• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.4 s.316
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• pp.15-20
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• 2007

Recently the prevalence rate of diabetes in Korea has been increasing rapidly due to high growth of economy and changes in dietary lifestyle. Vascular complication is one of diabetic complications which have frequently occurred by obesity, hyperglycemia and impaired glucose metabolism. Photoplethysmogram(PPG) measured from finger and toe is very useful for evaluation of vascular aging and sclerosis level since the PPG signal represents characteristics of peripheral vascular Several researchers have reported that second derivative of the finger PPG waveform was useful to evaluate vascular compliance and developed various analysis methods for vascular compliance. However, peripheral vascular compliance study for diabetic patient was never evaluated by using second derivative of PPG. Therefore, we aimed to objectively compare and to assess normal(n=850) and diabetic(n=50) groups vascular compliance using the second derivative of PPG waveform in this study. The evaluated factors of the second derivative of PPG are 'a', 'b', 'c', 'd', 'e' and b/a rapresents vascular compliance. This study found out that when vascular compliance is decreased, the absolute value of b/a is decreased. The average vascular compliance of 50 diabetic patients with neuropathy, $-1.09{\pm}0.14$ is statistically lower than the normal group, $-0.81{\pm}0.09$ (p<0.05). In conclusion, we suggest an objective evaluation of peripheral vascular compliance for diabetic patients and prevention of vascular complication.

• Journal of Biomedical Engineering Research
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• v.34 no.3
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• pp.105-110
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• 2013

Respiratory signal is one of the important physiological information indicating the status and function of the body. Recent studies have provided the possibility of being able to estimate the respiratory signal by using a change of PWV(pulse width variability), PRV(pulse rate variability) and PAV(pulse amplitude variability) in the PPG (photoplethysmography) signal during daily life. But, it is not clear whether the respiratory monitoring is possible even during sleep. Therefore, in this paper, we estimated the respiration from PWV, PRV and PAV of PPG signals during sleep. In addition, respiration rates of the estimated respiration signal were calculated through a time-frequency analysis, and errors between respiration rates calculated from each parameter and from reference signal were evaluated in terms of 1 sec, 10 sec and 1 min. As a result, it showed the errors in PWV(1s: $36.38{\pm}37.69$ mHz, 10s: $36.53{\pm}38.16$ mHz, 60s: $30.35{\pm}38.72$ mHz), in PRV(1s: $1.45{\pm}1.38$ mHz, 10s: $1.44{\pm}1.37$ mHz, 60s: $0.45{\pm}0.56$ mHz), and in PAV(1s: $1.05{\pm}0.81$ mHz, 10s: $1.05{\pm}0.79$ mHz, 60s: $0.56{\pm}0.93$ mHz). The errors in PRV and PAV are lower than that of PWV. Finally, we concluded that PRV and PAV are more effective than PWV in monitoring the respiration in daily life as well as during sleep.

• Journal of the Korea Convergence Society
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• v.11 no.7
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• pp.35-40
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• 2020

Recently, devices such as smart watches capable of measuring small biosignals have been released. Body composition, blood pressure, heart rate, and oxygen saturation can be easily obtained. However, the part that is not trusted by the user is accuracy. These biosignals are sensitive to the external environment and have large fluctuations depending on the conditions inside the subject's body. Blood pressure measurements, in particular, still give different results, depending on how the conditions in the body are handled. Therefore, in this study, PPG was analyzed to measure PTT at two points of 80% and 100%, the highest in PTT measurement. The effect of the measured value on SBP and DBP was analyzed and a method was proposed to increase the accuracy. As a result of the study, the measured value of PTT at 80% of the peak PPG is more effective in estimating blood pressure of SBP and DBP than the value measured at 100%. In the regression analysis of the rate of change blood pressure estimation, the coefficient of determination of SBP (80%) was 0.6946, and DBP (100%) was 0.547.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.6
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• pp.406-412
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• 2023

