RU2800898C1 - Device for measuring pulse wave velocity when measuring arterial pressure by oscillometric method with extended functions - Google Patents

Abstract

FIELD: medical equipment.

SUBSTANCE: invention relates to devices for simultaneous non-invasive measurement of blood pressure (BP) and pulse wave velocity (PWV) in blood vessels. The device includes an automatic blood pressure monitor for measuring blood pressure by the oscillometric method with two shoulder compression cuffs (5.1, 5.2) and four optical PPG sensors (6.1–6.4) attached to it. The tonometer contains an electronic block and two pneumatic blocks. Each pneumatic unit includes a cuff inflation unit, a pneumatic pressure relief valve, and a cuff air pressure sensor. The electronic unit includes a microprocessor, two blocks for processing signals from pressure sensors and four blocks for processing signals from PPG sensors. The microprocessor of the tonometer is configured to process all incoming signals from pneumatic units and PPG sensors, perform calculations for measuring PWV, and also control the operation of PPG sensors and pneumatic units. Each block for processing signals from pressure sensors contains an analog amplification block, a digitization block and a digital filtering block connected in series. Each block for processing signals from PPG sensors contains an analog amplification block, a digitization block and a digital filtering block connected in series with an adjustable delay in the appearance of a signal at the output of the block. The microprocessor has eight output channels for controlling the operation and switching on/off of the elements of pneumatic units and PPG sensors and is equipped with algorithms for calculating PWV in the aorta, left-sided and right-sided PWV for each PPG sensor, as well as the cardio-ankle vascular index and its analogues for the aorta and peripheral small arteries in the area "lower leg — toe" for the left and right sides of the body.

EFFECT: increased diagnostic information content of the device in the evaluation of PWV and expansion of its functionality by determining PWV in vessels of different hierarchies along the entire body simultaneously with the procedure for measuring blood pressure using the standard oscillometric method, taking measurements simultaneously from two sides of the body, which allows you to simultaneously assess the asymmetry of indicators from the left and right sides of the body and separately evaluate PWV in the aorta and in peripheral vessels.

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Description

FIELD OF TECHNOLOGY

The invention relates to medicine and medical technology, namely to non-invasive methods and devices for the simultaneous measurement of blood pressure (hereinafter referred to as BP) and pulse wave propagation velocity (hereinafter referred to as PWV) in blood vessels.

DESCRIPTION OF THE SOLVED MEDICAL AND TECHNICAL PROBLEM

A large number of cardiovascular diseases around the world and frequent severe complications from them indicate that it is extremely important to have at hand today, including at home for self-control, available methods for non-invasive express assessment of not only blood pressure, but also functional the state of the entire cardiovascular system as a whole, in particular the aorta and peripheral vessels. Currently, of the available medical devices in this regard for the population, there are only tonometers for measuring blood pressure. The work and condition of the vessels can only be assessed in the clinic using expensive and time-consuming ultrasound examinations (ultrasound), computed angiography methods, etc. At the same time, it is known that the functional state of the cardiovascular system is determined not only by the work of the heart and blood pressure, but also by different parameters of blood vessels - the elasticity of their walls, the tone of their smooth muscles, resistance to blood flow, etc. [see, for example, Karo K. et al. Mechanics of blood circulation: Per. from English. - M.: Mir, 1981. - 624 p., ill.].

Today it is known that one of the most important parameters characterizing the state of blood vessels is PWV [see, for example, Herman I. Physics of the human body. Per. from English: Scientific publication / I. German - Dolgoprudny: Publishing House "Intellect", 2011. - 992 p.]. PWV is a function of both blood pressure and the stiffness of the walls of blood vessels, their tone and a number of other characteristics, which generally characterizes the state of the cardiovascular system. Therefore, the PWV parameter was recognized in the early 2000s as an important independent predictor of cardiovascular complications [see. Boutouyrie P., et al. Aortic stiffness is an independent predictor of primary coronary events in hypertensive patients: a longitudinal study. hypertension. 2002; 39(1):10-15. DOI: 10.1161/hy0102.099031]. Since 2015, in accordance with the recommendations of the AHA (American Heart Association), the PWV parameter has already been recommended as the main parameter for assessing (class I; level of evidence A) arterial wall stiffness [see. Townsend R.R., et al.; American Heart Association Council on Hypertension. Recommendations for Improving and Standardizing Vascular Research on Arterial Stiffness. A Scientific Statement from the American Heart Association. J Hypertension 2015 Sep; 66(3): 698-722]. Accordingly, in a number of recent publications, PWV is now mentioned as the “gold standard” for assessing arterial wall stiffness [see. Tkachenko Yu.V. Adaptation of the pulse wave measurement technique for screening examinations in outpatient practice. Clinical practice. 2019; 10(1):48-56. DOI: 10.17816/clinpract10148-56].

At the same time, it is important to understand that, since PWV depends, among other things, on blood pressure [see. Younessi Heravi MA, et al. Continous and cuffless blood pressure monitoring using ECG and SpO2 signals. J Biomed. Phys. Eng. 2014; 4(1):27-32], and BP is highly variable and can fluctuate strongly over time intervals of even a few minutes, especially in patients with BP dysregulation [see. Manvelov L.S., Kadykov A.V. Arterial pressure and technique of its measurement. Ross.Med. Magazine. 2015; 21(1):49-51], for correct interpretation of PWV measurement results, all PWV measurements should be carried out simultaneously (simultaneously) with blood pressure measurements. Moreover, for a correct assessment of arterial wall stiffness by PWV, it is also necessary to use additional formulas for estimating the arterial wall stiffness index, leveling the effect of blood pressure on PWV. For example, the CAVI (cardio-ankle vascular index) index has recently become such a well-known index [see. K. Shirai et al. A novel blood pressure-independent arteriall wall stiffness parameter; cardio-ankle vascular index (CAVI). J. Atheroscler. Tromb., 2006; 13:101-107]. It is calculated by the formula:

where: PWV - PWV in the heart-ankle region, a and b - correction constants (if necessary, usually a=1, b=0), SBP - systolic blood pressure, DBP - diastolic blood pressure, PAP - pulse blood pressure (PAD=SBP- DBP), ρ - blood density (usually known average value for the population of people ρ = 1.06 g/cm ³ is used).

Numerous studies have shown that the CAVI index is less dependent on the level of blood pressure than just PWV, so it has become widespread in the study of the elastic properties of the walls of arteries, especially the aorta [see. Rogoza A.N. Non-invasive methods for determining the elastic properties of the vascular wall. Doctor. Ru, 2010, No. 3 (54), 23-29]. For the aorta, it is possible to calculate an analogue of the CAVI index - the aortic vascular index AVI, if PWV in the aorta is substituted into formula (1) for PWV.

But in addition to the aorta, it is desirable to evaluate such vascular indices, and, consequently, PWV, in the patient also integrally, both in all large main arteries and in smaller peripheral arteries and arterioles along the blood flow along the entire body of the patient, because in the general case, PWV is different in them (in the aorta, PWV is approximately 4–6 m/s, in the radial artery, 8–12 m/s, etc.). In each such link of the vascular bed, factors of vascular lesions can be identified by assessing PWV and vascular indices. However, non-invasive, simple, cheap devices that calculate vascular indices CAVI and (or) their analogues, are not available on the market today, either for doctors or for the public, measuring simultaneously with blood pressure and PWV in vessels of different hierarchies along the entire human body. Therefore the problem of developing such devices for the population is relevant.

BACKGROUND OF THE INVENTION

Everyone knows a non-invasive oscillometric method for measuring blood pressure using an inflatable compression cuff applied to a limb, for example, to the patient's shoulder, to create external pressure on the vessels of the shoulder. In this method, air is rapidly pumped into the cuff to values of air pressure in the cuff above the systolic blood pressure. Then the air is slowly released, and the exponentially decaying constant (absolute in mm Hg) of the P component of the air pressure in the cuff (see (a) Fig. 1), as well as the amplitude of the pulsations of the variable component of the air pressure in the cuff - sphygmogram (see (b) Fig. 1). In particular, the pulsation amplitudes Am, As, Ad are recorded, corresponding to the moments of time with maximum pulsations, with pulsations at the moment of passage of air pressure P in the cuff through the systolic BP point (SBP) and at the moment of passage of air pressure P in the cuff through the diastolic BP point ( DAD). At the time of pulsations with Am, the average blood pressure (BPmean) is determined from the exponential curve of the constant component of the pressure P of the air in the cuff, and then similarly determined by As - SBP and by Ad - DBP [see Fig. Forouzanfar, M., et al. Oscillometric Blood Pressure Estimation: Past, Present, and Future. IEEE Reviews in Biomed. engineering. 2015. 8(44):6310-516].

