LV13582B - A method and a device for continuous and non-invasive measurment of blood pressure - Google Patents

Abstract

Invention relates to diagnosing functions of blood circulation system and pathology of heart and blood vessels and particularly to continuous non-invasive measuring of arterial blood pressure by using registration and processing arterial pulse and heart rate by electrocardiography (ECG) and photopletizmography (PPG), measuring delta t (pulse wave flow) and calculation of maximal arterial blood pressure (ASmax) and average dynamic blood pressure (AS vid. din.) using delta t and linear regression of pressure values of each individual. Invention also describes a system used in implementation of this method.

Description

Method and device for non-invasive and continuous measurement of arterial blood pressure

International Classification Indexes (IPC) of the Invention: A61B 5/02

The present invention relates to the functional evaluation of the circulatory system and the diagnosis of cardiovascular pathologies, and in particular to the long-term non-invasive detection of arterial pressure.

Systemic arterial pressure (AS) is an essential parameter of the functional state of the circulatory system. AS pulsates with each pulse cycle, so its quantitative characterization uses both extreme values of pressure over one cycle (maximum AS _ma x and minimum AS _m in) and an imaginary non-pulsed pressure equivalent to real variable pressure in terms of hemodynamic effect pressure (AS _v id. dyn.) AS _max describes the contraction force of the heart muscle, AS _m i _n - total hydrodynamic resistance of the peripheral blood vessels (arterioles), AS _V id din. - Provides a quantitative summative assessment of hemodynamic function.

Control of arterial pressure is essential in medical diagnostics of circulatory disorders, including preventive health examination or self-control; long-term non-invasive arterial pressure monitoring is also important in sports physiology and medicine to assess the ability of the circulatory system to adapt to exercise and to judge objectively the effectiveness of training or rehabilitation measures.

Several non-invasive methods of measuring arterial pressure are known. Widely used are AS measuring devices, which press the artery in the tissues during measurement with a cuff and measure pressure values during the decompression period, with the restoration of normal blood flow (eg Korotkov auscultation, oscillometry) [Pickering TG, Hall JE, Appel LJ 2005. Recommendations for Blood Pressure Measurement in Humane and Experimental Animals. - Circulation, 111: 697-716; Staessen J. A., Fagard R., Thijs L. 1995. A Consensus View on the Technique of Ambulatory Blood Pressure Monitoring. - Hypertension, 26: 912-918]

Such methods do not allow continuous measurement of arterial pressure and discomfort caused by cuff pressure.

Arterial pressure values during each cycle can be determined by the Penaz Finger Cuff Method, which continuously maintains the pressure in the cuff to fully relieve the artery wall [Pickering TG, Hall JE, Appel LJ 2005. Recommendations for Blood Pressure Measurement in Human and Experimental Animals . - Circulation, 111: 697-716]. The main disadvantage of this method is that the subject is restricted in manual manipulation.

More convenient, simpler and more widely used methods may be those that use arterial pressure parameters to calculate arterial pressure, which are completely atraumatic, non-invasive, and unobtrusive to the subject. Such parameters could be pulse wave propagation time (At) or pulse wave propagation rate (PWV).

US005857975A is selected as a prototype of the invention, wherein the subject's arterial blood pressure is determined by recording the subject's ECG signal by selecting a single reference point on the ECG curve. The device registers changes in blood volume at a point on the subject's body, such as the fingertip. The time between the selected ECG curve reference point and the change in blood volume at a particular point on the body is measured. This time depends on the propagation time of the pulse wave and the shape of the pulse wave. The heart rate is obtained from an ECG record. Arterial pressure values are calculated from pulse wave delay time, volume pulse shape, and heart rate. The most appropriate reference point on the ECG curve is the R wave. A suitable method for recording changes in blood volume is photoplethysmography. The method describes the principles for the determination of systolic, diastolic and mean dynamic arterial blood pressure.

Detection and exclusion of artefacts is provided. The invention relates to a non-invasive, continuous measurement of blood pressure without the use of a cuff.

The object of the invention is to increase the reliability of the signals used in the calculation of AS, to increase the accuracy and informativeness of the determination of arterial pressure values, to provide a more convenient AS measurement.

