JP4830097B2 - Blood vessel state measuring device, control program, recording medium - Google Patents

Description

  The present invention relates to a blood vessel state measuring device for measuring a mechanical impedance (rigidity, viscosity) of a blood vessel, which is an index indicating a blood vessel lesion such as arteriosclerosis, and each means in the blood vessel state measuring device using a computer. The present invention relates to a control program described as executable and a recording medium on which the control program is recorded so as to be readable by a computer.

  Heart disease and cerebrovascular disease account for the second and third most common causes of death among Japanese nationals in the 2003 death rate by the Ministry of Health, Labor and Welfare. I understand that. It is said that the blood vessels of the arterial wall deteriorate in quality as the collagen in the arterial wall deteriorates and hardens with age and elastic fibers decrease.

  On the other hand, in recent years, factors that reduce the quality of blood vessels other than the normal aging process are increasing. Specifically, diabetes, hypertension, westernization of food, lack of exercise, smoking, and stress also affect blood circulation to tissues and organs due to increases in risk factors such as angiotensin and low density lipoprotein (LDL) cholesterol. Disability has been reported to occur.

  These blood vessel diseases are said to increase more and more. For early detection of diseases related to blood vessels such as the degree of progression of arteriosclerosis, it is necessary to quantitatively evaluate the vascular state, for example, mechanical properties such as the hardness and softness of blood vessels.

Therefore, various analyzes have been performed for the above evaluation. Non-Patent Document 1 proposes a method that uses photoplethysmogram to model the mechanical characteristics of a blood vessel wall using inertia, viscosity, and rigidity of mechanical impedance, and estimates the blood vessel state for each beat. ing. The photoplethysmogram can provide data for measuring a blood vessel state by irradiating a target site with light and detecting the transmitted light of the light.
Akira Sakane, Toshio Tsuji, Yoshiyuki Tanaka, Noboru Saeki, Masashi Kawamoto: Blood vessel state monitoring using plethysmogram, Journal of Measurement and Control Society, Vol.40, No12, pp.1236-1242, (2004)

  However, the photoplethysmogram, which is one of the biological signals used for impedance estimation, is limited to the peripheral part where the thickness of the measurement site is thin because it uses transmitted light. However, there is a problem that the above measurement cannot be performed at a site where an artery with a large blood vessel diameter exists.

  The present invention has been made in view of the above problems, and its purpose is to measure the movement of a blood vessel (change in the diameter of the blood vessel) using a strain gauge plethysmogram that is not limited to the measurement site, and An object of the present invention is to provide an apparatus for measuring the hardness and softness of blood vessels from the correspondence with blood pressure values.

  In order to solve the above problems, the blood vessel state measuring apparatus according to the present invention measures an electrocardiogram output means for measuring and outputting an electrocardiogram of a subject, and changes in the outer peripheral length of a portion including the artery in the subject. The blood pressure value detecting means for detecting the blood pressure value in the artery, the electrocardiogram, the change in the peripheral length, and the blood pressure value based on the viscosity and rigidity of the artery. And a state calculating means for calculating at least one of them and measuring the vascular state of the artery.

  According to the above configuration, since the outer circumference length measuring means for measuring the change in the outer circumference length of the part including the artery in the subject, for example, the strain gauge plethysmography, is provided, the blood vessel diameter that causes arteriosclerosis is a problem. Even at a site where a large artery exists, the change in the outer peripheral length of the site can be measured.

  Therefore, since the above configuration can calculate the volume change of the blood vessel from the measurement result of the change in the outer peripheral length, at least one of the viscosity and the rigidity is calculated by the state calculation unit based on the electrocardiogram, the blood pressure value, and the volume change. Thus, the hardness and softness of the artery can be measured.

  In the vascular state measuring apparatus, it is preferable that the state calculating means measures the vascular state of the artery using an R wave of the electrocardiogram as a trigger.

  According to the above configuration, the R wave of the subject's electrocardiogram, that is, the time when the myocardium is most contracted, is used as a trigger (measurement start point and end point). By measuring the change in the outer peripheral length, the movement of the artery accompanying the contraction and expansion of the myocardium can be measured more accurately.