Known devices, automatic and semi-automatic blood pressure monitors, to implement this method. They contain a compression cuff, a pump for pumping air into the cuff, an air pressure relief valve in the cuff, an air pressure sensor in the cuff, an electronic circuit for amplifying and filtering the electrical signal from the pressure sensor, an electronic circuit for controlling the pump and the pressure relief valve, buttons for controlling the operation of the device, as a minimum, a “start/stop” button, as well as a microprocessor designed to control the operation of all these elements, to collect and process measurement results with a display attached to it, visually displaying the measurement results [see. patents, for example, US 6719703 B2, publ. 04/13/2004, US 5170795 A, publ. December 15, 1992, etc.].

Also known separately are "single-point" and "two-point" methods for determining PWV and devices that implement them [see. Tkachenko Yu.V. Adaptation of the pulse wave measurement technique for screening examinations in outpatient practice. Clinical practice. 2019; 10(1): 48-56, DOI: 10.17816/clinpract 10148-56]. The simplest in terms of hardware implementation are "single-point" methods and devices that allow you to evaluate PWV in the aorta - aortic velocity PWVао . They are based on a morphological analysis of the form of a pulse wave (hereinafter referred to as PV) of pressure according to a registered sphygmogram (plethysmogram) at a selected "point" of the human body [see Fig. Fedotov A.A. Methods of morphological analysis of the pulse wave. Honey. technique. 2019. No. 4: 32-35.]. In devices that implement this method, PWV is determined by the propagation time of the reflected PV, which is displayed on the sphygmogram (plethysmogram) in each PV pulse on the form of the PV envelope in the form of the second peak (crest) of the PV following the first peak (crest) of the direct PV immediately after depression-incisura, which characterizes the moment of slamming of the aortic valve [see. Parfenov A.S. Express diagnostics of cardiovascular diseases. The world of measurements. 2008. No. 6:74-82.]. The propagating PV of blood pressure in the aorta after cardiac output is reflected from the branches of the aorta, mainly from the lower branch to the iliac arteries. As a result, two characteristic peaks (crests) appear on the sphygmogram for each PV pulse: a direct peak 1 and a reflected wave peak 2, separated by an incisura 3 (see Fig. 2). The delay time of the peak of the reflected wave in relation to the time of arrival of the peak of the direct wave, i.e. the time interval Δt on the sphygmogram between the peaks of these two waves characterizes the propagation time of PV along the aorta from the heart to the aortic branch point and back to the heart. Knowing the height of a person and the approximate length of the PV path in the aorta - the length of the aortic trunk, as well as the time interval Δt , calculate the aortic PWV using the formula:

where PWVао - PWV in the aorta; Δt is the delay time of the peak of the reflected PV in relation to the time of arrival of the peak of the direct PV on the sphygmogram; K is a scale factor for normalizing the obtained value (in order to describe the essence of this invention, K = 1); L is the length of the aortic trunk. In calculations, the distance from the upper edge of the sternum (sternum incisura jugularis) to the pubic bone (symphisis pubica) is usually taken as the length of the aorta L [see. Tkachenko Yu.V., Strazhesko I.D., Borisov E.N., Plisyuk A.G., Orlova Ya.A. Adaptation of the technique for measuring pulse wave velocity for screening examinations in outpatient practice. Clinical practice. 2019; 10(1):548-56. doi: 10.17816/clinpract10148-56.].

Such a “two-humped” pattern (envelope shape) of pressure PV in the aorta, containing an incisura, direct and reflected pressure waves, spreads further and through all smaller arteries, down to the smallest arterioles. However, as the PV spreads through smaller vessels, the “double-humped” pattern of the PV with incisura is blurred. Blood viscosity, vascular wall stiffness, presence of pathologies, and other factors have a “blurring” effect on the shape of the PV envelope, especially on its right side with an incisura and a reflected PV peak, up to the frequent complete disappearance of these morphological features on the periphery (in the skin of the extremities). PV on the sphygmogram (see Fig. 3). Therefore, the closer to the heart and aorta the PV is recorded, the more accurately it is determined by the “single-point” method PWVао .

Nevertheless, in the general case of the norm in a patient, such a “two-humped” form of PV can be fixed both on the fingers of the extremities and in a number of other localizations on the skin along the blood flow. To do this, "single-point" devices can use a wide variety of sensors - optical, for example, photoplethysmographic sensors (hereinafter referred to as PPG sensors), acoustic, ultrasonic and other sensors.

The described “single-point” method for determining PWV in the aorta is implemented, for example, in the Russian diagnostic system BPLab Vasotens (manufactured by Petr Telegin LLC, Nizhny Novgorod, Russia) [see Tkachenko Yu.V. in outpatient practice. Clinical practice. 2019; 10(1): 48-56, DOI: 10.17816/clinpract 10148-56]. , which analyzes the shape of the air pressure PV directly in the cuff according to the signal from the pressure sensor in the process of measuring blood pressure, i.e. this system evaluates PWV according to the PV signal (sphygmogram) in the tonometer cuff on the patient’s shoulder simultaneously with the measurement of blood pressure. Many foreign devices work similarly, for example, the single-cuff sphygmometer Arteriograph Tensiomed (Hungary) [see AR Zairova, AN Rogoza Volumetric sphygmography today. Medical alphabet.2018; No. 36(4): 8-18].

The disadvantage of this method is that only PWV in the aorta is determined by this method. Other vessels along the entire body of the patient along the course of blood flow cannot be characterized using them. Accordingly, the analysis of vessel wall stiffness is possible only for the aorta. In addition, these devices do not normalize PWV for blood pressure and do not calculate vascular indices. As a result of the foregoing, the discussed devices that implement the "single-point" method (method) are not sufficiently informative.

Even more significant shortcomings are inherent in the Russian "single-point" device "Angioscan". Unlike BPLab, it does not have a cuff, does not measure blood pressure, and is used to register PV not with an air pressure sensor in the tonometer cuff, but with an optical PPG sensor located on the patient's finger and recording a photoplethysmogram - an analogue of a sphygmogram, but containing, in addition to the variable component of the signal SA in the form of pulse waves (PV) is also a constant, slowly changing component of the SD signal (see Fig. 4). Individual pulse fluctuations are isolated from the variable component of the SA signal in the Angioscan device and their shape is analyzed, i.e. morphological analysis is carried out. However, as it was mentioned above, the “pattern” of the SP in the form of a two-humped shape of the SP envelope is blurred as the SP propagates to the periphery of the limb, its maxima are shifted, the delay time of the peak of the reflected wave Δt changes, therefore, the “single-point” Angioscan device is significantly less accurate for definitions of PWV.

In general, as a result, due to insufficient accuracy, no “single point” methods and devices have yet been studied in serious international prospective studies to assess the functioning of the entire cardiovascular system, and in international recommendations they are not recommended for use in real clinical practice [see . Vasyuk Yu.A., Baranov A.A. Agreed opinion of Russian experts on the assessment of arterial stiffness in clinical practice. Cardiovascular therapy and prevention. 2016. 15(2): 4-19].

More informative and accurate are "two-point" methods and devices that register direct PV pressure at two different "points" on the surface of the body, located at different distances from the heart. In these methods, the delay ΔT of the propagation time of the direct PV between these two points (Pulse transit time) is determined, and from this delay ΔT , taking into account the known distance between these "points", PWV is determined as the distance divided by ΔT .

"Two-point" methods and devices are also widely known and very diverse today. For example, there is a known method and device for measuring PWV, in which electrocardiographic (hereinafter - ECG) electrodes attached to the patient's chest are used as the first "point", and a catheter with a pressure sensor inserted into the radial artery is used as the second "point". (application US20150065828 A1, published 03/05/2015). In this variant, the time delay ΔT is determined between the ECG signal pulse and the arrival of the direct PV peak recorded in the artery by a pressure sensor. This device implements the most accurate method for determining PWV of all considered, however, it is expensive and invasive, not suitable for mass use, especially at home. In addition, it does not allow to fully evaluate the integral PWV for the purposes of the integral assessment of the stiffness of all vessels, since does not involve small arteries on the periphery of the limb, and also does not measure blood pressure simultaneously with PWV, which does not allow calculating either the CAVI index or its analogues.

