JPH06205747A - Pulse wave analyzer - Google Patents

Abstract

PURPOSE:To provide a pulse wave analyzer having an inexpensive structure and measuring the circulatory dynamic parameters without damaging the body of a patient. CONSTITUTION:A microcomputer 4 detects the radial artery wave of a patient via a pulse wave detecting device 1, performs a simulation based on this radial artery wave, i.e., the process to consolidate the values of elements of an electric circuit simulating the system from the central part to the peripheral region of the artery system of a human body so that the response wave-form coincides with the radial artery wave when the electric signal corresponding to the pressure wave at the start site of an aorta is applied, and the values of the elements obtained by this consolidation are outputted as circulatory dynamic parameters.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse wave analyzer used for diagnosing a human circulatory system.

[0002]

2. Description of the Related Art When diagnosing a condition of the circulatory system, blood pressure and heart rate are most commonly measured. However, in order to make a more detailed diagnosis, it is necessary to measure hemodynamic parameters such as viscous resistance and compliance (viscoelasticity) of blood vessels. Conventionally, in order to measure such hemodynamic parameters, it is necessary to measure the pressure waveform and blood flow at the aortic root and notch, and the measurement method is to insert a catheter into the artery and measure directly. There was a method of doing it or a method of measuring indirectly with ultrasonic waves.

[0003]

However, the former method of the above-mentioned conventional measuring methods has a problem that an invasive and large-scale apparatus is required. On the other hand, according to the latter method, blood flow in blood vessels can be observed non-invasively, but this method requires skill, and
There is a problem that the measuring device also becomes large-scale.

The present invention has been made in view of the above-mentioned circumstances, and an object thereof is to provide a pulse wave analyzer which has an inexpensive structure and which can non-invasively evaluate hemodynamic parameters. And

[0005]

The invention according to claim 1 is
A pulse wave detecting means for detecting a radial arterial wave, and a means for calculating the value of each element of an electric circuit simulating a system from the central part to the peripheral part of the human arterial system, which is a pressure wave at the origin of the aorta. And an evaluation means for calculating the value of each element of the electric circuit so that the output signal waveform obtained from the electric circuit becomes a waveform corresponding to the radial artery wave when an electric signal corresponding to Is characterized by. The invention according to claim 2 is characterized in that, in the invention according to claim 1, the pulse wave detecting means is a sensor for non-invasively detecting a pulse wave of a human body. The invention according to claim 3 is the invention according to claim 1, further comprising a recording means for recording a calculation result of each element of the electric circuit by the evaluating means, wherein the pulse wave detecting means detects the radial artery wave. It is characterized in that the value of each element of the electric circuit is repeatedly calculated on the basis of the radial artery wave detected by the pulse wave detecting means while repeatedly detecting. The invention according to claim 4 is a pulse wave detecting means for detecting a radial artery wave of a patient, a stroke volume detecting means for detecting a stroke volume of the patient, and an arterial central part to a peripheral part of a human body. As a model simulating the system leading to the above, the first resistance R _c corresponding to the vascular resistance due to the blood viscosity in the central part of the arterial system, the inductance L corresponding to the inertia of blood in the central part of the arterial system, the central part of the artery Has a capacitance C corresponding to the viscoelasticity of the blood vessel at the distal portion, and a second resistance R _p corresponding to the blood vessel resistance at the peripheral portion, and the first resistance and the second resistance R _p between the pair of input terminals. Assuming a four-element lumped constant model in which a series circuit including an inductance and a parallel circuit including the capacitance and the second resistance are sequentially inserted in series,
When an electric signal corresponding to the pressure wave at the aortic origin is applied between the input terminals, the electric signal corresponding to the radial artery wave is obtained from both ends of the capacitance and the second resistance. It is a means for specifying each constant of the element lumped constant model, calculates the value of the inductance based on the stroke volume, and calculates the value based on the value of the inductance, the angular frequency of the radial artery waveform, and the attenuation rate. First resistance,
And a parameter evaluation unit that calculates each value of the inductance, the electrostatic capacitance, and the second resistance, and outputs the calculation results as a circulation dynamic parameter. The invention according to claim 5 imitates a pulse wave detecting means for detecting a radial artery wave of a patient, a blood flow detecting means for detecting a blood flow volume of the patient, and a system from a central portion of an artery to a peripheral portion of a human body. As a model, a first resistance R _c corresponding to the vascular resistance due to blood viscosity in the central part of the arterial system, an inductance L corresponding to the inertia of blood in the central part of the arterial system, and a viscosity of the blood vessel in the central part of the arterial system. Capacitance C corresponding to elasticity and second resistance R _p corresponding to vascular resistance in the peripheral portion
And a series circuit including the first resistance and the inductance and a parallel circuit including the capacitance and the second resistance, which are sequentially inserted in series between a pair of input terminals. Assuming a constant model, when an electric signal corresponding to a pressure wave at the aortic origin is applied between the input terminals, an electric signal corresponding to the radial artery wave is generated from both ends of the capacitance and the second resistance. Means to identify each constant of the four-element lumped constant model as obtained, to calculate the value of the inductance based on the blood flow, the value of the inductance, the angular frequency of the radial artery waveform and the attenuation rate. Parameter evaluation means for calculating respective values of the first resistance, the inductance, the electrostatic capacitance, and the second resistance based on the above, and outputting the calculation results as a circulation dynamic parameter. And wherein the door. The invention according to claim 6 is the invention according to claim 4 or 5, wherein a periodic waveform having a period tP corresponding to the length of one pulse of the pulse wave is provided as an electric signal corresponding to the pressure wave at the aortic origin. e
(T) is used, and the periodic waveform e (t) is
t _p 1 <t _p1 which satisfies t _p, by using the voltage value E _m corresponding to the blood pressure difference between the voltage value E ₀ and systolic and diastolic blood pressure corresponding to the minimum blood pressure, of 0 ≦ t <t _p1 The period is e (t) = E ₀ + E _m (1- (t / t _p1 )) t _p1 ≦ t <t _p The period is represented by e (t) = E ₀ And

