JP2005312947A - Blood volume measuring method, measuring apparatus and biological signal monitoring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously monitor a patient's circulatory dynamics continuously and non-invasively,
Provided are a low-cost blood volume measuring method, measuring apparatus, and biological signal monitoring apparatus that do not require skill of a skilled medical staff such as insertion of a catheter, are less painful to a patient, do not invade, and do not cause infection. .
A blood volume measurement method for determining cardiac output from pulse wave propagation time, comprising:
CO = (αK * PWTT + βK) * HR
A method for measuring blood volume, wherein the cardiac output is obtained from an equation.
Where CO is cardiac output, PWTT is pulse wave propagation time, HR is heart rate, and α, β, and K are patient-specific coefficients.
[Selection] Figure 7

Description

The present invention relates to a blood volume measuring method, a measuring apparatus, and a biological signal monitoring apparatus for measuring a blood volume ejected by a heart beat.

In a medical facility, it is necessary to monitor circulatory dynamic changes continuously as much as possible for patients in the operating room, intensive care unit, emergency room, artificial dialysis room, and the like.
Conventionally, monitoring of such changes in the patient's circulatory dynamics has been performed mainly by direct blood pressure monitoring.
The living body adjusts the cardiac output and the vascular resistance so that the blood pressure in the central part falls within a certain range.
Therefore, in order to know the change in the circulatory dynamics of a patient at an early stage, it is necessary to know the cause when a change in blood pressure is observed, and it is not sufficient to monitor blood pressure directly.
Therefore, in addition to monitoring changes in blood pressure, it is necessary to monitor changes in cardiac output.
In order to monitor changes in circulatory dynamics for patients, methods for measuring changes in cardiac output include the following methods such as thermodilution, dye dilution, ultrasound, etc. The method is mentioned.

First, the thermal dilution method will be described.
The thermodilution method mainly involves inserting a swan gantz catheter from the jugular vein, injecting a certain amount of cold saline or cold glucose solution from the central vein or right atrium, and from the temperature change in the pulmonary artery. A method for measuring cardiac output.
Recently, there is also a thermodilution method in which blood is warmed through a catheter and the cardiac output is measured from the resulting temperature change. According to this method, the measurement can be automatically performed at regular intervals.

Next, the dye dilution method will be described.
In the dye dilution method, a certain amount of dye is injected through a vein, and the dye concentration is measured at the site where the dye is uniformly diluted and the concentration becomes constant. This is a method of measuring the amount of output.

Next, the ultrasonic method will be described.
The ultrasonic method is a method of measuring cardiac output by measuring the inner diameter of an arterial blood vessel such as the descending aorta and the blood flow velocity using ultrasonic waves transesophageally.

In addition, as a method for measuring blood volume, a technique for measuring the volume of blood ejected by the heartbeat in a biological signal monitor apparatus capable of continuously monitoring a patient's circulatory dynamics continuously and non-invasively is known. ing. (See Patent Document 1)

In addition, the following reports have been made on the measurement accuracy of a device that obtains stroke volume and further cardiac output from an arterial blood pressure waveform that is measured invasively. (See Non-Patent Document 1)
“In the patient who entered the ICU (intensive care unit) after surgery, when the vascular resistance changed by about 60% by administration of the vasoconstrictor phenylephrine, the measured value of the device shown above is the heat used as a standard. A remarkably higher bias than the measured value of the dilution-type cardiac output meter appears, and in such a case, it is necessary to recalibrate with a thermo-dilution cardiac output meter. "
JP 2002-253519 A (Claim 1) G Roodig; Continuous cardiac output measurement: pulse contur analysis vs thermodilution technique in cardiac surgical patients British Journal of Anaesthesia 82 (4): 525-30 (1999)

The conventional method for measuring cardiac output, which is performed as a monitoring of circulatory dynamic fluctuations for a patient as described above, has the following problems.
The thermodilution method has a problem that measurement is intermittent and continuous measurement is not possible.
In addition, insertion of a catheter in the thermodilution method is highly invasive for the patient and is associated with infection problems.
Furthermore, this thermodilution method is a method that requires skill of a skilled medical worker for the measurement and insertion of the catheter.
Recently, a continuous measurement method has also been developed in the thermodilution method, but the insertion of the catheter is necessary, and the above-mentioned problem in the insertion of the catheter cannot be solved.

