JP2004154376A - Circulation kinetics measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the circulation kinetics accurately without being affected by the blood pressures when the waves are inputted from the surfaces of the living bodies in a non-invasive fashion to analyze the condition of the blood or the like from the motion and the position thereof by being reflected on the humor flowing through the living bodies and the circulation kinetics are determined to evaluate the heath condition. <P>SOLUTION: The circulation kinetics measuring apparatus is basically constituted of a means which transmits or receives the waves from the skin surface to detect the circulation kinetics in vivo in a non-invasive fashion and a means for detecting the blood pressures at the sites to be measured. The correction factor determined from the diameter of the blood vessels and the average blood pressure value determined from the maximum and minimum blood pressure values are used for the correction, thereby achieving a precise measurement. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a measuring device for measuring a body fluid circulating in a living body and a tissue constituting a circulatory organ, and particularly relates to a technology for grasping a state of blood to evaluate health, diagnose a disease, evaluate an effect of a drug, and the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, various methods using blood information have been used in order to evaluate the health of a living body, diagnose a disease, grasp the influence of a drug on a living body, and the like. For example, medically, there is a method in which blood is collected from a living body, the blood is passed through a component analyzer, and circulatory dynamics are determined from the ratio of various blood components contained in the blood to evaluate a health condition. As a conventional example, the method presented by Yuji Kikuchi under the title "Measurement of whole blood fluidity using a capillary model", i.e., a microchannel manufactured by a lithographic method by collecting blood from a subject A method of measuring blood rheology from the transit time of a blood flow under a constant pressure using an array is known. (For example, see Non-Patent Document 1)
[0003]
[Non-patent document 1]
Yuji Kikuchi, "Fast and Quantitative Evaluation of Food Functionality by Blood Rheology Analyzer MC-FAN", Food Research Results Information, Food Research Institute, Heisei 10
Year, No. 11
[0004]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to evaluate health conditions and circulatory dynamics without taking blood and taking individual differences into account.
[0005]
In a conventional blood rheology measurement method using a microchannel array, in order to inevitably collect blood from a subject, a needle must be inserted into an elbow using an injection needle to collect blood. Therefore, even if an in vivo test is performed to determine the effect of food components on blood rheology, blood cannot be collected from the same person many times a day, making continuous testing difficult. In addition, even if individuals leave the medical institution and try to perform blood rheology measurement by collecting blood at home or the like by themselves, one method using a microchannel array as in the conventional example cannot place a device at home. However, there is also a problem that the measurement cannot be performed only at a medical institution because proper processing cannot be performed.
[0006]
[Means for Solving the Problems]
Means for solving the above problem is to transmit ultrasonic waves or other waves from the skin surface of the living body, receive reflected ultrasonic waves, detect the flow velocity of blood flowing through blood vessels in the form of a Doppler shift signal, and detect In this method, a temporal change component of the blood flow velocity is obtained from the Doppler shift signal, and a blood rheology, which is one of the circulatory dynamics, is measured from the change component to evaluate a health condition. Specifically, a blood rheology is obtained from the maximum velocity component of the blood flow velocity component during one pulse, and as a result, an evaluation method that gives an evaluation that the patient is healthy when the result that the blood rheology is small is performed. .
[0007]
Here, when determining blood rheology, it is important to accurately determine the flow velocity of blood flowing through a blood vessel. However, blood flow is greatly affected by blood pressure. Therefore, in order to accurately determine the blood flow, it is necessary to correct the influence of the blood pressure. This can easily be inferred from the Poiseuille equation shown below.
[0008]
Q = πr ⁴ · ΔP / (8ηl) (Equation 1)
Here, Q is the flow rate, r is the inner diameter of the pipe, η is the viscosity of the fluid, l is the length of the pipe, and ΔP is the pressure difference. Q is the maximum speed Vm and the inner diameter r of the tube.
Q = πr ² Vm / 2 (Equation 2)
It can be expressed as. By rearranging these two equations, Equation 3 is obtained.
