Pulse wave measuring method

Abstract

An object of the present invention is to provide a technique for diagnosing at which site of an aorta an aortic disease such as an aortic aneurysm or an aortic dissection has occurred, by a noninvasive and low-cost method.SOLUTION: The present invention is used in the method of estimating the pulse wave velocity of the aorta from the time difference between the pulse waves of the upper back and the lower back and the distance between the sensors of Japanese Patent Application No. 126583 / 2023, and provides a method of measuring the local PWV of the aorta by using a plurality of or moving the photoelectric pulse wave sensors 31 to 38 along the backbone, and finding the site where an aortic disease such as aortic aneurysm or aortic dissection has occurred from the amount of change.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pulse wave measuring method and a biological information measuring method. [Background technology]

[0002] As society ages, aortic diseases are also on the rise, and it is becoming clear that the incidence rate of not only aortic aneurysms but also aortic dissections is more than 10 cases per 100,000 people per year. In particular, in Japan, the spread of diagnostic imaging devices such as CT scans is progressing, and there are many facilities and opportunities to diagnose aortic diseases. With the development of a medical system, including emergency transport, further improvements in treatment outcomes can be expected.

[0003] To achieve this, it is becoming necessary to move away from the traditional medical system centered on cardiovascular surgery and toward a multidisciplinary medical system that involves not only cardiology, radiology, pathology, and clinical genetics, but also anesthesiology, emergency medicine, general medicine, clinical laboratory technicians, clinical engineers, and nurses.

[0004] However, even though the number of facilities and opportunities for diagnosing aortic diseases such as aortic aneurysms and aortic dissections has increased, imaging diagnostics such as CT and MRI are not used in regular health checkups. Therefore, there is a need for a non-invasive and simple aortic disease testing technique that can be used in health checkups for the purpose of screening to determine whether or not to perform imaging diagnostics. Furthermore, if it were possible to detect the areas where atherosclerosis has developed, which causes aortic aneurysms and aortic dissections, it would be a very effective testing method.

[0005] Aortic pulse wave velocity testing methods such as cfPWV (carotid-femoral PWV: PWV between the carotid artery and the femoral artery) and baPWV (brachial-ankle PWV: PWV between the brachial and ankle) and CAVI (Cardio-Ankle Vascular Index) utilize the basic property of materials that the propagation speed of waves is fast in hard materials and slow in soft materials. Based on the fact that healthy arterial walls are soft and elastic, while arteriosclerotic blood vessel walls are hard and brittle, these methods of testing for arteriosclerosis diagnose that the faster the measured pulse wave velocity, the more advanced the arteriosclerosis, and are considered effective methods for screening for aortic disease because they are minimally or non-invasive.

[0006] However, although these PWV measurement methods and the indices that apply them are all called aortic pulse wave velocity testing methods, they do not measure the pulse wave velocity of the aorta alone, but rather calculate the propagation velocity from the difference in propagation time of pulse waves that travel in different directions from the heart.As a result, in addition to the aorta, which is the elastic artery that is the intended target for evaluation, the measurement also includes muscular arteries such as those in the arms and legs, which are susceptible to the influence of the autonomic nervous system, making them unreliable and not a standard medical device used in health checkups.

[0007] Furthermore, these techniques cannot diagnose at which part of the aorta an aortic disease such as an aortic aneurysm or aortic dissection has occurred. [Prior art documents] [Patent documents]

[0008] For the purpose of measuring or estimating the aortic pulse wave velocity, the following methods have been proposed: (1) a method for measuring the time difference between the cardiac ejection time and the peripheral side (Patent Publication No. 2005-278965, Patent No. 6399852, Patent No. 6541214, Republished 2020 / 071480); (2) a method for separating the pulse wave measured peripherally into an ejection wave and a reflected wave and calculating the aortic PWV from the time difference between them (Patent No. 3495348, Patent No. 5681434, Patent No. 5741087); and (3) a method for using two photoelectric sensors to estimate the aortic pulse wave velocity from the time difference between the pulse waves on the upper and lower back and the distance between the sensors (Patent Application No. 2023-126583).