In this paper, we studied the effect of noise caused by ambient light on a reflective PPG measurement device using infrared light. Noise caused by ambient light was examined by dividing it into general situations and special situations. In the general situation, noise due to changes in time and ambient light sources was randomly observed, and in the special situation, a halogen lamp was used to observe the effect of noise variations. In the experiment, PPG signals were measured and data acquired in real-time depending on each situation, and the measured data was analyzed in the time domain and frequency domain. First, through a general situation experiments, it was visually observed that noise increases with the brightness of ambient light, and through frequency analysis, it was observed that the noise sources were white noise, power line noise, and internal noise of the circuit. Futhermore, using a halogen lamp, we experimented with the change in noise depending on the change in distance from the ambient light and calculated the SNR. As a result of the experiment, an SNR of 3.2 dB was shown at a distance of 50 cm with an irradiance of 278.3 W/m². It was observed that normal measurement was difficult at SNRs below that, and an irradiance of 27.7 W/m² was obtained. It showed a value of 18.2 dB at a distance of 2 m, and it was observed that normal PPG measurement was possible through a filter at values above that.

• Journal of Biomedical Engineering Research
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• v.32 no.2
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• pp.109-117
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• 2011

Assuming that photons absorbed by a vessel do not have acute variations, DC component reflect the basal blood volume (or diameter) before blood pulsation. Vascular stiffness and reflection is influenced by changes in basal blood volume (or diameter). This paper describes analysis of the characteristic variations of vascular stiffness, according to relative variations in DC components of the PPG signal (25-75%). For quantitative analysis, we have used parameters that were proposed previously, reflection and stiffness index, and the second derivative of PPG waveform, b/a and d/a. Significantly, the vascular stiffness and reflections were increased according to increase in DC component of the PPG signal for more than about 3% of baseline values. The systolic blood pressure were increased from $113.1{\times}13.18$ to $116.2{\times}13.319$ mmHg, about 2.76% (r = 0.991, P < 0.001) and the AC component of the PPG signal were decreased from $2.073{\times}2.287$ to $1.973{\times}2.2038$ arbitrary unit, about 5.09% (r = -0.993, P < 0.001). It is separated by DC median and correlation analysis was performed for analyzing vascular characteristics according to instantaneous DC variations. There are significant differences between two correlation coefficients in separated data.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.4
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• pp.917-924
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• 2015

In this study, we study that the video attributes captured by built-in camera in smart-phone can effect on the quality of PPG signal. The conditions of video attributes were composed of the bitrate, the resolution, the flash. As each condition, we measured a change in the red value of the video image and calculated a PPI(Pulse to Pulse Interval) for extracting the pulse wave signal. 20 subjects participated in the experiment and this experiment was carried out 18 tasks. The PPG signal was measured simultaneously for two minutes with the PPG sensor in the middle finger and Smart-phone in the forefinger of the right hand. By proceeding the correlation analysis, we obtained the highest correlation condition(83%, p=0.01), which the resolution was $640{\times}480$, bitrate was 5000kbps, flash was on. As a result, this study will be a useful guide for quality of signals in the pulse signal measurement system using built-in camera in smart-phone.

• Journal of Sensor Science and Technology
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• v.25 no.2
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• pp.131-137
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• 2016

In this study, a multilevel visible light communication (VLC) system based on resistor ladder circuit is designed to transmit medical data. VLC technology is being considered as an alternative wireless communication due to various advantages such as ubiquity, license free operation, low energy consumption, and no radio frequency (RF) radiation characteristics. With VLC even in places where traditional RF communication (e.g., Wi-Fi) is forbidden, significant bio-medical signal including the electrocardiography (ECG) and photoplethysmography (PPG) data can be transmitted. More lives could be saved anywhere by this potential advantage of VLC with a fast emergency response time. A multilevel transmission scheme is adopted to improve the data capacity with keeping simplicity, where data transmission rate can increase by log2m times (m is the number of voltage levels) than that of conventional VLC transmission based on on/off keying. In order to generate multi-amplitudes, resistor ladder circuit, which is a basic principle of digital to analog convertor, is employed, and information is transferred through LED (Light-Emitting Diode) with different voltage level. In the receiver side, multilevel signal is detected by optical receiver including a photo diode. Then, the collected data are analyzed to serve the necessary medical care to the concerned patient.

