RU2675066C1 - Monolithic three-chamber pneumatic sensor with integrated throttle channels for continuous non-invasive measurement of arterial pressure - Google Patents

Abstract

FIELD: medicine.SUBSTANCE: invention relates to medical technology, namely to a sensor for continuous measurement of blood pressure. Sensor contains applicator (10) with contact pad (100) and pneumatic chamber (12). Pneumatic chamber is open on flat surface (17) of the contact pad and is made in the body of the applicator. Pressure sensor is connected to the camera and connected via ADC (30) to data control (50) and processing unit with display device (60). Sensor contains high-pressure chamber (12). High-pressure chamber is in communication with air pump (42). Pneumatic chamber of the applicator is made of three identical working chambers (14, 15, 16). Chambers are open to the flat surface of the contact pad and placed on it in a straight line at equal distances from each other. Each working chamber is connected by means of tubes (20, 21, 22) with individual pressure sensor (23, 24, 25) and ADC (30). Ends of these tubes are recessed relative to the surface of the contact pad of the applicator by the size of gap (222) so that the total volume of the internal cavity of the tube and specified gap (222) does not exceed 1.5 mm. High-pressure chamber includes manifold (121). Collector is connected to the throttle channels with each of working chambers (14, 15, 16) with the provision of a constant mode of air bleeding from them.EFFECT: enhanced functionality is achieved while simplifying the design, improving performance and reliability.5 cl, 5 dwg

Description

The invention relates to medical equipment, in particular to non-invasive tonometers.

Known methods for non-invasive measurement of blood pressure (BP) mainly come down to manipulating the pressure in the cuff or applicator, compressing the artery (along with the limb), and determining systolic and diastolic pressure in the artery by pulsations of the pressure in the cuff (see, for example, Non-invasive continuous blood pressure monitoring: a review of current applications. Chung E, Chen G, Alexander B, Cannesson M. / Front Med. 2013 Mar; 7 (1): 91-101. Epub 2013 Jan 23). For most solutions, the method of volume compensation was used, based on the idea of "unloading the walls of blood vessels," because it is assumed that in the “unloaded” state the pressure inside the vessels is equal to the pressure outside them. The pressure in the cuff is adjusted in such a way as to keep the blood volume constant in time, equal to the volume which, when calibrated, is selected as the "unloading" vessel. In other solutions, the sensor presses the artery against the radius so that it compresses it sufficiently, makes contact with its wall flat, but does not squeeze until occlusion. Then, pulse changes in blood pressure are recorded through the walls of the vessel using lateral pressure strain gauges. The pressure required to flatten the artery walls, but not close it, is known as the “working pressure” and is calculated by a rather complex algorithm that includes preliminary estimates of systolic, diastolic and pulse pressures.

A device for continuous non-invasive pressure measurement is described (RU 2140187 C1, Medveyw, Inc. (US), 10.27.1999). It contains a means for applying a variable pressing pressure to a sensitive tool, a tool for calculating blood pressure based on perceived pulse pressure fluctuations inside a lower artery and a means to neutralize the forces created by the tissue near the lower artery, while ensuring compliance with the patient’s body area. A sensor having a sensitive surface for sensing blood pressure in a patient's lower artery comprises a transducer, a side wall, a flexible diaphragm, and a fluid connecting medium. The side wall is located at a certain distance from the transducer and supports it above the inferior artery. The fluid interconnects the sensitive surface of the transducer and the flexible diaphragm and transmits pulse fluctuations in blood pressure from the flexible diaphragm to the sensitive surface of the transducer.

The disadvantage of this device is that the adjustment of the variable pressing pressure to the sensitive medium is carried out to relatively slowly equalize the average pressure in the artery and does not monitor the unloading of the artery walls throughout the cycle, which will lead to distortion of the pressure pulsations transmitted by the liquid medium.

