Electronic tonometer

Abstract

FIELD: medical equipment.SUBSTANCE: electronic tonometer contains a two-chamber compression cuff, first and second pressure sensors, a pressure source containing a reservoir with a given volume of liquid and a device for supplying liquid to the first chamber of the compression cuff, an oscillation amplitude analyzer of the second chamber of the compression cuff, recording and indication units, a control unit for the pressure source of the first chamber of the compression cuff. The second chamber is located in the compression hydraulic cuff coaxially with the first chamber and below it and is made sealed to create excess pressure by transmitting excess pressure from the first chamber through a damping gasket between them, eliminating the transmission of pressure pulsations from the first chamber to the second. The second chamber is designed to be fixedly positioned on the forearm near the artery and coaxially with it. The pressure sensor of the first chamber is connected to the oscillation amplitude analyzer of the second chamber.EFFECT: increased accuracy of pressure measurement is achieved.1 cl, 5 dwg

Description

[0001] The invention relates to medical equipment and can be used to measure blood pressure and pulse.

[0002] The Korotkov method is considered the reference (standard) method for measuring pressure, which allows for fairly accurate (with a 7% error) measurement of blood pressure.

[0003] The method is based on creating excess pressure by blocking the artery by pumping air into the cuff and then releasing air from the cuff.

[0004] When the artery is occluded, heart sounds cease to form due to the artery's complete straightening (there is no turbulent flow causing vibrations that are transmitted proximally, i.e., below the cuff). When the cuff is deflated and the first heart sounds appear, the systolic (upper) pressure is recorded. When they cease, the diastolic (lower) pressure is recorded.

[0005] Known devices for isolating and transforming Korotkov tones contain a phonendoscope head, an acoustic chamber, which is connected to a microphone located outside the phonendoscope.

[0006] The disadvantages of the devices are low noise immunity of measurements, due to high sensitivity to relative movements and to ambient noise due to the presence of a microphone.

[0007] At the same time, when the pulse wave passes under the cuff, part of the pulse wave energy is spent on the movement and deformation of tissues (muscles, fat, skin).

[0008] These changes are transmitted to the air compression cuff, and creates additional pressure, which is used to compress the artery.

[0009] In this case, deviations in blood pressure measurements may exceed 15...28 mmHg.

[0010] Among the foreign companies developing and manufacturing tonometers, the most famous are: the developer Omron, Japan, the developer A&D, Japan, the developer PAUL HARTMANN AG, Germany, the developer B.Weil Swiss, Switzerland, as well as the Russian developer LLC "NPC MT" Armed ".

[0011] These devices utilize an oscillometric method for assessing hemodynamic parameters. This method records air pressure pulsations that occur as blood passes through a cuffed artery. Pulse waves are converted into oscillations by air compression cuffs. The oscillation amplitude is 2-3 mmHg. Oscillations are detected during decompression from cuff pressure in the range of 300-50 mmHg. The process of converting arterial pressure pulse waves into oscillations is accompanied by significant distortion of the pulse wave contour, the influence of motion artifacts, and the presence of noise. Overall, the error in pressure assessment with oscillometric tonometers based on an air compression cuff is estimated at 20-30%. Estimation of hemodynamic parameters based on systolic blood pressure (SBP) and diastolic blood pressure (DBP) values ​​in VaSera sphygmometers results in a significant error of up to 50%.

[0012] Among the patented technical solutions, the technical solution according to patent 2546918 “DEVICE FOR NON-INVASIVE MEASUREMENT OF BLOOD PRESSURE AND METHOD OF ITS MEASUREMENT”, application 2013107062 / 14 dated 05 / 17 / 2011, published 09 / 20 / 2014.

[0013] The device comprises a control module comprising a microprocessor connected to an air pressure sensor, a pressure cuff connected to the air pressure sensor and comprising a gas-filled cuff with a gas tube, and a pulse wave sensor connected to the control module. The pulse wave sensor is fixed in a position below the pressure cuff according to the direction of arterial blood flow. The microprocessor is configured to consider in real time a plurality of pulse wave amplitudes detected by the pulse wave sensor during a slow increase from zero and the corresponding pressure in the pressure cuff to determine the systolic pressure based on the pulse wave amplitudes near the systolic pressure.The microprocessor processes several periods of pulse delay between pulse waves and the corresponding AC pressure during periods of variable pulse delay to periods of constant pulse delay, and the corresponding cuff pressures to determine the diastolic pressure.