The gold standard today in the non-invasive determination of PWV by the “two-point” method is the carotid-femoral method, in which PWV is determined by the time delay in registering the pulse on the carotid and femoral arteries (see Van Bortel L.M., Laurent S., Boutouyrie P. et al. Expert consensus document on the measurement of aortic stiffness in daily practice using carotid-femoral pulse wave velocity // Journal of hypertension - 2012. - V. 30. - No. 3. - P. 445-448). An electrocardiogram signal is used as a reference signal against which the time delay is measured (see Millasseau S.C., Stewart A.D., Patel S.J., Redwood S.R., Chowienczyk P. J. Evaluation of carotid-femoral pulse wave velocity: influence of timing algorithm and heart rate // Hypertension - 2005. - V. 45. - No. 2. - P. 222-226). This method is implemented in the following commercial devices: PulsePen (manufactured by Diatecne, Italy), Pulse Trace PWV (manufactured by Micro Medical, Great Britain), Poly-Spectrum-SRPV (manufactured by NeuroSoft, RF). To register PV pressure - sphygmograms - on the periphery, such devices use applicator tonometry sensors, ultrasonic sensors and various other sensors. In particular, the well-known system "SphygmoCor" is equipped with a broadband piezoelectric probe, rearranging which registers the PV pressure sequentially, first on the carotid and then on the femoral artery [see Fig. Tkachenko Yu.V. Adaptation of the pulse wave measurement technique for screening examinations in outpatient practice. Clinical practice. 2019; 10(1): 48-56, DOI: 10.17816/clinpract 10148-56]. The disadvantage of the devices is the inconvenience of use by patients, a lengthy measurement procedure and the requirements for operator training for the correct positioning of the probe (sensor) on the carotid and femoral arteries. Independent use by the patient at home of such devices is excluded. In addition, the use of an ECG module makes such devices complex and expensive. Also, these devices do not have the ability to simultaneously measure blood pressure and use for the study of peripheral vessels of the extremities, especially small ones.

Also known is a device and a method for non-invasive measurement of carotid-femoral PWV by the method of volumetric sphygmography (application WO2011045806 A1, publ. 21.04.2011). The device that implements the corresponding method consists of four standard inflatable cuffs from a tonometer, attached to the limbs of the subject, and an ECG module. At the same time, two cuffs are attached to the shoulders of the arms and two to the lower parts of the legs, which involves all the main peripheral arteries of the limb for examination. Each cuff is connected to its own blood pressure monitor, which includes a pneumatic unit consisting of a rotary compressor (pump), a pneumatic valve and an air pressure sensor in the cuff, and an electronic unit for processing the pressure sensor signal, determining (calculating) blood pressure and controlling the operation of all units and device blocks.

The method consists of sequential execution of two stages. At the first stage, all cuffs are simultaneously inflated to a pressure that is obviously higher than the SBP, then they are slowly deflated and the SBP, DBP and BPmean for all 4 limbs are determined by the standard oscillometric method. The found values of SBP, DBP and BPav are stored in the memory of the microprocessor of the electronic unit for further analysis. At the second stage of measurements, all four cuffs are inflated to APmea, at which PV is most clearly manifested, and kept at this level during the entire required measurement time. During this time, pressure sphygmograms from all 4 cuff pressure sensors and electrocardiograms from two leads are recorded and stored. Further, PWV is determined separately for the left and right sides of the human body. Left-sided PWVLP (PWVLP) is determined by the time delay in the registration of pressure PV signals on the left arm and left leg according to the formula:

where DLP is the distance obtained by summing the distance from the cuff on the left upper limb to the heart and from the heart to the cuff on the left lower limb; while these distances are determined using a conventional measuring tape; and TLP - time delay PT between the arm and leg, recorded from the cuffs on the left upper limb and on the left lower limb.

Similarly, PWVRP (PWVRP) is calculated on the right side of the body:

where DRP is the distance obtained by summing the distance from the cuff on the right upper limb to the heart and from the heart to the cuff on the right lower limb, TRP is the time delay of PT between the arm and leg, recorded from the cuffs on the right upper limb and on the right lower limb.

Next, the median peripheral PWV (PWV) is determined by averaging the PWVLP and PWVRP values:

The final value of carotid-femoral PWV is calculated as:

where k is the coefficient of proportionality between carotid-femoral PWV and PWV from upper to lower limb, C is a numerical constant. The k and C coefficients are determined from a regression analysis of aortic parameters obtained from a statistically significant population set by standard ultrasound measurement methods.

This method and device are non-invasive, automated, do not require the participation of a qualified operator and, in general, allow obtaining almost simultaneously data on blood pressure and integral PWV on the left and right sides of the body - PWVLP, PWVRP and PWVCF. The device for volumetric sphygmography Vasera VS-1000 (manufactured by Fukuda Denshi, Japan), which allows calculating the cardio-ankle vascular index CAVI, works on a similar principle. However, the above method and device have the following important disadvantages:

1) Measurements of blood pressure and PWV are not simultaneous and spaced apart in time, although not much.

2) Measurements are performed in two stages, which is long and inconvenient for the patient.

3) The small arteries of the foot of the limb are not used for the analysis of the integral PWV (measurements are made to the lower part of the leg).

4) When measuring PWV in cuffs, it is necessary to create additional air pressure in the range from DBP to SBP, which affects the walls of blood vessels, changes their mobility, ability to stretch, as a result of which PWV is determined not for natural conditions in the vessels, but for artificially created external pressure and for modified conditions of PW damping in vessels, so this PWV does not quite correspond to the natural PWV. In addition, the creation of additional external pressure with a cuff on the vessels of the lower extremities and its retention is not recommended for patients with diseases of the arteries of the lower extremities (hereinafter referred to as LANK) due to their increased risk of thrombosis and ischemic lesions of the extremities (patients with vascular complications of diabetes, for example). Therefore, for them it is a risky and even dangerous method.

5) As you know, electronic circuits for amplifying and filtering signals, which in this case are used in the device to amplify and filter sphygmogram signals from air pressure sensors in cuffs, have some delay in signal propagation and can introduce distortions into the phase of the pulse signal (distort the propagation time of PV ) on the sphygmogram. In the described device, two such electronic circuits are used for one side of the human body, for two cuffs, but the signal delays in them in the device are not taken into account and are not synchronized. As a result, the measured delay in the propagation time of the SW can be performed with an error due to the inherent delays introduced by the electronic circuits, which reduces the accuracy of the PWV measurements.

Additionally, methods and devices are known today that combine a blood pressure tonometer and optical sensors for recording PV and its shape on the periphery of the limbs, including on the fingers - pulse oximetry and PPG sensors. Such sensors contain at least one source and one receiver of optical radiation and operate on the principles of absorption optical spectroscopy, recording the optical density of tissues in the visible and / or near infrared wavelength range, which, in turn, depends on the volume of blood supply to the studied area of the organ, skin, for example (see Allen J. Photoplethysmography and its application in clinical physiological measurement. Physiological measurement. 2007. 28 (3): R1-R39). As a result, a photoplethysmogram is recorded (see Fig. 4). For example, a device is known for non-invasive measurement of blood pressure using an inflatable cuff with an external optical pulse oximetry sensor to assess the quality of the pulse signal and recalibrate the device (see patent US9687161 B2, see 06/27/2017). However, this device measures only blood pressure and does not allow PWV to be measured, and the pulse oximetry sensor is used in it to obtain a reference PV signal, with which the pulse signal recorded by the device is then compared, and in case of large discrepancies in their forms, a decision is made to recalibrate the device.