To achieve this goal, a functional relationship between arterial pressure and pulse wave propagation time is used, which is directly proportional to the pulse wave propagation rate. There are already known methods of measuring arterial pressure

PW = uses arterial pulse wave propagation time or pulse wave propagation velocity as determined by recording vascular pulsation in the peripheral tissues of the body [Kazanavicius E., Girchys R., Machikenas E., Lugin S. 2003. Determination of Arterial Blood Pressure Using the Pulse Transit Time. - Information Technology and Management, 4 (29): 23 29; US5,857,975A, A61B 05/00, 1999; WO 01/54575 A1, A61B 5/0225, 2001].

The relation between arterial pressure and the velocity of pulse wave propagation is indicated by the Moena-Kortevega equation:

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2-r p

Pulse wave propagation velocity (PWV) in arteries is mainly dependent on their wall elastic modulus (E). As arterial pressure increases, the wall of the arteries is stretched more and its elasticity decreases, while the velocity of the pulse wave propagates. Reversal of pressure decreases [Smith R.P., Argod], Pepin J.L., Levy P.A. 1999. Pulse Transit Time: An Appraisal of Potential Clinical Applications. - Thorax, 54: 452 - 458], The arterial wall tension induced by arterial pressure also influences other determinants of the pulse wave propagation rate included in the Moena-Kortevega equation, such as arterial wall thickness (h) and internal radius (r). As the pressure increases, the wall thickness decreases and the inside radius increases. The effect of blood density (p) on the pulse wave propagation rate is negligible because of its relatively small range of variability under normal conditions.

Arterial pressure values fluctuate in a wavy fashion, corresponding to the phases of the cardiac cycle (first wave, period 0.5 - 1.2 s, amplitude - pulse pressure), respiratory phases (second wave, period 3 - 15 s, amplitude - up to 15 mmHg), vasomotor center activity shifts (third-order waves; irregular period and amplitude).

A series of clinical measurements (20 practically healthy subjects, AS and At measurements at 23 ± 2 ° C, before and after exercise) confirmed the linear relationship between AS and At, with linear regression coefficients specific to each individual and vascular bed. .

Using linear regression coefficients and pulse wave propagation time, arterial pressure can be calculated following the calibration procedure.

The process of detecting arterial pressure:

• Attach an optical PPG contact sensor to the subject's external ear shell.

• Place the ECG electrode strap on the subject's chest.

• Records ECG and PPG signals for 10-15 consecutive cardiac cycles simultaneously with arterial pressure measurements using a conventional method.

• After artifacts are excluded, the average pulse wave propagation time value is obtained for ten consecutive cardiac cycles ("smoothing" of second-order waves of arterial pressure).

• This measurement procedure shall be repeated at least twice, with AS values differing by at least 15 mmHg.

• The linear regression equation coefficients of the pulse wave propagation time mean values and the AS values (AS _max and AS average dynamics) are obtained.

• The instantaneous AS values for the individual subject are then calculated using the instantaneous pulse wave propagation time values and the resulting linear regression coefficients.

The device for non-invasive and continuous measurement of arterial pressure is illustrated by drawings showing:

FIG. 1 is a block diagram of a non-invasive and continuous measuring device for arterial pressure. Fig.2 - Schematic of pulse wave propagation time determination. Pulse wave propagation time is measured as the distance from the tip of the ECG R wave (ECG signal derivative 1 minimum) to the pulse wave "foot" (PPG signal derivative 1 peak).

FIG. 3 - Linear regression between arterial pressure (AS _ma x) and pulse wave propagation time and linear regression equation. Example of data from one subject.

FIG. 4 - Illustration of arterial pressure 2nd degree or breathing waves. Example of data from one subject.

Device for non-invasive determination of peak and mean dynamic arterial pressure values (Fig. 1), consisting of photoplethysmographic (PPG) optical signal contact sensor (1), electrocardiographic (ECG) signal sensor (2), electronic amplifiers (3, 4) the output signals are identified and excluded from the analysis by the processing unit (5) of the received signal processing unit (5), which performs data collection and storage, after calculating the AS _max by a conventional AS meter. and ASvid. dyn. values, Output Output Block (6) - such as a panel, monitor, or the like, showing AS _max and A8 _v jd. dyn. instantaneous values and their dynamics over time.