A device is known for continuous recording of mean arterial pressure (RU 2013992 C1, Eman A.A., 15.06.1994), which consists of a hydraulic filter, a pneumoelectronic follow-up system, including an ear pulse sensor, fixed with a pellet or cuff for artery occlusion connected through an air duct to the controlled pressure increase and decrease blocks, an amplifier connected in series with the input to the pulse sensor, an electronic filter and a threshold block, as well as registration and indication blocks, in series. The disadvantage of this device is that it is suitable only for recording average blood pressure and does not provide information about the dynamics of beat-to-beat blood pressure, nor even systolic and diastolic blood pressure values.

The use of a liquid chamber is described, the area of which is selected from the condition of reliable overlapping of the artery bed area and measuring the pulse wave pressure perceived at the exit of the artery close to the skin surface (RU 2281687 C1, Penza State University, 08.20.2006). The disadvantage is that graduation is necessary for each patient, which must take into account the external pressure of the liquid chamber against the limb during measurement and be used to recalculate the amplitude of the pulse oscillations in the values of the upper and lower blood pressure.

The device described in the application WO 2011135446 (A2), CARDIOSTAR, INC; BARON, EHUD, 03/03/2011, contains an applicator applied to the patient’s limbs, connected through a working chamber to a pressure sensor, an ADC, a controller with a processor, an air pump. The working chamber is located at the location of the artery, which is localized by normal palpation. The role of the controller is to implement the method of quasi-continuous blood pressure measurement and signal analysis, including based on wavelets to track the average blood pressure. The method, in fact, is a complicated oscillometric method for measuring systolic, diastolic and mean blood pressure. The disadvantage of the method is the inability to continuously measure the true value of beat-to-beat blood pressure.

The closest to the destination is a pneumatic sensor for continuous measurement of blood pressure, described in patent RU 2638712 C1, FGBUN Institute of Radio Engineering and Electronics. V.A. Kotelnikova of the Russian Academy of Sciences, JOINT STOCK COMPANY NEUROKOM, December 15, 2017 - prototype. The sensor contains an applicator, a working chamber with a pressure sensor connected via an ADC to a microcontroller, which is connected to an air pump and a display and data processing device. The working chamber is made in the form of a cavity formed in the body of the applicator, which is connected to a pressure sensor and, via an adjustment throttle, to a high-pressure chamber connected to an air pump, which contains a compressor and a receiver. The applicator has a contact pad for interaction with a controlled area of the artery. An opening is formed in the center of the contact area, connected through the channel with the cavity of the working chamber, open on a flat surface of the contact area with the possibility of free air flow in the controlled area of the artery, while around the specified holes are the inlet openings of the through channels of air exhaust, made with the possibility of maintaining pressure in the working chamber is equal to the pressure on the flat surface of the contact pad from the side of the skin and tissues above the unloaded artery wall.

However, the device has insufficient information content, since the sensor has one measuring platform, and the dimensions do not make it possible to assess the accuracy of positioning the applicator over the artery.

The present invention is directed to solving the problem of expanding functionality and improving the design of a device for continuous measurement of blood pressure

The patented sensor for continuous measurement of blood pressure contains an applicator with a contact pad and a pneumatic chamber open on a flat surface of the contact pad and made in the body of the applicator, a pressure sensor connected to the camera, connected via an ADC to the control and data processing unit with a display device, a high camera pressure communicated with the air pump.

The difference is that the pneumatic chamber of the applicator is made of three identical working chambers, openings on the flat surface of the contact pad and placed on it in a straight line at equal distances from each other.

Each working chamber is connected by means of tubes to an individual pressure transducer and ADC, and the ends of these tubes are recessed relative to the surface of the contact area of the applicator by the gap value so that the total volume of the inner cavity of the tube and the specified gap does not exceed 1.5 cubic meters. mm The high-pressure chamber includes a manifold connected by throttle channels from each of the working chambers with a constant bleeding mode of air.

The sensor can be characterized in that the diameter d of the openings of the working chambers on the flat surface of the contact pad is d = 0.7-0.9 mm, and the distance w between them is w = 1.5-2 mm, and also the fact that the applicator is made integral from polymethyl methacrylate.

