RU2755273C1 - Method for continuous non-invasive adaptive recording of central arterial pressure and apparatus for implementation thereof - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: group of inventions relates to medicine, namely to a method for continuous non-invasive adaptive recording of central arterial pressure (CAP) and to an apparatus for implementation thereof. In the supine position, elongated sensors are therein installed on the body of the patient orthogonally to the direction of the pulse wave to record mechanical oscillations. In the dorsal position of the patient, one sensor is placed directly under the aorta - under the scapulae of the person in the dorsal position, and a second sensor is placed on the posterior branches of the iliac artery - under the buttocks of the patient. In the prone position of the patient, one sensor is placed directly under the aorta - just below the nipples of the person in the prone position, and a second sensor is placed directly under the abdominal aorta - just above the navel of the person in the prone position. Mechanical oscillations caused by the passage of a pulse wave are simultaneously recorded on the surface of the body of the patient and converted into a digital signal. The received digital signals from each of the sensors are filtered in order to extract the cardiac components corresponding to one cardiac cycle therefrom. The time Τ of passage of the pulse wave between the installed sensors is determined as the time interval "t2" to "t1", wherein t1 is the time of passage of the J-peak of the cardiac component of the cardiac cycle "i" over the first sensor, and t2 is the time of passage of the J-peak of the cardiac component of the cardiac cycle "i" over the second sensor. J-peaks are automatically detected in each digital signal. The current CAP value is determined for each cardiac cycle based on the Moens-Korteweg equation.

EFFECT: CAP is determined for each cardiac cycle in a continuous mode without compressing negative pressure of the cuff on the patient and restrictions of the mobility of the patient in the supine position without any additional or special contact, except for what the patient already has in the supine position on the bed.

11 cl, 8 dwg

Description

The technical field to which the invention relates

The present invention relates to medicine, resuscitation, medical rehabilitation, and in particular to a method and device for non-contact registration of a patient's central arterial pressure in a continuous mode. Potential areas of application of non-contact continuous monitoring of central arterial pressure in medicine: rehabilitation, resuscitation, functional diagnostics, cardiology.

Background of the invention

Arterial pressure (BP) measured at the brachial artery can no longer be considered as the only marker of vascular status. Central arterial pressure (CAP) and arterial stiffness indicators are no less informative and prognostically valuable parameters, which are more closely associated with hypertrophy of the vascular wall, the severity of atherosclerotic vascular lesions and the frequency of cardiovascular complications than peripheral blood pressure and some other classical measured indicators of risk factors for hypertension. At the same time, the study of CAP cannot be considered as an alternative to the classical method of measuring blood pressure on the brachial artery; it only complements the understanding of a specific pathological process. The results of measurements of CAP can be used as additional diagnostic criteria for stratification of cardiovascular risk (predicting the course of the pathological process, assessing the potential of therapy and rational choice of drugs) in diseases of the cardiovascular and endocrine systems, diseases of the respiratory system, other organs and systems, and their complications. Early diagnosis of abnormalities in CAP (aortic hypertension or hypotension) will allow timely adjustments to therapy and prevent adverse consequences of hemodynamic disorders. Dynamic control over the level of CAP is advisable to use for the correction of therapeutic programs, in the rehabilitation of patients, in the treatment of patients in intensive care and intensive care units.

There are several approaches to measuring CAP. Some of them use various transforming functions to convert the obtained values into the DAC value. One of the methods is based on the registration of a pulse wave on the shoulder using a transforming function, followed by an assessment of arterial stiffness and indicators of central arterial pressure. There are various methods of pulse wave conversion and processing that allow assessing the CPP without using transforming functions. At the moment, two methods are known: one technique allows you to register the pulse wave on the shoulder, and the other is based on measuring the CPP by applanation tonometry on the radial artery and allows daily monitoring of the CPP.

However, when using the method of applanation tonometry on the radial artery, careful fixation of the device on the area of the radial artery is required, and due to the constant pressure of the transducer on the artery, the procedure becomes quite painful.

Prior art solutions for non-invasive measurement of central blood pressure are known, disclosed in US9414755 B2, EP2162063 A1, US2007185400 A1, Natarajan, K., Cheng, A., Liu, J. et al. Central Blood Pressure Monitoring via a Standard Automatic Arm Cuff. Sci Rep 7, 14441 (2017), which demonstrate interest in this topic.

Thus, the development of new methods for analyzing the pulse wave, as well as the interpretation of the results in order to obtain values of central arterial pressure is an urgent task.

The essence of the invention

The objective of the invention is to develop a method for monitoring CAP, the advantage of which is:

• registration of central arterial pressure values in a continuous mode without the pressing negative effect of the cuff on the patient and restrictions on the patient's mobility in the supine state;

• CAP measurement is adaptive; takes into account the individual data of the patient about his gender, age, body type, body weight.

A device that allows you to implement the method of monitoring the CAP has the following advantages:

• registration of mechanical vibrations of the patient's body in order to calculate the CAP for each cardiocycle;

• Integration with the hospital department data concentrator for data exchange via the cloud or on-premises server;

• integration with cloud service;

• the ability to transmit information about the patient's condition through various communication channels.

The technical result of the present invention consists in the development of a method for determining the CAP for each cardiocycle and a device for non-contact continuous recording of CAP in the supine state, which would achieve all of the above advantages. The contactlessness of the proposed method lies in the fact that the mattress on which the patient lies is a conductor of mechanical vibrations recorded by the device. In this case, no additional or special contact is required other than what the patient already has in a state of lying on the bed.

