JP4629430B2 - Vascular endothelial function measuring device - Google Patents

Description

  The present invention relates to a vascular endothelial function measuring apparatus that measures an index of vascular endothelial function using a vasodilator response before and after releasing a blood transfusion.

  Vascular endothelial cells regulate the tonus of blood vessels by producing and releasing endothelium-derived relaxation factor (EDRF), which is mainly carbon monoxide (NO), by stimulation such as acetylcholine and mechanical stress (or shear stress). It has become clear. In addition, it has been reported that the secretion reaction of EDRF is reduced in arteriosclerotic blood vessels. This means that endothelium-dependent vasorelaxant responses to stimulation are reduced in arteriosclerotic vessels.

  Therefore, if the degree of this endothelium-dependent vasorelaxation reaction can be measured, it can be used as an index representing the function of vascular endothelial cells, and early lesions of arteriosclerosis can be easily found.

  Conventionally, as a method for non-invasively measuring an endothelium-dependent vascular relaxation reaction, for example, a method using an ultrasonic device as described in Non-Patent Document 1 is known. This is done by placing an ultrasound probe on the body surface along the length direction of the blood vessel to be measured, for example, the brachial artery, and taking cross-sectional images in the length direction of the blood vessel before and after the blood transfusion for a certain time. In this method, the amount of expansion of the blood vessel is obtained from the change in the cross-sectional image.

“How to Diagnose Pulses-Clinical Application of New Pulse Waves”, edited by Clinical Arterial Society, published by Medical View Co., Ltd., April 10, 2003, pp. 102-105 JP 2003-245280 A

  However, for example, the vascular diameter of the brachial artery is about 5 mm, so that the vascular diameter is not so large, and the rate of increase in vascular diameter due to the endothelium-dependent vascular relaxation reaction is at most about 10% even in healthy individuals. It becomes even smaller in arteriosclerotic blood vessels. In order to accurately measure such a minute change, it is necessary to keep the ultrasonic probe in a position where the maximum diameter of the blood vessel is measured during the measurement.

  FIG. 10 is a diagram for explaining the influence of the positional relationship between the measurement target blood vessel and the ultrasonic probe on the measurement result. FIG. 10 shows a cross section of the blood vessel 10 to be measured in a direction orthogonal to the length direction, and the maximum diameter of the blood vessel 10 is assumed to be d. When an ultrasonic image is taken with respect to such a blood vessel, it is necessary to arrange the ultrasonic probe 11 at the position of the solid line. However, when the ultrasonic probe 11 is displaced in the left-right direction (for example, the position of the dotted line) in the drawing, an ultrasonic image of the blood vessel diameter d ′ (<d) is taken.

  Therefore, if the position of the probe is shifted during measurement, the blood vessel diameter increase rate before and after blood transfusion cannot be obtained with high accuracy. As described above, considering that the blood vessel diameter d is about 5 mm in the brachial artery, it is understood that it is very difficult to maintain the probe at a fixed position during the measurement.

  As a method for suppressing such a displacement of the ultrasonic probe, for example, in Patent Document 1, a proposal has been made to maintain the ultrasonic probe at a predetermined position using a robot arm. However, the mechanism is very large and is not a realistic solution at the present time.

  Even if the problem related to the position of the ultrasound probe is solved to some extent, the cross-sectional image obtained by the ultrasound device is a black and white image including subcutaneous tissue other than the blood vessel to be measured, and it is not always easy to identify the vascular endothelium. . The resolution of the probe is currently about 10 MHz, and the resolution is about 0.2 mm. The increase rate of the blood vessel diameter is about 10% even in a healthy person, and when the vascular endothelial function is reduced due to arteriosclerosis or the like, it may be about 3 to 4%, so the resolution is about 0.2 mm. It is very difficult to accurately measure the blood vessel diameter increase rate from an image captured by the probe.

  As described above, in the measurement of the increase rate of the blood vessel diameter based on the tomographic image of the blood vessel using the conventional ultrasonic probe, there is a variation in accuracy of the probe position and a variation in measuring the blood vessel diameter by identifying the inner wall of the blood vessel from the image. However, it was difficult to obtain stable measurement values.

  The present invention has been made in view of the above-described problems of the prior art, and it is an object of the present invention to provide a vascular endothelial function measuring apparatus capable of measuring an accurate index of vascular endothelial function by a simpler method.