  In the blood vessel state measuring apparatus, the outer peripheral length measuring means may be strain gauge plethysmography.

  In the vascular state measuring device, it is preferable that the outer peripheral length measuring means measures the change in the outer peripheral length based on the pulsation of the artery.

  According to the above configuration, since the change in the outer peripheral length is measured based on the pulsation of the artery, there is no need to use a measurement method that imposes a burden on the subject such as venous hemostasis. The state can be measured.

  In the vascular state measurement device, the blood pressure value detection means may include a non-invasive arterial pressure measurement unit.

  According to the above configuration, since the blood pressure value is measured noninvasively, there is no need to use a measurement method that imposes a burden on the subject such as puncture of the catheter into the artery. The state can be measured.

In order to solve the above problems, a control program according to the present invention is characterized in that each means in the blood vessel state measuring apparatus described in any of the above is described so as to be executable by a computer.
In order to solve the above problems, a recording medium according to the present invention is characterized in that the control program described above is recorded so as to be readable by a computer.

  As described above, the blood vessel state measuring apparatus according to the present invention measures an electrocardiogram output means for measuring and outputting an electrocardiogram of a subject, and measures a change in the outer peripheral length of a portion including an artery in the subject. Based on the peripheral length measuring means, the blood pressure value detecting means for detecting the blood pressure value in the artery, the electrocardiogram, the change in the peripheral length, and the blood pressure value, at least one of the viscosity and rigidity of the artery is determined. And a state calculation means for calculating and measuring the vascular state of the artery.

  Therefore, the above configuration includes the outer peripheral length measuring means for measuring the change in the outer peripheral length of the portion including the artery, so that even in a region where an artery having a large blood vessel where arteriosclerosis is a problem exists. The hardness and softness of the artery can be measured.

  As a result, the above configuration can measure the hardness and softness of the artery even in a region where an artery having a large blood vessel exists, and thus has an effect of more reliably evaluating a vascular lesion such as arteriosclerosis.

  An embodiment of a blood vessel state measuring apparatus according to the present invention will be described below with reference to FIGS. That is, in the blood vessel state measuring apparatus, as shown in FIG. 1, an electrocardiograph (electrocardiogram output means) 2, a strain gauge plethysmography apparatus (peripheral length measuring means) 3, a sphygmomanometer (blood pressure value detecting means) 4, A computer unit (state calculation means) 5 is also provided. Further, the blood vessel state measuring device may be provided with a display unit 6 such as a liquid crystal display capable of displaying a measurement result calculated by the computer unit 5, an electrocardiogram at the time of measurement, a plethysmogram, and a blood pressure value.

  The electrocardiograph 2 is for measuring and outputting an electrocardiogram (ECG: ElectroCardioGram) indicating the movement of the heart of the subject 1. Examples of the electrocardiograph 2 include BP-306 manufactured by Nippon Chorin Co., Ltd.

  The strain gauge plethysmography apparatus 3 is for measuring a change in the volume of the forearm 1a (PLS: PLethySmogram) by measuring, for example, a change in the outer peripheral length of the forearm (part including the artery) 1a in the subject 1. It is. Examples of the strain gauge plethysmography apparatus 3 include EC5R manufactured by Hokanson.

  The strain gauge plethysmography apparatus 3 includes a string-like strain gauge 3a, an apparatus main body 3b, and a cable 3c that electrically connects the two for the measurement.

  The strain gauge 3a includes a resin tube excellent in elasticity, for example, a silicon rubber tube having a thin film thickness, and a conductive liquid, such as mercury or Ga-In solution, filled in the silicon rubber tube, silicon And electrodes formed at both ends of the rubber tube.