The technical result is achieved by implementing a method for continuous non-invasive adaptive registration of central arterial pressure, which includes the following stages:

a) in the supine position on the patient's body, at least two elongated sensors are installed to register mechanical vibrations at predetermined locations,

b) simultaneously register mechanical vibrations on the patient's body surface caused by the passage of a pulse wave using at least two sensors and convert them into a digital signal,

c) filtering the received digital signals from each of the sensors in order to extract from them the cardiac component corresponding to one cardiocycle,

d) determine the time Τ of the pulse wave passing between the installed sensors as the time interval "t2" - "t1", where t1 is the time moment of the passage of the J-peak of the cardiac component of the cardiocycle "i" over the first sensor, isolated from the digital signal from the first sensor, a t2 - the time instant of passage of the J-peak of the cardiac component of the cardiocycle "i" over the second sensor, isolated from the digital signal from the second sensor,

at the same time, J-peaks are automatically determined in each digital signal received from each sensor, in the cardiac component selected as a result of filtering,

e) determine the current value of the central arterial pressure for each cardiocycle based on the Moens-Korteweg equation according to the formula

where

a - dimensionless coefficient;

L is the distance between the sensors;

Τ - the time of passage of the pulse wave between the installed sensors for recording mechanical vibrations;

h is the thickness of the aortic wall;

d is the inner diameter of the aorta;

p - blood density;

E ₀ - the initial value of the modulus of elasticity of the aortic wall, calculated by the formula E ₀ = Δp / Δd × d / h, where Δd is the difference between the diameters of the aorta in systole and diastole, Δp is the difference between the mean systolic and mean diastolic pressure.

In some embodiments of the invention, before the start of registration of mechanical vibrations of the patient's body surface, an initial calibration is performed, which includes entering data about the patient: age, weight, body type, gender of the patient, attitude to smoking, the presence of chronic diseases leading to a change in the morphology of the cardiovascular systems; pharmacological preparations taken by the patient, input of the specified distance between the installed sensors of mechanical vibrations, determination of the values of systolic and diastolic blood pressure in the brachial artery, determination of individual parameters of the aortic wall thickness h, internal aortic diameter d, coefficient a and blood density p based on the entered data, determination the difference Δd between the diameters of the aorta in systole and diastole and the difference Δp between the mean systolic and mean diastolic pressure - based on the entered and determined data.

In some embodiments, the initial calibration is performed within 5 minutes.

In some embodiments of the invention, regular calibration is performed during continuous recording of central arterial pressure.

In some embodiments of the invention, regular calibration is performed for 1 minute every 12 hours if the patient has not left the bed, or 1-5 minutes after the patient has gone to bed and stopped making active movements.

In some embodiments, the routine calibration includes measuring the patient's systolic and diastolic blood pressure using the Korotkoff method.

In some embodiments of the invention, the sensors for recording mechanical vibrations are made elongated, and they are located orthogonal to the direction of the pulse wave.

In some embodiments, the digital signal is filtered using a Butterworth bandpass filter.

In some embodiments of the invention, the automatic detection of J-peaks in the digital signal of the filtered cardiac component includes the following steps:

in a discrete signal x ₁ , x ₂ , ... x _N points of local extremum are distinguished - points of maximum x _i , for which x _i-1 <x _i and x _i ≥ _{x i + 1} and minimum - for which x _i-1 <x _i and x _i ≥x _{i + 1} ,

for each maximum J, the index Z (J) = X (J) -2X (I) + X (H) is calculated, where X (J) is the height of this peak, X (I) is the signal level corresponding to the previous failure, X (H) - the height of the previous peak,

as J-peaks, those maxima are selected for which the Z (J) index is greater than three adjacent peaks on the left and three adjacent peaks on the right.

In some embodiments of the invention, when the patient is supine, one sensor is located directly under the aorta - under the shoulder blades of the supine person, the second sensor is placed on the posterior branches of the iliac artery - under the patient's buttocks.

In some embodiments of the invention, with the patient lying prone, one sensor is positioned directly below the aorta - just below the nipples of the prone person, the second sensor is positioned directly under the abdominal aorta - just above the navel of the prone person.

Also, the technical result is achieved due to the fact that a device for continuous non-invasive adaptive registration of central arterial pressure, including: means for recording a signal of a ballistocardiogram and its primary processing, a cloud or a local server, configured to receive data from said means, process them and transmit processed data to the addressees, while the means for recording the ballistocardiogram signal and its primary processing includes:

at least two sensors for recording mechanical vibrations on the surface of the patient's body,

at least two analog signal amplifiers from each mechanical vibration sensor, analog filters, and an ADC,

one or more control modules programmed to carry out steps a-b) of the method described above,

the control module is configured to transmit data to a cloud or a local server, in which the steps of the method c) -e) of the method described above are carried out.

In some embodiments of the invention, the device for continuously recording the CAP includes an input device for data obtained from primary and / or regular calibration and a device for outputting measurements.

In some embodiments, the targets are mobile applications and a dispatch center console.

Brief Description of Drawings

The accompanying drawings, which are incorporated and form part of the present specification, illustrate embodiments of the invention and, together with the foregoing general description of the invention and the following detailed description of the embodiments, serve to explain the principles of the present invention.