  That is, the gist of the present invention is that a pressure pulse wave acquisition unit that acquires a pressure pulse wave in a predetermined blood vessel, a volume pulse wave measurement unit that acquires a volume pulse wave in a predetermined blood vessel, and a pressure pulse wave per predetermined time First calculation means for obtaining a ratio of the change amount and the change amount per predetermined time in the same phase as the pressure pulse wave of the volume pulse wave in a time series, and the cube of the maximum value of the ratio of the change amount in one heartbeat interval A second calculating means for obtaining a root; a cube root of a maximum value obtained at rest; and a cube root of a maximum value obtained over a predetermined time after a predetermined blood vessel is driven for a predetermined time and released. And a vascular dilation degree calculating means for obtaining a ratio of each of them as a vascular dilation degree.

  According to the present invention, with such a configuration, the non-invasive and easy-to-measure biological information such as the pressure pulse wave and the volume pulse wave is used, so that the vasodilation resulting from the endothelium-dependent vasorelaxation reaction can be simplified. It is possible to measure stably by a simple method.

■ (First embodiment)
Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the accompanying drawings.
In the vascular endothelial function measuring device according to the present embodiment, the blood vessel radius is proportional to the cube root of the blood vessel compliance, and the blood vessel compliance is obtained by measuring the pressure pulse wave and the volume pulse wave. A change rate (increase rate) of the blood vessel diameter is calculated based on the compliance obtained from the measurement of the volume pulse wave, and is measured as an index of the vascular endothelial function.

Before describing specific devices, the principle of the invention will be described.
The compliance C representing the flexibility of the blood vessel is a distributed constant line in the electric circuit theory, where the blood vessel (lumen) radius is R ₀ , σ ² is the Poisson's ratio of the blood vessel, and E is h. Modeling with the idea of
C = 2πR ₀ ³ (1-σ ² ) / Eh [ml / mmHg] (1)
(For example, Yoshiaki Masuda and Hiroshi Kanai, “Basic and Clinical Arterial Pulse Waves”, Kyoritsu Shuppan Co., Ltd., published on March 31, 2000, Volume 2, Chapter 3, “Modeling of the Cardiovascular System” "reference). That is, it can be seen that the blood vessel radius (hereinafter simply referred to as the blood vessel diameter) is proportional to the third root of compliance.

On the other hand, the blood vessel compliance C can also be expressed as a volume change ΔV with respect to the pressure change ΔP. That is,
C = ΔV / ΔP (2)
It is.

  The pressure change ΔP can be obtained from the pressure change (representing value) in a predetermined time unit in the pressure pulse wave. Similarly, the volume change ΔV can be obtained from the volume change (representing value) in a predetermined unit time in the volume pulse wave. Therefore, the pressure pulse wave and volume pulse wave for one heartbeat are divided into predetermined time units, and the maximum value max (ΔV / ΔP) of the change amount ratio ΔV / ΔP in each time unit is obtained, so that one heartbeat period is obtained. Blood vessel compliance C can be determined.

  Then, the third root of the compliance obtained in the same manner at rest before or after applying stimulation to blood vessels to be measured, administration of drugs acting on vascular endothelial cells, ingestion, exercise, etc., as a reference value ( Control) and the ratio of the 3rd root of the compliance measured sequentially from the time when the stimulation is stopped (released if it is a tourniquet) or when the stimulation is started, the blood vessel diameter increases The rate (degree of vasodilation) can be calculated. In the present invention, the increase rate of the blood vessel diameter is obtained as an index of the vascular endothelial function.

  When trying to obtain the actual value (mm) of the blood vessel diameter from the blood vessel compliance, it is necessary to measure the actual value (mmHg, ml) for the pressure change and the volume change, and invasive measurement is required. However, in the present invention, since the blood vessel diameter is proportional to the cube root of the blood vessel compliance, the ratio of the cube root (anonymous number) is determined, so that it is not necessary to measure the actual value and is non-invasive. It is possible to use a value (mV or the like) representing a change in blood pressure or volume measured by a general method.

