• 디지털정책학회지
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• 제2권4호
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• pp.25-32
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• 2023

논문은 PPG 기반 센서에서 측정한 심박수(HR), 심박변이도(HRV) 데이터를 기반으로 DNN(Deep Neural Network) 혈당예측 모델을 개발하는 연구이다. 혈당 예측은 다층퍼셉트론(MLP) 신경망을 이용하였다. DNN 심층학습은 11의 독립변수가 있는 입력층, 은닉층, 출력층으로 구성된다. 혈당 예측모델의 학습결과는 MAE=0.3781, MSE=0.8518, 및 RMSE=0.9229이며, 결정계수(R²)는 0.9994이다. PPG기반의 디지털기기를 이용한 비채혈적 생체신호를 이용하여 혈당관리의 가능성을 확인하였다. PPG기반의 표준화된 활력신호 획득 및 해석법, 다량의 데이터기반 심층학습(Deep Learning)의 데이터셋, 정확성를 실증하는 연구가 이어진다면 개의 혈당관리에 편이성과 대안적인 방법을 제공할 수 있을 것이다.

• 전기전자학회논문지
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• 제28권2호
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• pp.221-227
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• 2024

본 논문은 스마트폰 탈착형 혈관 탄성 모니터링 모듈을 제안한다. 제안하는 센서 모듈은 광용적맥파(photoplethysmogram, PPG)를 계측하고 가속도 맥파를 복원한다. 복원된 가속도 맥파로부터 특징점을 추출하며, 해당 특징점을 이용하여 혈관 탄성 수치를 추정한다. 해당 모듈은 스마트폰의 USB 단자를 통해 전원을 공급 받으며, 블루투스 방식으로 가속도 맥파 파형과 혈관 탄성 수치를 스마트폰으로 전송한다. 스마트폰으로 전송된 파형과 혈관 탄성 수치는 안드로이드 어플리케이션을 통해 화면에 디스플레이 된다. 본 연구는 PPG 계측의 일관성을 평가하는 기법을 제안하며, 해당 기법은 모듈의 프로세서 내에 구현되었다. 본 연구에서 개발한 혈관 탄성 모니터링 모듈은 PPG 신호의 계측 및 분석을 지원하지 않는 스마트폰에 쉽게 탈착이 가능한 형태로 적용이 가능하며, 혈관 탄성의 손쉬운 계측 및 수치 분석을 제공하는 특징을 지닌다. 구현된 혈관 탄성 모니터링 모듈의 성능 검증을 위해, 29명의 피험자를 대상으로 혈관 탄성 수치와 맥압을 측정하였다. 맥압은 상용 혈압계를 이용하여 획득하였으며, 해당 지표는 혈관 탄성을 나타내는 대표적 지표에 해당한다. 분석 결과, 제작된 혈관 탄성 모니터링 모듈로부터 획득한 혈관 탄성 수치와 맥압 간의 피어슨 상관계수는 0.778이며, 두 수치 간의 비교적 높은 상관 관계를 확인하였다.

• 설비공학논문집
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• 제27권11호
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• pp.596-602
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• 2015

In this study, experiments using bioelectronic signals and questionnaire surveys were carried out in learning conditions when temperatures changed from low- and high-uncomfortable to comfortable. As a result, the stress factor Photoplethysmography (PPG) decreased, while the Root Mean Square of Standard Deviation (RMSSD) of PPG increased when the indoor temperature was changed from low- or high-uncomfortable to comfortable. Additionally, the absolute power of the ${\alpha}$-wave in the brain increased. According to the analysis of the association between the questionnaire and bioelectronic signals, the standard deviation of the stress factor as measured by pulse was closely related to the result of the thermal sensation questionnaire. In addition, it was found that the concentration on studying improved under comfortable temperatures when compared to uncomfortable temperatures.

• 전기학회논문지
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• 제67권7호
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• pp.962-968
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• 2018

In this study, we developed novel indicators to assess postoperative pain based on PPG derivative waveform. As the candidate indicator of postoperative pain assessment, the time from the start of beating to the n-th peak($T_n$) and the n-th peak amplitude($A_n$) of the PPG derivative were selected. In order to verify derived indicators, each candidate indicator was derived from the PPG of 78 subjects before and after surgery, and it was confirmed whether significant changes were observed after surgery. Logistic classification was performed with each proposed indicator to calculate the pain classification accuracy, then the classification performance was compared with SPI(Surgical Pleth Index, GE Healthcare, Chicago, US). The results showed that there were significant differences(p < 0.01) in all indicators except for $T_3$ and $A_3$. The coefficient of variation(CV) of every time-related indicators were lower than the CV of SPI(30.43%), however, the CV in amplitude-related parameters were higher than that of SPI. Among the candidate indicators, amplitude of the first peak, $A_1$, showed that highest accuracy in post-operative pain classification, 68.72%, and it is 15.53% higher than SPI.