[0009] On the other hand, there have been no reports in the patent literature of a technology for non-invasively identifying the location of an aortic disease, such as an aortic aneurysm or aortic dissection, using a method other than diagnostic imaging. [Non-patent literature]

[0010] Hirofumi Midorikawa et al. reported in the Journal of the Japanese Society of Hematology 12;11-14, 2003, "A Study of Pulse Wave Velocity Before and After Abdominal Aortic Aneurysm Surgery," in which they reported that the presence or absence of abdominal aortic aneurysm has a significant impact on baPWV values.

[0011] Meanwhile, Shin-ichiro Katsuda et al. reported in AJH2004; 17:181-187, "Characteristic Change in Local Pulse Wave Velocity in Different Segments of the Atherosclerotic Aorta in KHC Rabbits." Although this was an animal experiment using rabbits, they inserted a pressure sensor into the aorta to measure local PWV, and reported that KHC (hereditary hypercholesterolemia) rabbits had a significantly increased PWV in the abdominal aorta compared to normal rabbits, and found that measuring local PWV makes it possible to divide and evaluate the aorta. Summary of the Invention [Problem to be solved by the invention]

[0012] There is no non-invasive, low-cost screening test technology for aortic disease that can be used in medical checkups and that can diagnose which part of the aorta has developed aortic disease such as aortic aneurysm or aortic dissection. [Means for solving the problem]

[0013] According to a report by Hirofumi Midorikawa et al. in the Journal of the Japanese Society of Blood Transplantation, the occurrence of abdominal aortic aneurysms affects the pulse wave velocity of the aorta, and according to a report by Shin-ichiro Katsuda et al. in AJH, it is possible to evaluate the aorta by dividing it into sections by measuring regional PWV.

[0014] The present invention focuses on these two findings and solves the above problems by providing a method for measuring local aortic PWV and detecting the location of aortic disease such as aortic aneurysm or aortic dissection from the amount of change in the PWV measured by using multiple photoplethysmographic sensors along the spine, or by moving the sensors, similar to the method described in Patent Application No. 2023-126583, which estimates the aortic pulse wave velocity from the time difference between the pulse waves in the upper and lower back and the distance between the sensors. [Effects of the Invention]

[0015] According to the present invention, it is now possible to easily measure the aortic pulse wave velocity, which has previously been difficult to measure accurately and non-invasively, and to perform early diagnosis of atherosclerosis of the aorta, particularly the abdominal aorta, where calcification of the vascular wall is believed to occur first in humans. [Brief explanation of the drawings]

[0016] [Figure 1] 1 illustrates an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing an example of a sensor array 30 of the present invention. [Figure 3] FIG. 2 is a diagram showing an example of a sensor array 30 of the present invention. [Figure 4] FIG. 10 is a diagram showing an example of measurement results according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, the mode for carrying out the present invention will be described in detail based on examples. [Example]

[0018] Example 1 of the present invention will be described using Figures 1, 2, and 4. In Example 1, eight photoelectric sensors (PULSE SENSOR EASY TO USE HEART RATE SENSOR) manufactured by WORLD FAMOUS ELECTRONICS LLC were prepared and mounted in holders made by hand using a 3D printer to produce eight photoplethysmographic sensors 31 to 38. These were then fixed at equal intervals of 4 cm to a stretchable urethane adhesive tape, REACTIS #50-STR1, manufactured by Toray Industries, to create the sensor array shown in Figure 2.

[0019] The subject was laid on his stomach, and the uppermost sensor 31 of the sensor array was adhesively fixed 2 cm to the left of the spine at the third intercostal space, and the lowermost sensor 38 was positioned 2 cm to the left of the spine at the tenth intercostal space by pulling the elastic tape of the sensor array 30, and the eight sensors were fixed so as to be positioned between the third intercostal space and the tenth intercostal space. The average inter-sensor distance L was calculated from the amount of stretch of the elastic tape at this time.

[0020] This sensor array 30 was connected to a photoelectric pulse wave control device 120 equipped with an AD converter and a microcomputer, Arduino Uno, via a connection cable 140, which was then connected to a pulse wave display analysis device 130 via a USB cable 141. The time difference between the peaks of pulse waveforms 61 to 68 corresponding to the eight sensors was analyzed, and local PWV analysis was performed by dividing the average inter-sensor distance L by the obtained time difference.