[0009]
Vm / ΔP = A · 1 / η (A = r ² / 4l) (Equation 3)
As shown in Expression 3, it is understood that there is a relationship between the flow velocity, the pressure difference, and the viscosity. If this is replaced with biological information, it can be said that there is a correlation between the flow velocity flowing through the blood vessel, blood pressure, and blood rheology. For example, even if the blood has the same blood rheology, if the blood pressure is different, the flow rate flowing through the blood vessel is different, and it is difficult to obtain an accurate blood rheology only from the flow rate flowing through the blood vessel. That is, when trying to obtain information in a living body, it can be said that it is difficult to obtain an accurate circulatory dynamics from the flow velocity of blood flowing through a blood vessel without considering blood pressure.
[0010]
Further, when correcting the influence of blood pressure, it is not known what blood pressure value (for example, a systolic blood pressure value or a diastolic blood pressure value) should be used for correction. In the present invention, when performing the correction, the average blood pressure value is considered as a representative value of the blood pressure of the person. The average blood pressure value is represented by Expression 4 described in standard physiology.
[0011]
Pm = Pd + Pp / 3 (Equation 4)
Here, Pm is an average blood pressure value, Pd is a diastolic blood pressure, and Pp is a pulse pressure. However, this equation is consistent with the measurement at the upper arm. For example, it cannot be applied to the aorta such as the carotid artery and the arterioles at the fingertips. That is, Equation 4 is the average blood pressure value measured at the upper arm site, but not the average blood pressure value measured at the other sites. This is because, as shown in FIG. 12, the blood pressure waveform differs depending on the region, and the average blood pressure value which is the center of gravity of the waveform also differs.
[0012]
Therefore, in order to perform correction using the average blood pressure value obtained by Expression 4 and to accurately obtain blood rheology, measurement must be performed at the upper arm.
[0013]
Therefore, the following means is used to select a measurement site, obtain an average blood pressure value, and accurately obtain blood rheology.
[0014]
First, a blood flow measurement unit is provided in the blood pressure measurement unit. Thus, the blood pressure measurement unit and the circulatory dynamics measurement unit match, so that when blood rheology is evaluated, the influence of blood pressure can be accurately corrected.
[0015]
The average blood pressure value is used as the blood pressure value for correcting the influence of the blood pressure. Since it cannot be said that the person's blood pressure can be completely expressed only by the systolic blood pressure value or the diastolic blood pressure value, the average blood pressure value is calculated and used by a formula including both.
[0016]
It is empirically known that when the blood pressure measurement unit is the upper arm, the blood pressure can be obtained by Expression 4. This has been confirmed from the blood pressure waveform at the upper arm. However, since the blood pressure waveform is different in other parts, an equation for obtaining an average blood pressure value corresponding to the waveform is prepared.
[0017]
The average blood pressure value used for the correction is obtained from Expression 5 using the systolic blood pressure value and the diastolic blood pressure value obtained by the blood pressure measuring unit and the correction coefficient C determined from the blood vessel diameter obtained by the circulatory dynamics measuring unit.
[0018]
Pm = Pd + (Ps-Pd) / C (Equation 5)
Here, Pd is a diastolic blood pressure value, Ps is a systolic blood pressure value, and C is a correction coefficient obtained from a blood vessel diameter. For example, in the case of the upper arm, C = 3 may be used. Also, C = 2 may be used for the aorta, and C = 4 may be used for the peripheral arteries. When these values are used, they become the same as the average blood pressure value obtained from the center of gravity of the blood pressure waveform.
[0019]
The relationship between the blood vessel diameter and the blood pressure is described in Standard Physiology and the like, and the blood pressure waveform can be estimated by measuring the blood vessel diameter. The average blood pressure value of the estimated blood pressure waveform is obtained by Expression 5. Since the correction coefficient C depends on the blood pressure waveform, the correction coefficient C can be determined by measuring the blood vessel diameter. Therefore, by using Equation 5, the average blood pressure value can be obtained regardless of the site, and the blood rheology can be obtained with high accuracy.