[0006]

According to the first aspect of the present invention, the hemodynamic parameter of the patient is calculated based on the radial artery waveform. According to the invention of claim 2, the hemodynamic parameter is calculated without damaging the patient's body. According to the invention of claim 3, the hemodynamic parameters of the patient can be continuously collected for a long time. According to the invention as claimed in claim 4 or 5, the four-element lumped constant model having a simple structure is used as the electrical model of the arterial system, and the inductance of the model is determined from the measurement result of the stroke volume. Since the value of is calculated, the hemodynamic parameter can be calculated by a simple calculation process. According to the invention of claim 6, the pressure wave at the aortic origin is modeled by a simple triangular wave, so that the circulatory dynamics parameter can be calculated by further simple arithmetic processing.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. <Structure of Embodiment> FIG. 1 is a block diagram showing the structure of a pulse wave analyzer according to an embodiment of the present invention. This device
Based on the information obtained from the human body by a non-invasive sensor, the hemodynamic parameters of the human arterial system are evaluated. The specific contents of the hemodynamic parameters handled in this example will be described later. In FIG. 1, 1 is a pulse wave detection device, and 2 is a stroke volume measuring device. Of these,
As shown in FIG. 2, the pulse wave detection device 1 detects the radial artery waveform via a pressure sensor S1 attached to the patient's wrist and the patient's blood pressure via a cuff band S2 attached to the patient's upper arm. To detect. Then, the radial artery waveform is calibrated with the blood pressure, and the calibrated radial artery waveform obtained as a result is output as an electric signal (analog signal). The analog signal output by the pulse wave detection device 1 is input to the A / D converter 3 and converted into a digital signal at every predetermined sampling cycle. Further, the stroke volume measuring device 2 is connected to the cuff band S2 as shown in FIG. 2, and is the amount of blood discharged from the heart at one beat through the cuff band S2. The stroke volume is measured, and the measurement result is output as stroke volume data (digital signal). As this type of stroke volume measuring device 2, a device for measuring by the so-called systolic area method can be used.

The microcomputer 4 has a keyboard 5
Each process listed below is performed according to the command input from. Pulse wave reading process for capturing the time-series digital signal of the radial artery waveform obtained through the A / D converter 3 into the built-in waveform memory. The radial artery waveform captured in the above waveform memory is averaged for each beat to correspond to one beat. Averaging process for obtaining radial artery waveform Process for taking in stroke volume data Obtaining a mathematical expression representing the radial artery waveform corresponding to one beat,
Parameter calculation process for calculating each parameter of the electrical model corresponding to the arterial system of the patient based on this mathematical formula The parameter obtained by the parameter calculation process is used as a circulatory dynamic parameter via an output device (not shown) (for example, printer, display device, etc.) Output processing for outputting as described above The details of these processings will be described in the description of the operation of the present embodiment.

<Regarding the electrical model adopted in this embodiment> A. Four-Element Lumped Constant Model In this embodiment, a four-element lumped constant model is adopted as an electrical model of the arterial system. This four-element lumped constant model is
Among the factors that determine the behavior of the human circulatory system, blood inertia in the central part of the arterial system, vascular resistance (viscous resistance) due to blood viscosity in the central part, vascular compliance (viscoelasticity) in the central part, and peripheral It focuses on four parameters of blood vessel resistance (viscous resistance) in the part and models them as an electric circuit. FIG. 4 shows a circuit diagram of the four-element lumped constant model. Hereinafter, the correspondence relationship between each element constituting the four-element lumped constant model and each of the above parameters will be shown. Inductance L: Inertia of blood in the central part of arterial system [dy
n · s ² / cm ⁵ ] Capacitance C: Compliance (viscoelasticity) of blood vessels in the central part of the arterial system [cm ⁵ / dyn] Note that compliance is a quantity that represents the softness of blood vessels, and That is. Electric resistance R _c : vascular resistance due to blood viscosity in the central part of the arterial system [dyn · s / cm ⁵ ] Electric resistance R _p : vascular resistance due to blood viscosity in the peripheral part of the arterial system [dyn · s / cm ⁵ ] The currents i, i _P , i _c flowing through each part in this electric circuit
Corresponds to the blood flow [cm ³ / s] flowing through each corresponding part. The input voltage e applied to this electric circuit corresponds to the pressure [dyn / cm ² ] at the origin of the aorta. The terminal voltage v _P of the capacitance C is the pressure [dyn / cm
² ].

B. Four-Element Lumped Element Model and Approximate Expression of Its Response Characteristic Next, a theoretical explanation will be given on the behavior of the four-element lumped parameter model shown in FIG. First, in the four-element lumped constant model shown in FIG. 4, the following differential equation holds. e = R _c i + L (di / dt) + v _p . ． ． ． (1) Here, current _{i, i = i c + i p} = C (dv p / dt) + (v p / R p). ． ． ． Since it can be expressed as (2), the above formula (1) is represented by the following formula (3)
Can be expressed as e = LC (d ² v _p / dt ² ) + {R _c C + (L / R _p )} (dv _p / dt) + (1+ (R _c / R _p )) v _p . ． ． ． (3) As is well known, the general solution of the quadratic constant coefficient ordinary differential equation as shown by the above equation (3) is defined by the special solution (steady solution) satisfying the above equation (3) and the following differential equation. It is given by the sum of satisfying transient solutions. 0 = LC (d ² v _p / dt ² ) + {R _c C + (L / R _p )} (dv _p / dt) + (1+ (R _c / R _p )) v _p . ． ． ． (4)

