• Journal of the Ergonomics Society of Korea
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• v.29 no.1
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• pp.113-120
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• 2010

This research is to evaluate the arousal level by using cardiovascular response. PPG was used in this study as one of the method of measuring it rather than ECG (Electrocardiography) for the purpose of solving ergonomic problem of sensing. The participants were in the age group of 20 (mean=24, standard deviation=1.25): five men and five women. Each experiment composed with four identical sets. First, a black screen was displayed for 30 second rest. Then, the prepared 6 pair images were randomly presented for 10 second stimulation and for 30 second non-stimulation. PPG was measured on the earlobes of experimenters at 200Hz sampling frequency. PPG amplitude, PPI(Pulse to Pulse Interval), and PRV(Pulse Rate Variability) were analyzed according to arousal level. T-test was performed to compare between the PPG variables of rest and relaxation, rest and arousal, and relaxation and arousal. Relative to the rest state, PPG amplitude decreased in relaxed state and increased in aroused state. Relative to the rest state, PPI decreased in both emotional states. However, more significant decline was observed in aroused state. PRV's LF and HF were used in the form of LF/HF to compare between the relaxed and the aroused state. Therefore, PPG signal showed significant differences between relaxed and aroused state. In conclusion, evaluation of human arousal level used in the PPG analysis demonstrated that PPG has better usability and comforter measurement than ECG and is clearly an alternative method of measuring arousal level.

• The Journal of Korean Medicine
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• v.29 no.2
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• pp.60-70
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• 2008

Objectives: The aim of the present investigation was to determine whether the finger photoplethysmography (PPG) of the young will become analogous to those of the old when the PPG harmonic components in the young decrease. Methods: The PPG was measured in 46 old men (21 males and 25 females) over the age of 60 years and 10 young men (5 males and 5 females). We acquired the representative pulse waveform of old men by averaging the PPG waveforms measured in the old men. after the PPG harmonic components in the young men were diminished with notch filtering, we compared the representative pulse waveform of old men and those of the young men. Results: The PPG waveform of the young males became analogous to the representative pulse waveform of the old as the PPG harmonic components in the young were diminished with notch filtering. Especially after the second harmonic component in the young was diminished with notch filtering, increase of the Pearson's correlation coefficient was prominent. On the other hand, the Pearson's correlation coefficient between the PPG waveforms of the young females and that of the old deceased after the second harmonic component diminished in the young. Conclusions: Decrease of the second harmonic component may be a precondition of typical age-related change of the pulse waveform in the healthy male.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.5
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• pp.138-142
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• 2017

Photoplethysmography (PPG) is a simple and low-cost optical technique that can be used to detect blood volume changes in the microvascular bed of tissue. It is often used non-invasively to make measurements at the skin surface. In this paper, we described the implementation heart rate monitoring system using PPG sensor. Proposed system is collected data using PPG sensor and heart rate was detected using second derivative method. In order to verify the effectiveness of the proposed method, we performed the measurements of RR-intervals with a commercial medical device.

• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.71-78
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• 2016

PPG signal measured by pulse oximeter can measure pulse and the oxygen saturation of arterial blood. But the PPG signal is distorted by finger movement or other movement in the body. To detect pulse from the PPG signal with motion artifact, we use band pass filter(BPF), Independent component analysis(ICA) and nonlinear autocorrelation(NAC). BPF is used to remove DC component and high frequency noise in the PPG signal with motion artifacts. ICA is used to separate pulse signal and motion artifact. However, pulse signal separated by ICA have no choice but to accompany signal distortion because pulse signal and motion artifact are not completely independent. So, we use nonlinear autocorrelation to emphasize the pure pulse signal from the distorted signal.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.8
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• pp.1431-1437
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• 2016

In mobile healthcare device, when to measure the heart rate by using the PPG signal, its performance is reduced according to the motion artifacts that is the movement of user. This is because the frequency range of motion (0.01-10 Hz) and that of PPG signals overlap. Also, the motion artifacts cannot be rectified by general filters. To solve the problem, this paper proposes a method using filter banks and independent component analysis (ICA). To evaluate the performance of the proposed method, we were artificially applied various movements and compared heart rate errors of the moving average filter and ICA. In the experimental results, heart rate error of the proposed method showed very low than moving average filter and ICA. In this way, it is possible to measure stable heart rate if the proposed method is applied to the healthcare terminal design.