[0020]
As a result, the blood pressure measurement unit and the circulatory dynamic measurement unit are not limited, and the health condition can be accurately evaluated regardless of the measurement site.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
The basic configuration of the circulatory dynamics measuring device of the present invention includes a means (circulation sensor) for non-invasively detecting circulatory dynamics in a living body by transmitting and receiving a wave from a skin surface, and a means for detecting blood pressure at a measurement site (blood pressure measurement). Part).
[0022]
The circulatory sensor detects biological information such as blood flow velocity, blood flow, blood vessel diameter, and blood vessel thickness by transmitting and receiving waves from the skin surface. The change in blood flow velocity is detected by measuring the amount of Doppler shift caused by the Doppler effect, and the blood vessel diameter is detected by measuring the delay in the time of reflection and return to the blood vessel. It is to be noted that an ultrasonic wave is generally used as a wave used for blood flow velocity detection, but another wave such as a laser may be used.
[0023]
In addition, by arranging a circulation sensor in the blood pressure measurement unit, the influence of blood pressure is accurately corrected. Further, the average blood pressure value used for correcting the blood pressure is obtained using Expression 5.
[0024]
Next, the measurement principle of the circulatory dynamics measuring device of the present invention will be described. The circulatory dynamics measurement method obtains the circulatory dynamics from the form of a temporal change of a circulating component that appears during a pulse. Specifically, blood rheology is determined as circulatory dynamics. FIG. 1 shows a graph of a temporal change with the pulsation of the blood flow velocity. As a characteristic component of blood rheology, there is a maximum blood flow velocity Vx corrected by the average blood pressure value, and there is a correlation between blood rheology and the maximum blood flow velocity Vx.
[0025]
Hereinafter, a circulatory dynamics measuring device according to an embodiment of the present invention will be described with reference to the accompanying drawings.
[0026]
【Example】
FIG. 2 is a diagram showing the appearance of the living body 2 and the pressure measuring unit 4. Examples of the part of the living body 2 include relatively easily exposed places such as a neck, an upper arm, a wrist, and a fingertip.
[0027]
FIG. 3 is an example showing the living body 2, the circulation sensor 1, the pressure measuring unit 4, and the blood vessel 21 in the living body of the circulatory dynamics measuring device. The circulation sensor 1 is installed so that the transmitting / receiving unit faces the living body, and is arranged so as to be in contact with the surface of the living body. In this embodiment, transmission and reception are performed using ultrasonic waves. By arranging the circulation sensor 1 in the pressure measurement unit 4, the blood pressure value of the blood flow measurement unit can be measured. As long as the microphone 42 and the circulation sensor 1 are at positions where the blood vessel 21 to be measured can be observed, there is no particular relationship with the direction of blood flow.
That is, the microphone 42 may be provided in the direction in which the blood flow flows (closer to the heart), or the circulation sensor 1 may be provided. There is no causal relationship between the order of the microphone 42 and the circulation sensor 1 and the measurement result.
[0028]
Although the circulation sensor 1 shown in FIG. 3 is an example in which the transmitting piezoelectric element 11 and the receiving piezoelectric element 12 are fixed in the resin 13, the circulation sensor 1 shown in FIG. In the circulation sensor 1 shown in FIG. 4, a transmitting piezoelectric element 11 and a receiving piezoelectric element 12 are fixed on a substrate 14 that attenuates the propagation of ultrasonic waves with a conductive adhesive 15. As a substrate to be used, for example, a glass epoxy substrate is used. The piezoelectric element can be arranged with higher accuracy than the method of fixing the piezoelectric element in the resin, the noise can be suppressed by using the substrate where the ultrasonic wave is attenuated, and the circulation sensor 1 having a high SN ratio can be manufactured. The transmitting piezoelectric element 11 and the receiving piezoelectric element 12 are connected to a pattern (not shown) on the substrate 14 by a wire bond 16 so that the transmitting piezoelectric element 11 and the receiving piezoelectric element 12 can be driven. The transmitting piezoelectric element 11 and the receiving piezoelectric element 12 are coated with a resin 17. The resin 13 protects the transmitting piezoelectric element 11 and the receiving piezoelectric element 12, and achieves acoustic matching with the living body, thereby efficiently transmitting and receiving ultrasonic waves to and from the living body. The resin 13 may have a multi-layer structure. If a soft resin that eliminates an air layer caused by wrinkles of the living body or skin phosphorus is used for a layer in contact with the living body, ultrasonic waves are not attenuated by the air layer and transmission and reception can be performed efficiently.