  Therefore, the strain gauge plethysmography apparatus 3 is used by winding the silicon rubber tube around the outer circumference of the forearm 1a including the artery 1b to be measured. The silicon rubber tube is preferably wound along a virtual line where a virtual plane substantially orthogonal to the blood flow direction of the artery 1b to be measured and the outer periphery of the forearm 1a intersect. The term “substantially orthogonal” only needs to be approximately orthogonal, specifically, 80 degrees or more with respect to the blood flow direction, more preferably 85 degrees or more, and 100 degrees or less with respect to the blood flow direction. Desirably, it is 95 degrees or less.

  When the silicon rubber tube is wound and a current is applied by applying a voltage to each electrode in the silicon rubber tube, when the volume change of the artery 1b changes with a change in blood pressure value, the winding portion in the forearm 1a The outer perimeter length changes. When the outer peripheral length changes in this way, the length of the silicon rubber tube wound around the changed outer peripheral also changes. As a result, the distance between the electrodes in the conductive liquid filled in the silicon rubber tube also changes, and the electrical resistance value between the electrodes of the liquid changes. This change in electrical resistance value is detected by the apparatus main body 3b via the cable 3c, and is output to the computer unit 5 as an electrical signal (PLS) indicating a plethysmogram.

  As shown in FIG. 2A, the strain gauge plethysmography apparatus 3 is used in a non-pressurized state with respect to the outer periphery of the forearm 1a including the artery 1b to be measured. However, as shown in FIG. 2B, it can also be used in a pressurized state such as a venous hemostasis method, which is a normal indirect (non-invasive) arterial pressure measurement method. FIG. 3 shows plethysmograms in the non-pressurized state and the pressurized state. In FIG. 3, blood flow accumulates sequentially in the pulsation part 2a corresponding to the pulsation part of the artery 1b in the non-pressurized state and the artery 1b in the pressurized state, and the diameter of the artery 1b increases sequentially. The trend part 2b which shows having shown.

  The blood pressure monitor 4 shown in FIG. 1 is for detecting a blood pressure value (IBP: Invasive Blood Pressure) in the artery 1b of the forearm 1a. An example of the sphygmomanometer 4 is SEN-6102M manufactured by Nihon Kohden Co., Ltd. The sphygmomanometer 4 includes a catheter 4a whose tip is punctured into the artery 1b, a detection unit 4b that collects blood from the catheter 4a and detects a blood pressure by a pressure-electric conversion element such as a piezoelectric element, and a detection unit 4b. And a blood pressure monitor main body 4c for calculating a blood pressure value from an electrical signal from the blood pressure meter.

  The computer unit 5 determines at least one of viscosity and stiffness, which are mechanical characteristics of the artery 1b, based on a change with time of the electrocardiogram, a change with time of the plethysmogram due to a change of the outer circumference length, and a change with time of the blood pressure value. The blood vessel state of the artery 1b can be measured by calculating by modeling described later.

  FIG. 4A shows an example of an electrocardiogram. R in the electrocardiogram indicates the position of the R wave. FIG. 4B shows an example of the blood pressure value corresponding to the change over time of the electrocardiogram. FIG. 4C shows a plethysmogram corresponding to the change in the blood pressure value over time.

  In the blood vessel state measuring device of the present invention, as shown in FIG. 5, in order to reduce unnecessary components such as noise and DC component included in the electrocardiogram, the plethysmogram, and the electrical signal indicating the change over time of the blood pressure value, Each of the electrical signals may be subjected to band pass filter (BPF) processing. Examples of the passband of the ECG bandpass filter include 14 to 28 (Hz). Examples of the pass band of the band pass filter for the plethysmogram and for the blood pressure value include 0.3 to 5.0 (Hz).

  Next, it will be described that the viscosity and stiffness, which are the mechanical characteristics of the artery 1b, can be calculated by modeling the artery 1b into a viscoelastic model based on the electrocardiogram, the change in the outer peripheral length, and the blood pressure value. Hereinafter, for convenience of explanation, first, the modeling, the plethysmogram, and the calculation method of the mechanical characteristic value will be described in order.

(Vessel wall modeling)
As shown in FIG. 6, the human artery 1b is composed of three layers of an intima 11, an intima 12, and an outer membrane 13, and each layer includes a specific constituent factor.