Here, the solution of the differential equation (4) is obtained as follows. First, a damped oscillation waveform represented by the following equation (5) is assumed as the solution of the differential equation (4). v _p = A exp (st). ． ． ． (5) When this equation (5) is substituted into the equation (4), the equation (4) is expressed as follows. {LCs ² + (R _c C + (L / R _p )) s + (1+ (R _c / R _p ))} v _p = 0. ． ． ． (6) When solving the above equation (6) for s, s = {- (R c C + (L / R p)) ± √ ((R c C + (L / R p)) 2 -4LC (1+ (R _c / R _p )))} / 2LC. ． ． ． (7) In the formula (7), (R _c C + (L / R _p )) ² <4LC (1+ (R _c / R _p )). ． ． ． In the case of (8), the square root √ of the second term becomes negative, and in this case, s is expressed as follows. s = {− (R _c C + (L / R _p )) ± j√ (4LC (1+ (R _c / R _p )) − (R _c C + (L / R _p )) ² )} / 2LC = −α ± jω. ． ． ． (9) α = (R _c C + (L / R _p )) / 2LC = (L + R _p R _c C) / 2LCR _p . ． ． ． (10) ω = {√ (4LC (1+ (R _c / R _p )) − (R _c C + (L / R _p )) ² )} / 2LC. ． ． ． (11) Here, A ₁ = LC. ． ． ． (12) A ₂ = (L + R _C R _P C) / R _p . ． ． ． (13) A ₃ = (R _C + R _P ) / R _p . ． ． ． Letting (14) be the above equations (10) and (11) can be expressed as follows. α = A ₂ / 2A ₁ . ． ． ． (15) ω = √ {(A ₃ / A ₁ ) −α ² } (16) In this way, the value of s is determined, and the differential equation (4) above is established.
A solution that satisfies is obtained. Based on the above findings, in the present embodiment, the above formula (5) is used as a formula for approximating the damping vibration component included in the response waveform of the four-element lumped constant model.

Next, the pressure waveform at the aortic origin is modeled. Generally, the pressure waveform at the aortic origin is as shown in FIG. Therefore, this pressure waveform will be approximated by the triangular wave shown in FIG. In FIG. 6, assuming that the amplitude and time of the approximate waveform are E _o , E _m , t _P , and t _P1 , the aortic pressure e at an arbitrary time t is expressed by the following equation. E _o is the minimum blood pressure (diastolic blood pressure), E _o + E _m is the maximum blood pressure (systolic blood pressure), t _P is the time of one beat, and t _P1 is the minimum blood pressure value from the rise of aortic pressure. It's time to go. Section of 0 ≦ t <t _P1 : e = E _o + E _m (1- (t / t _P1 )) (17) Section of t _P1 ≦ t <t _P : e = E _o (18) Then, in this embodiment, the response waveform v _p (corresponding to the radial artery wave) when the electric signal e represented by the above equations (17) and (18) is input to the equivalent circuit of FIG. It is approximated as follows. Section of 0 ≦ t <t _P1 : v _P = E _min + B (1-t / t _b ) + D _m1 exp (−αt) sin (ωt + θ ₁ ) ... (19) t _P1 ≦ t <t _P Interval: v _P = E _min + D _m2 · exp {−α (t−t _P1 )} · sin {ω (t−t _P1 ) + θ ₂ } ... (20) Third part on the right side in the above equation (19) And the above equation (2
The second term on the right side in (0) is the damping vibration component (corresponding to the above equation (5)) already described, and α and ω in these terms are given by the above equations (15) and (16).

C. Relationship between Parameters of Four-Element Concentrated Model and Radial Artery Waveform Hereinafter, other than the already determined α and ω among the constants in the above equations (19) and (20) will be examined. First, by substituting the equations (17) and (19) into the differential equation (3), the following equation (21) is obtained. E ₀ + E _m (1- (t / t _p1 )) = (1+ (R _c / R _p )) (E _min + B) − (B / t _b ) (R _c C + (L / R _p )) t + {LC (α ² −ω ² ) D _m1 −αD _m1 (R _c C + (L / R _p )) + D _m1 (1+ (R _c / R _p ))} exp (−αt) sin (ωt + θ ₁ ) + { ωD _m1 (R _c C + (L / R _p ))-2LCαωD _m1 } exp (−αt) cos (ωt + θ ₁ ). ． ． ． (21) The following conditions are necessary for the expression (21) to be satisfied. _{E 0 + E m = (1+} (R c / R p)) (E min + B) = E 0 + A 3 B- (B / t b) A 2. ． ． ． (22) E _m / t _p1 = (B / t _b ) (1+ (R _c / R _p )) = B / (t _b A ₃ ). ． ． ． (23) LC (α ² −ω ² ) −α (R _c C + (L / R _p )) + (1 + R _c / R _p ) = 0. ． ． ． (24) R _c C + (L / Rp) = 2LCα. ． ． ． (25) In the above equations, equations (24) and (25) constrain α and ω, but α and ω already obtained by equations (15) and (16) are naturally Satisfy these equations.

On the other hand, when the above equations (18) and (20) are substituted into the above differential equation (3), the following equation (26) is obtained. E ₀ = (1+ (R _c / R _p )) E min + {LC (α ² −ω ² ) D _m2 −α (R _c C + (L / R _p )) D _m2 + (1+ (R _c / R _p )) D _m2 } exp (−α (t−t _p1 )) sin (ω (t−t _p1 ) + θ ₂ ) + {ω (R _c C + (L / R _p )) D _m2 −2LCαωD _m2 } exp ( −α (t−t _p1 )) cos (ω (t−t _p1 ) + θ ₂ ). ． ． ． (26) In order for this equation (26) to hold, the above equation (23),
In addition to the condition (24) being satisfied, the following formula (27) must be satisfied. E ₀ = (1+ (R _c / R _p )) E _min = A ₃ E _min . ． ． ． (27)