The dye dilution method also has a problem that continuous measurement is not possible.
The measurement requires a skill of a skilled medical worker.
The ultrasonic method has a problem that the burden on the patient is large because the transducer is attached transesophageally.
Recently, there is also a method that is a kind of ultrasonic method and noninvasively performed from the body surface, but continuous measurement is impossible.

None of the above-mentioned methods can be performed easily and continuously, considering the high skill of medical personnel and the high degree of invasiveness to patients. It is difficult to continuously and continuously monitor changes in the patient's hemodynamics.

The problem (objective) of the present invention is that the patient's circulatory dynamics can be continuously monitored in a non-invasive manner, and the skill of a skilled medical staff such as insertion of a catheter is not required. A low-cost blood volume measurement method that is less invasive and less infectious,
An object of the present invention is to provide a measurement device and a biological signal monitor device.

In order to solve the above-mentioned problem, the invention according to claim 1 is a blood volume measuring method for obtaining a cardiac output from a pulse wave propagation time,
CO = (αK * PWTT + βK) * HR
It is characterized by obtaining cardiac output from an equation.
Where CO is cardiac output, PWTT is pulse wave propagation time, HR is heart rate, and α, β, and K are patient-specific coefficients.

The invention according to claim 2 is characterized in that at least one of the coefficients α, β, and K is calibrated based on a measured value obtained by calibration blood pressure measurement.
In the invention according to claim 3, the pulse wave propagation time is an arrival time from the electrocardiogram to the peripheral volume pulse wave.
According to a fourth aspect of the present invention, the blood volume measuring method is a case where a vasoconstrictor is administered.
The invention according to claim 5 is characterized in that the vasoconstrictor is phenylephrine.

In the invention described in claim 6, ECG measuring means for measuring an electrocardiogram, peripheral pulse wave measuring means, and PWTT measuring means for obtaining a pulse wave propagation time from the measurement results of the ECG measuring means and the peripheral pulse wave measuring means. And a blood volume measuring device comprising a blood volume calculating means,
The blood volume calculating means includes
CO = (αK * PWTT + βK) * HR
It is characterized by obtaining the blood volume from the equation.
Where CO is cardiac output, PWTT is pulse wave propagation time, HR is heart rate, and α, β, and K are patient-specific coefficients.
The invention described in claim 7 is characterized by comprising calibration means for calibrating at least one coefficient of the coefficients α, β, K based on a measured value obtained by calibration blood pressure measurement.
Moreover, in invention of Claim 8, it is a biological signal monitor apparatus containing the blood volume measuring apparatus of the said Claim 6 or 7.

In invention of Claims 1-8, the fluctuation | variation of a patient's circulatory dynamics can be continuously continuously monitored non-invasively, Furthermore, the technique of a skilled medical worker, such as insertion of a catheter, is unnecessary, There is little pain to the patient, and there is no risk of infection because it does not invade, and a low-cost blood volume measuring method, measuring device, and biological signal monitoring device can be realized.

The principle of measuring the volume of blood ejected by the heart beat (cardiac output) in the present invention will be described below.
Using the wind Kessel model shown in Fig. 1, the flow rate SV-Qs that flows into the aorta during systole, that is, the subtraction amount SV minus the flow rate Qs that flows out to the periphery during systole, Pressure (in this specification, pulse pressure refers to the difference between systolic blood pressure value and diastolic blood pressure value) PP.
SV−Qs = C * PP Formula 1

The flow rate Qd flowing out to the periphery during diastole is equal to SV-Qs.
Qs and Qd are obtained by dividing the systolic and diastolic arterial pressure V by the vascular resistance R and multiplying the systolic time Ts and the diastolic time Td. Is proportional to
(Qd =) SV−Qs = SV * Td / (Ts + Td) Equation 2
It is represented by

From Equation 1 and Equation 2
SV * Td / (Ts + Td) = C * PP
∴SV = C * PP * (1 + Ts / Td) Equation 3

Here, assuming that C and Ts / Td do not change during the measurement period, and C * (1 + Ts / Td) is K,
SV = K * PP Formula 4
∴PP = SV * 1 / K Equation 5
Thus, according to the wind Kessel model, the pulse pressure is proportional to SV.