Figure 1 shows an illustration of the additional blood volume that is absorbed by the pulse wave (S is the maximum area increment at the moment the pulse wave passes).

Figure 2 shows the distribution of pressure and blood velocity in the human vascular system. Ρ - blood pressure (left scale), V - blood flow velocity (right scale).

Figure 3 shows the dependence of blood pressure (P) on time (t) in the brachial artery. The numbers indicate the values: pulse (1), diastolic (2), mean (3) and systolic (4) pressure.

Figure 4 shows the orientation lines of the placement of the sensing elements of the device under the body of a recumbent patient in the supine position.

Figure 5 shows a scheme for registering elastic mechanical vibrations by a sensitive element of the device, caused by the passage of a pulse wave. View from above. The symbols indicate the following values: section of the patient's body (1), section of the mattress (2), section of the strip sensor (3) (elongated sensor of mechanical vibrations), section of the medical bed (5), section of the aorta (6), increment of the sectional area of the aorta due to the passage of the pulse waves (ΔV), the direction of propagation of an elastic mechanical wave along the patient's body due to an increase in the aortic area (7), including, along the shortest path (8), the direction of propagation of an elastic mechanical wave along the mattress (9), the direction of propagation of an elastic mechanical wave along band sensor (10).

Figure 6 shows a diagram of the registration of elastic mechanical vibrations by different sensitive elements of the device in order to calculate the speed of propagation of the pulse wave. Side view. The symbols indicate the following values: section of the patient's body (1), section of the mattress (2), section of the first strip sensor (3), section of the second strip sensor (4), section of the hospital bed (5), the distance between the projections of strip sensors on the aorta along the shortest path (L), the increment in the section of the aorta at the time of the passage of the pulse wave over the first strip sensor (d1), the increment in the section of the aorta at the moment of passage of the pulse wave over the second strip sensor (d2), the increment in the force with which the patient's body presses on the first strip center as a consequence the passage of the pulse wave over the first band sensor (Δf1), the increment in the force with which the patient's body presses on the second band center as a result of the passage of the pulse wave over the second band sensor (Δf2), the time instant of the pulse wave passing over the first band sensor (t1), the moment time of passage of the pulse wave over the second band sensor (t2).

Figure 7 shows a diagram of the C1 and C2 band sensors, the K1 and K2 protective keys, the U1 and U2 operational amplifiers of the U1 and U2 band sensors, the microprocessor unit of the terminal monitoring device for the digital center - MB.

Figure 8 shows a general view of a general-purpose ward with individual monitoring devices for the CAC.

Terms and Definitions

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

In the present description and in the claims, the terms “includes”, “including” and “includes”, “having”, “equipped”, “containing” 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 (ie, in the sense of "including"). Only expressions of the type “consisting of” should be considered as an exhaustive list.

The term "blood pressure (BP)" is a value that characterizes the force of pressure of the blood pushed out by the heart muscle on the walls of blood vessels. The highest blood pressure is called systolic blood pressure, and the lowest is called diastolic blood pressure. Blood pressure is usually measured in millimeters of mercury (mmHg) and presented as a Systolic / Diastolic ratio, such as 120/80 mmHg.

The term "central aortic systolic pressure (CASP)" or "central arterial pressure" is the pressure of blood at the level of the aortic bulb. CASP is generally lower than brachial systolic blood pressure. The difference between these values can be 30 mm Hg. in young healthy people. With age, the difference between central blood pressure and systolic blood pressure in the brachial artery becomes less pronounced. Similar changes can be observed in hypertension, in uncontrolled diabetes mellitus, as well as in other diseases and pathological conditions of the cardiovascular system.

The term "connected" means functionally connected, and any number or combination of intermediate elements between the 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 the enumerated objects.

Detailed description of the invention

The device and method for non-contact continuous measurement of the central arterial pressure of a patient in a supine state is aimed at the following types of users:

• elderly people over the age of 60;

• disabled, bedridden patients;

• people suffering from arterial hypertension;

• people with heart or cerebral diseases;

• people who have undergone various heart operations, heart attacks, strokes, but can be used in any other categories of patients.

The method for measuring central arterial pressure is based on the regularity of changes in the speed of propagation of the pulse wave with changes in central arterial pressure due to changes in the elasticity of the walls of arteries and arterioles.

A study of a model of a passive elastic tube for an approximate description of a large blood vessel was carried out by A.N. Volobuev in the journal "Uspekhi fizicheskikh nauk", February 1995, volume 165, No. 2, in the article "Fluid flow in tubes with elastic walls." In this work, the physical and mathematical aspects of the processes of fluid flow through a thin-walled elastic tube were considered. Nonlinear differential equations of these processes are derived and solved. The possibility of the existence of a self-oscillating mode of blood flow through the vessels is shown, which is confirmed in practice by registering Korotkov's noises with the cuff method for measuring blood pressure. Changes in the cross-sectional area of an elastic tube (large and middle artery) and fluid flow velocity along its length were investigated. The mathematical modeling of the pulse wave is carried out on the basis of the Korteweg - De Vries equation and the modified nonlinear Schrödinger equation. The pulse wave absorbs the volume of blood ejected by the heart (for the aorta, this is the stroke volume of the heart, schematically shown in Figure 1) and propagates at a speed different from the speed of blood flow.

The distribution of pressure and blood velocity in the human vascular system is schematically shown in Figure 2.