■ (Configuration of vascular endothelial function measuring device)
FIG. 1 is a block diagram illustrating a configuration example of a vascular endothelial function measuring device according to an embodiment of the present invention. In this embodiment, the volume pulse wave is measured by the impedance method, and the pressure pulse wave is measured by the pressure pulse wave sensor. However, the volume pulse wave is measured by using infrared transmission or reflection, or by using a cuff or an airbag. There are no particular restrictions on the measurement method of volume pulse wave or pressure pulse wave, such as measurement of pressure pulse wave or volume pulse wave (or both).

  In the figure, reference numeral 10 denotes an arithmetic control unit that controls the overall control of the vascular endothelial function measuring apparatus according to the present embodiment, and includes a CPU, a ROM, a RAM, and the like (not shown). For example, the CPU executes a program stored in the ROM. The control of the entire apparatus including the measurement process described later is executed.

  The arithmetic control unit 10 stimulates the blood vessel by driving the blood vessel to be measured for a predetermined time using the blood driving control unit 20. Then, the volume pulse wave is detected from the bioelectrical impedance value measured by the impedance converter 50 and the pressure pulse wave is detected from the pressure signal output from the pressure pulse wave sensor 30 for a predetermined time from the rest and at the time of releasing the blood pressure, respectively. Based on the principle, a blood vessel diameter increase rate as an index of vascular endothelial function is calculated. The arithmetic control unit 10 also includes a display unit 70 that can be configured from an LCD, a CRT, etc., a recording unit 75 such as a printer, a storage unit 80 that can be configured from a mass storage device such as an HDD, and an audio generation unit 85 such as a speaker. It is connected. The arithmetic control unit 10 can control these units. An operation unit 90 having, for example, a keyboard and a mouse is provided as a user interface for performing settings, inputs, and the like with respect to the arithmetic control unit 10.

The blood pressure control unit 20 performs pressurization and measurement control of the blood pressure cuff 22 to add and release a stimulus to the blood vessel to be measured.
The blood pressure control unit 20 includes a pressure sensor that detects the cuff internal pressure, a pressure pump that pressurizes the rubber sac 22a of the cuff 22, a constant speed exhaust valve that reduces the cuff internal pressure at a constant speed, for example, to measure blood pressure, It includes a quick exhaust valve for rapidly reducing the cuff internal pressure, such as in the case of canceling blood pressure. Since these configurations are known in blood pressure measurement devices and the like, detailed description thereof is omitted.

  The constant current supply unit 40 can supply a constant current of a predetermined frequency (for example, about 50 KHz, several hundreds μA) between the constant current electrodes 41 and 42, and has, for example, an oscillation circuit that oscillates a signal of about 50 KHz and a constant current source. is doing. A pair of voltage electrodes 51a and 51b are arranged between the constant current electrodes 41 and 42 at a predetermined distance. In the present specification, the pair of voltage electrodes 51 a and 51 b are collectively referred to as a voltage electrode pair 51.

  In the present embodiment, as will be described later, measurement is performed using a volume pulse wave sensor composed of constant current electrodes 41 and 42 and a voltage electrode pair 51 and a pulse wave measurement electrode in which the pressure pulse wave sensor 30 is fixedly arranged. I do. The pressure pulse wave sensor has a configuration in which a circular protrusion for pressing a blood vessel is provided at the center of a thin disk-shaped piezoelectric ceramic whose periphery is supported by a cushioning material such as rubber.

  As the voltage electrode pair 51, for example, an electrode made of a material suitable for measurement, such as an Ag-Agcl electrode, is used, and is directly fixed to the body surface (skin) of the subject. The vascular endothelial function measuring device of this embodiment measures a pulse wave as a bioimpedance waveform.

  The voltage electrode pair 51 is connected to the impedance converter 50. The impedance converter 50 detects the impedance value (biological impedance) between the voltage electrodes 51a and 51b mounted between the constant current electrodes 41 and 42.

  When a minute high-frequency current is passed between the constant current electrodes 41 and 42, the voltage electrode pair 51 detects a voltage proportional to the impedance of the living tissue existing between both electrodes. Since blood has an extremely high electrical conductivity compared to other living tissues, impedance detected by the voltage electrode pair 51 is mainly blood that is pumped from the heart, particularly in a portion where there is no other organ such as the upper arm or the lower limb. Is governed by the flow rate. Therefore, by measuring the impedance waveform (voltage waveform) measured by the voltage electrode pair 51, it is possible to obtain a change in the blood flow volume flowing through the part. Since the change in blood flow corresponds to a volume pulse wave that changes in response to the pulse of the heart, the volume pulse wave can be measured by measuring an impedance waveform that indicates a change in blood flow.