Actually, the actually measured pulse pressure PP1 is a pulse pressure PP2 based on Equation 5 (PP2 in Equation 5 is referred to as PP2 in the following description) and an increase in pulse pressure seen when using a vasoconstrictor. It consists of Oita PP3 and becomes Equation 6.
PP1 = PP2 + PP3 Formula 6

If there is no PP3, from Equation 4 and Equation 6
SV = K * PP1 Formula 7
Thus, SV can be actually measured from the actually measured blood pressure, but when using a vasoconstrictor, PP1 contains PP3, so SV is overestimated.
This has been a problem in calculating SV from blood pressure.

In addition, as described above, regarding the measurement accuracy of the device for calculating the stroke volume and further the cardiac output from the arterial blood pressure waveform measured invasively, “I entered the ICU (Intensive Care Unit) after surgery” When the vascular resistance changed by about 60% by administration of the vasoconstrictor phenylephrine, the measured value of the device shown above is based on the measured value of the thermodilution cardiac output meter used as a standard. However, it was necessary to recalibrate with a thermodilution cardiac output meter. ” In addition, when using a vasoconstrictor, it is known that the pulse pressure increases due to the influence of the reflected wave from the peripheral side, and PP3 corresponds to them.

The pulse wave propagation time (hereinafter referred to as PWTT), which is the arrival time from the electrocardiogram to the peripheral SPO2 pulse wave, consists of the following components.
PWTT = PEP + PWTT1 + PWTT2 Formula 8

Here, as shown in FIG. 6, PEP is the time for the progenitor of the heart, which is the time from the start of electrical excitation to the opening of the aortic valve.
PWTT1 is the time from when the aortic valve opens to the generation of a pulse wave in the aorta until it propagates to the peripheral artery that is normally invasively measuring blood pressure.
PWTT2 is the time until the pulse wave propagates from the peripheral artery to the blood vessel measuring the peripheral photoelectric pulse wave.

We measured the time from the ECG R wave to the rise of the femoral artery pulse as PEP + PWTT1 in 10 adult dogs, and included the relationship between PEP + PWTT1 time and blood pressure on the condition of vasoconstrictor administration. Measurements were made under the conditions of vasodilator administration, increased cardiac contraction force, reduced cardiac contraction force, and blood removal, and found that there was a good correlation between pulse pressure PP1 and PEP + PWTT1 time.
FIG. 2 is a diagram showing a relationship between typical PWTT and pulse pressure (PP) (Pulse-Pressure).

Therefore, the relationship between the pulse pressure PP1 and PEP + PWTT1 can be expressed as Equation 9.
PEP + PWTT1 = a * PP1 + b Equation 9
Also, the relationship between PWTT2 and PP1 is expressed as in Equation 10.
PWTT2 = c * PP1 + d + e Equation 10

  When PP3 appeared due to the use of a vasoconstrictor, etc., it was found that PWTT2 tends to be extended compared to other conditions, so the amount corresponding to the extension was designated as e. (Here, e is not always a constant.)

