the heart, the elastic tube 7 opens completely without creating hydraulic resistance to the blood flow from the left ventricle 3 to the NNP 1.

In the operating mode of pump 1 with a system for generating a pulsating flow 6, holes 9 are opened into the atmosphere and the clamping is removed from the tube, providing additional blood discharge through the shunt 10.

In FIG. Figure 3 shows a comparative diagram of pressures and flow rates obtained on the HS, when modeling heart failure when the pump is operating without a pulsator (a), with a pulsator (b) and with the claimed utility model (c) where P _ao is the pressure in the aorta, P _lp is the pressure in the left atrium, P _{lzh -} pressure in the left ventricle, Q _n - flow in the pump, Q _ao - flow in the aorta.

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

As can be seen from the table, the pulsating pressure ΔР _ao during the operation of NNP1 with the prototype of the proposed device increases by 2.15 times compared to the operation of NNP 1 when operating without hydraulic resistance, and the pulse flow in the pump ΔQ _n is 1.9 times higher when systemic blood flow Q _{ao is restored.} with a constant SIBP of the pump in conditions of bypassing the left ventricle of the heart.

As can be seen from the diagram (Fig. 3b), the amplitude of the pulse pressure during the operation of the NNP with hydraulic resistance is within the physiological limits (104/77 mm Hg) at an average fluid flow rate of 5 l/min. The fluid flow curve in the pump Q _n has a pronounced high-frequency flow pulsation in the diastolic phase, which negatively affects the injury of blood cells.

As can be seen from the diagram (Fig. 3c), the amplitude of the pulse pressure during the operation of the NNP with the proposed device is within the physiological limits (110/82 mm Hg) with an average fluid flow of 5 l/min. The liquid flow curve in the pump Q _n has a pronounced flow pulsation without chatter. The effect of smoothing the high-frequency pulsation of the flow occurs due to the throughput of the shunt in the range of 1±0.2 (l/min).

Claims (1)

A device for generating a pulsating blood flow in extracorporeal circulatory support systems, containing a hydraulic resistance in the form of a cylinder with a tube made of an elastic biocompatible material installed inside it, hermetically fixed by the ends along the ends of the cylinder from its inner side, configured to be connected to the inlet line connected to the left ventricle non-pulsating flow pump, wherein the wall of the cylinder has openings connecting the space between the tube of elastic biocompatible material and the inner surface of the cylinder with an atmosphere for the passage of air to provide cardiosynchronized pulsating blood flow, characterized in that a shunt in the form of a tube is installed parallel to the hydraulic resistance using tees of constant cross-section from a biocompatible material, the inner diameter of which is three times smaller than the inner diameter of the hydraulic resistance cylinder.

Images