[0029]
FIG. 5 is a block diagram showing the internal configuration of the signal processing unit 3 of the circulatory dynamics measuring apparatus according to the embodiment and the connection state of the signal processing unit 3, the circulation sensor 1, and the pressure measuring unit 4. As illustrated, the signal processing unit 3 is schematically configured by a driving unit 31, a receiving unit 32, a signal calculating unit 33, an output unit 34, and a pressure signal receiving unit 35.
[0030]
The drive unit 31 of the embodiment oscillates the transmitting piezoelectric element 11 installed in the circulation sensor 1 and transmits a driving voltage for causing ultrasonic waves to enter the blood vessel 21. The receiving unit 32 receives a voltage generated when the receiving piezoelectric element 12 installed in the circulation sensor 1 receives an ultrasonic wave. The blood pressure value measured by the pressure measuring unit 4 is converted into a voltage, and the signal is received by the pressure signal receiving unit 35. The pressure measurement unit 4 includes a compression band 41, a pressure operation unit (not shown), and a microphone 42. The pressure of the compression band 41 is adjusted by the pressure operation unit. The pressure operation unit measures the pressure value of the compression band 41.
When the pressure of the compression band 41 is equal to or higher than the systolic blood pressure value of the living body 2, the blood flow in the blood vessel 21 stops, and the sound from the blood vessel disappears. Further, even if the pressure of the compression band 41 is set to be equal to or lower than the minimum blood pressure value of the living body 2, the sound from the blood vessel disappears. This sound is detected by the microphone 42, and the pressure signal receiving unit 35 sends the data of the systolic blood pressure value and the diastolic blood pressure value to the signal calculation unit 33.
[0031]
The pressure measuring section 4 may be as shown in FIG. The pressure measurement unit 4 in FIG. 6 includes a compression band 41, a pressure operation unit (not shown), and a vibration sensor 43. The pressure of the compression band 41 is adjusted by the pressure operation unit. The pressure operation unit measures the pressure value of the compression band 41. When the pressure of the compression band 41 is equal to or higher than the systolic blood pressure value of the living body 2, the blood flow in the blood vessel 21 stops. Thereafter, when the pressure of the compression band 41 is reduced, the vibration increases with the blood flow, and when the pressure is further lowered, the vibration suddenly decreases. The vibration is detected by the vibration sensor 46, and the pressure signal receiving unit 35 transmits a signal to the signal calculation unit 33 with the pressure at which the vibration increases as the systolic blood pressure value and the pressure at which the vibration decreases as the minimum blood pressure value. With the structure as shown in FIG. 6, the vibration sensor 43 is connected to the compression band 41 by a pipe as shown, and if vibration is transmitted, there is no need to be near the compression band 41 and the structure can be simplified. There are advantages.
[0032]
Further, the pressure measuring section 4 may be as shown in FIG. The pressure measurement unit 4 in FIG. 7 includes a compression band 41, a pressure operation unit (not shown), and a pressure sensor 44. The pressure of the compression band 41 is adjusted to be equal to or lower than the systolic blood pressure value of the living body by the pressure operation unit. The compression band 41 can compress the living body 2 flat, and the pressure sensor 44 disposed on the blood vessel 21 detects a pressure corresponding to the pulsation of the blood vessel 21, that is, a pulse pressure. According to this method, a pressure waveform for each heartbeat can be obtained while non-invasive. The pressure signal receiving unit 35 transmits a pressure waveform signal to the signal calculation unit 33.