The human vascular system has a minimum cross-sectional area in the aortic region, where the maximum amplitude of pulse oscillations and the highest linear blood velocity are observed (about 0.5 m / s, see Figure 2, lower curve). With the transition to smaller blood vessels, their total cross-sectional area increases and, in accordance with the conditions of the continuity of the jet, the blood flow velocity in them decreases, amounting to about 0.5 mm / s in the capillaries. In the venous part of the vascular system, the total cross-sectional area of the vessels decreases, which leads to an increase in the blood flow velocity.

A pulse wave is a pressure wave that reaches the surface of the body and is reflected from it. Due to the rapid attenuation in the tissues of the human body due to tissue heterogeneity and a sharp narrowing of the section of vessels (arteries) in the direction of propagation of the pulse wave, the source of mechanical vibrations with the greatest amplitude reaching the body surface are the main arteries of the human body, which have a significant section and are located nearby with the surface of the body. Proceeding from this, the registration of the moment of passage of the pressure wave is advisable in places located in close proximity to large arteries close to the body surface.

When a person is lying on his stomach, such arteries are: the abdominal aorta, the common iliac artery, the median sacral artery, and the internal iliac artery. When a person is supine, such arteries are the arteries that bring blood to the gluteal muscles (the posterior branch of the iliac artery).

Thus, it is advisable to record mechanical vibrations in order to measure the speed of the pulse wave in two areas: in the immediate vicinity of the heart and away from it: for the prone position - in the navel area, for the supine position - in the buttocks area.

The pressure (P) on the walls of blood vessels at a certain point of the vascular system depends on the following parameters: time (t), distance from the heart to a given point (x), cyclic heart rate (ω), pulse wave propagation velocity (υ).

Pressure can be represented as two terms:

Ρ = P _cp + P (t),

where P _cf is the pressure due to a constant average level of blood filling (constant component), and P (t) is a term determined by pulse fluctuations in blood flow.

Pressure fluctuations cause changes in blood volume. Considering a large blood vessel to be a tube with elastic walls, the relationship between the blood volume (V) in a given section of the vessel at any time and pressure can be written as an equation:

V = V _o + k * P (t),

where k is the coefficient of proportionality between pressure and volume, which characterizes the elasticity of the blood vessel, and V _o is the volume of the cavity of the blood vessel at an average pressure P _cf.

Pulse pressure fluctuations have a rather complex shape, shown in Figure 3. However, like any complex periodic process, pulse fluctuations can be represented as a set of harmonic components by expanding in a Fourier series.

Harmonic analysis of pulse fluctuations in blood flow is one of the important methods of its study. The first harmonic component of the pressure (P ₁ ) of the pulse wave is determined by the following expression:

where P _o is the amplitude of pulse fluctuations of arterial pressure, t is the time, x is the distance from the heart to the point of measurement along the blood vessel, ω is the cyclic heart rate, υ is the pulse wave propagation velocity, α is the coefficient that depends on the elasticity properties blood vessels. The elasticity of the vessels changes, decreasing with increasing distance from the heart to the periphery. Morphologically, this is due to a change in the amount of elastin and collagen in the tissues of the vascular wall. So, in the common carotid artery, the ratio of elastin to collagen is 2: 1, and in the femoral artery - 1: 2. With distance from the heart, the proportion of smooth muscle fibers increases, which in the arterioles are already the main component of the vascular wall.

In large blood vessels (arteries), the speed of propagation of the pulse wave is determined by the Moens-Korteweg formula:

where Ε is the modulus of elasticity of the blood vessel wall, h is the thickness of the blood vessel wall, d is the diameter of the blood vessel, and ρ is the blood density.

According to the Moens-Korteweg formula, with an increase in vessel rigidity and an increase in its wall thickness, the pulse wave velocity increases. So, in the aorta it is 4-6 m / s, in the arteries of the muscle type - 8-12 m / s. In veins, which are more elastic, the pulse wave velocity is lower and, for example, in the vena cava, it is about 1 m / s. From these data, it follows that the speed of propagation of the pulse wave is much greater than the linear speed of blood flow, at rest not exceeding the value of 0.5 m / s (in the aorta).

With age, the elasticity of human vessels decreases (the modulus of elasticity increases) and, consequently, the speed of the pulse wave increases. The speed also increases with increasing pressure. With increased pressure, large blood vessels stretch slightly, become more "tense", and more force is required to further stretch them.

Thus, registering a jump or a trend in the increase in the pulse wave speed at the same points of registration of mechanical oscillations, it is permissible to state an increase in blood pressure, and vice versa, when registering a jump or a trend in a decrease in the pulse wave velocity, it is permissible to state a decrease in blood pressure.

Figure 4 shows the layout of two sensors for the position of the patient on the back, recording the passage of the pulse wave through large arteries located close to the body surface adjacent to the sensitive elements (blue dotted lines).

The first segment of the sensitive surface in the form of a tape (Sensor 1) is placed directly under the aorta - under the shoulder blades of the person lying on the back, the second segment in the form of a tape (Sensor 2) - under the gluteal arteries (posterior branches of the iliac artery), under the buttocks of the person lying on the back.

In the case of placement of sensitive elements under the body of a patient lying on his stomach, the first segment of the sensitive surface in the form of a tape (Sensor 1) is placed directly under the aorta - just below the nipples of a person lying on his stomach, the second segment in the form of a tape (Sensor 2) - directly under the abdominal aorta - just above the navel of a person lying on his stomach.

