RU2807240C1 - Device for studying hydromechanical properties of tubular blood vessel prostheses - Google Patents

Abstract

FIELD: medical technology.

SUBSTANCE: invention relates to medical technology, namely to a device for studying the hydromechanical properties of tubular blood vessel prostheses. The device consists of a pneumohydroaccumulator connected in series to a closed circuit with an air pump connected to it, an air pressure sensor and shut-off valves, a check valve, an auxiliary circulation pump, controlled by a pneumatic actuator unit, made with the possibility of supplying a compressor. Next, a check valve, control valves, and a liquid flow sensor are connected to the circuit, a thermoregulation unit, a temperature sensor, a socket of the first adapter connected via a dynamometer to the main caliper placed on the frame guides and equipped with a lock. The controlled pneumatic drive unit is designed with the ability to move along the frame guides along the axis of the tubular blood vessel prosthesis to set the tension of the examined tubular blood vessel prosthesis controlled by the dynamometer readings. In the socket of the first adapter is the first adapter with a pressure extraction channel, to which is connected to a working fluid pressure sensor with an electric analog output and a test prosthesis of a tubular blood vessel connected from the opposite end to a second adapter located in the socket of the second conductor mounted on the guides of the frame. A temperature sensor of the working fluid is introduced into the circuit, behind which there is a control valve connected to a pneumohydroaccumulator. On the guides of the frame there are also two auxiliary calipers, made with the possibility of locking fixators on which laser distance sensors with an electric analog output are installed, made with the possibility of measuring the radial movement of the wall of the examined tubular blood vessel prosthesis, with the possibility of moving relative to the axis of placement of the examined tubular blood vessel prosthesis along three mutually perpendicular axes. One of the axes is parallel to the axis of placement of the examined tubular blood vessel prosthesis, to position the axis of the laser beam perpendicular to the axis of placement of the examined tubular prosthesis a blood vessel. All four sensors are connected via an analog-to-digital converter to a computer.

EFFECT: technical result is an increase in the productivity of the device for studying the hydrodynamic properties of tubular blood vessel prostheses and ensuring the completeness of research by increasing the number of measured parameters; improving the quality of measurements, approximating measurement conditions to physiological ones.

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Description

The invention relates to the field of medicine, namely to testing and research equipment intended for studying the hydrodynamic properties of both tubular blood vessels and their artificial and biological prostheses.

The device has the greatest number of similar features, as well as the closeness of the technical essence to the claimed invention (Khlif, N. Development of a test bench assessing the hydrodynamic compliance of vascular prostheses / N. Khlif, S. Dhouib, N. Maatoug, S.B. Abdessalem, F Sakli // Journal of Textile Engineering & Fashion Technology. - 2018. - V. 4, No. 3. - P. 244-252), chosen as a prototype. This paper describes a device designed to study the hydromechanical properties of artificial tubular vascular prostheses. The design forms a closed circuit, which sequentially includes the output of a rotary pump, control valves, an adapter with a pressure sampling channel from the wall of the hydrodynamic channel to which a mechanical fluid pressure sensor is connected, a tubular vascular prosthesis under study, inside of which a rubber tube is placed, which is connected to the circuit instead of the prosthesis, adapter, control valves, solenoid valve, reservoir, rotary pump inlet. These nodes form a hydrodynamic channel. In this case, the rotary pump is equipped with a control pressure switch. The control valves, pressure sensor and adapters are fixed on two devices that orient the straight hydrodynamic channels formed by the given units coaxially, and set the distance between the inlet and outlet sections of the adapter holes. The tension of the vessel is ensured by moving the orienting devices along the axis of the vessel placement. Orienting devices with units attached to them are placed in a container with a drain tube, which prevents accidents associated with a violation of the tightness of the system. The vessel deformation is measured using a sensor with a contact probe, which converts its own movement into an electrical signal transmitted to a computer through an auxiliary system, while the sensor body is mounted on a tripod, which allows the sensor to be moved in any plane relative to the axis of the vessel. The systolic pressure in the circuit is set by a pressure switch connected to a rotary pump, with the help of which it is maintained. The pulsation frequency is set by two timers with set response times, which control the solenoid valve. To study hydrodynamic properties, the test product with a rubber tube placed inside is placed and fixed on the adapters, the necessary tension and position of the prosthesis are created by moving the orienting devices. The contact probe is brought into contact with the outer wall of the prosthesis being tested. The control pressure relay is set to the required value maintained by the pump, the frequency of operation of the solenoid valve is selected by switching timers, both valves are opened, the pump is started, and the solenoid valve is turned on. The radial movement of the prosthesis wall using a sensor with a contact probe is recorded by an auxiliary system and transmitted to the computer. Pressure is recorded by monitoring the pressure sensor readings. At the end of the measurement, the pump stops, the solenoid valve is turned off, and both valves are closed. The sensor with the contact probe is moved to the side, the prosthesis is removed from the adapters. From the received data, the necessary parameters are calculated.