Also known are “two-point” devices close in meaning to the definition of PWV, which, however, have not received wide distribution in practice, realizing, on the contrary, the technology of indirect non-invasive measurement of blood pressure (CNIBP technology) by delaying the time of passage of PV from one point of the body to another (Pulse transit time), which allows not to use an inflatable compression cuff (see patent application US20100081892 A1, publ. 01/01/2010). This is promising for 24-hour blood pressure monitoring systems. To register PV pulses, such devices use PPG sensors, one of which can be mounted on the head (forehead, earlobe) or chest, and the second on the wrist, fingertip, foot, etc. These devices can be additionally equipped with an ECG module, however, PWV is not directly measured or analyzed by such devices. According to the recorded delay in the passage of PV, taking into account the known dependence of blood pressure on PWV (see Elgendi M., Fletcher R., Liang Y., Howard N. et al. The use of photoplethysmography for assessing hypertension // NPJ digital medicine. 2019. 2(1): 1-11), these devices indirectly calculate blood pressure, but not accurately enough, because in general, BP depends not only on PWV, but also on other parameters of the cardiovascular system, in particular, cardiac output.

Closest to the claimed is a device for non-invasive measurement of PWV when measuring blood pressure by the oscillometric method (see RF patent No. 2750745, publ. PPG sensor, wherein the tonometer consists of a pneumatic unit, which includes a cuff pressure pumping unit, a pneumatic pressure relief valve and an air pressure sensor in the cuff, which are connected pneumatically in parallel with the compression cuff, as well as an electronic unit, which includes analog a block for amplifying the signal from the air pressure sensor in the cuff, a block for digitizing the analog pressure signal, a block for digital filtering the pressure signal with an adjustable group delay τ1 to obtain a sphygmogram of its pulsating part and a constant component of pressure in the cuff from the pressure signal, and a microprocessor. At the same time, the PPG sensor is configured to be connected to the microprocessor of the tonometer through the analog block for amplifying the signal from the PPG sensor, the block for digitizing the analog signal from the PPG sensor, and the block for digital filtering the signal from the PPG sensor with an adjustable group delay built into the electronic unit of the tonometer. τ2 to obtain a photoplestimogram signal, moreover, the control outputs of the microprocessor are connected to the control inputs of the cuff pressure pumping unit, the pneumatic pressure relief valve and the PPG sensor, and the tonometer microprocessor is configured to process all incoming signals from the pneumatic unit and the optical PPG sensor, to perform calculations to measure PWV, as well as control the operation of the PPG sensor and the pneumatic unit.

In some embodiments, the PPG sensor includes at least one emitter, the input of which is connected to the control output of the microprocessor of the tonometer, and a photodetector, the output of which is connected to the analog signal amplification unit. The sampling frequency of the block for digitizing the analog signal from the PPG sensor and the block for digitizing the analog signal from the air pressure sensor in the cuff is the same and is at least 250 Hz.

Also, in some embodiments of the device, the block for digital filtering of the pressure signal and the block for digital filtering of the signal from the PPG sensor are digital Butterworth filters, or Chebyshev filters, or Bessel filters, or a combination of them. They are tunable, and the filter parameters are selected in such a way that the PV signals that simultaneously arrive at the air pressure sensor in the cuff and the PPG sensor are simultaneously transmitted to the microprocessor of the tonometer by adjusting the time delays of the signal in these filters.

In this device, simultaneously with the measurement of blood pressure by the known oscillometric method, the integral PWV is determined by the "two-point" method along the entire body along the blood flow in the "heart - big toe" area (see Fig. 5) by registering the time delay ∆T _i of the propagation of PV blood pressure between the shoulder (arm) and leg, defined as the difference in time between the “bottom” (beginning) of the i-th direct wave of the photoplethysmogram recorded by the PPG sensor on the leg, and the “foot” (beginning) of the corresponding i-th PV pressure on sphygmogram recorded by the pressure sensor of the tonometer in the compression cuff on the shoulder, which makes it possible to avoid errors and errors in PWV measurements associated with the effect of “blurring” the PV shape as it spreads through the vessels and shifting the maximum (peak) PV on the photoplethysmogram in peripheral vessels. The concept of "foot" is also clearly defined in the description of the patent for the device taken as a prototype, and the procedure for calculating the "foot" points on photoplethysmograms and sphygmograms by finding the maxima of the second derivative of the signal is also proposed there.

This device is safe for patients with LAD because there is no need for cuffs and additional external pressure for the lower extremities, as in volumetric sphygmography devices. The advantage of the device is that it is used to determine the integral PWV along the entire body along the blood flow simultaneously with the measurement of blood pressure by the standard oscillometric method. However, the device also has a number of disadvantages:

1. Simultaneous measurements of blood pressure and PWV are possible only on one side of the body. Using this device, in order to reveal the asymmetry of BP and PWV parameters on the left and right sides of the body, it is necessary to take two consecutive measurements on each side of the body, which will no longer be simultaneous. Sequential measurements, as has recently been shown [cf. Glazkov A.A. Asymmetry of microcirculation parameters in the skin of extremities during sequential measurements. Laser medicine, 2021, v.25, no. 3S, p. 58. https://doi.org/10.37895/2071-8004-2021-25-3S-58] can lead to errors due to dynamic processes of blood flow redistribution and adaptation of the cardiovascular system to the measurement conditions right during measurements .

2. Using the described device, it is impossible to separately assess PWV in the aorta and in peripheral vessels, including in the small arteries of the limb. The device determines one integral PWV, which is important for functional diagnostics, but not as informative as if it were possible to separately measure PWV in the aorta, in large and small peripheral vessels.

3. The vascular index CAVI and (or) its analogues are not calculated, because initially, no transducer for recording PV on the lower leg close to the ankle is declared, and vascular indices for the aorta (AVI) and vascular indices for peripheral small arteries (PVI) are not calculated, respectively.

Thus, there is an urgent need in medicine for a more advanced and more functional device for non-invasive simultaneous measurement of blood pressure and PWV, devoid of these disadvantages.

DISCLOSURE OF THE INVENTION

The objective of the present invention is to develop an improved and more functional device for the non-invasive determination of PWV in vessels of different hierarchies along the entire body simultaneously with the procedure for measuring blood pressure using the standard oscillometric method, which would allow measurements to be taken simultaneously from both sides of the body and to record PWV separately for the aorta, peripheral large and small arteries of the extremities, as well as calculate the CAVI index and its analogues according to formula (1) for all the indicated links of the vascular bed separately.

The technical result achieved by using the invention is to increase the diagnostic informativeness of the device in assessing PWV and to expand its functionality.

The technical result is achieved due to the fact that the device for measuring PWV when measuring blood pressure by the oscillometric method with extended functions includes an automatic tonometer for measuring blood pressure by the oscillometric method with an attached shoulder compression cuff and an optical PPG sensor. The tonometer consists of a pneumatic unit, which includes a cuff pressure pumping unit, a pneumatic pressure relief valve and an air pressure sensor in the cuff, each of which is pneumatically connected in parallel to each other and to the cuff, and an electronic unit, which includes a microprocessor to which are connected keyboard and display. PPG-sensor is made with the possibility of connection to the tonometer microprocessor. The control outputs of the microprocessor are connected to the control inputs of the cuff pressure pumping unit, the pneumatic pressure relief valve and the PPG sensor. The microprocessor of the tonometer is configured to process all incoming signals from the pneumatic unit and the optical PPG sensor, perform calculations for measuring PWV, and also control the operation of the PPG sensor and the pneumatic unit. Differences of the device is that it contains two mentioned compression cuffs and four mentioned PPG sensors. The tonometer includes two identical mentioned pneumatic blocks. The electronic unit of the tonometer includes two blocks for processing signals from air pressure sensors in the cuffs of pneumatic blocks connected to the output of the corresponding sensors for air pressure in the cuff for each pneumatic block, and outputs to the microprocessor, and four blocks for processing signals from PPG sensors connected by inputs to the outputs of the corresponding PPG sensors, and the outputs to the microprocessor. Each block for processing signals from air pressure sensors in the cuff contains a series-connected analog block for amplifying the signal from the air pressure sensor in the cuff, a block for digitizing the analog pressure signal and a block for digital filtering the total pressure signal. Each block for processing signals from PPG sensors contains a series-connected analog block for amplifying a signal from a PPG sensor, a block for digitizing an analog signal from a PPG sensor, and a block for digitally filtering a signal from a PPG sensor with an adjustable delay in the appearance of a signal at the output of the block. The microprocessor has eight output channels for controlling the operation and switching on / off of the corresponding elements of pneumatic units and PPG sensors and is equipped with algorithms for calculating PWV in the aorta, left-sided and right-sided PWV for each PPG sensor, as well as the cardio-ankle vascular index and its analogues for the aorta and peripheral small arteries in the area "lower leg - toe", and separately for the left and right sides of the body. The frequency of operation of the said analog signal digitizing units is set to at least 320 Hz.

