KR101306553B1 - Estimation Scheme of the Cardiac Output using Arterial Blood Pressure - Google Patents
Estimation Scheme of the Cardiac Output using Arterial Blood Pressure Download PDFInfo
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Abstract
The present invention relates to a method for measuring cardiac output from blood pressure data, and has the following effects.
First, the method of measuring cardiac output from aortic blood pressure has an effect of making it easier to measure than the prior art.
Second, the cardiac output measurement method using the time constant that the circulatory vascular resistance and the arterial blood vessel capacity, starting from the blood pressure data of the present invention, is a method of estimating the cardiac output from a conventional blood pressure waveform in which inaccuracy has been found (Pulse contour cardiac). It is judged to be an alternative method of output, PCCO and it is easy to calibrate. The cardiac output is measured for this purpose, in particular by the method of claim 1.
Description
The present invention relates to a method for measuring cardiac output from blood pressure data. More specifically, the present invention relates to a method for measuring cardiac output for determining whether the disease and function of the heart are normal from the attenuation waveform of arterial pressure obtained using invasive blood pressure measurement (IBP).
Cardiac output is a data that must be measured to determine the normal condition of heart disease and function. However, current thermal dilution or indicator dilution is not easy to measure and provides continuous cardiac output, such as intubation into the carotid artery, right atrium, right ventricle, or pulmonary vein using a catheter to measure cardiac output. .
In order to measure continuous cardiac output by thermal dilution method, a method of applying continuous heat energy and measuring temperature change using a hot wire connected to blood has been developed, but side effects such as abnormally raising the body temperature of the patient have been developed. Easy cardiac output measurement methods need to be developed.
The blood flow measurement device using the ultrasonic sensor should be attached directly to the blood vessel and the sensor is attached through surgery, so it is difficult to be used to measure the cardiac output of the patient.In addition, the ultrasound imaging device can measure the temporary cardiac output by an expert. It is difficult to measure a patient's disease continuously for a long time.
The pulse contour cardiac output (PCCO) is a method of estimating cardiac output from a conventional blood pressure waveform that infers cardiac output from blood pressure. The cardiac output calculation is based on the assumption that it is proportional to the stroke volume. This method determined statistically constant SVR and arteriovascular capacity that changes every moment, and simultaneously corrected both parameters of circulatory vascular resistance and arterial vessel capacity even if the blood flow rate was determined by thermal dilution. It is impossible to do. In addition, when the circulatory vascular resistance and the arteriovascular capacity increase or decrease together, it is difficult to clearly distinguish between the increase and decrease of cardiac output. The basis for the inaccuracy of the PCCO method is already described in NWFLinton and RAFLinton, "Estimation of changes in cardiac output from the arterial blood pressure waveform in the upper limb", British Journal of Anaesthesia, Vol86, No. 4, pp486-96, 2001. ] In the paper.
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a new technique for measuring cardiac output from blood pressure data obtained by an invasive blood pressure measurement (IBP) method.
Obtaining data necessary for measuring cardiac output from the waveform of arterial pressure obtained by the blood pressure measurement method according to the present invention to achieve this object;
Calculating a time constant from the data; Calculating a change in blood flow rate ΔF from the calculated time constant; Calculating the stroke volume (SV) of the heart by the product of the change in blood flow rate (ΔF), the time during which the aortic valve is open (t1), and the compensation value constant k according to the attenuation waveform of the arterial pressure. ; And calculating the cardiac output volume (amount of blood ejected from the heart for 1 minute) by multiplying the cardiac output volume (SV) by the heart rate per minute; Characterized in that it comprises a.
In the step of obtaining the data, the step of calculating the change amount of pressure by differentiating the waveform of arterial pressure with time to calculate the change amount of pressure (dP / dt) is characterized in that it further comprises.
In the step of calculating the pressure change (dP / dt), it is characterized by detecting the time point at which the aortic valve (Arterial valve) is closed from the pressure change (dP / dt).