[0033]
The signal calculation unit 33 executes various processes related to the measurement of circulatory dynamics by executing a processing program stored in a storage area (not shown) provided therein, and outputs the processing results to the output unit 34. . The signal calculation unit 33 calculates the Doppler effect due to the blood flow by comparing the frequency of the ultrasonic wave emitted from the receiving piezoelectric element 12 with the frequency of the received ultrasonic wave. Then, the speed of the blood flow flowing through the blood vessel 21 is calculated from the change in the frequency, and the time change of the speed is obtained. In addition, in the signal calculation unit 33, the blood pressure in the living body changes due to the tension or the like, and the blood flow speed changes. Therefore, the time change of the speed is determined by using the signal obtained from the pressure measurement unit 4. Execute the calculation to be corrected. Therefore, it is possible to correct the effects of tension and the like and the effects of blood pressure due to individual differences, and to obtain accurate blood rheology. For example, if the blood flow rate is different due to the difference in blood pressure value while having the same blood rheology, the blood rheology will be different from the calculation of the blood rheology only from the blood flow rate. This can be prevented by measuring the blood pressure value. Also, when measuring the blood flow measurement unit and the blood pressure measurement unit at different parts, for example, by performing the blood pressure measurement at the upper arm and performing the blood flow measurement at the fingertip to correct, the blood pressure value of the upper arm and the fingertip is Because they are different, they cannot be accurately reflected in obtaining blood rheology. However, these problems can be solved by using this embodiment. The temporal change of the blood flow velocity that appears during the pulse pulsation has a correlation with the blood rheology, and the blood rheology is obtained as the circulation dynamics from the blood flow velocity change that appears during the pulse pulsation. For example, if the blood flow change is large, it can be said that the blood has a low viscosity.
[0034]
When calculating the average blood pressure value Pm in the signal calculation unit 33, Expression 5 is used.
[0035]
C transmits ultrasonic waves as pulses from the transmitting piezoelectric element 11 of the circulation sensor 1 and measures the time of reception by the receiving piezoelectric element 12, thereby measuring the blood vessel diameter and determining C. C need not be an integer, and Pm is determined using an appropriate C, for example, C = 3.5, according to the blood vessel diameter. By calculating the average blood pressure value as in Expression 5, the average blood pressure value can be calculated by Expression 5 regardless of the measurement site. Using this average blood pressure value, blood flow velocity is corrected to obtain blood rheology.
[0036]
Next, the results of the rheology measuring device using the device of the present invention and the results of evaluating the accuracy will be shown. As reference data, a measurement result of a blood rheology measurement device (MC-FAN) using a microchannel array described in the conventional example was used. The MC-FAN is an apparatus for flowing collected blood through a microchannel array and evaluating blood rheology based on the passage time of blood. FIG. 11 shows measurement data of the whole blood passage time, the maximum blood flow velocity Vx, and the blood pressure values (systolic blood pressure value and diastolic blood pressure value) in the MC-FAN of 10 subjects. The measurement site was the index finger of the left hand. The maximum blood flow velocity Vx was obtained from the Doppler shift amount obtained from the circulation sensor 1.
[0037]
FIG. 8 shows the result when the blood pressure value is not corrected, and FIG. 10 shows the result obtained by this method. Even when the blood flow value was not corrected, there was a correlation between the maximum blood flow velocity Vx and the whole blood passage time, but an abnormal value was recognized. This is due to the effect of individual differences in blood pressure, and such a problem can be eliminated by using this method.
[0038]
In addition, in the case of correction using the average blood pressure value, FIG. 9 shows a result obtained by using the generally known formula 4, and FIG. 10 shows a result obtained by the present method. As a specific method of correction, the correction was obtained by multiplying the maximum blood flow velocity Vx by the reciprocal of the calculated average blood pressure value. In FIG. 10, 2.5 was used as the correction coefficient obtained from the blood vessel diameter.
Comparing the correlation coefficient ^{R 2} in this case, when corrected by equation 4 for ^R 2 = 0.7195, the result of the present method was ^R 2 = .7255. From this, it can be said that it is effective to correct the maximum blood flow velocity Vx with the average blood pressure value obtained by the present method.
[0039]
【The invention's effect】
As described above, according to the present invention, a measuring device for transmitting and receiving a wave from the surface of a living body to the inside to detect circulatory information inside the living body has a function of detecting a circulating state and a function of detecting a blood pressure of the living body. By using the mean blood pressure value calculated using the correction coefficient obtained from the blood vessel diameter, it became possible to obtain highly accurate measurement of circulatory dynamics. In addition, since measurement can be performed without collecting blood, a continuous test can be easily performed, and measurement can be performed at home or the like without being restricted by measurement locations.