Conditional expressions (22) to (25) for establishing the differential equation (3) obtained as described above,
Based on (27), each constant in equations (19) and (20) is calculated. First, E _min is obtained from the above equation (27), E _min = E _o / A ₃ ... (28) Next, from equation (23), B is B = (t _{b Em} ) / (t _P1 A ₃ ) ・ ・ ・ ・ (29). Next Solving for t _b by substituting the above equation (29) into the equation _{(22), t b = (} t P1 A 3 + A 2) / A 3. ． ． ． (30)

The remaining constants D _1m , D _2m , θ ₁ and θ ₂ are values such that the radial artery waveform v _p can maintain continuity at t = 0, t _p1 , t _p , that is, Condition a
A value that satisfies ~ d is selected. a. V _p (t _p1 ) in equation (19) and v _{p in} equation (20)
match _p (t _p1 ) b. V _p of v _p (t _p) and formula (19) in equation (20) (0)
Must match c. The differential coefficients at t = t _p1 in the equations (19) and (20) match, d. Derivative of t = 0 in equation (19) and equation (20)
I.e. t = t _p in the differential coefficient matching, D _{1 m} and theta _{1 is, D 1m = √ {(D} 11 2 + D 12 2)} / ω. ． ． ． (31) The value θ ₁ = D ₁₁ / D ₁₂ (32) is selected. However, in each of the above equations, D ₁₁ = (v _O1 −B) ω. ． ． ． (33) D ₁₂ = (v _O1 −B) α + (B / t ₀ ) + (i _O1 / C). ． ． ． (34), and v _O1 and i _O1 are initial values of v _P and i _P at t = 0. Further, D _2m and θ ₂ are D _2m = √ (D ₂₁ ² + D ₂₂ ² ) / ω. ． ． ． (35) The value θ ₂ = D ₂₁ / D ₂₂ (36) is selected. However, in each of the above equations, D ₂₁ = v _O2 · ω. ． ． ． (37) D ₂₂ = v _O2 · α + (i _O2 / C). ． ． ． (38) and v _O2 and l _O2 are initial values of v _P and i _P at t = t _P1 . In this way, the constants of equations (19) and (20) were obtained.

By back calculating from the angular frequency ω in the equation (16), the vascular resistance R _C at the central portion is R _C = {L-2R _P √ (LC (1-ω ² LC))} / CR It becomes _r・ ・ ・ (39). Here, the conditions R _C is a real number a and positive is ^{_{4R r 2 C / {l +}} (2ωR P C) 2} ≦ L ≦ 1 / ω 2 C ···· (40). Generally, the order of R _P is about 10 ³ (dyn · s / cm ⁵ ), C is about 10 ⁻⁴ (cm ⁵ / dyn), and ω is the angular frequency of the vibration component superimposed on the pulse wave. Because there is 10
(Rad / s) or higher. Therefore, the formula (4
The lower limit of 0) can be regarded as approximately 1 / ω ² C. Therefore, when L is approximately set to L = 1 / (ω ² C) ··· (41) for simplification, R _C is R _C = L / (CR _P ) ··· ( 42). Further, from the relationship between the equations (41) and (42), the damping constant α of the equation (15) becomes α = 1 / (CR _P ) ... (43). Using the relations of equations (41) to (43), one of α and ω and four constants, for example, the inertia L of blood, is used to represent the remaining parameters. R _C = αL. ． ． ． (44) R _P = ω ² L / α. ． ． ． (45) C = 1 / (ω ² L) ... (46) From the above equations (44) to (46), it is clear that the model parameters are determined by obtaining α, ω and L.

Here, α and ω can be obtained from the actually measured waveform of the radial artery wave. On the other hand, L can be calculated based on the stroke volume SV. The procedure for calculating L based on the stroke volume SV will be described below. First, the average value E ₀₁ of the pressure wave at the aortic origin is given by the following equation (47). E ₀₁ = {E ₀ t _p + (t _p1 E _m / 2)} / t _p . ． ． ． (47) On the other hand, between Rc, Rp, α, ω and L, the following formula (48)
Is established. R _c + R _p = αL + (ω ² L / α) = (α ² + ω ² ) L / α. ． ． ． (48) Then, the average current flowing through the four-element lumped constant model, that is, the above E ₀₁ divided by R _c + R _p is equivalent to the average value (SV / t _p ) of the blood flow through the artery due to pulsation. Therefore, the following equation (49) is established. _{SV / t p = 1333.22 (1} / t p) {E 0 t p + (t p1 E m / 2)} (α 2 + ω 2) / (αL). ． ． ． (49) Note that 1333.22 in the above equation (49) is a proportional constant for converting the unit of pressure value from mmHg to dyn / cm ² .
By solving the equation (49) thus obtained for L, the equation (5
0) is obtained as follows. L = 1333.22 {E ₀ t _p + (t _p1 E _m / 2)} (α ² + ω ² ) / (α · SV). ． ． ． (50) In addition, seeking a value corresponding to the above formula (49) the average current in _{(1 / t p) {E} 0 t p + (t p1 E m / 2)} By measuring the blood flow, this The inductance L may be calculated based on the result. As a device for measuring blood flow, an impedance method, a Doppler method, and the like are known. In addition, the blood flow measuring device by the Doppler method includes a device using ultrasonic waves and a device using laser.

The relationship between the radial artery wave and stroke volume and the values of the respective elements of the four-element lumped constant model has been described above. The microcomputer 4 in this embodiment calculates the value of each element of the four-element lumped constant model based on the relationship described above.

<Operation of Embodiment> FIGS. 6 to 10 are flowcharts showing the operation of the pulse wave analyzing apparatus. Also, FIG.
1 is a waveform diagram showing a radial artery waveform obtained by the averaging process, and FIG. 9 is a radial artery waveform W2 obtained by the parameter calculation process and a radial artery waveform W1 obtained by the averaging process.
It is a waveform diagram which contrasted with. The operation of this embodiment will be described below with reference to these drawings.

