Shouhei Koyama

Basic experiment of blood-pressure measurement which uses FBG sensors

Needs for vital sign measurement systems have been increasing. Non-invasive and non-restraining systems are required that it can monitor health status over a prolonged period. In this study, we use FGB (Fiber Bragg Grating) sensors. We have devoted significant efforts in developing a vital sign measurement system that can address the above-described problems. Using an FBG sensor, we acquired waveforms of strains from the body surfaces. These waveforms are pulse waves caused by the expansions and contractions of arteries. Systolic blood pressure value was calculated from a waveform of the time difference between the two places. We have confirmed the validity of the principle of systolic blood pressure measurement by FBG sensors.

Influence of Individual Differences on the Calculation Method for FBG-Type Blood Pressure Sensors

In this paper, we propose a blood pressure calculation and associated measurement method that by using a fiber Bragg grating (FBG) sensor. There are several points at which the pulse can be measured on the surface of the human body, and when a FBG sensor located at any of these points, the pulse wave signal can be measured. The measured waveform is similar to the acceleration pulse wave. The pulse wave signal changes depending on several factors, including whether or not the individual is healthy and/or elderly. The measured pulse wave signal can be used to calculate the blood pressure using a calibration curve, which is constructed by a partial least squares (PLS) regression analysis using a reference blood pressure and the pulse wave signal. In this paper, we focus on the influence of individual differences from calculated blood pressure based on each calibration curve. In our study, the calculated blood pressure from both the individual and overall calibration curves were compared, and our results show that the calculated blood pressure based on the overall calibration curve had a lower measurement accuracy than that based on an individual calibration curve. We also found that the influence of the individual differences on the calculated blood pressure when using the FBG sensor method were very low. Therefore, the FBG sensor method that we developed for measuring the blood pressure was found to be suitable for use by many people.

Influence on Calculated Blood Pressure of Measurement Posture for the Development of Wearable Vital Sign Sensors

We studied a wearable blood pressure sensor using a fiber Bragg grating (FBG) sensor, which is a highly accurate strain sensor. This sensor is installed at the pulsation point of the human body to measure the pulse wave signal. A calibration curve is built that calculates the blood pressure by multivariate analysis using the pulse wave signal and a reference blood pressure measurement. However, if the measurement height of the FBG sensor is different from the reference measurement height, an error is included in the reference blood pressure. We verified the accuracy of the blood pressure calculation with respect to the measurement height difference and the posture of the subject. As the difference between the measurement height of the FBG sensor and the reference blood pressure measurement increased, the accuracy of the blood pressure calculation decreased. When the measurement height was identical and only posture was changed, good accuracy was achieved. In addition, when calibration curves were built using data measured in multiple postures, the blood pressure of each posture could be calculated from a single calibration curve. This will allow miniaturization of the necessary electronics of the sensor system, which is important for a wearable sensor.

Measurement of purity index in textile based on IR spectroscopy

This paper describes the measurement of purity index of textile. The measuring system used in this study was Fourier transformed infrared spectroscopy. Two kinds measuring method were tested One was diffuse reflectance method and the other was optical fiber probe method. Human lipid dirt and sweat on sample cotton pieces was used by forehead wiping. After qualitative study of the human dirt by using infrared spectrum, PLS regression calibration was carried out to measure the content of the dirt elements. This paper also describes the parameters of the optimum PLS calibration model.

Cleanliness evaluation method using spectroscopic analysis for medical instruments that are rapidly measured and not rewashed

In order to reuse medical instruments, evaluation of cleanliness after washing is necessary. This cleanliness evaluation method is required to quickly and objectively evaluate the presence or absence of dirt. In this study, a new cleanliness evaluation method for medical instruments is proposed. Absorption spectra of medical instruments were measured using near-infrared spectroscopy, and the presence or absence of dirt was analyzed from the spectra obtained by the Soft Independent Modeling of Class Analogy method. Cleanliness evaluation using absorption spectra measured from various medical instruments could not classify the presence or absence of dirt. On the other hand, cleanliness evaluation using absorption spectra measured from only one type of medical instrument could classify the presence or absence of dirt with high accuracy. Further, the advantages and problems associated with this evaluation method are described.

Research for wearable multiple vital sign sensor using fiber Bragg Grating — Verification of several pulsate points in human body surface

The concern for human welfare has produced great demands for a rapid and continuous sensing system for vital signs in humans. In particular, wearable systems are required because they can monitor health status over a prolonged period. We have used a Fiber Bragg Grating (FBG) sensor to develop a wearable multiple vital sign sensor. The FBG sensor is installed at the pulsate points in a human body surface. The FBG sensor can measure human pulse waves. In this paper, the measurement result at several pulsate points on a human body surface is presented. The measurement pulsate points are the temple, finger, ankle, and dorsum pedis. The pulse wave signal can be measured by an FBG sensor. The pulse rate and blood pressure (BP) are calculated using these measured signals. The pulse rate can be measured using the interval of measured pulse waves. The calculated BP value is different from the reference BP value due to the difference between the waveform of the measured signal at each pulsate points and the measurement method of the reference BP value. If attention is given to these factors, the vital signs measured at each pulsate points can be obtained.

Verification of Non-Invasive Blood Glucose Measurement Method Based on Pulse Wave Signal Detected by FBG Sensor System

This paper describes and verifies a non-invasive blood glucose measurement method using a fiber Bragg grating (FBG) sensor system. The FBG sensor is installed on the radial artery, and the strain (pulse wave) that is propagated from the heartbeat is measured. The measured pulse wave signal was used as a collection of feature vectors for multivariate analysis aiming to determine the blood glucose level. The time axis of the pulse wave signal was normalized by two signal processing methods: the shortest-time-cut process and 1-s-normalization process. The measurement accuracy of the calculated blood glucose level was compared with the accuracy of these signal processing methods. It was impossible to calculate a blood glucose level exceeding 200 mg/dL in the calibration curve that was constructed by the shortest-time-cut process. In the 1-s-normalization process, the measurement accuracy of the blood glucose level was improved, and a blood glucose level exceeding 200 mg/dL could be calculated. By verifying the loading vector of each calibration curve to calculate the blood glucose level with a high measurement accuracy, we found the gradient of the peak of the pulse wave at the acceleration plethysmogram greatly affected.