[0014] The device's drawbacks include the algorithmic determination of systolic and diastolic pressure based on the approximation of three points of the pulsation sensor's amplitude, which leads to significant errors. With a maximum cuff pressure measurement error of ±3 mmHg (technical specifications for oscillator-type tonometers), the oscillation amplitude measurement error is 200%. Artifacts (noise, mechanical movement, and displacement) also cause changes in amplitude and its drift, leading to significant errors.

[0015] In hydrocuff tonometers, the oscillation circuit accurately reproduces the arterial pulse wave circuit with a significant increase in pulsation amplitude of 15–25 mmHg. With the oscillatory type of oscillation in the air cuff, as the pulse wave passes under the cuff, the pressure fluctuates by 2–3 mmHg.

[0016] The maximum oscillation amplitude, Amax, corresponds to the pulse pressure value (the difference between the systolic (upper) and diastolic (lower) pressures). Half the oscillation amplitude (0.5*Amax) corresponds to the systolic pressure value, and half (0.8*Amax) corresponds to the diastolic pressure value. When determining blood pressure values, the oscillation amplitude assessment significantly affects the instrumental error. Increasing the amplitude helps reduce the instrumental error.

[0017] These advantages allow for pulse wave analysis to identify various pathologies in the early stages of cardiovascular diseases and reduce the error in assessing hemodynamic parameters.

[0018] A GERASHCHENKO TONOMETER is known (Patent of the Russian Federation No. 104437 U8, IPC A61B 5 / 022, published on 20.05.2011, Bulletin No. 14), comprising a compression cuff, a pressure sensor, registration and indication units, a pulse pressure source, a pressure source control unit, a differential amplifier, a second pressure sensor, a second pressure source control unit, wherein the compression cuff is made two-chambered, and liquid is introduced as the working fluid, wherein the pressure sensors are connected by their inputs to the first and second chambers of the compression cuff and the outputs of the pressure source control units, respectively, and by their outputs to the differential amplifier, the output of which is connected to the input of the registration unit, which in turn is connected to the indication unit, wherein the pulse pressure source contains a reservoir with a given volume of liquid and a bulb for applying pressure.

[0019] The disadvantage of the device is low accuracy, caused by changes in the amplitude of pulsations during decompression and distortion of the function of the moment of determining systolic and diastolic pressures, caused by the appearance of a difference signal at the output of the differential amplifier due to the influence of the first chamber on the amplitude of oscillations of the second chamber of the compression cuff.

[0020] The closest to the claimed technical solution is the patent for the invention “Electronic tonometer” (Patent of the Russian Federation No. 2652070 C1, IPC A61B 4 / 0225, application 2017117129 dated 05 / 16 / 2017, published 04 / 24 / 2018 Bulletin No. 12).

[0021] The electronic tonometer comprises a dual-chamber compression cuff, two pressure sensors, recording and display units, a pressure source containing a reservoir containing a predetermined volume of fluid and a device for delivering fluid to the chambers of the compression cuff, first and second pressure source control units, and an additional oscillation amplitude analyzer for the second chamber of the compression cuff. The output of the second chamber pressure sensor is connected to the input of the oscillation amplitude analyzer for the second chamber of the compression cuff, the output of which is connected to the inputs of the pressure source, the second pressure source control unit, and the recording unit.

[0022] The disadvantage of the device is the low accuracy of pressure measurement, caused by the destabilization of the vascular occlusion process.

[0023] The aim of the invention is to improve the accuracy of pressure measurement.