  The bioimpedance waveform output from the impedance conversion unit 50 is input to the calculation control unit 10. The arithmetic control unit 10 can store the obtained bioimpedance waveform in the recording unit 75 and display it on the display unit 70.

  On the other hand, the pressure pulse wave sensor 30 is composed of, for example, a piezoelectric body and is held in a state where the blood vessel is slightly pressed from the body surface. And the blood pressure change which changes with pulsations is detected on the body surface. This pressure change corresponds to a pressure pulse wave.

  70 is a display unit capable of displaying various operation guidance, measurement results, diagnostic indicators, etc. 75 is a recording unit capable of recording and outputting measurement results, diagnostic indicators, etc. 80 is a storage for storing and saving measurement results, diagnostic indicators, etc. And an external storage device using an optical / magnetic recording medium or a semiconductor memory. Reference numeral 85 denotes a voice generation unit capable of outputting guidance output by voice and various notification sounds.

■ (Electrode arrangement)
FIG. 2 is a diagram showing the arrangement of the pressure pulse wave sensor 30, the constant current electrodes 41 and 42, and the voltage electrode pair 51 in the present embodiment.
As can be seen from FIG. 2, in the present embodiment, each electrode is disposed on a straight line that is substantially orthogonal to the direction of travel of the blood vessel (artery) that measures the pulse wave. The electrodes 41, 42 and 51 for measuring the volume pulse wave are arranged to face each other with a blood vessel (artery) for measuring the pulse wave interposed therebetween, and the pressure pulse wave sensor 30 is arranged immediately above the artery.

Thus, by arranging the electrodes so as to be located across the artery, there are the following advantages.
1) When the electrodes are arranged apart from each other in the blood vessel running direction, the averaged pulse wave is measured according to the distance between the voltage electrodes, whereas the observed blood vessel length is shortened, so that it is sharp. An impedance waveform can be obtained.
2) Since the blood vessel length to be observed is short, the local pulse wave of the artery can be measured.
3) Since it is not necessary to dispose the electrodes separately in the direction of blood vessel travel, measurement can be performed in a narrow range, and the influence on other parts of the subject is extremely small.
4) Since the pulse wave can be measured as long as the measurement site has an arterial direction, the measurement site can be easily determined.
5) A pulse wave can be measured by selecting a specific artery at a site where a plurality of arteries exist (for example, an ankle).
6) The pressure pulse wave and the volume pulse wave can be measured at the same position of the same blood vessel, and there is no need to consider the time lag between the measured pulse waves.

  The position where the electrode is mounted is not particularly limited, but is preferably a site where the living tissue structure is simple. For example, it is preferable to wear it on the limbs, neck, fingers and the like.

■ (Configuration of electrode for pulse wave measurement)
In order to easily realize the electrode arrangement shown in FIG. 2, in this embodiment, a pulse wave measurement electrode in which the pressure pulse wave sensor 30, the constant current electrodes 41 and 42, and the voltage electrode pair 51 are attached at predetermined positions is used. . 3A and 3B are diagrams showing a configuration example of the pulse wave measurement electrode in the present embodiment. FIG. 3A is a plan view seen from the electrode surface, and FIG. 3B is a side view.

  As shown in FIG. 3, the pulse wave measurement electrode 100 includes a support 53 formed of an insulator such as plastic and rubber, a pressure pulse wave sensor 30, constant current electrodes 41 and 42, and a voltage electrode pair 51. Composed. Although not shown in FIG. 3, the support 53 is actually a cable, a connector, or the like for electrically connecting each electrode and sensor to the constant current supply unit 40, the impedance conversion unit 50, and the calculation control unit 10. It extends from the outside.

  The support 53 is arranged so that all of the pressure pulse wave sensor 30, the constant current electrodes 41 and 42, and the voltage electrode pair 51 are brought into contact with the subject body surface in a positional relationship as shown in FIG. The surface on which the constant current electrodes 41 and 42 are disposed is not in the same plane but extends from the surface on which the voltage electrode pair 51 is disposed. It has a shape inclined in the opposite direction. That is, the constant current electrode is so that the constant current flows evenly in the thickness direction of the tissue between the constant current electrodes 41, 42, and the constant current electrodes 41, 42 are sufficiently adhered to the curved body surface such as the extremities. 41 and 42 are provided on the inclined surface in the opposite direction.