Therefore, when Equation 8 is rewritten as Equation 9 and Equation 10,
PWTT = (a * PP1 + b) + (c * PP1 + d + e)
∴ PP1 = 1 / (a + c) * (PWTT−b−d−e) Equation 11

Substituting the right side of Equation 5 into PP2 in Equation 6
PP1 = SV * 1 / K + PP3 Formula 12
From Equations 11 and 12, 1 / (a + c) * PWTT− (b + d) / (a + c) = SV * 1 / K + PP3 + e / (a + c)
∴SV = K * (1 / (a + c) * PWTT− (b + d) / (a + c)) − K * (PP3 + e / (a + c)) Equation 13

As described above, when PP3 appears by using a vasoconstrictor or the like, it was experimentally found that PWTT2 tends to be extended, and the relationship is shown in FIG.
When phenylephrine is administered, PP3 appears and PP1 increases as shown in FIG.
There is no longer any relationship between PWTT2 and PP1 as with blood removal or pentobarbital administration, and PWTT2 tends to prolong.
Therefore, as shown in FIG. 4, even when phenylephrine is administered, a negative correlation similar to that under other conditions is maintained between SV and PWTT, so the second term K * (PP3 + e / (a + c) )) Was experimentally found to be almost negligible.

Therefore, 1 / (a + c) = α, − (b + d) / (a + c) = β
SV = K * (α * PWTT + β) Equation 14
α and β are coefficients inherent to the patient obtained experimentally.

Furthermore, the cardiac output can be calculated by the following formula.
esCO = K * (α * PWTT + β) * HR Equation 15
Here, esCO is a cardiac output expressed in L / min, and K is a constant specific to a patient that is experimentally obtained.

Equation 15 can also be replaced by Equation 16.
esCO = (αK * PWTT + βK) * HR Equation 16
αK and βK are coefficients inherent to patients that are experimentally determined.

When SV and esCO are calculated using PWTT as shown in Equations 14, 15, and 16, even when the pulse pressure increases, such as using a vasoconstrictor as shown in FIG. 3, it is shown in FIG. Thus, since the same relationship as that of other conditions is maintained between SV and PWTT, the problems seen when calculating SV using conventional blood pressure can be solved.
Naturally, CO is not overestimated.
3 and 4 show the relationship between SV and PP1 and SV and PWTT measured during vasoconstriction, blood removal, and cardiac suppression in animal experiments.
When phenylephrine was administered, there was an increase in vascular resistance exceeding 60%.

Next, an embodiment of a biological signal monitoring apparatus to which the blood volume measuring method according to the present invention is applied will be described in detail with reference to the drawings.
FIG. 7 is a block diagram for explaining a configuration of an embodiment of the biological signal monitoring apparatus, and FIG. 8 is a schematic view for explaining an example of a measurement form by the biological signal monitoring apparatus according to the present invention.
FIG. 6 is a diagram showing the waveform of each measured pulse wave.

As shown in FIG. 7, the systolic / diastolic blood pressure measuring means 20 includes a cuff 25, a pressurizing pump 27, a pressure sensor 28, a cuff pressure detecting unit 29, an A / D converter 22, and the like.

Specifically, as shown in FIG. 8, measurement is performed with the cuff 25 attached to the upper arm of the patient.
The inside of the cuff 25 is opened or closed with respect to the atmosphere by an exhaust valve 26 provided in the biological signal monitoring apparatus main body 10.
Further, air is supplied to the cuff 25 by a pressurizing pump 27 provided in the biological signal monitoring apparatus main body 10.
A pressure sensor 28 (cuff pulse wave sensor) is attached in the biological signal monitoring apparatus main body 10, and the sensor output is detected by the cuff pressure detection unit 29.
The output of the cuff pressure detector 29 is converted into a digital signal by the A / D converter 22 and is taken into the cardiac output calculation means 40 (in FIG. 8, the cuff pressure detector 29, the A / D converter). 22, the cardiac output calculating means 40 is included in the biological signal monitor main body 10).

FIG. 6A shows an electrocardiogram waveform, and the aortic pressure immediately after leaving the heart has a waveform as shown in FIG.
Further, the peripheral artery waveform and the peripheral pulse waveform as shown in FIGS. 6C and 6D are obtained.

  As shown in FIG. 7, the pulse wave propagation time measurement means 30 includes a time interval detection reference point measurement means 31, an A / D converter 32, a photoelectric pulse wave detection sensor 33, a pulse wave detection unit 34, and an A / D converter. 35, etc.