Detecting data based on a time point at which the aortic valve is closed in the waveform of the arterial pressure; Detecting, from the waveform of arterial pressure, ΔP defined as the difference between the pressure P2 and the lowest blood pressure when the aortic valve is closed; Detecting, from the waveform of arterial pressure,? P 'defined as dividing the difference between the pressure P1 when the flow velocity of blood is maximum and the pressure P2 when the aortic valve is closed by time? T; Detecting, from the waveform of the arterial pressure, the median value P of the pressure P1 when the flow rate of blood is maximum and the pressure P2 when the aortic valve is closed; Detecting, from the waveform of arterial pressure, one stroke period T of the heart based on the time point at which the aortic valve is closed; Detecting, from the waveform of arterial pressure, the time t1 during which the aortic valve is open; And further comprising:
In the step of calculating the time constant, the time constant is time constant 1 (τ ′) including the component due to the instantaneous blood flow rate change and time constant 2 (τ) not including the component due to the instantaneous blood flow rate change. It features.
Time constant 1 (τ ') is characterized in that it is calculated by the following equation (1).
[Equation 1]
τ ′ = C ′ * SVR ′ = P /-(dP / dt) = P /-△ P ′
[(dP / dt) = ΔP ']
(C ′: capacity of arterial vessel, SVR ′: unit of Systemic Vascular Resistance, where time constant 1 (τ ′): unit of sec, C ′: unit of ml / mmHg, SVR ′ : mmHg * sec / ml, P unit: mmHg, ΔP 'unit: mmHg / sec.)
Time constant 2 (τ) is characterized in that it is calculated by the following equation (2).
&Quot; (2) "
τ = C * SVR =
[C: capacity of arterial vessel, SVR: Systemic Vascular Resistance, where unit of time constant 2 (τ): sec, unit of C: ml / mmHg, unit of SVR: mmHg * sec / ml.]
The change in blood flow rate ΔF is calculated by
&Quot; (3) "
[L: coefficient of inertia of the moving blood after the aortic valve is closed, where ΔF is in units of ml / sec and L is in mmHg * sec / ml.]
The inertial coefficient L of blood moving after the aortic valve is closed is calculated by a method of statistically determining the patient's age or body size.
After the aortic valve is closed, the coefficient of inertia (L) of the moving blood is characterized in that the volume of the aorta measured by the ultrasound image is determined according to the volume.
Single ejection amount (SV) of the heart is characterized in that it is calculated by
&Quot; (4) "
SV = △ F * t1 * k
(SV: single ejection of heart, ΔF: change of blood flow rate, k: constant of compensation value according to the waveform of arterial pressure)
In order to correct the inertial coefficient (L) of the moving blood after the aortic valve is closed, the inertial coefficient of blood (L) is made to be equal to the cardiac output measured by the thermal dilution method and the cardiac output obtained from the waveform of arterial pressure. Correcting the value); And further comprising:
As described above, the present invention has the following effects.
First, the method of measuring cardiac output from aortic blood pressure has an effect of making it easier to measure than the prior art.
Second, the cardiac output measuring method using the time constant produced by the body blood vessel resistance (SVR) and the arterial capacitive capacity (C), starting from the blood pressure data of the present invention, estimates the cardiac output from a conventional blood pressure waveform in which inaccuracy has been found. It is judged to be an alternative to the pulse contour cardiac outpu (PCCO) and has the effect of easy calibration.
1 is a graph showing the names of each point and section in a waveform of arterial pressure in which a portion of FIG. 2 is enlarged;
2 is a graph converted from the blood pressure to the waveform of arterial pressure;
FIG. 3 is a graph showing the point at which the aortic valve is closed on the dP / dt diagram obtained by differentially dividing the waveform of arterial pressure with time;
4 is a graph showing the lowest pressure point in the waveform of arterial pressure with an arrow,
Fig. 5 is a graph measuring pressure P1 at the maximum flow rate and pressure P2 when the aortic valve is closed.