  Further, between the voltage electrode pair 51, a pressing portion (projection portion) 52 that protrudes slightly from the surface on which the voltage electrode pair 51 is disposed is provided, and the pressure pulse wave sensor 30 is disposed at the tip thereof. The pressing unit 52 not only presses and closely contacts the pressure pulse wave sensor 30 to the body surface, but also eliminates venous blood existing between the skin and the arterial blood vessel, gives rigidity to the soft tissue, and impedance waveform due to pulsation of the artery This has the effect of suppressing the distortion.

  Moreover, it is preferable that the press part 52 contacts the mounting part surface (skin) in a plane for the purpose. Further, the size (contact area) is preferably determined so as to suppress the distortion of the impedance waveform.

  As shown in FIG. 4, at the time of measurement, the pressing portion 52 is positioned on the artery 54 to be measured, the pressure pulse wave sensor 30 is disposed immediately above the artery 54, and an appropriate holder is attached to the support portion 53. Use or hold it by hand to lightly press the whole pulse wave measuring electrode 100 against the surface of the body to be measured.

  When fixing the pulse wave measurement electrode 100 at the time of measurement, a method that does not hinder the venous perfusion returning from the periphery to the center at the measurement site is used so as not to affect the pulse waveform or pulse wave velocity. preferable.

  When the size (contact area) of the pressing portion 52 is increased, it is necessary to increase the pressing force at the time of measurement, the biological tissue is generally not uniform, and the advantages of local pulse wave measurement are obtained. It is preferable that the distance between each electrode (51a, 51b) which comprises an electrode pair is the minimum distance required in order to acquire a bioimpedance waveform favorably. Further, the distance between the constant current electrodes 41 and 42 is preferably shorter from the viewpoint of allowing a constant current to flow stably to a portion where the pressing portion 52 is in contact. However, in order to adjust the sensitivity to the depth at which the blood vessel to be measured exists, it is preferable that the distance between the constant current electrodes 41 and 42 be adjustable. A plurality of types of measurement electrodes having different electrode distances may be prepared, and the distance can be adjusted by any means such as making the electrodes movable.

■ (Measurement processing)
Next, measurement processing in the vascular endothelial function measuring apparatus according to the present embodiment will be described using the flowchart shown in FIG. As described above, this measurement process is realized by the CPU executing a program stored in the ROM in the arithmetic control unit 10 and controlling each component of the vascular endothelial function measuring apparatus.

  First, as preparation before measurement, for example, as shown in FIG. 5, the pulse wave measurement electrode 100 is attached to the upper arm portion 200 of the subject and the cuff is attached to the arm. The pulse wave measurement electrode 100 may be fixed to the upper arm by a band (not shown) or the like.

  For example, when an instruction to start measurement is given via the operation unit 90, the volume pulse wave and the pressure pulse wave at rest are measured (step S101). Specifically, first, a predetermined high-frequency constant current is supplied from the constant current supply unit 40 between the constant current electrodes 41 and 42. As described above, the constant current applied to the living body is about 50 KHz and about several hundred μA.

  Then, the acquisition of the pressure pulse wave signal output from the pressure pulse wave sensor 30 and the impedance waveform (volume pulse wave signal) output from the impedance converter 50 is started. The acquired pressure pulse wave and volume pulse wave signal are sampled at a predetermined frequency and converted into digital data, and data for a predetermined time is stored in the storage unit 80, for example.

Next, in step S103, compliance is determined using the pulse wave data stored in the storage unit 80, and the third root is calculated.
Specifically, first, as shown in FIG. 7, changes ΔP and ΔV per predetermined time Δt are sequentially obtained for each of the pressure pulse wave and the volume pulse wave, and the maximum ΔV / ΔP is obtained for each heartbeat interval. Detect value.