Using a system of two segments of the sensitive surface (sensors), the problem of recording the time of passage of the pulse wave through the arteries from the aorta, through the abdominal artery and further to the gluteal arteries is solved by measuring the difference in pressure exerted by the body of a recumbent person on two segments of the sensitive surface, with an accurate by measuring the time delay between the impact on them, determined by the speed of passage of the pulse wave.

Measuring the time interval of the passage of the pulse wave between the sensors for each cardiocycle makes it possible to obtain a time series of measurements of the speed of propagation of the pulse wave. Time series presentation of the measured metric allows standard reliable numerical methods to be used for filtering noise. When registering a stable change in speed, using the Moens-Korteweg equation, Young's modulus and then central arterial pressure are calculated. With an increase in pressure, the speed of propagation of the pulse wave increases due to the fact that at increased pressure, large blood vessels are somewhat stretched, become more "tense", and more effort is required for their further stretching.

In addition to the above, according to the latest recommendations of the European Society of Cardiology (ESC) and the European Society of Hypertension (ESH), a carotid-femoral pulse wave velocity (PWV) of more than 10 m / s means asymptomatic target organ damage, therefore it plays a role in cardiovascular risk stratification similar to the diagnosis of diabetes mellitus. The American Heart Association (AHA) position paper also recommends carotid-femoral PWV (grade I; level of evidence A) as a diagnostic criterion.

The proposed method for continuous non-invasive measurement of central arterial pressure (arterial pressure in the aorta) is based on the recommendations of ESC, ESH and AHA.

Central arterial pressure (CAP) is calculated by measuring the pulse wave velocity (PWV), which changes due to the elasticity of the aortic wall due to changes in the CAP. The elasticity of the aortic wall is an individual indicator of each person. Elasticity changes during life rather slowly, it changes due to various chronic diseases and aging of the body.

The proposed method for continuous measurement of CAP assumes two modes of operation of the measuring device: device calibration mode and continuous pressure measurement mode.

The calibration mode assumes initial calibration and regular recalibrations.

The initial calibration of the device takes 5 minutes and is the input of data on age, height, weight, body type, gender of the patient, chronic diseases of the cardiovascular system (morphological changes), input of data on the distance between measurement points of the pulse wave propagation velocity ( between the installed sensors of mechanical vibrations), about the value of systolic and diastolic blood pressure.

The calibration parameters of the systolic and diastolic blood pressure values in the brachial artery of the patient are obtained by measuring the patient's blood pressure by the Korotkoff method with a calibrating sensor. For this, a calibrating sensor is connected to the air supply line to the cuff placed on the patient's forearm. After that, the value of systolic blood pressure is recorded by measuring the air pressure in the line at the time of the appearance of cavitation noises in the brachial artery (Korotkov's noises). The value of diastolic blood pressure is recorded by measuring the air pressure in the line at the time of the termination of cavitation noise in the brachial artery (Korotkoff murmur).

On the basis of the entered data at the stage of primary calibration, the values of blood density p, the thickness of the aortic wall h and the inner diameter of the aorta d and the values of the empirical coefficient "α", which has a value in the range of 0.016-0.018, are determined - the values of the difference between the diameters of the aorta in systole and diastole "Δd" and the difference between mean systolic and mean diastolic pressure "Δp".

The values of these parameters are selected on the basis of a table compiled as a result of measurements for a statistically significant group of patients.

After the initial calibration, the device switches to the normal operating mode, in which the central arterial pressure is measured and repeated regular calibration is performed during the entire time the patient is in the hospital bed. The mode of continuous measurement of CPP between regular calibrations lasts no more than 12 hours.

Regular recalibrations are performed on a periodic basis for 1 minute every 12 hours in automatic mode if the patient does not leave the bed (in case the patients are lying down), or 1-5 minutes after the patient has gone to bed and stopped making active movements ... When the device is connected to another patient, the device is initially calibrated.

Regular recalibration is necessary to correct device performance, as the dependence of CAP on PWV changes over time due to the action of some pharmacological agents.

For measurement purposes, the pulse wave is regarded as a temporary increment in the artery profile (denoted in Figure 5 as “ΔV”) caused by the ejection of “stroke volume” from the heart. The increment in the profile of the artery propagates in the direction from the heart to the peripheral vessels with the speed of propagation of the pulse wave (PWV).

The PWT changes over a known range of values. In this case, the speed is determined by the profile of the artery, the individual characteristics of the stiffness of the walls of the arteries and the current value of blood pressure. With age, with various diseases, depending on the action of some pharmacological drugs, the elasticity of the arterial walls decreases, which leads to a change in PWV.

A pulse wave in the ascending part of the aorta, aortic arch, abdominal aorta and smaller arteries of the next order is the source of a rapidly decaying spherical mechanical wave in the body tissues adjacent to the arteries (indicated in Figure 5 as "3"), propagating in the direction from the local increment of the artery profile with a speed approximately equal to the speed of sound in water (1485 m / s). The effect of rapid attenuation of a spherical mechanical wave in body tissues avoids parasitic harmonic oscillations caused by the reflection of a mechanical wave from the body surface, and therefore allows recording the moment of passage of a pulse wave at a specific point, for example, the abdominal aorta (indicated in Figure 6 as "t1" and " t2 ") and arteries of the following order departing from it.