  The outer membrane 13 includes factors affecting arterial stiffness and compliance such as connective tissue, elastin, and collagen, and also includes vascular blood vessels that supply nutrients to the vascular wall of the aorta.

  The intima 11 contains vascular endothelium that produces endothelium-derived vasoactive substances such as nitric oxide (NO) and EDHF (endothelium-derived hyperpolarizing factor).

  The media 12 includes smooth muscle such as elastin and collagen. Here, smooth muscle contracts when stimulated by sympathetic nerves or hormones, and has a function of lowering blood flow.

  Therefore, the artery 1b contracts or relaxes by the action of smooth muscle contained in the media 12. Therefore, in the present embodiment, the artery 1b is modeled as a mechanical impedance (viscoelasticity) model as means for digitizing the degree of contraction or relaxation of the artery 1b.

  FIG. 7 shows an impedance model of the artery 1b. Here, the inertia (M) of the impedance parameter is ignored (M = 0), and the impedance characteristic is determined from the force F (t) that the blood flow acts on the blood vessel wall of the artery 1b and the displacement r (t) of the blood vessel wall. Is expressed as follows. Here, dr (t) ′ represents the first derivative of dr (t).

dF (t) = Bdr (t) ′ + Kdr (t) (1)
Here, the impedance parameters B and K indicate the viscosity and rigidity of the blood vessel wall, respectively, and r (t) ′ is the displacement speed of the blood vessel wall, dF (t) = F (t) −F (t0), dr ( t) = r (t) -r (t0), and t0 is the time at which the R wave of the electrocardiogram is generated. In order to estimate the impedance parameter of the equation (1), it is necessary to measure F (t) and r (t). Here, F (t) is expressed as follows using the arterial blood pressure value.

F (t) = k _f P _b (t) (2)
Here, k _f is a proportionality constant, and P _b (t) is a blood pressure value of the artery 1b. On the other hand, the change of the radius r _l (t) of the forearm 1a as an example of the limb is expressed using the measured value of the strain gauge plethysmogram P _l (t) showing the volume change of the forearm 1a shown in FIG. Try that. The following correspondence can be obtained for the change of the strain gauge plethysmogram value and the radius of the forearm 1a (RJWhitney: The Measurement of Volume Changes in Human Limbs, J. Physiol., Vol. 121, pp. 1-27, 1953.).

P _l (t) = dC (t) / C ^* = 2 dr _l (t) / r _l ^* (3)
Here, C (t) represents the volume per unit length of the forearm 1a. DC (t) = C (t) −C ^* , dr _l (t) = r _l (t) −r _l ^* , where C ^* and r _l ^* are the values of the forearm 1a measured at rest. The volume per unit length and the radius of the forearm 1a. From the above relationships, the blood vessel radius r of the radius r _l (t) and arterial 1b of the forearm 1a (t) is Assuming that _{r (t) = k p r} l (t) -r m,
r (t) = k _p [(r _l ^* / 2) P _l (t) + r _l ^* ] − r _m (4)
It is expressed.

Here k _p is a proportional constant, r _m is the length obtained by removing the artery from the radius of the forearm 1a, was assumed constant. Therefore, the force acting on the blood vessel wall is expressed by the blood pressure value P _b (t) (expression (2)) of the artery 1b, and the strain gauge plethysmogram P _l (t) (expression (4)) indicating the blood vessel radius of the artery 1b. (1) is expressed as follows.

dP _b (t) = B bar · dP _l (t) ′ + K bar dP _l (t) (5)
here,
B bar = (2 / (k _f k _p r _l ^* )) B,
K bar = (2 / (k _f k _p r _l ^* )) K (6)
It is.

Next, the strain gauge plethysmogram P _l (t) shown in FIG. 9 (a) and P _l (t) ′ which is the first derivative of the above P _l (t) shown in FIG. 9 (b). The change over time in the blood pressure value of the evaluation value (Estimated) calculated from the above equation (5) is shown by a broken line in FIG. For comparison, the measured value (Measured) of the blood pressure value over time is shown by a solid line in FIG. From the result of FIG. 9C, the evaluation value and the actual measurement value are in good agreement, indicating the effectiveness of the evaluation value based on modeling.