• Journal of the Korea Convergence Society
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• v.10 no.8
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• pp.53-58
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• 2019

Recently, product research has been continuously conducted to enhance accessibility to blood pressure measurement for the purpose of healthcare for the chronic patient. In previous studies, electrocardiogram (ECG) and photoelectric pulse wave (PPG) are analyzed to calculate systolic and diastolic blood pressure. The problem is the development of analysis algorithms for accuracy and reproducibility. In this study, in the development stage of a micro blood pressure measuring device, the size of the device was reduced and the measurement method was simplified, while the algorithm was to extract systolic blood pressure (SBP) using only two PPGs and obtain diastolic blood pressure (DBP). The difference value of PPG, DF_P, is inversely related to SBP, and has a proportional relationship with DBP, which can be leaked by algorithm, and DBP can be tracked through SBP.

• International Journal of Control, Automation, and Systems
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• v.5 no.6
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• pp.701-706
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• 2007

The measurement accuracy for heart rate or $SpO_2$ using photoplethysmography (PPG) is influenced by how well the noise from motion artifacts and other sources can be removed. Eliminating the motion artifacts is particularly difficult since its frequency band overlaps that of the basic PPG signal. Therefore, we propose the Periodic Moving Average Filter (PMAF) to remove motion artifacts. The PMAF is based on the quasi-periodicity of the PPG signals. After segmenting the PPG signal on periodic boundaries, we average the $m^{th}$ samples of each period. As a result, we remove the motion artifacts well without the deterioration of the characteristic point.

• Annual Conference of KIPS
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• 2015.10a
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• pp.572-574
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• 2015

최근 스마트폰 내장 카메라와 플래시를 사용하여 PPG 신호를 측정하고 생체정보를 측정하는 연구가 많이 진행되고 있다. 그러나 스마트폰 카메라를 사용하여 측정하는 PPG신호는 스마트폰 카메라와 플래시 위치에 따라 각 측정 영역의 신호의 세기가 다르다. 본 논문에서는 스마트폰 카메라와 플래시 위치에 따라 강한 PPG 신호를 가지는 ROI를 찾기 위해 비교, 분석하였다. ROI를 계산하기 위해 PPG 신호를 측정하고 ROI를 선정할 수 있는 스마트폰 애플리케이션을 개발하여 각 ROI의 PPG 신호의 편차를 계산하고 가장 최적의 영역을 실험을 통해 비교분석하였다.

• Journal of Biomedical Engineering Research
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• v.28 no.6
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• pp.777-785
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• 2007

In this paper, Finger-Toe Index (FTI) is proposed as an analytic parameter for the characterization of arterial vessel. Different from the currently being employed pulse wave velocity (PWV) information of the volume pulse wave measured from 4 arterial channels, the proposed FTI uses the ratio of the shorter of the two up-stroke time of PPG from fingers ($UT_{finger}$) and that of PPG (Photoplethysmography) from toes ($UT_{toe}$). To verify the usefulness of the proposed method, Finger-Toe Indexes were derived from the volume pulse waves acquired from 50 people under examination aged from 12 to 81 years old, and they were then compared with blood pressure ankle-brachial index (ABI). It was successfully demonstrated that the arterial stiffness can be estimated with respect to age and FTI is more strongly correlated with the pulse transit time than ABI. From the regression analysis, we also found that FTI has significant correlation PWV for a quantitative index of arterial stiffness and provides more accurate information than ABI for the characterization of arterial vessel.

• IEMEK Journal of Embedded Systems and Applications
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• v.18 no.2
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• pp.51-58
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• 2023

This paper proposes a deep learning method for estimating the heart rate from facial videos. Our proposed method estimates remote photoplethysmography (rPPG) signals to predict the heart rate. Although there have been proposed several methods for estimating rPPG signals, most previous methods can not be utilized in low-power single board computers due to their computational complexity. To address this problem, we construct a lightweight student model and employ a knowledge distillation technique to reduce the performance degradation of a deeper network model. The teacher model consists of 795k parameters, whereas the student model only contains 24k parameters, and therefore, the inference time was reduced with the factor of 10. By distilling the knowledge of the intermediate feature maps of the teacher model, we improved the accuracy of the student model for estimating the heart rate. Experiments were conducted on the UBFC-rPPG dataset to demonstrate the effectiveness of the proposed method. Moreover, we collected our own dataset to verify the accuracy and processing time of the proposed method on a real-world dataset. Experimental results on a NVIDIA Jetson Nano board demonstrate that our proposed method can infer the heart rate in real time with the mean absolute error of 2.5183 bpm.