Expressed as a formula:
First, the change amount ΔP of the pressure pulse wave P (t) per predetermined time Δt is:
ΔP = P (t + Δt) −P (t),
The amount of change ΔV of the pressure pulse wave V (t) per predetermined time Δt is:
ΔV = V (t + Δt) −V (t),
Therefore, the ratio ΔV / ΔP is
ΔV / ΔP = (V (t + Δt) −V (t>) / (P (t + Δt) −P (t)) (3)
As required.
And what is necessary is just to obtain | require maximum value Max ((DELTA) V / (DELTA) P) for every heartbeat area.

  In this embodiment, since the pressure pulse wave and the volume pulse wave are measured at substantially the same position in the length direction of the blood vessel to be measured, it is assumed that there is no time lag between the pressure pulse wave and the volume pulse wave. be able to. Therefore, if the amount of change is calculated sequentially for the same unit time Δt from the measurement start time and the ratio is obtained, the amount of change per unit time in the same phase of the pressure pulse wave and the volume pulse wave can be calculated. . Further, the division of one heartbeat interval can be performed by a known method such as detection of a feature point of a pulse wave.

When the maximum value max (ΔV / ΔP) of ΔV / ΔP is obtained for each of the predetermined heart beat sections (for example, 10 beats), the average value is obtained and set as the vascular compliance (reference compliance) C ₀ at rest. Then, the third root of the reference compliance C ₀ is calculated as a value D ₀ (reference blood vessel diameter index) representing the resting blood vessel diameter and stored in the storage unit 80.

  Next, in step S105, air is sent to the rubber sac 22a of the cuff 22 using the pressurizing pump of the blood driving control unit 20, and blood driving is started. The blood transfusion is performed by pressing the cuff 22 attachment site with a pressure of the subject's maximum systolic blood pressure + 30 mmHg.

  In step S107, the blood feeding is continued until a predetermined blood feeding time has been detected. In this embodiment, the tourniquet time can be set arbitrarily, but can be set to about 5 minutes, for example. When the tourniquet time elapses, the rapid exhaust valve of the tourniquet control unit 20 is controlled to remove air from the rubber sac 22a of the cuff 22 and release the tourniquet (step S109).

Simultaneously with the release of the blood transfusion, in steps S111 and S113, measurement of the pressure pulse wave and volume pulse wave, compliance, and calculation of the cube root thereof are performed in the same manner as in steps S101 and S103. Further, a ratio (vascular dilation degree) D / D ₀ between the calculated cube root D and the reference blood vessel diameter index D ₀ obtained at rest is obtained as an index of the vascular endothelial function (step S115).

The pulse wave measured in steps S111, S113, and S115 and the calculated value are stored in the storage unit 80.
Steps S111, 113, and 115 are repeatedly executed until the elapse of a predetermined time (for example, 15 minutes) is detected in Step S117 after releasing the blood transfusion. When the predetermined time has elapsed, in step S119, the calculated vascular dilation degree is displayed in a graph, for example.

  FIG. 9 is a diagram schematically showing an example of a graph display. In this example, a two-dimensional graph is shown in which the elapsed time after the release of blood transfusion is plotted on the horizontal axis and the degree of vasodilation is plotted on the vertical axis. For example, standard values corresponding to the sex and age of the subject are shown. A graph may be displayed together with the measured value. It is also possible to color the background according to the value of the degree of vasodilation so that the degree of risk of arteriosclerosis can be grasped. In addition, as an index reflecting how long the dilation of the blood vessel lasted, the area of the section where the vascular dilation degree exceeds 1 (vertical axis, the area surrounded by the waveform and the straight line of the vascular dilation degree = 1) is calculated, The value may be displayed. Here, the display on the display unit 70 is described as an example, but any method for visually outputting can be adopted. For example, it is possible to perform print output by the recording unit 75 such as report output.

  As described above, according to the present embodiment, the degree of endothelium-dependent vasorelaxation, which is a vascular endothelial function, is noninvasively calculated by calculating the degree of vasodilation using the pressure pulse wave and the volume pulse wave. In addition, it can be measured stably by an easy method. Further, by using the pressure pulse wave and the volume pulse wave, it is possible to measure a continuous vasodilation degree for each beat.

■ (Second Embodiment)
The first embodiment has described the case where the pressure pulse wave and the volume pulse wave can be measured at substantially the same position in the direction of blood vessel travel. This embodiment demonstrates the case where a pressure pulse wave and a volume pulse wave are measured in the different position in the strike direction of the same blood vessel.