The described device has a number of disadvantages, which are as follows.

The creation of a pulse wave in the vessel under study is ensured by the activation of an electromagnetic valve, which periodically opens and closes the hydrodynamic channel into which pressure is injected by a pump. In this case, the electromagnetic valve is located after the vessel under study in the direction of movement of the working fluid. This method of setting a pulse wave does not provide an imitation of physiological incision in the vessel under study due to the forced closure of the hydrodynamic channel and the impossibility of moving the working fluid in the opposite direction due to the mechanism of operation of the rotary pump. The minimums and maximums after the plateau observed in the sphygmograms presented in the work are caused by damped oscillations of the rubber tube inside the vessel. These vibrations appear due to the inertial movement of the walls of the elastic tube located inside the vessel in the radial direction to the axis of the tube after the force applied to them, stretching them, ceases.

The connection of the system with the atmosphere through an open reservoir does not allow setting any desired values of systolic and diastolic pressure, which in this case simultaneously depend only on the degree of blocking of the channel by the control valves, and the time the solenoid valve is in the open state. When changing the time of holding the solenoid valve in the open state, the pulsation rhythm and the volume of release of the working fluid will change, which will lead to a deviation of the system parameters from physiological values.

Placing a rubber tube inside the vessel under study and connecting it to the circuit instead of the vessel significantly distorts the measurement results. The tube creates additional resistance to radial stretching, which distorts the compliance value of the vessel under study. In addition, its presence leads to the appearance of oscillations of the walls of the tube in the radial direction after the termination of the application of a tensile force to them, which makes it difficult to determine the position of the outer wall of the vessel at diastolic pressure.

The absence of a fluid flow sensor in the circuit does not make it possible to determine the volume of working fluid ejected in the cycle of simulating cardiac contraction.

The working fluid and the vessel are not subject to thermoregulation, and measurements take place at room temperature, which moves the functioning conditions of the vessels away from physiological ones.

The use of a pointer mechanical pressure sensor as the main one makes it impossible to record the liquid pressure curve in the vessel under study and compare it with the sphygmogram, which leads to an increase in the number of errors and a decrease in the reliability of measurements.

The use of a single sensor for radial movement of the wall of the vessel under study does not allow determining the speed of propagation of the pulse wave in this vessel.

Using a sensor with a contact probe to measure the radial movement of the wall of the vessel under study increases the preparation time for measurement due to the need to bring the probe into mechanical contact with the wall of the vessel while maintaining its tension. In addition, such a sensor is susceptible to vibrations that inevitably arise when the subject performing the measurements interacts with the outside world, which leads to interference.

The absence of guide orienting devices makes it difficult to ensure the alignment of the adapters, which makes it difficult to work with the system and increases the time spent on measurements.

The absence of a mechanism for measuring vessel tension does not allow setting the required tension of the vessel and eliminating its sagging or excessive stretching, which lead to unreliable measurements.

The technical results of the proposed device are: increasing the performance of the device for studying the hydrodynamic properties of tubular blood vessel prostheses;

ensuring the completeness of research by increasing the number of measured parameters; improving the quality of measurements, bringing measurement conditions closer to physiological ones.