FIG. 6 is a graph showing the periods of T (blue) and t1 (red) based on the time when the aortic valve is closed;
Fig. 7 is a graph showing the integration of blood pressure waveforms during blue (blue) and the integration of blood pressure waveforms during red (red);
8 is a graph comparing time constant 1 (τ ′) (red) and time constant 2 (τ) (blue),
9 is a graph comparing blood flow rate change (ΔF) (blue) and cardiac output (CO) (red);
10 is a graph comparing the correlation between blood pressure and blood flow through an animal experiment;
11 is a flowchart illustrating a method of measuring cardiac output from blood pressure data of the present invention.
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same components of the drawings are denoted by the same reference numerals and signs as possible even if they are shown on different drawings. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.
1. Obtaining the waveform of arterial pressure by blood pressure measurement < S201 >
In this step, the waveform of the arterial pressure obtained by invasive blood pressure measurement (IBP measurement) among the blood pressure measurement method [Fig. 2] is obtained.
To supplement the blood pressure measurement method, blood pressure measurement methods are typically ANIBP (Automatic Noninvasive Blood Pressure), IBP (Invasive Blood Pressure), MNIBP (Manual Noninvasive Blood Pressure) Measurement).
Blood pressure is obtained through the sum of potential energy, pressure energy and kinetic energy of blood. Potential energy is not taken into account when measuring blood pressure, because the difference in left and right pressure in a straight posture is small.
Therefore, blood pressure is generally a sum of blood pressure and kinetic energy. In the non-invasive measurements of the non-invasive automatic blood pressure measurement (ANIBP) and the traditional blood pressure measurement (MNIBP) series, only the blood pressure is measured because the cuff is examined outside the blood vessel.
On the other hand, the invasive measurement of the IBP series can measure kinetic energy by inserting a thin tube into the blood vessel. IBP measures the blood pressure coming into the tube by converting it into an electrical signal. As described above, since the IBP provides the most accurate blood pressure data among the three blood pressure measuring methods, the present invention uses the blood pressure data based on the invasive blood pressure measuring method.
2. Obtaining data necessary to measure cardiac output < S202 >
In this step, a method for obtaining data necessary for measuring cardiac output from the waveform of the arterial pressure obtained by IBP blood pressure measurement [FIG. 2] is defined. Data are defined in FIG. 1, which shows an enlarged waveform of arterial pressure [FIG. 2]. The graphs in all figures were detected using Microsoft's Excel program.
As a method of detecting each term, first, a portion protruding downward as shown in [Fig. 3] by measuring the change in pressure (dP / dt) by differentiating the waveform of the arterial pressure [Fig. Point) is detected as the aortic valve is closed.
Next, the lowest pressure point indicated by an arrow in [Fig. 4] of the waveform of the arterial pressure [Fig. 2] is detected on the basis of the detected time of closing the aortic valve.
Next, as shown in [Fig. 2] and [Fig. 5] of the waveform of the arterial pressure, the pressure P1 when the blood flow rate is maximum and the pressure P2 when the aortic valve is closed are detected.
Next, based on the timing of the closing of the aortic valve in the waveform of the arterial pressure [FIG. 2], the ejection cycle T of the heart and the time t1 during the open section of the aortic valve are detected as shown in FIG. 6.
The time and pressure values of the respective points detected with reference to the drawings are applied to the next step of the method of measuring cardiac output from the blood pressure data below.
3. Time constant calculation step < S203 >
In this step, the time constant 1 (τ ′) including the component due to the instantaneous blood flow rate change and the time constant 2 (τ) including the component due to the instantaneous blood flow rate change are calculated. Step.
First, the time constant 1 (τ ′) including the instantaneous blood flow rate change component is obtained. The difference between the pressure P1 at the maximum flow rate of blood detected from the waveform of the arterial pressure and the pressure P2 when the aortic valve is closed is obtained. Is divided by time (Δt) to calculate ΔP 'and the median value of (P1) when the flow velocity is maximum and the pressure (P2) when the aortic valve is closed ((P1 + P2) / 2) This is obtained by substituting the equation of time constant 1 (τ '). Time constant 1 (τ ′) is the expression F = -C * dP expressed as the combination of F = -C * dP / dt (blood flow rate including the instantaneous blood flow rate change component) and F = P / SVR (Ohm's law application). Equation obtained by modifying / dt = P / SVR to meet the definition of 'time constant'
[Equation 1]
τ ′ = C ′ * SVR ′ = P /-(dP / dt) = P /-△ P ′
[defined as dP / dt = △ P ′]
Is defined as time constant 1 (τ ′), and C of time constant 1 (τ ′) is denoted as C ′ and SVR is denoted as SVR ′. (Time constant is defined as the product of arteriovascular capacity (C) and circulatory vascular resistance (SVR).)