Each PPG sensor can include at least one emitter, the input of which is connected to the control output of the microprocessor of the tonometer, and a photodetector, the output of which is connected to the corresponding analog signal amplification unit.

Blocks of digital filtering of the pressure signal and blocks of digital filtering of the signal from PPG sensors can be digital Butterworth filters, or Chebyshev filters, or Bessel filters, or a combination of them.

The design of the proposed device provides the possibility of simultaneous measurement of blood pressure by the standard oscillometric method, PWV in the aorta by the "single-point" method and PWV on the periphery in several locations on the leg (or arm) by the "two-point" method simultaneously from the left and right sides of the body due to additional PPG sensors and additional blocks for digitizing and filtering signals, which, from a medical point of view, additionally allows:

- simultaneously assess the asymmetry of indicators on the left and right sides of the body;

- separately evaluate PWV in the aorta and in peripheral vessels, including small arteries of the extremities,

- calculate vascular indices, similar to CAVI, separately for the aorta, for the main main arteries in the "heart - lower leg (ankle)" section and for small peripheral arteries in the "lower leg - toe" section, and separately for the left and right sides of the body,

and in the aggregate it allows to increase the diagnostic information content of the device and the reliability of diagnosing the state of blood vessels due to the use of a larger number of collected diagnostic data, separate for vessels of different hierarchies.

The proposed new device is also safe for patients with LAD, because. there is no need for cuffs and additional external pressure for the lower extremities, as in volumetric sphygmography devices.

TERMS (DEFINITIONS)

For a better understanding of the present invention, the main terms used in the present description of the invention are given and explained below. Unless otherwise defined, the technical and scientific terms in this application have the standard meanings generally accepted in the scientific and technical literature.

As used herein and in the claims, the terms "comprises", "comprising" and "includes", "having", "provided", "comprising" and their other grammatical forms are not intended to be construed in an exclusive sense, but, on the contrary, are used in a non-exclusive sense (i.e., in the sense of "having in its composition"). As an exhaustive list, only expressions like "consisting of" should be considered.

Under the PWV in a vessel with blood, measured by the proposed new device, is meant the distance that the registered PV passes between two “points” selected for measurements along the vessel, measured or known in advance in meters, divided by the propagation delay time of the PV in seconds between these “points” registered by any PV sensors. In this case, if the vessel is bent, for example, like an aortic arch, then the distance is considered along the axis of the vessel, i.e. considering bending.

The integral PWV , which in combination characterizes the distribution of PV along a group of vessels of different hierarchies, with different PWV in each individual vessel, is understood as the distance that the recorded PV passes between two “points” selected for measurements along this group of vessels along the blood flow, measured or known in advance in meters, divided by the propagation time of the PW in seconds, recorded by any PW sensors at these two selected "points". In this case, small bends and branching of vessels are not taken into account. So, if one sensor is located in the region of the heart, and the other on the toe, then for a distance, i.e. for the path that the PV passes, the shortest distance measured by a tape measure between these two “points” in the prone position with straightened legs is taken directly.

The constant pressure component in this description is the exponentially decreasing component of the air pressure "P" in the compression cuff in mm Hg, measured by the manometric pressure sensor of the tonometer in the phase of depressurizing the air in the cuff, without taking into account the pulse fluctuations in the air pressure in this cuff .

Sphygmogram - a graph of pulse fluctuations in the air pressure in the tonometer cuff during the measurement of blood pressure, which can be obtained by filtering the total air pressure in the cuff, measured by the tonometer's manometric pressure sensor, and cutting off the constant component of the air pressure in the cuff from the total pressure.

Photoplethysmogram - a graph of pulsating changes in blood volume in tissues and organs, obtained by the optical method of absorption spectroscopy for transmission or reflection, which is similar to a sphygmogram, but unlike a sphygmogram, in addition to the variable component of the SA signal in the form of PV, it also contains a constant, slowly changing component of the signal SD, reflecting the constant volume of blood supply to the organ.

The terms sphygmogram, oscillogram, and plethysmogram are synonymous for purposes of explaining the features of this application for the invention.

The term "connected" means functionally connected, and any number or combination of intermediate elements between connected components (including the absence of intermediate elements) can be used.

In addition, the terms "first", "second", "third", etc. are used simply as conditional markers, without imposing any numerical or other restrictions on enumerable objects.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

The accompanying illustrations, which are incorporated in and form an integral part of this specification, explain the invention and embodiments of the invention, which, together with the above general description of the invention and the following detailed description of embodiments, serve to explain the principles of the present invention. In the illustrations, like reference numbers are used to refer to like parts.

In FIG. 1 schematically shows the exponentially decaying constant component of air pressure "P" in a compression cuff in the phase of depressurization of air in the cuff when measuring blood pressure with a variable pressure component (a) visible on it, which, being filtered by a digital filter, is a sphygmogram of pulse pressure fluctuations cuff air in the cuff depressurization phase (b). Also indicated on the sphygmogram (b) are the approximate ranges of selection of the oscillation amplitudes As, Am and Ad, corresponding to systolic, mean and diastolic blood pressure.

In FIG. Figure 2 schematically shows a sphygmogram and, on an enlarged scale, the shape of the envelope of a separately isolated PV on a sphygmogram, the analysis of which makes it possible to identify its main morphological features: 1 - peak (ridge) of the direct PV, 2 - peak (ridge) of the reverse (reflected) PV, 3 - incisura. The time interval between the registration of the peaks of the direct and reflected waves Δt (the time interval of the delay of the reverse PV relative to the direct PV) determines the time for calculating PWV in the aorta .

In FIG. Figure 3 schematically shows on an enlarged scale the forms of PV recorded by some PPG sensor after their partial or complete “blurring” in comparison with the sphygmogram as they spread through the vessels from the center to the periphery for different subjects. (a) - partially "blurred" picture, (b) - lack of a clear separation of SP into direct and reflected.

In FIG. 4 schematically shows the complete photoplethysmogram recorded by the PPG sensor with a constant and slowly varying component of the SD signal and a variable component of the SA signal in the form of PV.

In FIG. 5 schematically shows the location of the sensors on the human body and the determination of the distances between them for the device taken as a prototype.

In FIG. 6 shows a block diagram of the proposed new device.

In FIG. 7 schematically shows the location of the compression cuff and PPG sensors on the left side of the human body and the determination of the distances between them for the proposed device. On the right side, the cuff and PPG sensors are located by analogy.

In FIG. 8 provides an explanation for determining the time delays ΔT _i along the "foot" of the PV on the graphs of the sphygmogram and the variable component of the photoplethysmogram signal. "Points of the foot", while on each graph are determined by the second derivatives of the signals similar to the procedure used in the device adopted for the prototype.

NOTATION

4 - automatic tonometer (device),

5.1 and 5.2 - left and right compression cuffs of the tonometer,

6.1, 6.2, 6.3, 6.4 - PPG sensors for placement, two on each side of the body,

7.1 and 7.2 - left and right pneumatic blocks of the tonometer,

8 - electronic unit of the tonometer,

61 - analog block for amplifying the signal from the PPG sensor,

62 - block for digitizing an analog signal from a PPG sensor,

63 - block for digital filtering of the PV signal from the PPG sensor with an adjustable time delay τ1 for extracting the PV signal from the photoplethysmogram relative to the PV pulses of the sphygmogram in the compression cuff on the corresponding side of the body,

64 - PPG sensor emitter,

65 - PPG sensor photodetector,

71 - block for pumping pressure in the cuff,

72 - pneumatic pressure relief valve,

73 - air pressure sensor in the cuff,

8.1 - microprocessor,

8.2 - button block for controlling the operation of the microprocessor and the entire device as a whole,

8.3 - measurement results indication block (display),

8.4.1 and 8.4.2 - blocks for processing pressure signals from pressure sensors 73 of the left and right pneumatic blocks of the tonometer,

74 - analog block for amplifying the total signal from the pressure sensor,

75 - block for digitizing the total analog pressure signal,

76 - block of digital filtering of the total pressure signal, separating from the total pressure separately its exponentially decreasing constant component, the sphygmogram graph and the contours of individual pressure PVs on the sphygmogram,

8.5.1, 8.5.2, 8.5.3, 8.5.4 - blocks for processing signals from PPG sensors.