The sensor may also be characterized in that the air pump comprises a compressor and a receiver configured to maintain a predetermined pressure in the high-pressure chamber manifold in the range up to 300 mmHg. Art., as well as the fact that the throttle channels are made with a cross section that provides a change in pressure in the cavity of the working chamber from zero to about 200 mm RT. Art. in units of milliseconds.

The technical result is the expansion of functionality while simplifying the design, increasing speed and reliability. This is achieved by measuring pressure simultaneously at three points, which allows the applicator to be positioned relative to the artery. Simplification of the design while increasing reliability is achieved by performing a throttle channel directly in the applicator body. Reducing the volume of the working chamber makes it possible to increase performance while maintaining the laminar flow of outflowing air, while the artery is not pinched and blood flow is not blocked.

The invention is illustrated in the drawings, where:

in FIG. 1 shows a block diagram of a device with an applicator design;

in FIG. 2 is a view of the applicator from the side of the contact surface;

in FIG. 3 - view of a single channel in a longitudinal section, enlarged;

in FIG. 4 is the same as in FIG. 3, view of a single channel from the side of the working surface;

in FIG. 5 - experimental pressure curves in three working chambers when the applicator is located above the radial artery in a position close to optimal.

The block diagram of the device and the design of the applicator are shown in FIG. 1-4. The device comprises an applicator 10, which is an element adapted for installation on an extremity 100. The applicator 10 has a housing 11 in which a cavity is formed of a high-pressure chamber 12 with a collector 121. The working surface 17, brought into contact with the limb 100 when registering blood pressure, contains three working chambers 14, 15, 16. which are not communicated with each other. Each chamber is connected by means of flexible tubes 20, 21, 22 to pressure sensors 23, 24, 25. Sensors 23-25 are connected to the input of the ADC 30, the output of which is connected to the control unit 50. The information output of block 50 is connected to computer 60.

The creation and control of high pressure in the cavity of the manifold 121 is provided by an air pump, for which the cavity of the manifold 121 is connected by a pneumatic line 40 to the pressure sensor 41 and an air pump formed by the receiver 42 and the compressor 43 connected to it. The air pump serves to maintain the desired high pressure in the manifold 121 in the range up to 300 mm RT. Art ..

To increase the information content and solve the problem of positioning the sensor, it is necessary to control the pressure on several, optimally three, sites located in a straight line with gaps of w = 1.5-2 mm. In FIG. 2, positions 20, 21, 22 show the placement of the working chambers 14, 15, 16 from the side of the working surface 17. It is convenient and technologically possible to form the working chambers by making a gap 222 between the ends of the flexible tubes 20, 21, 22 and the working surface 17.

In FIG. 3, 4, the structure of a single channel, in particular, chamber 14, is shown enlarged. In the housing 11, a hole is made with a diameter matching the outer diameter of the flexible tube 22, where the specified tube is inserted with a gap 222 between its end (end). The manifold 121 of the high-pressure chamber 12 is connected to the gap 222 of the working chamber 14 via throttle channels 226. Such channels 226 are also present in each chamber 15, 16. Their purpose is to provide pneumatic communication between the manifold 121 through the gap 222 into the channel 221 of the tube 22, including case, when the working surface is in pneumatic contact with the surface 100. The direction of throttling is shown by the dotted line and arrows 224-225. The throttle channels 226 are made with a cross section that provides a change in pressure in the cavity of the working chamber from zero to about 200 mm RT. Art. in units of milliseconds.

The reduction in the dimensions of each chamber is solved by changing the design of the throttle and moving the pressure sensor out of the housing 11. The pressure sensor is connected by a flexible PVC pipe to the working chamber 14 (15, 16), the total volume of which also includes the internal volume of the cavity 221 of the tube 22. This requires minimizing how length and internal diameter of the tube. The layout of the board with pressure sensors close to the sensor reduces the length of the tubes to 20 mm. The inner diameter of the tube is about 0.3 mm with an outer diameter of 0.8 mm. The volume of the cavity 221 of the tube 22 at these sizes does not exceed 1.5 mm3.