These results are achieved by the fact that the device:

- to measure the radial movement of the wall of the vessel under study, two laser distance sensors are used, the devices holding and orienting the vessel are placed on the frame, the sensors for the radial movement of the wall of the vessel under study are mechanically connected to the frame; the data registration process is automated;

- between the auxiliary circulatory pump (ACP) and the thermoregulation unit, a fluid flow sensor is integrated into the circuit through the control valves; temperature sensors of the working fluid are located before and after the test vessel in the direction of movement of the working fluid; the test vessel is connected to the support through a dynamometer; radial movement of the wall of the test vessel measured by two sensors mutually spaced along the axis of the vessel at a given distance;

- the directional movement of the working fluid in the circuit is ensured by an NVK with inlet and outlet check valves, controlled by a pneumatic drive unit, powered by a compressor; instead of an open reservoir, the circuit includes a pneumatic-hydraulic accumulator with a gas pressure sensor and an air pump; a thermoregulation unit is included in front of the vessel under study in the direction of movement of the working fluid; the tension of the test vessel is set under the control of the dynamometer readings, the test vessel is connected directly to the hydrodynamic channel; sensors for radial movement of the wall of the vessel under study, a working fluid pressure sensor and a fluid flow sensor are connected to a computer through an analog-to-digital converter (ADC).

In the design of the proposed device, an NVC with check valves at the inlet and outlet is used as a pump, providing one-way movement of the working fluid, controlled by a pneumatic drive unit powered by a compressor, which makes it possible to create the closest to the physiological nature of the fluid movement in the circuit, obtaining the correct profile of sphygmograms of the studied vessels.

Controlling the communication of the system with the atmosphere by means of shut-off valves of the pneumatic-hydraulic accumulator, as well as the ability to set the air pressure in the pneumatic-hydraulic accumulator using an air pump and a gas pressure sensor, allows you to set any values of systolic and diastolic pressure in the vessel within the measurement limits of the sensors used, providing the parameters necessary for research.

Fixation of the vessel through replaceable adapters installed in sockets, one of which is fixed in the frame, and the other is connected through a dynamometer to the main support that is movable along the axis of the vessel along the frame guides, allows testing the entire range of vessels of both biological and artificial origin, as well as also set the tension of the vessels, providing the parameters necessary for research.

The inclusion of a liquid flow sensor with an analog electrical output in the circuit allows you to determine the volume of liquid passing through the vessel under study during the pulsation cycle, ensuring the completeness of the research.

The use of two laser distance sensors with an analog electrical output as sensors for moving the vessel wall in the radial direction, placed on two supports movable along the frame guides, ensuring movement of the sensors along three mutually perpendicular axes relative to the axis of the vessel placement, one of which is parallel to the axis of the vessel placement, allows you to measure the speed of propagation of the pulse wave inside the vessel under study, ensuring completeness of research, simplifying the work with the device, providing non-contact measurements and eliminating the need to orient the sensors along one of three axes with each new measurement.

Using a pressure sensor with an analog electrical output as a pressure sensor for the working fluid in a vessel allows you to record a pressure curve and compare it with the readings of distance sensors and a fluid flow sensor, ensuring the completeness of the research and the reliability of the results.

Direct inclusion of the vessel under study in the circuit ensures the absence of parasitic vibrations reflected in sphygmograms, and the reliability of measurements due to the absence of excess resistance to radial stretching of the vessel.

The inclusion of a thermoregulation unit in the circuit in front of the vessel in the direction of movement of the working fluid, as well as placing temperature sensors in the circuit of sensitive elements before and after the vessel, makes it possible to conduct research at temperatures of the vessel and working fluid close to the temperature inside the body, ensuring the reliability of the research.

Registration of data obtained by sensors in a computer allows you to obtain measured values in high temporal resolution, compare them and quickly process them, which simplifies the operation of the device and increases its productivity.