IMPLEMENTATION OF THE INVENTION

In general, the present invention relates to devices for non-invasive measurement of PWV in the main and peripheral blood vessels, from which the CAVI index and its analogues are then calculated to assess the stiffness of the walls of vessels of different hierarchies and, in combination with the measured blood pressure, are used to assess the overall functional state of the cardiovascular system. the vascular system as a whole.

The claimed device includes an automatic tonometer 4 for measuring blood pressure by the oscillometric method with two shoulder compression cuffs 5.1 and 5.2 attached to it for measuring blood pressure simultaneously on the left and right sides of the body, and four optical PPG sensors 6.1, 6.2, 6.3 and 6.4, according to 2 on each side of the body, to obtain photoplethysmograms from the limbs of the left and right sides of the body. The tonometer 4 consists of two identical pneumatic blocks 7.1 and 7.2, each of which includes a block for pumping pressure in the cuff 71, a pneumatic pressure relief valve 72 and an air pressure sensor in the cuff 73, which are connected pneumatically in parallel with each other and with the corresponding cuff 5.1 or 5.2, and an electronic unit 8. The electronic unit 8 includes an 8.1 microprocessor with an 8.2 keypad attached to it to set the initial parameters for calculations and implement the start / stop function and an 8.3 display to indicate the measurement results, two identical blocks 8.4.1 . and 8.4.2 processing signals from pressure sensors 73 of pneumatic blocks 7.1 and 7.2, connected with their inputs to the output of the corresponding air pressure sensors in the cuff 73 for each pneumatic block 7.1 and 7.2, and with their outputs to the microprocessor 8.1, and four identical blocks 8.5.1 , 8.5.2, 8.5.3 and 8.5.4 processing signals from PPG sensors 6.1, 6.2, 6.3 and 6.4, connected with their inputs to the outputs of the corresponding PPG sensors, and with their outputs to the microprocessor 8.1. The microprocessor has 8 output channels for controlling the operation and “on/off” of the corresponding elements of pneumatic blocks 7 and PPG sensors and is equipped with algorithms for calculating the PV velocity in the aorta according to the formula (2), left-sided and right-sided PWV in the “heart-shin (ankle)” section according to formulas (3) and (4) for each PPG sensor located on the shin, close to the ankle, left-sided and right-sided PWV in the “shin-toe” section according to formulas similar to (3) and (4), for each PPG - a sensor located in the area of the big toe, as well as CAVI indices and its analogues for the aorta and peripheral small arteries in the “shin-toe” section, and separately for the left and right sides of the body. Blocks 8.4.1 and 8.4.2 contain series-connected analog signal amplification unit 74 from the cuff air pressure sensor 73, a unit for digitizing the analog pressure signal 75, and a digital filtering unit for the total pressure signal 76, extracting its exponentially decaying constant component from the total pressure signal separately , sphygmogram graph, i.e. variable pressure component, as well as the contours of individual PV pressure on the sphygmogram. Blocks 8.5.1, 8.5.2, 8.5.3 and 8.5.4 contain identical and serially connected analog signal amplification unit 61 from the PPG sensor, a block for digitizing the analog signal 62 from the PPG sensor and a digital signal filtering unit 63 from the PPG sensor , which extracts the photoplethysmogram signal with an adjustable time shift τ1 relative to the PV pulses of the sphygmogram in the compression cuff on the corresponding side of the body.

The proposed device can use any known PPG sensors, including those operating on superluminescent diodes (SLED or SLD) or laser diodes.

In some embodiments, each PPG sensor may include at least one emitter 64, the input of which is connected to the control output of the microprocessor 8.1 of the tonometer 4, and a photodetector 65, the output of which is connected to the corresponding analog signal amplification unit 61.

In addition, in some embodiments, the pressure signal digital filtering blocks 76 and the PPG signal digital filtering blocks 63 may be digital Butterworth filters, or Chebyshev filters, or Bessel filters, or a combination of both. However, in all variants, the design and parameters of digital filtering units 63 must be selected in such a way as to provide an adjustable time delay for the appearance of a signal at the output of the block compared to the appearance of a signal at the output of blocks 76 to configure the device so that pressure sensors and PPGs simultaneously received from outside -sensors, the PV signals were simultaneously transmitted to the microprocessor 8.1, i.e. so that, as they propagate through the electronic blocks of the device up to the microprocessor 8.1, the signals do not undergo a mismatched time delay in these blocks.

In the claimed device, the frequency of data digitization blocks 62 and 75 (analog-to-digital conversion frequency) must be set to at least 320 Hz to obtain a temporal resolution of the recorded signal from the pressure sensor and the signal from the PPG sensor no worse than 5 ms.

Blood pressure is measured by the proposed device known oscillometric method simultaneously on the left and right sides of the body using compression cuffs 5.1 and 5.2, located respectively on the left and right shoulder of the patient.

PWV is recorded in the proposed device during the procedure for measuring blood pressure also on the left and right sides of the body simultaneously in the depressurization phase in the corresponding compression cuff in the interval between SBP and DBP on this side of the body, which is determined by the excess of the amplitudes of pressure pulsations Ap on the sphygmogram of some pre-selected threshold value Ap_thr:

The selection of such a working interval for measurements is necessary for more reliable registration of the PV pressure in the tonometer cuff. Outside this interval, the pressure pulsations in the compression cuff are unstable and comparable with the noise level in the pneumatic system of the tonometer, which sharply reduces the accuracy and reproducibility of the measurement results.

The specific numerical value of Ap_thor depends on the sensitivity of the pressure sensor used in the device, the signal gain of the pressure sensor by the electronic signal amplification and filtering circuit, etc. and is determined empirically for each side of the body separately when setting up the device in production. For example, as Ap_pores, the amplitude of pulsations can be selected as 5% (0.05) of the average value of the maximum amplitudes of pulsations Ap_max recorded by the device in 10 test debugging measurements per 10 subjects.

Within the specified pressure interval between SBP and DBP, which is determined by the excess of the amplitudes of pressure pulsations Ap of some pre-selected threshold value Ap_pore, pressure pulsations in each of the cuffs are taken as working ones for measuring PWV.

The aortic PWV (PV velocity in the aorta) is determined from these pulsations using the proposed device using the “single-point” method known from the prior art by morphological analysis of the PV shape separately in each compression cuff and by determining the time delays Δt _i between the peaks (maxima) of the recorded direct about the reflected PV in the aorta according to the sphygmogram from the blocks of digital filtering of the total pressure signal 76, according to the explanations of Fig. 2. Since a compression cuff is used close to the heart, the "smearing" of the PV signal is minimal here, and wave peaks can be used to measure Δt _i . Time delays Δt _i are determined by the specified well-known "single-point" method in the proposed device for all i pulses of pressure PV on the sphygmogram exceeding Ap_pore, and are further averaged for each side of the body j according to the formula:

where N is the number of PVs in the recorded sphygmogram signal on the selected side of the patient's body, and j conditionally denotes the side of the body: j =1 - left side, j =2 - right side.

After that, the average Δt _cf is calculated using the formula:

Where - average according to the formula (8) time delays on the left and right sides of the body, respectively.

Next, for the aorta, the average aortic PWV is calculated according to formula (2), substituting the found value into this formulaΔt _Wed placeΔt:

According to this PWVao , at the next step of data processing, an analogue of the vascular index CAVI for the aorta is determined according to formula (1), substituting PWVao into it instead of PVW , and instead of SBP, DBP and PBP - the average between the left and right sides of the body of their measured values. For example, instead of SBP, SADav is substituted, which is calculated by the formula:

Where - the values of the measured systolic pressure on the left and right sides of the body, respectively.

Similarly, DAPav and PADav are calculated and substituted into formula (1).

In this case, all calculations according to these formulas are automatically performed by the microprocessor 8.1 of the device using the software embedded in it, containing the above formulas.