  When the pressure pulse wave and the volume pulse wave are measured at different positions in the same blood vessel, a time lag occurs in the obtained pulse wave. Therefore, in order to obtain ΔV / ΔP in the same phase section, it is necessary to correct the time shift.

  The present embodiment is characterized in that the time lag between the pressure pulse wave and the volume pulse wave is compensated by obtaining the difference between the characteristic points (for example, rising points) of the respective pulse waves.

  Various methods are known as methods for detecting feature points in a pulse wave, and any of these known methods can be used. For example, the characteristic points (rising points) of the pressure pulse wave and the volume pulse wave are obtained. Then, the pressure pulse wave or the volume pulse wave is corrected by using the time difference d = | fpp−fpv | between the rising point fpp of the pressure pulse wave and the rising point fvv of the volume pulse wave, and the time difference is compensated.

  Then, the corrected pressure pulse wave and volume pulse wave are used to obtain the compliance in the same manner as in the above (1), and thereafter, the vasodilation degree may be obtained in the same manner as in the first embodiment.

  The rising point of the pressure pulse wave and the volume pulse wave can be detected using, for example, the method disclosed by the applicant in Japanese Patent Application Laid-Open No. 2004-33614. This method first detects a minimum value, a maximum value, a difference between the minimum value and the maximum value, and an inflection point existing between the minimum value and the maximum value within a predetermined period of the pulse wave. Then, a straight line that intersects with the pulse wave at a first time that goes back a first predetermined time from the time when the minimum value is detected and that has a slope that is determined from the difference between the minimum value and the maximum value and the second predetermined time is obtained. . In the section from the time when the minimum value is detected to the third time corresponding to the inflection point, the point on the pulse wave farthest from the straight line is set as the rising feature point (for details, see the above publication) See) Of course, it is needless to say that the feature points of the pulse wave may be detected using other methods.

  According to this embodiment, there is a time lag between the measured pulse waves, such as when there is a shift in the measurement position of the pressure pulse wave and the volume pulse wave, or when a delay occurs due to the propagation characteristics of the measurement system. Even if it is a case, the pulse wave which compensated the time gap can be obtained easily. Then, by calculating the degree of vasodilation using the pulse wave that compensates for the time lag, the degree of endothelium-dependent vasorelaxation, which is a vascular endothelial function, can be determined non-invasively and easily, as in the first embodiment. Can be measured stably.

■ (Other embodiments)
In the first and second embodiments described above, the reference compliance C ₀ is measured at the time of rest before the blood pumping. However, the reference compliance C ₀ may be measured at the time of rest after the blood pressure is released.

In this case, in the procedure described with reference to FIG. 6, the reference compliance C ₀ calculation process (steps S101 and S102) is performed after step S117, and the vasodilation calculation process (step S115) is performed after the reference compliance C ₀ calculation process. You just have to do it. Therefore, in the processing loop until the predetermined time has elapsed after canceling the blood transfusion, only the compliance and its cube root are calculated and stored.

  In the above-described embodiment, the case where the volume pulse wave is measured by the impedance method has been described. However, as described above, the measurement method of the pressure pulse wave and the volume pulse wave is an essential matter in the present invention. Instead, it may be measured using any other method.

  For example, as the simplest example, as shown in FIG. 8, a light emitting unit 55 and a light receiving unit 56 are arranged instead of the electrodes 41, 42 and 51 for impedance measurement, and the light is emitted from the light emitting unit 55 toward the blood vessel. By detecting the reflected light of the infrared light by the light receiving unit 56, a known photoelectric volume pulse wave measurement (reflection type) can be realized.

  Further, in the above-described embodiment, only the apparatus for driving blood pressure and the apparatus for measuring the pressure pulse wave and the volume pulse wave have been described, but the resting pulse wave measured by another apparatus and The configuration may be such that the pulse wave after the release of tourniquet is acquired online or offline.

  Further, in the above-described embodiment, the case where blood driving is used as an operation for stimulating vascular endothelial cells has been described. However, various operations and methods for stimulating vascular endothelial cells are known in addition to blood pumping, and these well-known operations and methods can also be used in the present invention. Specifically, (1) a method of stimulating the vascular endothelium by applying exercise load to the subject and increasing the blood flow volume, (2) a drug that affects the vascular endothelial cells (for example, nitroglycerin) The method of administration is roughly divided. The latter includes intake of substances that stimulate the vascular endothelial cells, such as smoking.