A. Normal measurement process Pulse wave reading process When assessing hemodynamic parameters, the diagnostician
As shown in, the pressure sensor S1 and the cuff band S2 are attached to the patient, and a measurement instruction is input from the keyboard 5. In response to this command, the microcomputer 4 first sends a measurement instruction to the pulse wave detection device 1. As a result, the pulse wave detection device 1 detects the radial artery wave, the time-series digital signal representing the radial artery wave is output from the A / D converter 3, and the microcomputer is used for a fixed time (about 1 minute). Taken in 4. In this way, the microcomputer 4
A time-series digital signal of radial artery waveforms for multiple beats is captured at.

Averaging Process Next, the microcomputer 4 superimposes the radial artery waveforms corresponding to a plurality of beats thus captured on a beat-by-beat basis to obtain an average waveform per beat in one minute, and this average is calculated. The waveform is stored in the built-in memory as a representative waveform of the radial artery waveform (above, step S1). FIG. 8 illustrates a representative waveform W1 of the radial artery waveform thus stored in the memory.

Single stroke volume data acquisition process Upon completion of the averaging process, the microcomputer 4
Sends a measurement instruction to the stroke volume measuring device 2. As a result, 1
The stroke volume of the patient is measured by the stroke volume measuring device 2,
The stroke volume data indicating the result is taken into the microcomputer 4 (step S2).

Parameter Calculation Processing Next, the processing of the microcomputer 4 proceeds to step S3, and the parameter calculation processing routine whose flow is shown in FIGS. 7 and 8 is executed. Further, along with the execution of this routine, an α, ω calculation routine whose flow is shown in FIG. 9 is executed (steps S109 and S117), and with the execution of this α, ω calculation routine, an ω calculation routine whose flow is shown in FIG. Is executed (step S203). The processing contents of these routines will be described below.

First, the microcomputer 4 stores the time t ₁ and the blood pressure value y ₁ corresponding to the first point P1 at which the blood pressure becomes maximum, and the blood pressure value y ₁ after the first point in the radial artery waveform for one beat loaded in the memory. , Blood pressure drops once
The time t ₂ corresponding to the point and the blood pressure value y _2, and the time t ₃ corresponding to the third point P3 which is the second peak point.
And the blood pressure value y ₃ are calculated. Further, regarding the radial artery waveform stored in the memory, the time t _P of one beat and the minimum blood pressure value Emin
(Corresponding to the first item of equations (3) and (4)) is calculated (step S101). Through the above processing, the data exemplified below can be obtained as each data necessary for the parameter calculation processing. First point: t ₁ = 0.104 (s), y ₁ = 123.
4 (mmHg) Second point: t ₂ = 0.264 (s), y ₂ = 93.8
(MmHg) Third point: t ₃ = 0.38. (S), y ₃ = 103.
1 (mmHg) 1 beat time: t _P = 0.784 (s) Minimum blood pressure: E _min = 87.7 (mmHg) Stroke volume data: SV = 90 (cc / beat) Second point In the case of a gentle pulse wave in which it is difficult to distinguish P2 from the third point P3, the blood pressure value at that point is determined by setting the times of the second and third points to t ₂ = 2t ₁ and t ₃ = 3t _1. To do.

Then, in order to simplify the calculation, the blood pressure value y ₀ at the point A shown in FIG. 13 is used to normalize y ₁ to y ₃ (steps S102 and S103), and the value of B is changed to (y _0). /
2) Initialize to -0.1 (step S104).

Then, the optimum values of B, t _b , α and ω are obtained by the following procedure. a. First, B a is varied in the range of y ₀ / 2~y ₀ changing the t _b in the range of t _p / 2~t _p simultaneously (+0.1 intervals), each B and t _b for v _p (t ₁ ) -y ₁ , vp
(T ₂ ) −y ₂ , v _p (t ₃ ) −y ₃ is determined to be minimum α and ω. b. Among B, t _b , α and ω obtained in a, v
B, t _b , α, and ω that minimize _p (t ₁ ) -y ₁ , v _p (t ₂ ) -y ₂ , v _p (t ₃ ) -y ₃ are obtained. c. B obtained in b, based on the t _{b, B} ± 0.
The above a and b are executed again within the range of 05, t _b ± 0.05. d. In the processing of a to c, α has a range of 3 to 10 of 0.
The value is changed at intervals of 1 and the optimum ω is calculated for each α.
ω was obtained by using the bisection method at the point where dv _p (t ₂ ) / dt = 0 in each α (see FIG. 10). Note that the initial value v _o1 of the equation (33) is set to zero _when calculating the value of v _p in each of the above processes. By such processing, each data is determined as exemplified below. α = 4.2 (s ⁻¹ ), ω = 24.325 (rad / s) B = 27.2 (mmHg), t _b = 0.602 (s)

F. Then, t _P1 , E _m , and E _o are given by equation (28)
To (30) and (44) to (46) (steps S123 and S124). The results illustrated below are obtained. t _P1 = 0.588 (s) E _m = 46.5 (mmHg) E _o = 90.3 (mmHg) g. Then, the value of L is calculated from the stroke volume using the equation (50) (step S125), and the remaining parameter values are obtained by the equations (44) to (46) (step S12).
6). As a result, the parameters exemplified below are obtained. L = 7.021 (dyn · s ² / cm ⁵ ) C = 2.407 × 10 ⁻⁴ (cm ⁵ / dyn) R _C = 29.5 (dyn · s / cm ⁵ ) R _P = 958.2 ( dyn · s / cm ⁵ ) Moreover, direct current (average) total peripheral vascular resistance TPR is calculated as follows. _{TPR = R C + R P =} 1018.7 becomes ^{(dyn · s / cm 5)} .

Output Process Upon completion of the parameter calculation process described above, the microcomputer 4 outputs L, C, R _C and R _P from the output device (step S4).

For confirmation, the equation (4
0) is calculated to be 6.969 ≦ L ≦ 7.036, and it can be said that the approximation of the equation (41) is appropriate. Further, as shown in FIG. 12, it can be said that the radial artery waveform calculated using the calculated parameters and the actually measured waveform (average waveform for 1 minute) match very well.