To register the moment of passage of the pulse wave to the patient in the supine position, two elongated sensors are installed to register mechanical vibrations at predetermined locations on the line indicated in Figure 4, while the distance between the sensors is set and strictly defined as "L" (determined at the stage of primary calibration) ... As described above, the location of the sensors depends on the position of the patient: on the back or on the stomach. For example, if the patient is lying on his stomach, the first sensor is placed directly under the aorta - just below the nipples of the person lying on the stomach, the second sensor - directly under the abdominal aorta - just above the navel of the person lying on the stomach.

Both transducers are positioned orthogonally to the direction of the pulse wave, for example, along the abdominal aorta (designated as "3" in Figure 5) in order to increase the signal-to-noise ratio.

To measure the speed of the pulse wave, for example, at a specific point of the abdominal aorta, two ballistocardiogram (BCG) signals are simultaneously recorded using two identical elongated transducers (labeled 6 as "3" and "4" in the figure). Since time is required for the propagation of the pulse wave along the area of the abdominal aorta between the sensors, it is calculated by the delay of the wave of the area of the abdominal aorta, under which the second sensor is located, relative to the wave of the area of the aorta, under which the first sensor is located. Knowing the distance between the two sensors, the velocity of the pulse wave can be calculated.

In more detail, the pulse wave velocity is measured as follows.

Mechanical vibrations of the patient's body caused by the passage of the pulse wave are converted into a digital signal by means of sensors. Each of the signals from both sensors is processed.

In particular, the signals of the ballistocardiogram (BCG) recorded by the sensors, in addition to the dynamics caused by the work of the heart muscle, contain other movements of the patient's body, such as breathing and motor activity, as well as external mechanical noises. Thus, it is required to extract useful components from the BCG signals, for example, it is required to isolate the cardiac component.

In preferred embodiments of the invention, the cardiac component corresponding to one cardiac cycle is isolated from the BCG signal using a Butterworth bandpass filter. However, other approaches based on discrete wavelet transform, Hilbert transform, low-frequency and band-pass filtering, etc. can be used to filter the cardiac component from the BCG signal.

After filtering, the data is sent to the data center (cloud or local server).

The signal of the cardiac component of one cardiocycle represents on the graph a structure known as the "HIJKLMN complex", consisting of four peaks and three dips, following each other, while the J-peak (the second peak of the "complex") is usually the highest in a person with pathologies of the heart muscle and corresponds to the response of the left ventricle of the patient's heart. Under "severe pathology" is understood, for example, myocardial infarction (deep damage / destruction of the heart muscle - myocardium).

The interval between heartbeats is defined as the interval between the J-peaks of two consecutive cardiocycles.

The time interval "t1-t2" (denoted as "t1" and "t2" in Figure 6) between the J-peak passes of one cardiocycle over each sensor (denoted as “3” and “4” in Figure 6) is used to calculate the propagation velocity pulse wave. That is, in fact, the time delay of the passage of the J-peak of the "i-th" cardiac cycle of the cardiac component isolated from the BCG signal, which is recorded by the second sensor, is determined relative to the recording time of the J-peak of the "i-th" cardiac cycle of the cardiac component isolated from the BCG signal, which is recorded first sensor.

Automatic detection of J-peaks in the digital signal of the cardiac component selected as a result of filtering includes the following steps:

1) in a discrete signal x ₁ , x ₂ , ... x _N points of local extremum are distinguished - points of maximum x _i , for which x _i-1 <x _i and x _i ≥ _{x i + 1} and minimum - for which x _i-1 <x _i and x _i ≥x _{i + 1} ;

2) for each maximum J, the index Z (J) = X (J) -2X (I) + X (H) is calculated, where X (J) is the height of this peak, X (I) is the signal level corresponding to the previous failure , X (H) - the height of the previous peak;

3) as J-peaks, those maxima are selected for which the Z (J) index is greater than three neighboring peaks on the left and three adjacent peaks on the right.

Using the travel time of the J-peak of the cardiocycle "i" over the first sensor (in Figure 6, denoted as "t1") and the travel time of the J-peak of the cardiac cycle "i" over the second sensor (in Figure 6, denoted as "t2") and knowing the fixed distance between the sensors, calculate the velocity of propagation of the pulse wave (PWV) for the cardiocycle "i" using the equation

v = L / T, where

L is the distance between the sensors;

Τ - time interval "t2-t1" (in Figure 6, designated as “t1” and “t2”) between the J-peaks of the cardiocycle recorded using two sensors (in Figure 6, designated as “3” and “4”).

Thus, measuring the time interval of the passage of the pulse wave between the sensors (Δt) makes it possible to obtain the PWV value.

Having measured the velocity of propagation of the pulse wave (PWV) for the cardiocycle "i" and having practically unchanged values of the vessel wall thickness, blood density and diameter of the vessels during the time interval between successive cardiocycles, the elasticity index of the arterial wall is calculated using the Moens-Korteweg equation ( Young's modulus) Ε for cardiocycle "i"

where

h - vessel wall thickness: an individual value, a constant is used that is adapted to gender, age, body type, weight and morphological changes in the patient's vessels,

d is the inner diameter of the aorta: a constant is used that is adapted to gender, age, body type, weight and morphological changes in the patient's vessels (determined at the stage of initial calibration),

p - blood density: an individual indicator of blood density for each person can be considered a constant value, which usually has a value in the range of 1.050-1.060 g / cm ³ (determined at the stage of initial calibration),

v is the pulse wave propagation velocity calculated at the previous stage.