The time interval detection reference point measuring means 31 is for detecting the generation time point of the R wave of the electrocardiogram, and the output of this detection unit is converted into a digital signal by the A / D converter 32 to output the cardiac output. It is taken into the quantity calculation means 40.
Specifically, the time interval detection reference point measuring means 31 includes an electrocardiogram electrode 31a (electrocardiogram measuring means) attached to the subject's chest as shown in FIG.
Measurement data is wirelessly transmitted to the biological signal monitoring apparatus body 10 from the measurement data transmitter 50 electrically connected to the electrocardiogram electrode 31a.
The transmitted measurement data is converted into a digital signal by the A / D converter 32 in the biological signal monitoring apparatus main body 10 and is taken into the cardiac output calculation means 40. In this way, an electrocardiogram waveform as shown in FIG.

On the other hand, as shown in FIG. 8, the photoelectric pulse wave detection sensor 33 is attached to the peripheral part of a patient such as a finger,
For example, SPO2 measurement is performed to obtain the pulse wave propagation time.
The photoelectric pulse wave detection sensor 33 is electrically connected to the measurement data transmitter 50, and the measurement data transmitter 50 wirelessly transmits the measurement data to the biological signal monitor apparatus body 10.
This measurement data is sent to the pulse wave detection unit 34 in the biological signal monitor main body 10 to detect the pulse wave (photoelectric pulse wave) of the patient's wearing site.
The output of the pulse wave detector 34 is converted into a digital signal by the A / D converter 35 and taken into the cardiac output calculation means 40.
In this way, a photoelectric pulse wave waveform (peripheral waveform) as shown in FIG. 6D is obtained.

Next, calculation processing for obtaining esCO from the above equation 16, esCO = (αK * PWTT + βK) * HR will be described with reference to FIGS.

First, a procedure for calculating βes by calibration using the initial value αK and calculating esCO will be described with reference to FIG.
・ Read the initial value of αK. (Step S1)
・ Acquire PWTT and HR. (Step S2)
Next, it is determined whether or not βK exists. (Step S3)
• If the determination in step S3 is NO, a calibration CO value input request is displayed. (Step S4)
・ Judge whether a calibration CO value has been input. (Step S5)
If the determination in step S5 is YES, the input CO value and the acquired PWTT and HR are stored in the register as CO1, PWTT1 and HR1. (Step S6)
・ ΒK = CO1 / HR1-αK * PWTT1 is obtained from the equation βK. (Step S7)
・ Calculate esCO from esCO = (αK * PWTT + βK) * HR using the obtained βK. (Step S8)
Similarly, when the determination in step S3 is YES, the esCO is calculated from esCO = (αK * PWTT + βK) * HR. (Step S8)
・ Display esCO obtained by calculation. (Step S9)
The above process is repeated sequentially.

Next, a procedure for calculating αes and βK by calibration and calculating esCO will be described with reference to FIG.
・ Read the initial value of αK. (Step S1)
・ Acquire PWTT and HR. (Step S2)
Next, it is determined whether or not βK exists. (Step S3)
• If the determination in step S3 is NO, a calibration CO value input request is displayed. (Step S4)
・ Judge whether a calibration CO value has been input. (Step S5)
If the determination in step S5 is YES, the input CO value and the acquired PWTT and HR are stored in the register as CO1, PWTT1 and HR1. (Step S6)
・ ΒK = CO1 / HR1-αK * PWTT1 is obtained from the equation βK. (Step S7)
・ Calculate esCO from esCO = (αK * PWTT + βK) * HR using the obtained βK. (Step S8)
• If the determination in step S3 is YES, determine whether to recalibrate αK. (Step S10)
If the determination in step S10 is NO, the esCO is calculated from esCO = (αK * PWTT + βK) * HR as described above. (Step S8)
• If the determination in step S10 is YES, a calibration CO value input request is displayed. (Step S11)
・ Judge whether a calibration CO value has been input. (Step S12)
If the determination in step S12 is YES, the input CO value and the acquired PWTT and HR are stored in the register as CO2, PWTT2 and HR2. (Step S13)
・ ΑK and βK
CO1 = (αK * PWTT1 + βK) * HR1
CO2 = (αK * PWTT2 + βK) * HR2
It calculates from these two formulas. (Step S14)
Using the obtained αK and βK, an operation for obtaining esCO from esCO = (αK * PWTT + βK) * HR is performed. (Step S8)
If the determination in step S10 is NO, the esCO is calculated from esCO = (αK * PWTT + βK) * HR as described above. (Step S8)
・ Display esCO obtained by calculation. (Step S9)
The above process is repeated sequentially.