[0021] The pulse wave display and analysis device 130 is composed of a PC and the self-developed PWV analysis software AYA-PMulti, and is capable of synchronously capturing waveform data from eight photoplethysmographic sensors at a sampling frequency of 1 kHz, thereby enabling highly accurate PWV analysis.

[0022] Using this measurement system, we performed a regional PWV analysis on five healthy subjects and five subjects with abdominal aortic aneurysms. The results are shown in Figure 4. The horizontal axis indicates the positions where the sensors were placed, from the third intercostal space to the tenth intercostal space, and the vertical axis indicates the regional PWV obtained.

[0023] Figure 4 shows that the local PWV values ​​between the seventh and eighth intercostal spaces, which correspond to the abdomen, were significantly higher in subjects with abdominal aortic aneurysms than in healthy subjects. [Example]

[0024] The sensor array produced in Example 2 is shown in Figure 3. In Example 1, the photoplethysmographic sensors were connected one-to-one via connection cables 140 to the photoplethysmographic control device 120, but in this example, the sensors are digitized and connected via a bus line, simplifying the wiring as shown in Figure 3.

[0025] Measurements of five healthy subjects using the sensor arrays of Examples 1 and 2 were compared, but no significant difference was observed. [Example]

[0026] In Example 3, instead of using the sensor array 30, two sensors were used, and one sensor was adhesively fixed, for example, at a position 2 cm to the left of the spine in the third intercostal space, and the other sensor was moved along the spine at a position 2 cm to the left of the spine, and the local PWV at each position was measured.

[0027] Similar to Example 2, a comparative experiment was conducted on five healthy subjects, but no significant difference was observed. The position of the fixed sensor was not limited to the third intercostal space, and could be any location.

[0028] <Other Embodiments> The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0029] (1) In the above example, a photoelectric sensor (PULSE SENSOR EASY TO USE HEART RATE SENSOR) manufactured by WORLD FAMOUS ELECTRONICS LLC. and equipped with a green LED was used as the photoelectric pulse wave sensor. However, a photoelectric pulse wave sensor evaluation board BH1792GLC-EVK-001 manufactured by ROHM Co., Ltd., similarly equipped with a green LED, or a photoelectric pulse wave sensor equipped with a red or near-infrared LED used for measuring blood oxygen levels, etc., may also be used.

[0030] (2) In the above example, the pulse wave measurement site was 2 cm to the left of the spine between the third and tenth intercostal spaces. However, it has been found that pulse waves can also be detected by the photoplethysmographic sensor via arterioles at other sites, so the location is not limited to this. [Industrial Applicability]

[0031] According to the present invention, it is now possible to non-invasively, simply, and at low cost diagnose which part of the aorta is suffering from aortic diseases such as aortic aneurysms and aortic dissections, something that could previously only be done using diagnostic imaging. By introducing this technology into health checkups, it will be possible to detect aortic diseases early. [Explanation of symbols]

[0032] 10: Aorta 20: Dorsal / abdominal arterioles 30: Sensor array 31-38: Photoplethysmographic sensor 61-68: Pulse waveforms corresponding to each photoplethysmographic sensor 31-38 120: Photoplethysmography control device 130: Pulse wave display and analysis device 140: Connection cable 141: USB connection cable 170: Elastic adhesive tape with multiple sensors 200: Regional PWV in healthy subjects 300: Regional PWV in subjects with abdominal aortic aneurysms

Claims

1. A method for measuring local pulse wave velocity in which multiple photoplethysmographic sensors are attached to the back along the spine and the time difference between the pulse waves from the sensors is measured to measure the pulse wave velocity of each part of the aorta.

2. A local pulse wave velocity measurement method in which multiple photoelectric pulse wave sensors are attached to the back, the sensors are moved along the spine, the time difference of the pulse waves between the sensors is measured, and the pulse wave velocity of each part of the aorta is divided and measured.

3. 3. The method for measuring local pulse wave velocity according to claim 1 or 2, wherein the photoplethysmographic sensor is placed or moved along the spine.

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