Distinctive features of the proposed technical solution from the prototype are the following:

1) instead of an open reservoir, the circuit includes a pneumatic-hydraulic accumulator with an air pump, a pressure sensor and shut-off valves connected to it, connecting it to the atmosphere;

2) to impart directional movement to the working fluid, an NVC with check valves at the inlet and outlet is used, controlled by a pneumatic drive unit powered by the compressor;

3) after the control valves located in front of the vessel under study in the direction of movement of the working fluid, a liquid flow sensor with an analog electrical output connected via an ADC to the computer, a thermoregulation unit and a liquid temperature sensor are sequentially included in the circuit;

4) between the vessel under study and the shut-off valve located in front of the pneumatic accumulator in the direction of movement of the working fluid, a working fluid temperature sensor is included in the circuit;

5) to fix the vessel under study and set its tension, a frame with guides and a liquid collection tank is used under the axis of placement of the vessel with a drain hole, and the vessel is installed on adapters with a fitting diameter corresponding to the vessel, and the adapter located in front of the vessel in the direction of movement of the working fluid has a channel for selecting pressure from the wall of the hydrodynamic channel, and is installed in a seat connected through a dynamometer to the main support located on the frame guides, and the second adapter is installed in a seat rigidly fixed to the frame;

6) to obtain sphygmograms of the vessel under study, two laser distance sensors with analog electrical outputs are used, connected via an ADC to a computer, which are mounted on auxiliary supports placed on the frame guides, ensuring movement of the sensors along three mutually perpendicular axes, with one of the axes parallel to the placement axis the vessel being examined;

7) as a sensor for measuring the pressure of the working fluid, a sensor with an analog electrical output is used, connected via an ADC to the computer.

The essence of the invention is illustrated by the attached figure. In FIG. 1 shows the general diagram of the device.

The device includes a pneumatic hydraulic accumulator 1, to which an air pump 2 and an air pressure sensor 3 are connected. 1 communicates with the atmosphere through shut-off valves 4. From 1, the working fluid moves through check valve 5 to the auxiliary circulation pump (ACP) 6, which is controlled by a pneumatic drive unit (BPP) 8, powered by compressor 9. In 6, when the membrane moves forward under the influence of excess air pressure supplied from the pneumatic drive unit towards the working fluid, the pressure in the NVC increases, 5 closes, and the liquid moves through the check valve 7 to the control valve 10 Passing 10, the working fluid passes a liquid flow sensor with an electrical analog output 11. After 11, the liquid enters the thermoregulation unit 12, where it is heated, and after which there is a working fluid temperature sensor 13, which controls the temperature of the liquid entering the vessel under study. After 13 there is an adapter socket 16, connected through a dynamometer 17 to the main support 15, located on the guides of the frame 14. 15 can move along the guides of the frame 14 along the axis of placement of the vessel. An adapter with a pressure sampling channel 18 is placed in 16, to which a working fluid pressure sensor with an electrical analogue output 19 is connected. The test prosthesis of a tubular blood vessel 24 is connected to 18, connected from the opposite end to an adapter 25 placed in the socket of the adapter 26, fixed to 14 After 26, a working fluid temperature sensor 27 is included in the hydrodynamic channel, behind which there is a control valve 28 connected to 1. On the guides of the frame 14 there are also two auxiliary supports 20 and 22, on which laser distance sensors with an electrical analogue output 21 and 23, respectively, which can move relative to the axis of the vessel placement along three mutually perpendicular axes, with one of the axes parallel to the axis of the vessel placement, measuring the radial movement of the wall of the tubular blood vessel prosthesis under study 24, 11, 19, 21 and 23 are connected via an ADC 29 to a computer 30 , where the received information is stored and processed. The main support 15 has a lock 31.

The inventive device for studying the hydromechanical properties of tubular vessels operates as follows.