B. Continuous measurement The device according to the present embodiment is equipped with a timer (not shown), and by using this timer, the hemodynamic parameters can be continuously measured for a long time. When performing this continuous measurement, the diagnostician inputs a continuous measurement instruction from the keyboard 5. As a result, after step S4 (output process) in FIG. 6 is completed, the timer is set, and after the timer measures a certain time, execution is started again from step S1 and the circulatory dynamics parameter is measured (step S3) is recorded on recording paper or a storage medium (step S4). In this way, continuous measurement of hemodynamic parameters is performed at regular time intervals.

<Modifications> The present invention can be implemented in the modes listed below in addition to the modes described above. (1) Without measuring the stroke volume SV, L is assumed to be a predetermined value, and the hemodynamic parameter is obtained only from the radial artery waveform. In order to compensate for the decrease in calculation accuracy, a monitor is provided to display the radial artery waveform obtained by the calculation and the radial artery waveform obtained by the measurement as shown in FIG. 12, and the diagnostician sets the value of L. You may get it. With this configuration, the diagnostician can set L to an optimum value by trial and error so that the measured radial artery waveform matches the calculated radial artery waveform. (2) A trapezoidal wave as shown in FIG. 14 is used instead of a triangular wave as a model of the pressure waveform at the aortic root. In this case, since it is closer to the actual pressure waveform than the triangular wave, the circulatory dynamics parameter can be obtained more accurately. (3) In the above embodiment, the circulatory dynamic parameters were calculated by using mathematical expressions. However, each response waveform of the model when each circulatory dynamic parameter was changed within a predetermined range was simulated by a circuit simulator or the like, The hemodynamic parameter that best matches the actually measured radial artery waveform may be selected and output. In this case, as the electrical model of the arterial system and the model of the pressure waveform at the origin of the aorta, more complicated ones can be used, and the measurement accuracy is further improved. (4) The measurement points of the radial artery wave and the stroke volume are not limited to those shown in FIG. For example, both the radial artery waveform and the stroke volume may be measured at the wrist. In this case, the patient does not have to wrap his arm, which reduces the burden on the patient. Further, the stroke volume may be measured at the wrist and the arterial waveform may be measured at the finger, and vice versa. Further, both the stroke volume and the arterial waveform may be measured with a finger.

[0033]

As described above, according to the present invention, it is possible to realize a pulse wave analyzer having an inexpensive structure and measuring a hemodynamic parameter without damaging a patient's body. There is.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a pulse wave analysis device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a measurement mode using a pulse wave detection device 1 and a stroke volume measuring device 2 in the same Example.

FIG. 3 is a circuit diagram showing a four-element lumped constant model used as a model of the human arterial system in the same Example.

FIG. 4 is a diagram showing a blood pressure waveform at the aortic root of a human body.

FIG. 5 is a waveform diagram showing a waveform obtained by modeling the blood pressure waveform of the aortic origin.

FIG. 6 is a flowchart showing the operation of the embodiment.

FIG. 7 is a flowchart showing the operation of the embodiment.

FIG. 8 is a flowchart showing the operation of the embodiment.

FIG. 9 is a flowchart showing the operation of the embodiment.

FIG. 10 is a flowchart showing the operation of the embodiment.

FIG. 11 is a waveform diagram illustrating a radial artery waveform obtained by the averaging process of the example.

FIG. 12 is a waveform diagram in which the radial artery waveform obtained by the arithmetic processing of the embodiment and the radial artery waveform obtained by the averaging processing are displayed in an overlapping manner.

FIG. 13 is a diagram illustrating the radial artery waveform obtained by the averaging process of the same example and explaining the contents of the process applied to the waveform.

FIG. 14 is a waveform diagram showing another model of the blood pressure waveform at the aortic root.

[Explanation of symbols]

1 …… Pulse wave detector, 2 …… single stroke volume measuring instrument, 4 ……
Microcomputer.

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[Procedure amendment]

[Submission date] November 26, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

Embodiments of the present invention will be described below with reference to the drawings. <Structure of Embodiment> FIG. 1 is a block diagram showing the structure of a pulse wave analyzer according to an embodiment of the present invention. This device
Based on the information obtained from the human body by a non-invasive sensor, the hemodynamic parameters of the human arterial system are evaluated. The specific contents of the hemodynamic parameters handled in this example will be described later. In FIG. 1, 1 is a pulse wave detection device, and 2 is a stroke volume measuring device. Of these,
As shown in FIG. 2, the pulse wave detection device 1 detects the radial artery waveform via a pressure sensor S2 attached to the wrist of the patient and also detects the blood pressure of the patient via a cuff band S1 attached to the upper arm of the patient. To detect. Then, the radial artery waveform is calibrated with the blood pressure, and the calibrated radial artery waveform obtained as a result is output as an electric signal (analog signal). The analog signal output by the pulse wave detection device 1 is input to the A / D converter 3 and converted into a digital signal at every predetermined sampling cycle. Further, the stroke volume measuring device 2 is connected to the cuff band S1 as shown in FIG. 2, and is the amount of blood discharged from the heart at one stroke through the cuff band S1. The stroke volume is measured, and the measurement result is output as stroke volume data (digital signal). As this type of stroke volume measuring device 2, a device for measuring by the so-called systolic area method can be used.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