  Next, another experimental example showing that the mechanical impedance of the artery 1b can be estimated will be described. First, as an experimental method, an electrocardiogram, a blood pressure value, and a strain gauge plethysmogram were simultaneously measured. Each data is stored in a personal computer at a sampling frequency of 1 kHz, blood pressure is measured by inserting the tip of the catheter 4a into the artery 1b of the left elbow, and a strain gauge plethysmogram is measured at the elbow on the same side. did.

  Using such a vascular state measuring apparatus, an attempt was made to estimate the mechanical impedance of the vascular wall of the artery 1b when a vasorelaxant (sodium nitroprusside) was injected into the subject 1. Subject 1 is a healthy male (21 years old), and the stiffness and viscosity are compared when the concentration of vasorelaxant (3 patterns, 0.375 μg / ml, 0.75 μg / ml, 1.5 μg / ml) is changed. It was.

  FIG. 10 shows the calculation results of K bar (rigidity) and B bar (viscosity) as indices indicating the vascular wall impedance of the artery 1b. From the calculation results, it can be seen that the stiffness and viscosity decrease as the amount of vasorelaxant administered increases, so the vascular state measurement device of the present invention quantitatively evaluates the mechanical characteristics of the artery 1b. I understand that I can do it.

  In the above embodiment, the blood pressure value is measured by puncturing the distal end portion of the catheter 4a into the artery 1b. However, the blood pressure value may be measured noninvasively.

  As a non-invasive blood pressure measurement method, venous hemostasis, which is a normal indirect arterial pressure measurement method, is used, for example, to stop blood flow in the vein with a cuff that expands the upper arm of the forearm 1a with air pressure. The method of measuring the pressure of the air pressure from which the blood flow begins to flow by decreasing the air pressure sequentially. In this case, the strain gauge plethysmography device 3 can be used for the point where only the cuff is added and the blood flow begins to flow (see the trend part 2b described above).

  Further, as another method for measuring the non-invasive blood pressure value, there is a method of measuring the blood pressure value of the artery on the downstream side of the artery 1b to be measured, for example, the artery at the fingertip by photoplethysmography.

  Note that each unit of the blood vessel state measurement apparatus described in the above embodiments may be realized by causing the computer to read the control program as a computer-executable control program. Alternatively, it may be recorded. As a result, it is possible to provide a portable recording medium on which the control program is recorded.

  The recording medium may be a program medium such as a memory (not shown) such as a ROM (Read Only Memory), which is not shown because the processing is performed by a microcomputer. Although not provided, a program reading device may be provided as an external storage device, and the program medium may be read by inserting a recording medium therein.

  In any case, the stored program may be configured to be accessed and executed by the microprocessor, or in any case, the program is read and the read program is illustrated in the microcomputer. The program may be downloaded to a non-program storage area and executed. It is assumed that this download program is stored in the main device in advance.

  Here, the program medium is a recording medium configured to be separable from the main body, such as a tape system such as a magnetic tape or a cassette tape, a magnetic disk such as a floppy (registered trademark) disk or a hard disk, or a CD-ROM / MO /. Disk systems for optical disks such as MD / DVD, card systems such as IC cards (including memory cards) / optical cards, mask ROM, EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), flash It may be a medium that carries a fixed program including a semiconductor memory such as a ROM.

  In the present embodiment, the computer unit 5 may be configured to be connectable to a communication network including the Internet, and may be a medium that fluidly carries a control program so as to download the program from the communication network. When the control program is downloaded from the communication network in this way, the download program may be stored in the main device in advance or installed from another recording medium. The recording medium is read by a program reading device provided in the computer unit 5 to execute the above-described processing.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and the embodiments can be obtained by appropriately combining the respective technical means disclosed in the above-described embodiments. The form is also included in the technical scope of the present invention.