[0024] The technical result is achieved in that in an electronic tonometer containing a two-chamber compression hydrocuff (1, 2), first (3) and second (4) pressure sensors, a pressure source (5) containing a reservoir with a given volume of liquid and a device for feeding liquid into the first chamber of the compression hydrocuff, an oscillation amplitude analyzer (6) of the second chamber (2) of the compression hydrocuff, recording units (7) and indication units (8), a control unit (9) of the pressure source (5) of the first chamber (1) of the compression hydrocuff, wherein the pressure sensors are connected by inputs to the first and second chambers of the compression hydrocuff, the pressure sensor of the first chamber of the compression hydrocuff is connected to the input of the recording unit (7) and the output of the control unit of the pressure source of the first chamber of the compression hydrocuff, which is connected to the first chamber of the compression hydrocuff and the pressure source of the first chamber of the compression hydrocuff,the output of the recording unit (7) is connected to the input of the display unit (8), the oscillation amplitude analyzer (6) of the second chamber (2) of the compression cuff is connected to the input of the recording unit (7), the input of the pressure source (5) of the first chamber of the compression cuff and the output of the second pressure sensor, according to the invention, the second chamber (2) of the compression cuff is located in the compression cuff coaxially with the first chamber and under it and is made sealed with the possibility of creating excess pressure in the second chamber of the compression cuff due to the transfer of excess pressure from the first chamber of the compression cuff through an additionally introduced damping gasket (10) between them, excluding the transfer of pressure pulsations from the first chamber (1) to the second (2), wherein the volume and shape of the second chamber of the compression cuff correspond to the possibility of perceiving pulse waves of the artery,wherein the second chamber of the compression cuff is designed with the possibility of its fixed placement on the forearm near the artery and coaxially with it when the compression cuff is installed on the surface of the skin, wherein the pressure sensor (3) of the first chamber (1) of the compression cuff is connected to the oscillation amplitude analyzer (6) of the second chamber of the compression cuff.

[0025] Thus, the set of common essential features ensures the technical result specified in the purpose of the invention.

[0026] The essence of the claimed technical solution is further explained by drawings:

[0027] Fig. 1 shows a block diagram of an electronic tonometer;

[0028] Fig. 2 shows the relative position of the first (1) and second (2) chambers of the compression cuff over the artery;

[0029] Fig. 3 shows in section the location of the first (1) and second (2) chambers of the compression cuff on the forearm;

[0030] Fig. 4 shows graphs of pressure changes in the first (1) and second (2) chambers of the compression cuff during compression and decompression for assessing the systolic arterial pressure (SAP) values, where the appearance of the first pulsation in the second chamber of the compression cuff determines the systolic pressure value based on the pressure value in the first chamber of the cuff. The moment of the appearance of pulsations in the second (2) chamber corresponds to a pressure of 144 mm Hg. It characterizes the end of the occlusion process when the pressures of the artery and the cuff are equalized;

[0031] Fig. 5 is a section of the graph that explains the determination of the diastolic blood pressure (DBP) value and is 92 mmHg.

[0032] An electronic tonometer comprising a two-chamber compression cuff (1,2), first (3) and second (4) pressure sensors, a pressure source (5) comprising a reservoir with a given volume of liquid and a device for feeding liquid into the first chamber of the compression cuff, an oscillation amplitude analyzer (6) of the second chamber (2) of the compression cuff, recording units (7) and indication units (8), a control unit (9) of the pressure source (5) of the first chamber (1) of the compression cuff, wherein the pressure sensors are connected by inputs to the first and second chambers of the compression cuff, the pressure sensor of the first chamber of the compression cuff is connected to the input of the recording unit (7) and the output of the control unit of the pressure source of the first chamber of the compression cuff, which is connected to the first chamber of the compression cuff and the pressure source of the first chamber of the compression cuff, the output of the recording unit (7) is connected to the input of the indication unit (8),the oscillation amplitude analyzer (6) of the second chamber (2) of the compression cuff is connected to the input of the recording unit (7), the input of the pressure source (5) of the first chamber of the compression cuff and the output of the second pressure sensor, wherein the second chamber (2) of the compression cuff is located in the compression cuff coaxially with the first chamber and under it and is made sealed with the possibility of creating excess pressure in the second chamber of the compression cuff due to the transfer of excess pressure from the first chamber of the compression cuff through an additionally introduced damping gasket (10) between them, excluding the transfer of pressure pulsations from the first chamber (1) to the second (2), wherein the volume and shape of the second chamber of the compression cuff correspond to the possibility of perceiving pulse waves of the artery,wherein the second chamber of the compression hydrocuff is designed with the possibility of its fixed placement on the forearm near the artery and coaxially with it when the compression hydrocuff is installed on the surface of the skin, wherein the pressure sensor (3) of the first chamber (1) of the compression hydrocuff is connected to the oscillation amplitude analyzer (6) of the second chamber of the compression hydrocuff.