Next, the pressure waveform at the aortic origin is modeled. Generally, the pressure waveform at the aortic origin is as shown in FIG. Therefore, to be approximated by the triangular wave indicating this pressure waveform in FIG. In FIG. 5 , assuming that the amplitude and time of the approximate waveform are E _o , E _m , t _P , and t _P1 , the aortic pressure e at an arbitrary time t is expressed by the following equation. E _o is the minimum blood pressure (diastolic blood pressure), E _o + E _m is the maximum blood pressure (systolic blood pressure), t _P is the time of one beat, and t _P1 is the minimum blood pressure value from the rise of aortic pressure. It's time to go. Section of 0 ≦ t <t _P1 : e = E _o + E _m (1- (t / t _P1 )) (17) Section of t _P1 ≦ t <t _P : e = E _o (18) Then, in this embodiment, the response waveform v _p (corresponding to the radial artery wave) when the electric signal e represented by the above equations (17) and (18) is input to the equivalent circuit of FIG. It is approximated as follows. Section of 0 ≦ t <t _P1 : v _P = E _min + B (1-t / t _b ) + D _m1 exp (−αt) sin (ωt + θ ₁ ) ... (19) t _P1 ≦ t <t _P Interval: v _P = E _min + D _m2 · exp {−α (t−t _P1 )} · sin {ω (t−t _P1 ) + θ ₂ } ... (20) Third part on the right side in the above equation (19) And the above equation (2
The second term on the right-hand side in (0) is the damping vibration part (corresponding to the above equation (5)) already described, and α and ω in these terms are given by the above equations (15) and (16).

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

The remaining constants D _1m , D _2m , θ ₁ and θ ₂ are values such that the radial artery waveform v _p can maintain continuity at t = 0, t _p1 , t _p , that is, Condition a
A value that satisfies ~ d is selected. a. V _p (t _p1 ) in equation (19) and v _{p in} equation (20)
match _p (t _p1 ) b. V _p of v _p (t _p) and formula (19) in equation (20) (0)
Must match c. The differential coefficients at t = t _p1 in the equations (19) and (20) match, d. Derivative of t = 0 in equation (19) and equation (20)
I.e. the derivative of the t = t _p are matched, D _{1 m} and theta _{1 is, D 1m = √ {(D} 11 2 + D 12 2)} / ω ···· (31) θ 1 = tan -1 The value of (D ₁₁ / D ₁₂ ) ... (32) is selected. However, in the above _{formulas, D 11 = (v 01 -B} -E min) ω ···· (33) D 12 = (v 01 -B-E min) α + (B / t b) + (i 01 / C) ... (34) , and v ₀₁ and i ₀₁ are initial values of v _P and i _c at t = 0. Further, D _2m and θ ₂ are D _2m = √ (D ₂₁ ² + D ₂₂ ² ) / ω ··· (35) θ ₂ = tan ⁻¹ (D ₂₁ / D ₂₂ ) ·· (36) Is selected. However, in the above equations, D ₂₁ = (v ₀₂ −E _min ) ω ··· (37) D ₂₂ = (v ₀₂ −E _min ) α + (i ₀₂ / C) ··· (38) , V ₀₂ and i ₀₂ are initial values of v _P and i _c at t = t _P1 . In this way, the constants of equations (19) and (20) were obtained.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

By back calculating from the angular frequency ω of the equation (16), the vascular resistance R _c at the central portion is R _c = {L-2R _P √ (LC (1-ω ² LC))} / CR It becomes _P ... (39). Here, the condition for R _c is a real number a and positive is ^{_{4R P 2 C / {1+ (}} 2ωR P C) 2} ≦ L ≦ 1 / ω 2 C ···· (40). Generally, the order of R _P is about 10 ³ (dyn · s / cm ⁵ ), C is about 10 ⁻⁴ (cm ⁵ / dyn), and ω is the angular frequency of the vibration component superimposed on the pulse wave. Because there is 10
(Rad / s) or higher. Therefore, the formula (4
The lower limit of 0) can be regarded as approximately 1 / ω ² C. Therefore, when L is approximately set to L = 1 / (ω ² C) ··· (41) for simplification, R _c is R _c = L / (CR _P ) ··· (( 42). Further, from the relationship between the equations (41) and (42), the damping constant α of the equation (15) becomes α = 1 / (CR _P ) ... (43). Using the relationships of equations (41) to (43), if one of α and ω and four constants, for example, the inertia L of blood, is used to represent the remaining parameters, R _c = αL ... (44) R _P = ω ² L / α (45) C = 1 / (ω ² L) (46) From the above equations (44) to (46), it is clear that the model parameters are determined by obtaining α, ω and L.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

<Operation of Embodiment> FIGS. 6 to 10 are flowcharts showing the operation of the pulse wave analyzing apparatus. Also, FIG.
1 is a waveform diagram showing the radial artery waveform obtained by the averaging process, and FIG. 12 is the radial artery waveform W2 obtained by the parameter calculating process and the radial artery waveform W obtained by the averaging process.
It is a waveform diagram which compared with 1. The operation of this embodiment will be described below with reference to these drawings.

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

First, the microcomputer 4 stores the time t ₁ and the blood pressure value y ₁ corresponding to the first point P1 at which the blood pressure becomes maximum, and the blood pressure value y ₁ after the first point in the radial artery waveform for one beat loaded in the memory. , Blood pressure drops once
The time t ₂ corresponding to the point and the blood pressure value y _2, and the time t ₃ corresponding to the third point P3 which is the second peak point.
And the blood pressure value y ₃ are calculated. Further, regarding the radial artery waveform stored in the memory, the time t _P of one beat and the minimum blood pressure value Emin
(Corresponding to the first item of equations (3) and (4)) is calculated (step S101). Through the above processing, the data exemplified below can be obtained as each data necessary for the parameter calculation processing. First point: t ₁ = 0.104 (s), y ₁ = 123.
4 (mmHg) Second point: t ₂ = 0.264 (s), y ₂ = 93.8
(MmHg) Third point: t ₃ = 0.38. (S), y ₃ = 103.
1 (mmHg) 1 beat time: t _P = 0.784 (s) Minimum blood pressure: E _min = 87.7 (mmHg) Stroke volume data: SV = 103.19 (cc / beat) In the case of a gentle pulse wave in which it is difficult to distinguish the second point P2 and the third point P3, the time between the second and third points is set to t ₂ = 2t ₁ , t ₃ = 3t _{1 and} the blood pressure value at that point is set. To decide.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