Integral PWV in the central and peripheral vessels at the "heart-shin (ankle)" site on each side of the body is determined by the proposed device using the "two-point method" by the delay ΔT of the propagation time of the PV from the compression cuff (heart level) to the corresponding PPG sensor located on the lower leg close to the ankle, usually on the side or on the back of the lower leg, on the same side of the body with the cuff (see Fig. 7). The distances D ₁ , D ₂ and D ₃ between the level of the heart, the cuff and the corresponding PPG sensors are measured by any known method, for example, but not limited to, in the usual way using a tape measure. In this case, the point of projection onto the anterior surface of the body of the middle point of the aortic arch, where the main branching of blood flow occurs down the aorta or into the arm along the subclavian artery, which in humans approximately corresponds to the center of the sternum handle (see I.D. Kirpatovsky , E.D. Smirnova.Clinical anatomy.Book I: Head, neck, torso.Tutorial guide. - M. Medical Information Agency, 2003. - 421 p.). The delay ΔT in the propagation time of the PV from the compression cuff to the PPG sensor on the lower leg in the new device is defined, as in the device adopted as a prototype, as the delay in the appearance of the PV on the photoplethysmogram relative to the appearance of the PV on the sphygmogram at the foot of the PV impulses.

Integral PWV in small peripheral vessels in the “shin-big toe” area on each side of the body is determined by the delay ΔT of the PV propagation time from one PPG sensor located on the lower leg close to the ankle on the selected side of the body to another PPG sensor located in the area of the patient's big toe (for example, the distal phalanx of the finger from the plantar side) at a distance D ₃ from the first PPG sensor (see Fig. 7) on the same side of the body. In some embodiments, the site of the big toe is the distal phalanx of the big toe. In some embodiments, the site of the big toe is the distal phalanx of the big toe. If the patient has no or severe damage to the big toe (for example, with a diabetic foot), it is possible to take measurements with a PPG sensor on the ball of the foot at the base of the big toe.

In general, this design of the device allows simultaneously with SBP and DBP to measure aortic PWV (PWVao) and calculate an analog of the CAVI index for the aorta - the aortic vascular index AVI - using a formula similar to formula (1), substituting PWVao into it instead of PWV, to measure PWV on in the “heart-calf (ankle)” (PWVca) region on two sides of the body simultaneously and calculate the standard CAVI indices for the left and right sides of the body using formula (1), as well as measure PWV in small peripheral arteries on the left and right lower extremities (PWVp) and calculate with their help the peripheral vascular index PVI according to the formula (1), as an analogue of the CAVI index, substituting into the formula instead of PWV the measured PWVp in small peripheral arteries on the left and right lower extremities, respectively.

The central distinguishing feature of the design of the proposed new device in comparison with the device taken as a prototype is the possibility of implementing a combination of "single-point" and "two-point" methods for measuring PWV, which structurally consists in using a digital filtering unit for the total pressure signal 76, as well as the presence of an additional PPG- sensor, which is attached to the lower leg. This sensor makes it possible to measure PV close to the ankle, as implemented in volumetric sphygmography devices, to calculate the standard CAVI index, but without creating additional external pressure on the cuff on the lower leg, which creates natural conditions for measuring PWV and calculating CAVI in this place, in contrast to situations with cuffs on the lower leg in volumetric sphygmography. Moreover, this PPG sensor, together with the second PPG sensor in the area of the big toe, opens up the possibility to simultaneously measure PWV in small peripheral arteries in the “shin-toe” area and calculate the corresponding peripheral vascular index PVI.

The proposed device for measuring PWV simultaneously with measuring blood pressure by the standard oscillometric method during measurements works as follows. It is assumed that the manufacturer of the device, during its production, correctly configured the device in advance for the purposes of measurements, namely: set the group signal propagation delays τ1 in the blocks 63 of digital filtering of the PV signals so that the device does not additionally introduce a mismatched delay of the PV signals in the channels of sphygmography and photoplethysmography, and determined for this device in the left and right cuffs the threshold value Ap_pore of the amplitudes of the pulsations of the air pressure PV, which is used to determine the pressure gap in the cuff in the range between SBP and DBP. The examined patient is located for measurements lying on the couch on his back, arms extended along the body. Turn on the device for taking measurements. In the patient, a tape measure on each side of the body measures the distances D₁, D₂ and D₃, according to the diagram in Fig. 7. The values of these distances before starting measurements using the keyboard of the device 8.2 are entered into the memory of the microprocessor 8.1 of the device. On the shoulders of the patient, compression cuffs 5.1 and 5.2 of the tonometer 4 are attached. 7,fix optical PPG sensors of the device 6.1 and 6.2. Similarly, PPG sensors 6.3 and 6.4 are attached to the right side of the body.

Next, the standard procedure for measuring blood pressure begins with pumping with pump 71 and depressurizing the pressure in the compression cuffs with valve 72 by pressing the "start/stop" button on the keyboard of device 8.2. During inflation and depressurization, the total pressure signal from sensors 73 in the cuffs is amplified in device blocks 74, digitized in blocks 75, and divided in block 76 into an exponentially decreasing constant pressure component, a sphygmogram, and individual PV pressure contours. During the release of pressure on these signals from each cuff by the microprocessor 8.1 of the device, the systolic (SBP) and diastolic (DBP) pressures are determined by the standard oscillometric method, and in the interval between the points of systolic (SBP) and diastolic (DBP) pressures, which are determined by the excess of the recorded amplitudes Ap pulsations of PV air pressure in the cuff of the set threshold value for the device Ap_por, are stored as a function of time pulses of PV pressure on the sphygmogram and their contours (shape). At the same time, photoplethysmograms are recorded by PPG sensors 6.1, 6.2, 6.3 and 6.4 on the lower extremities, signals from PPG sensors are amplified in blocks 61, digitized in blocks 62, and in blocks 63, PV pressure pulses are extracted with a predetermined time delay τ1 relative to the pulses PV of the corresponding sphygmogram in a compression cuff on the corresponding side of the body. All these signals are also recorded in the microprocessor 8.1 simultaneously for the left and right sides of the body.

During this recording in real time, the microprocessor 8.1 determines the “foot” of the direct PV pulses for sphygmograms and photoplethysmograms by calculating the second derivatives of the sphygmogram and photoplethysmogram signals and finding local maxima of the second derivatives in a known way, as described for the device adopted as a prototype. » microprocessor 8.1 then determines the delay times ΔT _i of the arrival of the i- th “foot” of the variable component of the photoplethysmogram signal for the PPG sensor on the lower leg relative to the time of arrival of the i- th “foot” of the sphygmogram, as shown in Fig. 8. Similarly, the microprocessor 8.1 determines the delay times ΔT _{i of} the arrival of the i- th “foot” of the variable component of the photoplethysmogram signal from the PPG sensor from the area of the big toe, relative to the time of arrival of the i- th “foot” of the variable component of the photoplethysmogram signal from the PPG sensor located on the shins. The thus determined ΔT _i for each area under consideration and each side of the body is then averaged similarly to formula (8) to obtain ΔT _cf for each examined area and each side of the body.

At the same time, during the recording of sphygmograms in the microprocessor 8.1, in the interval between the points of systolic (SBP) and diastolic (DBP) pressures, which are determined by the excess of the recorded amplitudes of the PV pulsations of the air pressure in the cuff on each side of the body of the set threshold value for the Ap_por device, peaks (ridges ) direct and reflected waves for PV on sphygmograms, and time delays Δt _i of registration of peaks (ridges) of reflected PV relative to peaks (ridges) of direct PV are calculated. They are also then summed and averaged according to formulas (8) and (9) to find the average Δt _cf .

After that, for each side of the body, the corresponding integral PWVs are calculated from the average ΔT _cf for the “heart - lower leg (ankle)” section, taking into account the measured distances D ₁ and D ₂ according to the formula:

where D ₁ is the distance between the heart and the middle of the patient's shoulder, on which the tonometer cuff is attached, D ₂ is the distance between the heart and the PPG sensor on the lower leg, - integral PWV in the area "heart - lower leg (ankle)".

For the “lower leg - big toe” section, for each side of the body, the corresponding integral PWVs in the peripheral vessels are calculated taking into account the measured distances D ₃ according to the formula:

where D ₃ is the distance between PPG sensors on the lower leg and in the area of the big toe, - integral PWV in the area "lower leg - big toe".