  When stimulating vascular endothelial cells by a method other than these methods of driving blood, there is no change in the method for measuring the vascular diameter at rest. In addition, the timing for starting to measure the expansion of the blood vessel diameter can be determined as appropriate. For example, when an exercise load is applied using a bicycle ergometer, the exercise is stopped after applying an exercise load of a predetermined intensity and a predetermined time, and then a pressure pulse wave and a volume pulse wave can be measured at predetermined time intervals. . Alternatively, measurement may be performed every predetermined time after starting to apply exercise load.

In addition, the pressure pulse wave and volume pulse wave can be measured at predetermined time intervals while the drug is continuously administered (that is, increasing), or can be measured at predetermined time intervals even after drug administration is stopped. it can. In addition, prohibit smoking for the time required for measurement at rest, measure the pressure pulse wave and volume pulse wave at rest, then stimulate vascular endothelial cells with nicotine spray or actual smoking, and then prescribed A method of measuring a pressure pulse wave or a volume pulse wave at a time interval can be employed. As described above, the present invention can be applied before and after the application of any method in which the result of stimulation of vascular endothelial cells can be observed as an expansion of the vascular diameter. It is possible to measure the degree of dilation of the blood vessel diameter based on the pressure pulse wave and volume pulse wave measured in the above.
In addition, when a method other than blood driving is applied as a method for stimulating vascular endothelial cells, a configuration for performing blood driving is not necessary.

It is a block diagram which shows the structural example of the vascular endothelial function measuring apparatus concerning embodiment of this invention. It is a figure which shows the example of the electrode arrangement | positioning in 1st Embodiment. It is a figure which shows the example of the electrode structure in 1st Embodiment. It is a figure explaining the electrode mounting state at the time of a measurement. It is a figure explaining the example of the mounting position of a cuff and an electrode. It is a flowchart explaining the measurement process in 1st Embodiment. It is a figure explaining the calculation principle of a compliance. It is a figure which shows the other structural example of the electrode for pulse wave measurement. It is a figure which shows the example of a graph display. It is a figure explaining the position shift and measurement error of an ultrasonic probe.

Claims (5)

Pressure pulse wave acquisition means for acquiring a pressure pulse wave in a predetermined blood vessel;
Volume pulse wave measuring means for acquiring a volume pulse wave in the predetermined blood vessel;
First calculation means for obtaining a ratio of the amount of change per predetermined time of the pressure pulse wave and the amount of change per predetermined time in the same phase as the pressure pulse wave of the volume pulse wave;
A second calculating means for obtaining a cube root of the maximum value of the ratio of the change amount in one heartbeat section;
The ratio of the cube root of the maximum value obtained at rest and each cube root of the maximum value obtained after performing an operation for stimulating the endothelial cells of the predetermined blood vessel is obtained as the degree of vasodilation. An apparatus for measuring vascular endothelial function, comprising: a vasodilation calculating means. Feature point detection means for detecting feature points of the pressure pulse wave and the volume pulse wave;
From the characteristic points of the pressure pulse wave and the volume pulse wave, a time lag detection means for obtaining a time difference between the pressure pulse wave and the volume pulse wave;
Compensation means for compensating for the time lag between the pressure pulse wave and the volume pulse wave using the time difference obtained by the time lag detection means,
2. The vascular endothelial function measurement according to claim 1, wherein the first calculating unit obtains the ratio of the amount of change using the pressure pulse wave and the volume pulse wave in which the compensation unit compensates for the time lag. apparatus.   The vascular endothelial function measuring device according to claim 1 or 2, further comprising an output means for visually outputting a change in the degree of vasodilatation over time.   The vascular endothelial function according to any one of claims 1 to 3, wherein the operation for stimulating the endothelial cells of the blood vessels is any one of blood pumping, drug administration, and exercise load application. measuring device.   2. The operation of applying stimulation to the endothelial cells of the blood vessels is blood driving, and the resting time is before the blood driving or after a predetermined time has elapsed after the release of the blood driving. The vascular endothelial function measuring device according to any one of claims 3 to 3.

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