[0033] Working principle.

[0034] Before starting the measurement, the two-chamber compression hydrocuff is installed on the patient's forearm in such a way that the second chamber (2) of the compression hydrocuff, filled with liquid, made hermetically sealed and placed in the compression hydrocuff coaxially with the first chamber and under it, is fixedly located near the brachial artery and coaxially with it.

[0035] Next, excess pressure is created in the first chamber (1) by supplying fluid from the pressure source (5) to the first chamber (1) of the compression cuff. This creates excess pressure in the chamber. The pressure sensor (3) of the first chamber (1) of the compression cuff records the pressure value in it, and when the expected systolic pressure exceeds 20 mmHg, the compression process stops and the decompression process begins. The oscillation amplitude analyzer (6) of the second chamber (2) of the compression cuff evaluates the changes in oscillation amplitude.

[0036] During decompression, when the first pressure pulsation occurs in the second chamber, the pressure in the first chamber of the compression cuff is recorded. This value is considered the systolic pressure. Decompression then continues until the maximum amplitude is reached in the second chamber of the compression cuff. This value is considered the diastolic pressure. The measurement process ends, and fluid is discharged from the first chamber (1) of the compression cuff into the pressure source reservoir (5). The second chamber (2) of the compression cuff has high sensitivity, detecting the presence or absence of pulse waves. This detects the onset of blood flow. The absence or increase in the amplitude of pulsations in the second chamber (2) of the compression cuff indicates the absence of an effect on the artery. In other words, this indicates the end of arterial compression.The full opening of the artery corresponds to the value of the maximum oscillation amplitude in the second chamber and corresponds to the value of diastolic pressure.

[0037] Due to the high sensitivity of the hydrocuff due to the second chamber being sealed, filled with liquid and with a volume and shape corresponding to the ability to perceive the pulse waves of the artery, the process of determining the moments of the appearance of oscillations and their maximum amplitude is stabilized.

[0038] The use of a hydrocuff also stabilizes the process of determining the moment of the end of occlusion due to the absence of the effects of changes in the cuff volume caused by the lack of compressibility of the liquid.

[0039] The use of the proposed technical solution can improve the accuracy of pressure measurement.

Claims

An electronic tonometer comprising a two-chamber compression cuff, first and second pressure sensors, a pressure source comprising a reservoir with a given volume of liquid and a device for feeding liquid into the first chamber of the compression cuff, an oscillation amplitude analyzer of the second chamber of the compression cuff, recording and indication units, a control unit for the pressure source of the first chamber of the compression cuff, wherein the pressure sensors are connected by inputs to the first and second chambers of the compression cuff, the pressure sensor of the first chamber of the compression cuff is connected to the input of the recording unit and the output of the control unit for the pressure source of the first chamber of the compression cuff, which is connected to the first chamber of the compression cuff and the pressure source of the first chamber of the compression cuff, the output of the recording unit is connected to the input of the indication unit,an oscillation amplitude analyzer of the second chamber of the compression cuff is connected to the input of the recording unit, the input of the pressure source of the first chamber of the compression cuff and the output of the second pressure sensor, characterized in that the second chamber of the compression cuff is located in the compression cuff coaxially with the first chamber and under it and is made sealed with the ability to create excess pressure in the second chamber of the compression cuff due to the ability to transmit excess pressure from the first chamber of the compression cuff through an additionally introduced damping gasket between them, excluding the transmission of pressure pulsations from the first chamber to the second, wherein the volume and shape of the second chamber of the compression cuff correspond to the ability to perceive pulse waves of the artery,wherein the second chamber of the compression cuff is designed with the possibility of its fixed placement on the forearm near the artery and coaxially with it when the compression cuff is installed on the surface of the skin, wherein the pressure sensor of the first chamber of the compression cuff is connected to the oscillation amplitude analyzer of the second chamber of the compression cuff.

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