Further, a procedure for calculating esCO by obtaining α as an initial value and obtaining β and K by calibration will be described with reference to FIG. (Β calibration is performed when there is no increase in pulse pressure due to administration of vasoconstrictor, etc.)
・ Read the initial value of α. (Step S1)
・ Acquire PWTT and HR. (Step S2)
Next, it is determined whether or not β is present. (Step S15)
• If NO in step S15, a calibration blood pressure measurement request is displayed. (Step S16)
・ Determine whether calibration blood pressure measurement has been performed. (Step S17)
If YES in step S17, the measured PP value and the acquired PWTT and HR are stored in the register as PP1, PWTT1, and HR1. (Step S18)
・ Β is calculated by the equation β = PP1−α * PWTT1. (Step S19)
If the determination in step S15 is YES, and after calculating β in step S19, it is determined whether or not there is K. (Step S20)
• If the determination in step S20 is NO, a calibration CO value input request is displayed. (Step S21)
・ Judge whether a calibration CO value has been input. (Step S22)
If the determination in step 22 is YES, the input CO value is stored in the register as CO1. (Step S23)
・ K = CO1 / (α * PWTT1 + β) * HR1 is calculated. (Step S24)
-If the determination in step S20 is YES and after calculating K in step S24,
esCO = K * (α * PWTT + β) * Calculate esCO from the formula HR. (Step S25)
・ Display esCO obtained by calculation. (Step S26)
The above process is repeated sequentially.

A procedure for calculating α, β, and K by calibration and calculating esCO will be described with reference to FIG.
(Calibration of α and β is performed when there is no increase in pulse pressure due to administration of vasoconstrictor, etc.)
・ Read the initial value of α. (Step S1)
・ Acquire PWTT and HR. (Step S2)
Next, it is determined whether or not β is present. (Step S15)
• If NO in step S15, a calibration blood pressure measurement request is displayed. (Step S16)
・ Determine whether calibration blood pressure measurement has been performed. (Step S17)
If YES in step S17, the measured PP value and the acquired PWTT and HR are stored in the register as PP1, PWTT1, and HR1. (Step S18)
・ Β is calculated by the equation β = PP1−α * PWTT1. (Step S19)
If YES in step S15, it is determined whether or not α is recalibrated. (Step S27)
If YES in step S27, a calibration blood pressure measurement request is displayed. (Step
S28)
・ Determine whether calibration blood pressure measurement has been performed. (Step S29)
If YES in step S29, the measured PP value and the acquired PWTT and HR are stored in the register as PP2, PWTT2, and HR2. (Step S30)
・ PP1 = α * PWTT1 + β
PP2 = α * PWTT2 + β
Α and β are calculated from these two equations. (Step S31)
If the determination in step S27 is NO, and after the processing in steps S19 and S31, it is determined whether or not K is present. (Step S20)
• If the determination in step S20 is NO, a calibration CO value input request is displayed. (Step S21)
・ Judge whether a calibration CO value has been input. (Step S22)
If the determination in step S22 is YES, the input CO value is stored in the register as CO1. (Step S23)
・ K = CO1 / (α * PWTT1 + β) * HR1 is obtained from the equation. (Step S24)
-If the determination in step S20 is YES and after calculating K in step S24,
esCO = K * (α * PWTT + β) * Calculate esCO from the formula HR. (Step S25)
・ Display esCO obtained by calculation. (Step S26)
The above process is repeated sequentially.

The blood pressure value measured with another sphygmomanometer may be key-input without performing the calibration blood pressure measurement.
Further, peripheral pulse waves include those representing volume changes in addition to SpO2 pulse waves.