Throttle channels 226 for dosed air leakage from the manifold 121 of the high-pressure chamber to the working chambers 14 (15, 16) can be performed, for example, by means of gap-forming embedded elements, while the volume of these working chambers is practically equal only to the volume of the internal cavity of the tube.

The principle of operation of the device is based on maintaining the air pressure in the working chambers 14, 15, 16, equal to the pressures on the corresponding areas (positions 20, 21, 22 in Fig. 2) of the applicator 10 from the side of the artery and skin layers (surface 100), which is similar to " valves ", relieving excess pressure in the working chambers 14, 15, 16.

In more detail, the principle is illustrated by the example of the functioning of one of the cameras (see Fig. 3). Due to the constant flow of air into the chamber 14 through the throttle channel 226, the pressure in the chamber 14 will increase until the “valve” opens, the response level of which is set by the current pressure on the applicator surface in the projection of the working chamber from the artery. The difference from a conventional safety valve is that excess air is discharged continuously and a change in pressure on the surface of the applicator 17 causes a corresponding change in pressure in the working chamber 14 without disturbing the stable mode of air outflow. The direction of throttling is shown by the dashed line and arrow 224, and the direction of the outflow of air from the working chamber is shown by arrows 225.

The device operates as follows.

When measuring, the applicator 10 is applied to the surface of the wrist 100 in the projection of the radial artery so that all three working chambers 14, 15, 16, structurally made on one straight line, are located in a line perpendicular to the artery. Observing on the computer monitor 60 the pressure pulsations in the working chambers 14, 15, 16, the applicator 10 is positioned in the direction tangential to the artery with respect to the pulsation symmetry in the side working chambers 14 and 16, and in the radial direction, at the maximum pressure amplitude in the central working chamber 15 An approximate form of pressure pulsations of a correctly positioned applicator is shown in Fig. 5, where curve 1 is the pressure in the central working chamber 15, curves 2 and 3 are the pressure in the side working chambers 14 and 16, respectively.

The resulting pressure signal in the working chamber 15 in real time repeats the change in blood pressure in the artery. In this case, the artery is not pinched and the blood flow is not blocked, which allows for a continuous continuous non-invasive measurement of blood pressure.

Claims (9)

1. A sensor for continuous measurement of blood pressure, comprising an applicator with a contact pad and a pneumatic chamber open on a flat surface of the contact pad and made in the body of the applicator, a pressure sensor connected to the camera, connected via an ADC to a control and data processing unit with a display device, a high pressure chamber in communication with the air pump, characterized in that the pneumatic chamber of the applicator is made of three identical working chambers open with holes on the flat surface of the contact pad and placed on it in a straight line at equal distances from each other, while each working chamber is connected by means of tubes to an individual pressure transducer and ADC, and the ends of these tubes are recessed relative to the surface of the contact area of the applicator by the gap value so that the total volume of the inner cavity of the tube and the specified gap does not exceed 1.5 cubic meters. mm, moreover the high-pressure chamber includes a manifold connected by throttle channels from each of the working chambers with a constant bleeding mode of air from them. 2. The sensor according to claim 1, characterized in that the diameter d of the openings of the working chambers on the flat surface of the contact pad is d = 0.7-0.9 mm, and the distance w between them is w = 1.5-2 mm. 3. The sensor according to claim 1, characterized in that the applicator is made monolithic of polymethyl methacrylate. 4. The sensor of claim 1, wherein the air pump comprises a compressor and a receiver configured to maintain a predetermined pressure in the high-pressure chamber manifold in the range up to 300 mm Hg. 5. The sensor according to claim 1, characterized in that the throttle channels are made with a cross section that provides a change in pressure in the cavity of the working chamber from zero to about 200 mm Hg. in units of milliseconds.

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