Next, we obtain time constant 2 (τ) which does not contain the instantaneous blood flow rate change component.When blood flows from the ventricles into the aorta, the increase in blood pressure caused by this (ΔP is the pressure at the closing of the aortic valve. Difference in minimum blood pressure and flow rate in real time (
&Quot; (2) "
.
4. Calculation of blood flow rate change (△ F) < S204 >
The time constant 1 (τ ′) obtained above is different from the time constant 2 (τ) because it includes the component due to the instantaneous flow rate change. Time constant 2
&Quot; (3) "
.
5. Calculation of single ejection volume ( SV ) of the heart < S205 >
Assuming that the flow rate of blood ejected from the heart varies from zero to a maximum, the heart blood flow varies from zero to ΔF. Therefore, the single ejection volume SV of the heart is the product of ΔF, the time t1 during which the arterial valve is open, and the compensation value constant k depending on the shape of the attenuation waveform.
&Quot; (4) "
SV = △ F * t1 * k
(SV: single ejection of heart, ΔF: change of blood flow rate, k: constant of compensation value according to the waveform of arterial pressure)
6. Cardiac output ( CO ) calculation step < S206 >
Cardiac output (CO) is the amount of blood drawn for 1 minute, multiplied by the single heart rate (SV) and heart rate per minute.
7. Calibration step < S207 >
Finally, in order to increase the accuracy of the present invention, the inertia coefficient L of blood is corrected so that the cardiac output amount measured by the thermal dilution method and the cardiac output value obtained from the waveform of arterial pressure are the same. The correction process for the inertia coefficient (L) can be omitted, and it is used for the correction of the initial measured cardiac output and not necessarily applied to all cardiac output measurements.
In addition, the blood inertia coefficient (L) is an index related to the cross-sectional area, length, shape of blood vessels, and the viscosity of blood, and the inertia coefficient (L) obtained from ultrasound data and blood test data or age, sex, and body size of a patient. It can be replaced by the inertia coefficient (L) obtained from the statistical data.
Referring to FIG. 10 comparing the correlation between blood pressure and blood flow through an animal experiment, the above graph of FIG. 10 is a graph showing blood pressure data measured by invasive blood pressure measurement (IBP) as a waveform of arterial pressure. In the graph below, the Measured Cardiac Output line is a highly accurate average instantaneous blood flow measured by implanting an ultrasound probe into the aortic vessel through surgery, and the Estimated Cardiac Output line is an average instant measured by a method of measuring cardiac output from blood pressure data according to the present invention. Blood flow is shown. Using the Excel program, calculating the average of the areas of the two mean instantaneous blood flows yields almost identical results.
Claims (12)
Calculating a time constant from the data;
Calculating a change in blood flow rate ΔF from the calculated time constant;
The stroke volume (SV) of the heart is calculated by multiplying the blood flow rate change (ΔF), the time during the opening of the aortic valve (t1) and the compensation value constant k according to the attenuation waveform of the arterial pressure. step; And
Calculating a cardiac output (amount of blood ejected from the heart for 1 minute) by multiplying the cardiac output volume (SV) by the heart rate per minute; Cardiac output measurement method comprising a.
In the step of obtaining the data,
And calculating a change amount of pressure for differentiating the waveform of arterial pressure with time to calculate a change amount of pressure (dP / dt).
In the pressure change amount (dP / dt) calculation step,
Detecting a time point at which the aortic valve is closed from the change in pressure dP / dt.
