SU1581322A1 - Method of measuring artificial cardiac ventricle productivity - Google Patents

Abstract

The invention relates to the field of medical technology, namely the design of ancillary circulatory system and an artificial heart. The purpose of the invention is to improve the measurement accuracy by eliminating the error determined by the leakage of artificial valves. The productivity of the artificial ventricle of the heart is determined by measuring at each working cycle the change in the volume of the fluid chamber of the ventricle, the duration of the phases of the working cycle and the difference between the mean values of pressure in the system and diastole, and the value of productivity per working cycle is calculated by the formula.

Description

The invention relates to medical technology, namely the design of circulatory and artificial heart systems, l

The goal is to improve the accuracy of measuring the performance of an artificial ventricle of the heart.

The method is carried out using a device for its implementation.

FIG. 1 shows a functional diagram of the device that implements the proposed method; in fig. 2 shows diagrams explaining the measurement method; in fig. 3 shows an algorithm for calculating the magnitude of the impact volume.

The device (Fig. 1) contains a pressure pulse generator 1, comprising a motor control unit 2, a linear electric motor 3 and a piston mechanical pneumatic converter 4, the rod of which is rigidly connected

With the motor core 3. With the piston rod of the mechanopneumatic transducer 4, the sensor 5 of the final diastolic position of the piston, the sensor 6 of the final systolic position of the piston and the sensor 7 of the piston movement are connected. The pneumatic chamber of the mechano-pneumatic converter 4 through the pneumatic line 8 through the flow pressure sensor 9 is connected to the pneumatic chamber of the artificial ventricle 10 of the heart, equipped with inlet 11 and outlet 12 valves installed in the nozzles connected to the fluid chamber of the ventricle. The outputs of the sensors 5, 6, 7, and 9 are connected to the corresponding inputs of the computing device 13. The composition of the computing device 13 includes an analog-to-digital converter 14, a trigger 15, a pulse generator 16 interrupters

00

from to to y

nor, the clock generator 17 and the computer 18,

The information input of the converter 14 is connected to the output of the sensor 9, the control input of the converter 14 is connected to the output 1 of the computer 18, the output of the converter 14 is connected to the input

1 computer 18. Input 1 trigger 15 is connected to the output of the sensor 5, input 2 trigger 15 is connected to the output of the sensor 6, the output of the trigger 15 is connected to the input

2 computers 18. The output of sensor 7 is connected to input 3 of computer 18. The output of generator 16 is connected to input 4 of computer 18, the output of generator 17 is connected to input 5 of computer. 18. The output of the calculation results is via output 2 of the computer 18.

During operation of the device, the pressure pulse generator 1 and the ventricle 10 interact as follows.

In the initial state, the fluid chamber of the ventricle 10 is filled, for example, with blood, the pressure in it is equalized with the pressure of blood in the vascular system of the perfused object, valves 11 and 12 are closed. In the course of operation of the generator 1, under the influence of the core of the electric motor 3, the piston of the mechano-pneumatic converter 4 reciprocates, as a result of which the motion of the core is converted into air pressure pulses.

The actuator pneumatic section, which includes the sub piston space of the cylinder of the mechanopneumatic converter 4 pneumatic line 8 and the pneumatic chamber of the ventricle 10, forms a closed volume

eat filled with gas. When the piston moves toward the ventricle, due to a decrease in the magnitude of the closed volume, the gas pressure increases and is transmitted through the left membrane separating the pneumatic and fluid chambers of the ventricle of blood in the fluid chamber.

When the pressure inside the ventricle exceeds the blood pressure in the output line, the ventricular outlet valve 12 opens and further movement of the piston is accompanied by the expulsion of blood from the ventricle into the arterial vessels of the perfused object. When the piston moves backward, the outlet valve 12 then decreases to less than pressure

five

0

Q

five

0

five

0

five

0

five

blood in the venous vessels. Thereafter, the inlet valve 11 is opened and the further movement of the piston is accompanied by blood sampling from the inlet line into the fluid chamber of the ventricle 10.

As a result of filling the fluid chamber through the inlet valve 11 and emptying through the outlet valve 12, a certain volume of blood is pumped by the ventricle from the venous line of the perfused object into the arterial one.

Sensors 5, 6, and 7 are connected to the piston rod of a mechano-pneumatic converter 4. Sensor 5 generates a pulse signal when the piston reaches its final diastolic position (chart a in Fig. 2). Sensor 6 produces a pulse signal when the piston reaches its final systolic position (chart b in Fig. 2). The piston displacement sensor 7 generates a sequence of pulses in the amount of N proportional to the piston displacement value H. The pressure sensor 9 generates an analog signal proportional to the current value of the pressure value in the pneumatic line 8 (diagram in Fig. 2).

Computing device 13 operates as follows.