In the non-working state of the device, 24 is missing, 8, 9, 11, 12, 13, 21, 23, 27, 29 and 30 are disabled, 10 and 28 are closed, 4 is open, 18 and 25 are separate from 16 and 26, respectively, 18 is disconnected from 19, and latch 31 is loosened. To study the hydromechanical properties of tubular vessels and their prostheses, 30, 29, 23, 21, 19, 11, 13 and 27 are included, 25 is placed in 26, and 18 is placed in 16. 24 is placed in 18 and 25, thereby closing the circuit. 19 is connected to 18. If necessary, working fluid is added to 1. 10 and 28 are opened, the circuit is filled with working fluid so as to exclude the presence of gas bubbles in it. 15 is moved along the guides of the frame 14 so as to set 24 the required tension, monitoring the readings 17, after which 15 is locked with a latch, the readings 17 are recorded. 21 and 23 using 20 and 22 are moved so that the axis of the laser beam is perpendicular to the axis of the vessel, 20 and 22 are locked with clamps. They block 4, turn on 9 first, then 8. Using 8, the frequency of the NVK pulses, using 2, 3, 8, 10 and 28 set the required systolic and diastolic pressure, monitoring the readings of 19 through 30. Turn on and adjust 12, wait for the required to be established temperature values at 13 and 27. During the required period of time, record readings 11, 19, 21 and 23 at 30. Having completed the measurements, turn off 12, wait at least a minute until the heating element cools down. 8 and 9 are turned off, 4 is opened, 10 and 28 are closed. 24 is removed from 18 and 25, the working fluid from the hydrodynamic channel is drained into the drain, the main caliper 15, auxiliary calipers 20 and 22 are weakened. If necessary, install another 24 on the existing 18 and 25, or change 18 and 25 to the size required for the study, and install 24 of a different size, repeat the described operations.

At the end of the measurements, 11, 13, 27, 19, 21, 23, 29 and 30 are turned off. The received and recorded data are processed.

Example.

A device was manufactured to study the hydromechanical properties of tubular blood vessel prostheses and tests were carried out on the Ecoflon blood vessel prosthesis. During testing, it was found that the vascular prosthesis is easy to install for research. The presence of displacement, flow, pressure, temperature sensors and synchronous recording of all parameters made it possible to conduct a comprehensive study of the blood vessel prosthesis, including measurement of the speed of propagation of the pulse wave, which increases the accuracy of tests and research and reduces test time. The presence of thermoregulation and the use of NVC as a control unit for the movement of the test liquid brought the testing conditions closer to the conditions in the human body.

Claims (1)

A device for studying the hydromechanical properties of tubular blood vessel prostheses, consisting of a pneumatic-hydraulic accumulator connected in series in a closed circuit with an air pump connected to it, an air pressure sensor and shut-off valves, a check valve, an auxiliary circulation pump, a controlled pneumatic drive unit configured to be powered by a compressor, further a check valve, control valves, a liquid flow sensor, a thermoregulation unit, a temperature sensor, a socket of the first adapter are connected to the circuit, connected through a dynamometer to the main caliper located on the frame guides and equipped with a lock, and with the ability to move along the frame guides along the axis of the tubular circulatory prosthesis vessel, to set the tension of the test tubular blood vessel prosthesis, controlled by the dynamometer readings, in the socket of the first adapter there is a first adapter with a pressure sampling channel, to which is connected a working fluid pressure sensor with an electrical analog output and the test tubular blood vessel prosthesis, connected at the opposite end to with the second adapter located in the socket of the second conductor, mounted on the frame guides, then a working fluid temperature sensor is introduced into the circuit, behind which there is a control valve connected to a pneumatic-hydraulic accumulator, and on the frame guides there are also two auxiliary supports, made with the possibility of locking with clamps, on in which laser distance sensors with an electrical analogue output are installed, configured to measure the radial movement of the wall of the test tubular blood vessel prosthesis, with the ability to move relative to the axis of placement of the test tubular blood vessel prosthesis along three mutually perpendicular axes, one of the axes being parallel to the axis of placement of the test tubular prosthesis blood vessel, to position the axis of the laser beam perpendicular to the axis of placement of the tubular blood vessel prosthesis under study, all four sensors are connected through an analog-to-digital converter to the computer.

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