In invention of Claims 1-8, the fluctuation | variation of a patient's circulatory dynamics can be continuously continuously monitored non-invasively, Furthermore, the technique of a skilled medical worker, such as insertion of a catheter, is unnecessary, Since there is little pain to the patient and it does not invade, there is no risk of infection, and a low-cost blood volume measuring method, measuring device, and biological signal monitoring device can be realized, so that the industrial applicability is extremely large.

It is a figure which shows the wind kessel model applied to this invention. It is a figure which shows the relationship between typical PWTT and pulse pressure (PP) (Pulse-Pressure). It is a figure which shows the relationship between SV measured by the animal experiment at the time of blood-vessel contraction, blood removal, and cardiac suppression, and PP1. It is a figure which shows the relationship between SV and PWTT measured at the time of vasoconstriction, blood removal, and cardiac suppression in the animal experiment. It is a figure which shows the relationship between PP1 and PWTT2 which were measured at the time of vasoconstriction, blood removal, and cardiac suppression in an animal experiment. It is a figure which shows the relationship between PEP, PWTT1, PWTT2, and PWTT. It is a block diagram for demonstrating the structure of one Embodiment of a biological signal monitor apparatus. It is a figure which shows an example of the mounting state to the patient of the electrocardiogram measurement means and the peripheral pulse wave detection means. It is a flowchart which shows the procedure which calibrates βK using the initial value αK and calculates esCO. It is a flowchart which shows the procedure which correct | amends (alpha) K and (beta) K and calculates esCO. It is a flowchart which shows the procedure which correct | amends (beta) and K using the initial value (alpha), and calculates esCO. It is a flowchart which shows the procedure which calibrates K, (alpha), and (beta), and calculates esCO.

Explanation of symbols

17 Input means 20 Systolic / diastolic blood pressure measurement means 22 A / D converter 25 Cuff 26 Exhaust valve 27 Pressure pump 28 Pressure sensor 29 Cuff pressure detection unit 30 Pulse wave propagation time measurement means 31 Time interval detection reference point measurement means 32 A / D converter 33 Photoelectric pulse wave detection sensor 34 Pulse wave detection unit 35 A / D converter 36 Pulse period detection means 40 Cardiac output calculation means 41 Display part 42 Alarm

Claims (8)

A blood volume measurement method for determining cardiac output from pulse wave propagation time,
CO = (αK * PWTT + βK) * HR
A method for measuring blood volume, wherein the cardiac output is obtained from an equation.
Where CO is cardiac output, PWTT is pulse wave propagation time, HR is heart rate, and α, β, and K are patient-specific coefficients. The blood volume measurement method according to claim 1, wherein at least one of the coefficients α, β, and K is calibrated based on a measurement value obtained by calibration blood pressure measurement. The blood volume measurement method according to claim 1 or 2, wherein the pulse wave propagation time is an arrival time from an electrocardiogram to a peripheral volume pulse wave. The blood volume measurement method according to any one of claims 1 to 3, wherein the blood volume measurement method is a case where a vasoconstrictor is administered. The blood volume measuring method according to claim 4, wherein the vasoconstrictor is phenylephrine. ECG measurement means for measuring an electrocardiogram, peripheral pulse wave measurement means,
PWTT measurement means for obtaining the pulse wave propagation time from the measurement results of the ECG measurement means and the peripheral pulse wave measurement means,
Blood volume calculating means;
A blood volume measuring device comprising:
The blood volume calculating means includes
CO = (αK * PWTT + βK) * HR
A blood volume measuring apparatus characterized by obtaining a blood volume from an equation.
Where CO is cardiac output, PWTT is pulse wave propagation time, HR is heart rate, and α, β, and K are patient-specific coefficients. The blood volume measuring device according to claim 6, further comprising a calibration unit that calibrates at least one of the coefficients α, β, and K based on a measurement value obtained by calibration blood pressure measurement. A biological signal monitoring device comprising the blood volume measuring device according to claim 6 or 7.

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