  The blood vessel state measuring apparatus, control program, and recording medium of the present invention can be used in the medical field because the blood vessel disease such as arteriosclerosis can be more reliably evaluated.

An outline at the time of using a blood vessel state measuring device of the present invention for a subject is shown, (a) is a lineblock diagram and (b) is an important section enlarged view of the above (a). The forearm at the time of measurement by the blood vessel state measuring device is shown, (a) shows a non-pressurized state on the forearm, and (b) shows a pressurized state on the forearm. It is a plethysmogram which respectively shows the volume change of the said forearm in the time of the non-pressurization state to the forearm (pulsation part), and the time of the pressurization state to the forearm (trend part). It is a graph which shows one measurement result of the above-mentioned blood vessel state measuring device, (a) shows an electrocardiogram, (b) shows a blood pressure value of an artery, and (c) shows a plethysmogram. It is a graph which shows the example which filtered the said one measurement result, (a) is the said electrocardiogram, (b) is the said plethysmogram, (c) shows the blood pressure value of the said artery. It is a partially broken perspective view in a test subject's arterial blood vessel. It is a block diagram which shows modeling of the mechanical impedance (rigidity, viscosity) of the blood vessel of the artery in the said blood vessel state measuring apparatus. It is principal part sectional drawing of the said forearm which shows the change of the test subject's forearm accompanying the diameter change by the said pulsation of the blood vessel. It is a graph which shows the effectiveness of the said modeling, (a) is the plethysmogram by modeling, (b) is the 1st derivative of the said plethysmogram, (c) is the measured value (Measured) of a blood pressure value with a continuous line. The evaluation value (Estimated) of the blood pressure value calculated and evaluated by the plethysmogram and the first derivative of the plethysmogram is indicated by a broken line. It is the graph of the result which showed that the mechanical characteristic of the artery in the said vascular state measuring apparatus can be evaluated quantitatively, changing the dosage of the blood vessel relaxant, (a) is K bar (rigidity), (b) is B bar (viscosity) is shown.

Explanation of symbols

1 Subject 1a Forearm (part including arteries)
1b artery 2 electrocardiograph (electrocardiogram output means)
3 Plethysmography device (peripheral length measuring means)
4 Sphygmomanometer (blood pressure detection means)
5 Computer part (state calculation means)

Claims (6)

An electrocardiogram output means for measuring and outputting the electrocardiogram of the subject;
In the subject, the change in the outer peripheral length due to the temporal change in the blood pressure value of the artery including the artery is measured, and the displacement over time and the displacement speed of the displacement in the blood vessel wall of the artery are measured. An outer peripheral length measuring means for detecting;
Blood pressure value detecting means for detecting the blood pressure value;
A state calculating means for calculating at least one of viscosity and rigidity of the artery based on the electrocardiogram, the displacement and the displacement speed, and the blood pressure value, and measuring the vascular state of the artery ;
The peripheral length measuring means, the blood vessel measuring apparatus according to claim strain gauge plethysmography der Rukoto.   The vascular state measuring apparatus according to claim 1, wherein the state calculating means measures the vascular state of the artery using an R wave of the electrocardiogram as a trigger. The blood vessel state measuring device according to claim 1 or 2 , wherein the outer peripheral length measuring means measures a change in the outer peripheral length based on the pulsation of an artery. The vascular state measuring device according to any one of claims 1 to 3 , wherein the blood pressure value detecting means includes a non-invasive arterial pressure measuring unit. Measure the subject's ECG,
In the subject, the change in the peripheral length due to the change over time of the blood pressure value of the artery including the artery is measured by strain gauge plethysmography,
Detecting a displacement and a displacement speed over time according to the blood pressure value in a blood vessel wall of the artery due to a change in the outer peripheral length;
Detecting the blood pressure value;
And calculating at least one of viscosity and rigidity of the artery based on the electrocardiogram, the displacement and the displacement speed, and the blood pressure value, and measuring the vascular state of the artery. Control program. A recording medium in which the control program according to claim 5 is recorded so as to be readable by a computer.

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