Example of application of the proposed method.

Investigator - 19-year-old female. The subject is exposed to the ECG electrode strap and PPG contact sensor in the ear. At the same time AS values (ASi _zra ) are determined and ECG and PPG signals are recorded. Two different pressure values were used for calibration: AS _max i = 114mmHg, AS _maX 2 = 131mmHg. Corresponding values of At: Ati = 0.1165, At ₂ = 0.0895. Using the AS and At values, calculate the linear regression equation coefficients used to calculate the non-invasive AS values (AS _apr ) for the dosed veloergometric load (120W, 3min) in the early recovery period every 0.5 min. Example with ASmax values. ASjzmi = 131 mmHg, AS _Apr i = 130 mmHg, AS _size 2 = 126 mmHg, AS _Apr 2 = 126 mmHg, ASJ _zm3 = 115 mmHg, AS _apr3 = 112 mmHg, ASi _zm4 = 112 mmHg, AS _apr4 = 110 mmHg, ASj _zra5 = 110 mmHg, AS _apr5 = 111 mmHg.

The proposed method is more convenient to use than other methods that use pulse wave propagation time or velocity information to calculate arterial pressure - sensor placement does not restrict movement as well as causes of artefacts. The operations included in the method for "smoothing" second-stage pressure waves increase the comprehensibility of the method for non-medical users and provide additional information to the specialist.

Claims (14)

Formula of the Invention 1. A method and device for non-invasive and continuous control of arterial blood pressure using ECG signal and arterial pulse signal from body peripheral tissue, distance from tip of ECG R wave to defined point in PPG curve (At), calculation of arterial pressure from At and detection of artifacts other than in that the resulting pressure value (AS _max ., AS _V id. dyn.) is calculated by processing the data with a second order wave smoothing operation of arterial pressure oscillations and the results are presented simultaneously in analogue and numerical form. 2. The method of claim 1, wherein the ECG electrodes are located in a band placed on the chest. 3. The method according to I.p. and 2, characterized in that the PPG sensor is positioned on the outer ear shell. 4. The method of claims 1-3, wherein for calculating arterial pressure At is measured as the distance from the tip of the R wave to the peak of derivative 1 of the PPG curve. 5. The method of claims 1-4, wherein linear calibration equations for arterial pressure values (AS _m ax., AS av. Din.) And mean A for 10 consecutive cardiac cycles are calculated during calibration. 6. The method according to claims 1-5, wherein the arterial pressure is calculated during each heartbeat cycle using the mean value of At for 10 consecutive heartbeat cycles and the linear regression coefficients determined during calibration. 7. The method according to claims 1-6, wherein the value of At which differs from the previous At value by more than 10% is recognized as an artifact. 8. A method according to any of claims 1-7, wherein the artefact is found not to show a computed pressure value but to resume computation after obtaining 10 qualitative At values. The device for non-invasive and continuous measurement of arterial pressure according to claim 1, comprising a photoplethysmographic (PPG) optical signal contact sensor (1), an electrocardiographic (ECG) signal sensor (2), electronic amplifiers (3, 4) output amplifying signals, collecting and storing data from the received signal processing unit (5), identifying and excluding erroneous signals from the analysis, AS _max . and AS _v id. dyn. to calculate the value, the output output unit (6) - for example, panel, monitor or the like, AS _max and ASvid. dyn. instantaneous values and their dynamics for a given period of time for presentation. 10. A device according to claim 9, characterized in that it comprises a storage medium containing the software of claims 1-8. for the implementation of the methods described in paragraph. 11. The device of claim 9. and 10, characterized in that the output unit has a signal function for failed calibration and the need for recalibration. The device according to claims 9 to 11, characterized in that the output unit has a signal function for detecting artefacts created during measurement and for displaying a percentage of the total number of measurements. 13. A device according to any one of claims 9 to 12, characterized in that it has a storage and storage function for the individual calibration coefficients and recorded data of the subject. Device according to claims 9 to 13, characterized in that it has an authorization function for accessing only individual data according to the selected user.