In the step of obtaining the data,
Detecting a minimum pressure based on a time point at which the aortic valve is closed in the waveform of the arterial pressure;
Detecting ΔP from the waveform of the arterial pressure, which is defined as the difference between the pressure P2 and the lowest blood pressure when the aortic valve is closed;
Detecting ΔP ′ defined by dividing the difference between the pressure P1 at the maximum flow rate of blood and the pressure P2 at the closing of the aortic valve by the time Δt from the waveform of the arterial pressure;
Detecting, from the waveform of the arterial pressure, a median value P between the pressure P1 at the maximum flow rate of blood and the pressure P2 when the aortic valve is closed;
Detecting, from the waveform of the arterial pressure, one stroke period (T) of the heart based on the time point at which the aortic valve is closed;
Detecting, from the waveform of arterial pressure, the time t1 during which the aortic valve is open; Cardiac output amount measuring method further comprising a.
In calculating the time constant,
The time constant is a cardiac output measuring method characterized in that the time constant 1 (τ ') containing the component by the instantaneous blood flow rate change and the time constant 2 (τ) does not contain the component by the instantaneous blood flow rate change .
The time constant 1 (τ ′) is a cardiac output measuring method characterized in that it is calculated by the following Equation 1.
[Equation 1]
τ ′ = C ′ * SVR ′ = P /-(dP / dt) = P /-△ P ′
[(dP / dt) = ΔP ']
[C ′: capacity of arterial vessel, SVR ′: unit of Systemic Vascular Resistance, where time constant 1 (τ ′): unit of sec, C ′: unit of ml / mmHg, SVR ′ : mmHg * sec / ml, P unit: mmHg, ΔP 'unit: mmHg / sec.]
The time constant 2 (τ) is a cardiac output measuring method characterized in that it is calculated by the following Equation 2.
&Quot; (2) "
τ = C * SVR =
[C: capacity of arterial vessel, SVR: Systemic Vascular Resistance, where unit of time constant 2 (τ): sec, unit of C: ml / mmHg, unit of SVR: mmHg * sec / ml.]
The blood flow rate change ΔF is calculated according to Equation 3 below.
&Quot; (3) "
[L: Inertia coefficient of blood moving after aortic valve closing, τ ′ is time constant 1, τ is time constant 2, Δt is time, where ΔF is unit: ml / sec, L is unit: mmHg * sec / ml.]
The inertia coefficient (L) of the blood moving after the aortic valve is closed is calculated by the method of statistically determined according to the age or body size of the patient.
The inertial coefficient L of the blood moving after the aortic valve is closed is
Cardiac output measuring method characterized in that the size of the aorta measured by the ultrasound image is determined according to the volume.
Heart ejection amount (SV) of the heart is a cardiac output measuring method, characterized in that calculated by Equation 4 below.
[Equation 4]
SV = △ F * t1 * k
(SV: single ejection of heart, ΔF: change of blood flow rate, k: constant of compensation value according to the waveform of arterial pressure)
In order to correct the inertial coefficient (L) of the moving blood after the aortic valve is closed, the inertial coefficient of blood (L) is made to be equal to the cardiac output measured by the thermal dilution method and the cardiac output obtained from the waveform of arterial pressure. Correcting the value); Cardiac output amount measuring method further comprising a.
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| KR20200025738A (en) | 2018-08-31 | 2020-03-10 | 재단법인 아산사회복지재단 | Method, apparatus and program for obtaining information of cardiovascular system using heart sound |
| KR20210136226A (en) | 2020-05-06 | 2021-11-17 | 재단법인 아산사회복지재단 | Method, program and system for analyzing the data related to stroke volume by using ai |
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| KR101517071B1 (en) * | 2014-09-30 | 2015-05-04 | 이의호 | Method to measure left ventricular stroke volume and device thereof |
| KR20190134433A (en) | 2018-05-25 | 2019-12-04 | 주식회사 피지오닉스 | Cardiac output signal analyzer and method |
| KR102098561B1 (en) * | 2018-07-10 | 2020-04-08 | 재단법인 아산사회복지재단 | Method and program for stroke volume acquisition using arterial pressure waveform |
| KR102377609B1 (en) * | 2020-02-25 | 2022-03-23 | 서울대학교병원 | Apparatus and method for calculating cardiac output using AI |
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