• Journal of Broadcast Engineering
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• v.18 no.4
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• pp.543-549
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• 2013

Motion artifacts of central and autonomic nervous system signals degrades the performance of the bio-signal based human factor analysis. Firstly, we propose a defining method of motion artifact section by analyzing successive image frames. Motion artifact section is defined when the amount of motion is greater than the pre-defined threshold. In here, the amount of motion is estimated by first derivation of image frames at temporal domain. Secondly, we propose another defining method of motion artifact section through designing 2D Gaussian probability density function model by analyzing feature vectors of one cycle of signal such as length and amplitude. The defined motion artifact sections are interpolated on the basis of 1D Gaussian function. At result of applying the method into photoplethysmography signal, we confirmed that the calculated heartbeat rate from the restored photoplethysmography came up to the one from electrocardiography. Also, we found that the video based method generated relatively more false acceptance of motion artifact section and the probability density function based method generated relatively more false rejection of motion artifact section.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.489-492
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• 2005

Even though the blood pressure is one of the most widely used index for the healthcare monitoring of hypertensive and normotensive persons, there is no non-intrusive measurement method which is commercialized until now. Pulse Arrival Time (PAT) is known that it has close relation with the systolic blood pressure (SBP) and arterial stiffness. In this study, SBP estimation methods by non-intrusive measurement of PAT are suggested. For the unconstrained measurement of PAT, the first method used the electrically non contact electrocardiogram (ENC-ECG) technique and the reflective type of Photoplethysmography (PPG) sensor on the computer mouse. In the second method, ENC-ECG and the air pressure sensor in the seat cushion on a chair were measured. The third method used ECG electrodes and PPG sensors on the toilet seat cover. The validation and regression analysis of the relationship of PAT and SBP are summarized. These methods have considerable errors to be used for all people. But these can be applied for each subject after the parameter customization within acceptable error. So, it is feasible for suggested methods to be used for monitoring of SBP in daily life in non-intrusive way when there is personal identification system of each subject.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2001.11a
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• pp.96-103
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• 2001

그동안 정서의 실험적 유도의 어려움과 많은 제약으로 인해 성인 위주로만 이루어져 오던 정서연구가 최근 수 년 간의 정서연구에 대한 방법론의 발달로 아동에게까지 그 범위가 확대되고 있다. 본 연구에서는 아동의 다섯 가지 정서 (기쁨, 분노, 슬픔, 스트레스, 놀람)에 의해 유발되는 아동의 자율신경계 패턴을 확인하고자 한다. 놀람 정서를 추가한 "아동용 정서유발 프로토콜 (양경혜 등, 2000)"을 사용하여 아동에게 정서를 유발시키고, 정서가 유발되는 도안의 자율신경계 반응(KST, ECG, EDA, PPG)을 측정하였다. 초등학교 1, 2 학년인 34명(남: 18, 여:16)의 아동이 실험에 참여하였다. 실험 결과 다섯 가지 정서가 아동들에게 적절하고 효과적으로 유발되었으며, 정서에 따른 생리반응 변화가 관찰되었다. 분석에 사용된 12개 생리반응 변수 중 8개 변수에서 정서에 따른 차이가 발견되었으며, 정서에 따라 다른 자율신경계 반응 패턴을 얻을 수 있었다. 또한, 동일한 방법으로 수행한 본 연구실의 선행 연구와도 일치하는 결과를 보였다. 이는 아동용 정서유발 프로토콜이 표준화된 아동정서 유발자극으로 사용될 수 있으며, 생리반응 주형(template)을 이용하여 아동정서를 구분할 수 있음을 제시한다.