Analog-to-digital converter 14 converts the analog signal from pressure sensor 9 into a digital code to provide information compatibility with a computer. The trigger 15 generates a two-level signal that allows the phase of the ventricle to be determined. The level of logical O corresponds to systole, and the level of logical 1 diastole. The interrupt pulse generator 16 controls the operation of the computer. The clock pulse generator 17 ensures the operation of the computer, the computer 18 calculates the magnitude of the stroke volume from the signals from sensors 5, 6, 7 and 9 in accordance with the algorithm shown in FIG. 3, where the following symbols are accepted: ic is the counter of pressure signal counts at systole; i is the counter of the pressure signal on diastole; i CQ is the measurement cycle counter; prk is a sign that a pressure signal has reached a level; Pr is the sign of resolution of the calculation; N - pulse counter from the displacement sensor; THAT

tested input: on systole, on diastole; kHz - frequency

clock generator. one

The algorithm in FIG. 3 defines the operation of the computer 18 for calculating the magnitude of the impact volume in accordance with the proposed method.

As in the known method, the measurement according to the proposed method is based on measuring the change in the volume of the fluid chamber of the ventricle in terms of the displacement of the actuator piston between the instants of reaching the control values of pressure in the ventricular chambers in systole and diastole. To do this, set the reference pressure level Рц, which chooses taking into account the following condition: the value of the control pressure level must be greater than the closing pressure of the inlet valve, but less than the opening pressure of the output valve, i.e. the level of the control pressure value must lie within the range of pressure values at which both ventricular valves are closed. This valve condition corresponds to periods of pre-compression in systole and pre-expansion in diastole. Further, with continuous control of the gas pressure in the pneumatic section, the instant when the current pressure RS in the systole reaches the reference value (Pa Pk) is determined and the displacement of the piston H is measured from this moment to the reverse of the piston. During the reverse movement of the piston in diastole, displacement of the piston from the moment of reversal to the moment of reaching the control value of pressure

0

five

the diastolic position of the piston (diagram a in fig. 2). The current value of the pressure in the actuator pneumatic path is continuously measured and compared with the reference pressure level (chart in figure 2). From the moment corresponding to the equality of the current value of pressure tKc, the displacement of the piston (diagram d in FIG. 2) to the reversal signal (FIG. B in FIG. 2) and the displacement of the piston Nl during the time from the reversal signal are measured at the control pressure level. tH & until tK "comparing the current pressure value in diastole with the control pressure level.

The magnitude of the displacement H of the piston is determined, for example, by multiplying the number N at the output of the displacement sensor by a coefficient K, equal to the displacement of the piston equivalent to one pulse.

H KH-N. Thus, the change in the volume of the fluid chamber of the ventricle in the working cycle is determined in accordance with the formula

YU

LU KM (NCNJ)

where Nc Nn 0

the number corresponding to the measured movement in systole;

the number corresponding to the measured movement in the dia / table. To measure the amount of leakage through the valves, measure the duration of the phases of the operating cycle.

(Rs Rk). Thus, the magnitude of the change in volume displaced by the piston is calculated by the formula:

„Vn

v UA (n s - n5

Where

Sn is the cross-sectional area of the piston.

The proposed method takes into account the return flow of the valves, which provides an increase in the accuracy of measuring the performance. In this case, the changes in the volume of the liquid chamber are determined by the change in the position of the piston, i.e. 4VX 4Vn.

In accordance with the proposed method, the signal t Hc from the end sensor is taken as the beginning of the measurement cycle.

H

- t

(

NA

t T9

NA.

- t

9

and the average for the time T s and T ,, the pressure values of Pc and P).

The total amount of leakage of the valves Vyr is calculated by the formula

f

РСРЗ (к «тз + квТс) 55

The productivity of the ventricle per working cycle is calculated by the formula

VVA YUZH

-fF

(K "V

w The proposed method for measuring the performance of the artificial ventricle of the heart improves the measurement accuracy by eliminating the error caused by valve leakage.

Claims (1)

Invention Formula A method for measuring the performance of an artificial ventricle of the heart, including determining the change in the volume of the fluid chamber of the ventricle in each working cycle, about f l and the fact that, in order to improve the measurement accuracy, the duration of the phases of the working cycle and the difference in average values of pressure values are additionally measured systole and diastole of the ventricle, and the value of the performance of Uud in one working cycle is determined by the formula l 7J- g  dV,  Sieg RAYAST (KLT H kW) five 0 where is UV% day st Tc T1 K, -the change in the volume of the fluid chamber of the ventricle in the working cycle, RSIST YAG average systolic pressure in the chambers of the ventricle; average diastolic pressure in the ventricular chambers; - duration of systole; the duration of diastole; coefficient of proportionality, determined by the design parameters of the output valve; - coefficient of proportionality, defined by design parameters of the inlet valve. L d 7 ten 12 g