F. Then, t _P1 , E _m , and E _o are given by equation (28).
To (30) and (44) to (46) (steps S123 and S124). The results illustrated below are obtained. t _P1 = 0.588 (s) E _m = 27.4 (mmHg) E _o = 90.3 (mmHg) g. Then, the value of L is calculated from the stroke volume using the equation (50) (step S125), and the remaining parameter values are obtained by the equations (44) to (46) (step S12).
6). As a result, the parameters exemplified below are obtained. L = 7.021 (dyn · s ² / cm ⁵ ) C = 2.407 × 10 ⁻⁴ (cm ⁵ / dyn) R _c = 29.5 (dyn · s / cm ⁵ ) R _P = 958.2 ( dyn · s / cm ⁵ ) Moreover, direct current (average) total peripheral vascular resistance TPR is calculated as follows. _{TPR = R c + R P =} 1018.7 becomes ^{(dyn · s / cm 5)} .

[Procedure Amendment 8]

[Document name to be amended] Statement

[Name of item to be corrected] 0030

[Correction method] Change

[Correction content]

For confirmation, the equation (4
0) is calculated to be 6.969 ≦ L ≦ 7.021 , and it can be said that the approximation of the equation (41) is appropriate. Further, as shown in FIG. 12, it can be said that the radial artery waveform calculated using the calculated parameters and the actually measured waveform (average waveform for 1 minute) match very well.

Claims (6)

[Claims] 1. A pulse wave detecting means for detecting a radial artery wave, and a means for calculating values of respective elements of an electric circuit simulating a system from a central portion to a peripheral portion of an arterial system of a human body, comprising: Evaluation means for calculating the value of each element of the electric circuit so that when an electric signal corresponding to the pressure wave at the beginning is applied, the output signal waveform obtained from the electric circuit becomes a waveform corresponding to the radial artery wave. A pulse wave analysis apparatus comprising: 2. The pulse wave analyzing apparatus according to claim 1, wherein the pulse wave detecting means is a sensor for non-invasively detecting a pulse wave of a human body. 3. A recording means for recording the calculation result of each element of the electric circuit by the evaluation means, wherein the pulse wave detection means repeatedly detects the radial artery wave and the evaluation means detects the pulse wave. 2. The pulse wave analyzing apparatus according to claim 1, wherein the value of each element of the electric circuit is repeatedly calculated based on the radial artery wave detected by the means. 4. A pulse wave detecting means for detecting a radial artery wave of a patient, a stroke volume detecting means for detecting a stroke volume of the patient, and a system from a central portion of an artery to a peripheral portion of a human body. As a model imitating the above, a first resistance corresponding to vascular resistance due to blood viscosity in the central part of the arterial system, an inductance corresponding to inertia of blood in the central part of the arterial system, a viscosity of blood vessels in the central part of the artery. Capacitance corresponding to elasticity,
And a second resistance corresponding to the blood vessel resistance in the peripheral portion, and a series circuit including the first resistance and the inductance, and the capacitance and the second resistance between a pair of input terminals. Assuming a four-element lumped constant model in which parallel circuits are sequentially inserted in series, the capacitance and the second capacitance are applied when an electric signal corresponding to a pressure wave at the aortic origin is applied between the input terminals. Is a means for identifying each constant of the four-element lumped constant model so that an electric signal corresponding to the radial artery wave can be obtained from both ends of the resistance of the resistance, and the value of the inductance is calculated based on the stroke volume. Then, the values of the first resistance, the inductance, the capacitance, and the second resistance are calculated on the basis of the value of the inductance, the angular frequency of the radial artery waveform, and the attenuation rate, and the calculated results are circulatory dynamics. Pa Pulse wave analyzing apparatus characterized by comprising a parameter evaluating means for outputting as a meter, the. 5. A pulse wave detecting means for detecting a radial artery wave of a patient, a blood flow detecting means for detecting a blood flow of the patient, and a model simulating a system from a central portion of an artery to a peripheral portion of a human body, A first resistance corresponding to vascular resistance due to blood viscosity in the central part of the arterial system, an inductance corresponding to inertia of blood in the central part of the arterial system, and an electrostatic corresponding to viscoelasticity of blood vessels in the central part of the arterial system. capacity,
And a second resistance corresponding to the blood vessel resistance in the peripheral portion, and a series circuit including the first resistance and the inductance, and the capacitance and the second resistance between a pair of input terminals. Assuming a four-element lumped constant model in which parallel circuits are sequentially inserted in series, the capacitance and the second capacitance are applied when an electric signal corresponding to a pressure wave at the aortic origin is applied between the input terminals. Is a means for identifying each constant of the four-element lumped constant model so as to obtain an electrical signal corresponding to the radial artery wave from both ends of the resistance, calculating the value of the inductance based on the blood flow, The values of the first resistance, the inductance, the electrostatic capacitance, and the second resistance are calculated based on the value of the inductance, the angular frequency of the radial artery waveform, and the attenuation rate, and the calculated results are used as circulatory dynamic parameters. Pulse wave analyzing apparatus characterized by comprising a parameter evaluating means for outputting a data, a. 6. A periodic waveform e (t) having a period t _P corresponding to the length of one pulse of a pulse wave is used as an electric signal corresponding to the pressure wave at the aortic origin, waveform e (t), by using the t _p1 <satisfies t _p t _p1, the voltage value E _m corresponding to the blood pressure difference between the voltage value E ₀ and systolic and diastolic blood pressure corresponding to the minimum blood pressure, 0 During the period of ≦ t <t _p1 , e (t) = E ₀ + E _m (1- (t / t _p1 )) t _p1 During the period of ≦ t <t _p , e (t) = E ₀ is represented. The pulse wave analysis device according to claim 4, wherein the pulse wave analysis device is a device.