For the aorta, using Δtav , the average aortic _PWV is calculated using formula (2).

At the final stage, these rates are used to calculate the vascular indices CAVI and their analogues according to formula (1), where these PWVs are substituted for PWVs.

Based on the calculated values of PWV and vascular indices, the doctor receives information about the stiffness of the walls of the patient's vessels of various hierarchies and, in combination with the measured blood pressure, evaluates the general functional state of the patient's cardiovascular system.

Example No. 1: Subject N, age 33, male, height 170 cm, aortic length L = 51 cm without serious cardiovascular diseases, was examined on a prototype of the proposed device. The measured values on the left and right sides of the body are shown in Table 1.

Table 1. Parameter Left On right SBP, mmHg 126 128 DBP, mmHg 80 84 D ₁ , m 0.33 0.47 _D2 , m 1.48 1.48 _D3 , m 0.24 0.24 Δtav _, s 0.075 0.078 Heart-shin
ΔT _cf , s 0.162 0.148 shin toe
ΔT _cf , s 0.032 0.034

Estimated values of PWV and vascular indices are presented in Table 2.

Table 2. Parameter Left On right PWVao, m/s 6.7 6.7 PWVca, m/s 7.1 6.8 PWVp, m/s 7.5 7.1 AVI 6.9 6.9 CAVI 7.9 7.1 PVI 8.8 7.6

According to well-known data in medicine, such indicators can be characterized as the norm. There were no abnormalities in the work of the heart and vascular pathologies.

Alternatively, some patients may experience elevated SBP and DBP, for example, up to levels of 150 mm Hg and 100 mm Hg, respectively, but at the same time, normal PWV values (below 10 m/s) and normal values of vascular indices (below 9.5). This will characterize arterial hypertension and increased cardiac output as its cause.

As another option, reduced SBP and DBP values may be recorded with reduced PWV values (below 3 m/s). This situation will be an indicator of uncompensated low blood pressure due to reduced vascular tone.

If the patient has elevated SBP and DBP values with elevated PWV values (PWV is equal to or greater than 10 m/s), this is typical for arterial hypertension with the primary cause of the pathology in the form of vascular dysfunction, for example, due to calcification of their walls, an increase in their tone, etc. This situation is illustrated by example No. 2.

Example No. 2: Patient M, aged 54 years, height 180 cm, aortic length L = 54 cm, with complaints of periodic increase in blood pressure, was examined on a prototype of the proposed device. The measured values on the left and right sides of the body are presented in Table 3.

Table 3 Parameter Left On right SBP, mmHg 141 139 DBP, mmHg 93 87 D ₁ , m 0.35 0.48 _D2 , m 1.54 1.54 _D3 , m 0.27 0.27 Δtav _, s 0.089 0.087 Heart-shin
ΔT _cf , s 0.132 0.143 shin toe
ΔT _cf , s 0.033 0.036

Estimated values of PWV and vascular indices are presented in Table 4.

Table 4 Parameter Left On right PWVao, m/s 6.1 6.1 PWVca, m/s 9.0 7.4 PWVp, m/s 8.2 7.5 AVI 5.3 5.3 CAVI 11.2 7.9 PVI 9.2 8.1

According to well-known data in medicine, such indicators can be characterized as the initial (mild) stage of arterial hypertension with the presence of calcification of the femoral arteries or lower leg on the left side of the body, tk. on the left side of the body, elevated values of PWVca and vascular index CAVI were detected, with normal values of PWVao and AVI in the aorta, i.e. the stiffness of the aortic walls is within the normal range, and the disorders are localized precisely in the area of the vascular bed of the thigh and (or) lower leg of the left leg. Also in this example, the asymmetry of indicators on the left and right sides of the body is clearly manifested, which is difficult to detect with a tonometer device without simultaneous bilateral measurements.

It should be noted that the direct medical interpretation of the results obtained using this device, including the PWV boundary values of 3 m/s and 10 m/s, CAVI indices of 9.5, etc. is not the subject of the present invention. This interpretation is well known in medicine, and is given here only as an example of the operation of the device and the biomedical information obtained with its help. Since there are quite a lot of indicators registered with the proposed new device and calculated indicators, their different combinations are possible in different clinical situations. Accordingly, the examples given do not exhaust the whole variety of signal options and options for their medical interpretation. While the invention has been described with reference to the disclosed embodiments, it should be apparent to those skilled in the art that the specific detailed examples are provided for the sole purpose of illustrating the operation of the novel apparatus and examples of uses of the present invention and should not be construed. as in any way limiting the scope of the invention. It should be clear that various modifications are possible without departing from the essence of the present invention.

Thus, the proposed device does not require measurements in two stages for two sides of the body and allows you to simultaneously measure blood pressure, as well as "single-point" for the aorta and "two-point" for peripheral vessels PWV measurement methods on the left and right sides of the body. The presence in comparison with the device adopted for the prototype, additional PPG sensor, located in the lower part of the leg next to the ankle, allows you to calculate the vascular index CAVI in the area of the heart-ankle. Also, the proposed design, due to the "single-point" method of measuring PWV in the aorta and the "two-point" method of measuring PWV in the area "shin - big toe", allows you to obtain and analyze the values of vascular indices separately for the aorta, peripheral arteries of the thigh and leg, and small arteries of the foot, which more accurately allows you to determine the location of the localization of vascular pathologies.

Claims (3)

1. A device for measuring the speed of propagation of a pulse wave when measuring blood pressure by the oscillometric method with advanced functions, including an automatic tonometer for measuring blood pressure by the oscillometric method with an attached shoulder compression cuff and an optical PPG sensor, the tonometer consists of a pneumatic unit, including a cuff pressure pumping unit, a pneumatic pressure relief valve and an air pressure sensor in the cuff, each of which is pneumatically connected in parallel to each other and to the cuff, and an electronic unit that includes a microprocessor to which a keyboard and a display are connected, while PPG- the sensor is configured to be connected to the tonometer microprocessor, the control outputs of the microprocessor are connected to the control inputs of the cuff pressure pumping unit, the pneumatic pressure relief valve and the PPG sensor, and the tonometer microprocessor is configured to process all incoming signals from the pneumatic unit and the optical PPG sensor , perform calculations to measure the speed of propagation of a pulse wave, as well as control the operation of the PPG sensor and the pneumatic unit, characterized in that it contains two said compression cuffs and four mentioned PPG sensors, the tonometer includes two identical mentioned pneumatic blocks, and the electronic unit The tonometer includes two blocks for processing signals from air pressure sensors in the cuffs of pneumatic blocks connected to the output of the corresponding sensors for air pressure in the cuff for each pneumatic block, and with outputs to the microprocessor, and four blocks for processing signals from PPG sensors connected by inputs to outputs corresponding PPG sensors, and outputs to the microprocessor, wherein each block for processing signals from air pressure sensors in the cuff contains a series-connected analog block for amplifying the signal from the air pressure sensor in the cuff, a block for digitizing the analog pressure signal and a block for digital filtering the total pressure signal, and each block for processing signals from PPG sensors contains a series-connected analog block for amplifying the signal from the PPG sensor, a block for digitizing the analog signal from the PPG sensor and a block for digital filtering the signal from the PPG sensor with an adjustable delay in the appearance of the signal at the output of the block, the microprocessor has eight output channels for controlling the operation and switching on / off of the corresponding elements of pneumatic blocks and PPG sensors and is equipped with algorithms for calculating the speed of propagation of a pulse wave in the aorta, left-sided and right-sided speeds of propagation of a pulse wave for each PPG sensor, as well as the cardio-ankle vascular index and its analogues for aorta and peripheral small arteries in the "shin - toe" section, and separately for the left and right sides of the body, and the frequency of operation of the mentioned analog signal digitizing units is set to at least 320 Hz. 2. The device according to claim 1, characterized in that each PPG sensor includes at least one emitter, the input of which is connected to the control output of the tonometer microprocessor, and a photodetector, the output of which is connected to the corresponding analog signal amplification unit. 3. The device according to claim 1, characterized in that the blocks for digital filtering of the pressure signal and the blocks for digital filtering of the signal from PPG sensors are digital Butterworth filters, or Chebyshev filters, or Bessel filters, or a combination of them.