[Brief description of the drawings]
FIG. 1 is a graph showing a temporal change of a blood flow velocity measured by a circulatory dynamics measuring apparatus according to the present invention in accordance with a pulse.
FIG. 2 is a diagram illustrating the appearance of a living body and a blood pressure measurement unit according to the present embodiment.
FIG. 3 is a diagram illustrating a relationship between a living body, a circulation sensor, and a blood pressure measurement unit in the example.
FIG. 4 is a diagram illustrating an example of a circulation sensor.
FIG. 5 is a block diagram illustrating an internal configuration of a signal processing unit and a connection state between a circulation sensor and a blood pressure measurement unit according to the embodiment.
FIG. 6 is a diagram illustrating an example of a blood pressure measurement unit.
FIG. 7 is a diagram illustrating an example of a blood pressure measurement unit.
FIG. 8 is a diagram showing the relationship between the maximum blood flow velocity Vx and the whole blood passage time when no correction is made.
FIG. 9 is a diagram showing the relationship between the maximum blood flow velocity Vx and the whole blood passage time when corrected with the average blood pressure value obtained using Expression 4.
FIG. 10 is a diagram showing the relationship between the maximum blood flow velocity Vx and the whole blood passage time when corrected using the present method.
FIG. 11 is a diagram showing a table of measurement data.
FIG. 12 is a diagram showing a relationship between a blood vessel diameter and a pressure waveform.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Circulation sensor 2 Living body 3 Signal processing part 4 Pressure measurement part 11 Piezoelectric element for transmission 12 Piezoelectric element for reception 13 Resin 14 Substrate 15 Conductive adhesive 16 Wire bond 21 Blood vessel 31 Driving part 32 Receiving part 33 Signal calculating part 34 Output part 35 pressure signal receiving section 41 compression band 42 microphone 43 vibration sensor 44 pressure sensor

Claims (5)

A circulatory dynamics measuring device that transmits and receives a wave from the surface of a living body to blood inside the living body and detects the circulating dynamics of blood circulating in the living body. A signal receiving unit for receiving a signal from the circulating sensor, a blood pressure measuring unit for measuring the blood pressure of the living body, a signal calculating unit for executing a processing program related to blood pressure obtained from the blood pressure measuring unit and the circulatory dynamics And an output unit that outputs a result regarding the circulatory dynamics, wherein the circulatory sensor is configured in the blood pressure measurement unit, and the signal operation unit, a value correlated with a blood flow velocity flowing through a blood vessel in the living body, A blood flow rheology is obtained by using a blood pressure value obtained from the blood pressure measurement unit and an average blood pressure value calculated using a correction coefficient. 2. The circulatory dynamics measuring device according to claim 1, wherein the signal calculation unit obtains the correction coefficient using a blood vessel diameter of the blood vessel measured by the circulation sensor when obtaining the blood flow velocity, and calculates the correction coefficient using the correction coefficient. A blood flow rheology is obtained by using a calculated average blood pressure value and a value correlated with a blood flow velocity flowing through a blood vessel in the living body. 3. The circulatory dynamic measurement device according to claim 2, wherein the signal calculation unit uses the diastolic blood pressure value and the systolic blood pressure value obtained from the blood pressure value to determine the average blood pressure value as Pm, the diastolic blood pressure value as Pd, and the systolic blood pressure value. Is Ps and the correction coefficient is C, Pm = Pd + (Ps−Pd) / C
A blood flow rheology is obtained by using an average blood pressure value calculated by a formula represented by the following formula and a value correlated with a blood flow velocity flowing through a blood vessel in the living body. 4. The circulatory dynamics measurement apparatus according to claim 1, wherein the signal calculation unit obtains blood rheology by multiplying a value correlated with the blood flow velocity by a reciprocal of the average blood pressure value. apparatus. The circulatory dynamics measuring device according to claim 1, wherein the circulating sensor is provided inside the blood pressure measuring unit.

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