The values of the elasticity index of the aortic wall (Young's modulus) Ε change in direct proportion to changes in central arterial pressure in the case of persistent changes in central arterial pressure, while the thickness of the aortic wall changes slowly, since these are morphological (structural) changes in the vessel.

Using the empirical dependence of Young's modulus Ε on blood pressure

Ε = Е ₀ е ^аР , where " ₀ " is the initial value of the elastic modulus of the vessel wall, "α" is an empirical coefficient that has a value in the range of 0.016-0.018 and whose values are selected on the basis of a table compiled as a result of measurements for a statistically significant group patients at the stage of primary calibration, "P" - central arterial pressure,

calculate the central arterial pressure Ρ for the cardiocycle "i" as

"E ₀ " is determined by the formula Ε ₀ = Δp / Δd × d / h, where "d" is the inner diameter of the aorta, "Δd" is the difference between the diameters of the aorta in systole and diastole (for each position of the sensors (sensors), a constant is used, adapted to gender, age, body type, patient weight and sensor location, the values of which are selected on the basis of a table compiled as a result of measurements for a statistically significant group of patients at the primary calibration stage, is determined at the primary calibration stage), "Δp" is the difference between mean systolic and mean diastolic pressure calculated in the mode of primary and / or regular recalibration.

"L" - distance between measurement points;

"T" - time interval "Δt" between the times of passage of the J-peaks of one cardiocycle over the sensors (transducers);

"H" is the thickness of the aortic wall;

"D" is the inner diameter of the aorta;

"P" is the density of the blood.

The method described above is implemented using a device that generally includes:

the technical solution can be implemented in the form of a distributed computer system, the components of which are cloud or local servers;

equipment for monitoring the patient's CAC, which is configured to record patient data, primary data processing and send the registered data to the cloud or a local server;

a cloud or a local server, which are configured to receive and process monitoring data, as well as save and analyze them for various categories of events. Stored monitoring data and events are available to external applications or platforms through an external application.

An external application is software that is integrated with the cloud or local server. An external analytics and data visualization platform, a mobile application, a web application, and other software can act as such an application.

Equipment for monitoring the patient's CAP includes at least two sensors for recording mechanical vibrations of the patient's body, at least two analog amplifiers of signals from each sensor of mechanical vibrations with a high resolution, analog filters allowing to remove noise exceeding the useful signal by three orders of magnitude at least two ADCs, one or more microprocessor modules, input / output interfaces, means of networking, data input / output devices.

The scheme of the device operation in the continuous monitoring of the patient's CAP is illustrated in Figure 7 and consists of the following.

Sensors for registration of mechanical vibrations of the patient's body are connected to an individual control module (microprocessor unit of the terminal monitoring device "MB"), which, through a secure connection, sends this data to the cloud or to a local server. The control module can be configured as a client, server, mobile device, or any other computing device that interacts with data in a network-based collaboration system. Depending on the implementation, the control module can be one data processing device and provide all the steps of the method, or it can include several data processing devices, each of which will carry out only separate steps. In one configuration, the control module typically includes at least one microprocessor module and a data storage device.

A data storage device includes, but is not limited to, random access memory (RAM), read only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory or other technology, CD ROM. disk (CD-ROM), versatile digital disks (DVD) or other optical storage devices, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and to which the control module can access. Any such storage device can be part of a control module.

The data storage device usually includes the individual patient data entered during the initial and / or regular calibration, as well as one or more application programs, the instructions of which embody the determination of the required parameters based on the entered data and the execution of the basic operations necessary for the preprocessing of the digital signal derived from the BCG signal. In particular, the preprocessing of the digital signal received from each sensor includes the extraction of the cardiac component from the digitized BCG signal.

A microprocessor module reads and executes machine instructions (programs) from one or more storage devices. Storage devices may include, but are not limited to, hard disk drives (HDD), flash memory, ROM (read only memory), solid state drives (SSD), optical drives, cloud storage, or a combination thereof.

The control module may also include input device (s) such as a keyboard, mouse, stylus, voice input device, touch input device, and so on.

Output device (s), such as display, speakers, printer and the like, can also be included in the control module and / or device for monitoring the DAC.

The microprocessor module transmits the preprocessed data to the cloud or a local server, where calculations of the travel time of the pulse wave between the mechanical vibration sensors and the calculation of the central arterial pressure for each cardiocycle are performed. A cloud or a local server receives monitoring data, processes it and places it in the archive storage. Archive storage supports MapReduce data access, which allows simultaneous access to large datasets.

The cloud or local server also, if necessary, generates and delivers data to the addressees. The addressees of the events are mobile applications and the control center of the dispatch center.

The mobile application allows you to get to the persistent data storage interface to perform queries for the definition and upload of various datasets.

The control room console allows you to receive information from all patients living in a certain area that is part of the control room's area of responsibility. When alarming events appear, as a result of actions according to the established protocol for checking the relevance of an emergency call, the dispatcher calls emergency assistance to the patient.

The components of the device are linked via a common data bus.

The interfaces are standard means for connecting and working with the server side, for example, USB, RS232, RJ45, LPT, COM, HDMI, PS / 2, Lightning, FireWire, etc.

Networking means are selected from devices that provide network reception and transmission of data, for example, Ethernet card, WLAN / Wi-Fi module, Bluetooth module, BLE module, NFC module, IrDa, RFID module, GSM modem, etc. With the help of networking tools, it is possible to organize data exchange via a wired or wireless data transmission channel, for example, WAN, PAN, LAN, Intranet, Internet, WLAN, WMAN or GSM.