• 대한의용생체공학회:의공학회지
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• 제38권3호
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• pp.95-101
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• 2017

In this study, photoplethysmography(PPG) was suggested as a way to replace the ankle-brachial index(ABI) in diagnosing PAD. The method using the PPG was presented for the simplification of the PAD diagnosis method which was used before. And the index related to the health condition of the artery from the PPG measured in both big toes of the subjects through the experiment was drawn. The indexes showing the significant relativeness in the Pearson correlation analysis with the ABI were the stiffness index(SI), reflection index(RI); it was confirmed each of them had the correlation coefficient of 0.688, and 0.637 at p < 0.05. The explanation ability of the linear regression equation derived using ABI, SI and RI was 52.5%. The explanation ability of the secondary curve regression equation derived using ABI, squared SI was 54.7%. It is expected to provide patients with significant results and draw the index associated with PAD by measuring PPG easily in the real life instead of the ambulatory care field.

• 전기학회논문지
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• 제64권2호
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• pp.304-309
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• 2015

Applicable range of Photoplethysmography (PPG) becomes wider as a non-invasive physiological measurement technique. However, PPG waveform is easy to be distorted by ambient light or vascular variation from temperature changes. Especially, irregular variation of PPG waveform caused by ambient temperature not only severely distorts the PPG, but also leads miss interpretation in clinical applications. Therefore, the investigation of between temperature and PPG waveform is quite important in using PPG. The purpose of this research is to quantify the PPG waveform characteristic and to investigate the waveform variation following the temperature change on measuring site. To quantify the fluctuation of PPG waveform, we use two techniques; detrended fluctuation analysis (DFA) and AC/DC analysis of PPG. We record PPG under temperature stress, which applied by medical use heat pack ($40^{\circ}C$) and ice pack ($0^{\circ}C$). Ten participants were applied to the experiment, and the result was evaluated to approve the temperature effect with statistical method, Wilcoxon signed rank test. The result shows that the AC component (p<0.05) and perfusion index DFS scale exponent (p<0.01) of PPG have the significance to temperature stress except for a DC component of PPG.

• 센서학회지
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• 제17권6호
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• pp.447-453
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• 2008

Respiration rate is one of the important vital signs. Photo-plethysmography (PPG) measurement especially on a finger has been widely used in pulse oximetry and also used in estimating respiration rate. It is well known that PPG contains respiration-induced intensity variation (RIIV) signal. However, the accuracy of finger PPG method has been controversial. We introduced a new technique of enhancing motion artifact by respiration. This was achieved simply by measuring PPG on the thorax. We examined the accuracy of these two PPG methods by comparing with two existing methods based on thoracic volume and nostril temperature changes. PPG sensing on finger tip, which is the most common site of measurement, produced 6.1 % error. On the other hand, our method of PPG sensing on the thorax achieved 0.4 % error which was a significant improvement. Finger PPG is sensitive to motion artifact and it is difficult to recover fully small respiratory signal buried in waveform dominated by absorption due to blood volume changes. Thorax PPG is poor to represent blood volumes changes since it contains substantial motion artifact due to respiration. Ironically, this inferior quality ensures higher accuracy in terms of respiration measurement. Extreme low-cost and small-sized LED/silicon detector and non-constrained reflection measurement provide a great candidate for respiration estimation in ubiquitous or personal health monitoring.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 춘계학술대회
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• pp.819-821
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• 2014

본 연구는 스마트폰과 결합할 수 있는 생체신호 측정용 태그 설계법을 제안하였다. 제안된 태그에서 측정 가능한 생체신호는 심전도 및 광용적 맥파이며, 스마트폰에서는 이 신호로부터 심박수 및 분포, 평균혈압 추정, 동맥경화도, 자율신경 균형 등을 추출하게 태그를 설계 하였다. 추출된 정보를 이용하여 개인이 스마트폰 상에서 스스로 자신의 건강상태를 관리할 수 있게 확인할 수 있게 한 것이다.

• 한국정보통신학회논문지
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• 제14권3호
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• pp.723-728
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• 2010

본 연구는 국내의 간호 인력 부족으로 인하여 발생되는 간호 업무 부하를 감소시키기 위해 PPG 신호를 이용한 휴대형 심박수 측정 장치의 설계 방법과 환자의 움직임인 동잡음에서도 신뢰성이 높은 심박수 측정 알고리즘을 제안하였다. 제안된 심박수 측정방법은 생체 신호의 하모닉 특성을 기반한 적응필터로 동잡음을 제거하고 심박수를 측정하는 방법이다. 제안된 기법으로 구현된 심박수 측정기의 성능을 평가하기 위해 손가락 떨림, 손목 움직임 등의 동잡음을 발생시켜 실험하고, 일반적인 방법인 이동평균 필터의 성능과 비교 평가 하였다. 이 실험 결과에서 제안된 기법의 성능이 이동평균 필터의 성능보다 우수한 성능을 보였다. 따라서 본 연구에서 제안한 휴대형 심박수 측정기를 간호업무에 도입한다면, 간호 업무 개선과 보다 선뢰성이 높은 심박수 측정이 가능할 것으로 사료된다.

• 대한의용생체공학회:의공학회지
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• 제34권3호
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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.