Although the invention has been described with reference to the disclosed embodiments, it should be apparent to those skilled in the art that the specific experiments described in detail are provided for the purpose of illustrating the present invention only and should not be construed as in any way limiting the scope of the invention. It should be understood that various modifications are possible without departing from the spirit of the present invention.

Claims (35)

1. A method for continuous non-invasive adaptive registration of central arterial pressure, including the following steps: a) in the supine position on the patient's body, at least two elongated sensors are installed to register mechanical vibrations at predetermined locations so that they are located orthogonal to the direction of the pulse wave: when the patient is supine, one sensor is placed directly under the aorta - under the shoulder blades of the person lying on the back, the second sensor is placed on the posterior branches of the iliac artery - under the patient's buttocks, when the patient is lying on his stomach, one sensor is placed directly under the aorta - below the nipples of the person lying on his stomach, the second sensor is placed directly under the abdominal aorta - above the navel of the person lying on his stomach, b) simultaneously register mechanical vibrations on the patient's body surface caused by the passage of a pulse wave using at least two sensors and convert them into a digital signal, c) filtering the received digital signals from each of the sensors in order to extract from them the cardiac component corresponding to one cardiocycle, d) determine the time T of the pulse wave passing between the installed sensors as the time interval "t2" - "t1", where t1 is the time instant of the passage of the J-peak of the cardiac component of the cardiac cycle "i" over the first sensor, isolated from the digital signal from the first sensor, a t2 - the time instant of passage of the J-peak of the cardiac component of the cardiocycle "i" over the second sensor, isolated from the digital signal from the second sensor, at the same time, J-peaks are automatically determined in each digital signal received from each sensor, in the cardiac component selected as a result of filtering, e) determine the current value of the central arterial pressure for each cardiocycle based on the Moens-Korteweg equation according to the formula

where a - dimensionless coefficient; L is the distance between the sensors; T is the time of passage of the pulse wave between the installed sensors for recording mechanical vibrations; h is the thickness of the aortic wall; d is the inner diameter of the aorta; p - blood density; E ₀ is the initial value of the modulus of elasticity of the aortic wall, calculated by the formula E ₀ = Δp / Δd × d / h, where Δd is the difference between the diameters of the aorta in systole and diastole, Δp is the difference between the mean systolic and mean diastolic pressure. 2. The method according to claim 1, in which, before the start of registration of mechanical vibrations of the patient's body surface, primary calibration is performed, which includes entering data about the patient: age, weight, body type, gender of the patient, attitude to smoking, the presence of chronic diseases leading to changes in the morphology of the cardiovascular system; pharmacological preparations taken by the patient, input of the specified distance between the installed sensors of mechanical vibrations, determination of the values of systolic and diastolic blood pressure in the brachial artery, determination of individual parameters of the wall thickness of the aorta h, internal diameter of the aorta d, coefficient a and blood density p based on the entered data, determination the difference Δd between the diameters of the aorta in systole and diastole and the difference Δp between the mean systolic and mean diastolic pressure - based on the entered and determined data. 3. The method of claim 2, wherein the primary calibration is performed within 5 minutes. 4. The method according to. 1 in which regular calibration is performed during continuous recording of central arterial pressure. 5. The method of claim 4, wherein the regular calibration is performed for 1 minute every 12 hours if the patient has not left the bed, or 1-5 minutes after the patient has gone to bed and stopped making active movements. 6. The method of claim 5, wherein the regular calibration comprises measuring the patient's systolic and diastolic blood pressure using the Korotkoff method. 7. The method of claim 1, wherein the digital signal is filtered using a Butterworth bandpass filter. 8. The method according to claim 1, wherein the automatic determination of J-peaks in the digital signal of the cardiac component selected as a result of filtering includes the following steps: in a discrete signal x ₁ , x ₂ , ... x _N points of local extremum are distinguished - points of maximum x _i , for which x _i-1 <x _i and x _i ≥ _{x i + 1} and minimum, for which x _i-1 > x _i and x _i ≤x _{i + 1} , for each maximum J, the index Z (J) = X (J) -2X (I) + X (H) is calculated, where X (J) is the height of this peak, X (I) is the signal level corresponding to the previous failure, X (H) - the height of the previous peak, as J-peaks, those maxima are selected for which the Z (J) index is greater than three adjacent peaks on the left and three adjacent peaks on the right. 9. A device for continuous non-invasive adaptive registration of central arterial pressure, including: means for recording a ballistocardiogram signal and its primary processing, a cloud or a local server, configured to receive data from said means, process them and transmit the processed data to addressees, while the means for registration of a ballistocardiogram signal and its primary processing includes: at least two sensors for recording mechanical vibrations on the surface of the patient's body, at least two analog signal amplifiers from each mechanical vibration sensor, analog filters and an ADC, one or more control modules programmed to carry out steps a-b) of the method according to claim 1, wherein the control module is configured to transmit data to the cloud or a local server, in which the steps of the method according to c) -d) of the method according to claim 1 are carried out. 10. The device according to claim 9, further comprising a device for inputting data obtained from primary and / or regular calibration, and a device for outputting measurement results. 11. The device according to claim 9, in which the addressees are mobile applications and the control panel of the dispatch center.

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