• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.473-474
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• 2007

본 연구는 체내 이식형 Pacemaker를 연구하면서 심장 질환을 Therapy 해 주는 방법에 대해 저전력 및 성능향상에 중점을 두고 연구 및 실험을 하였다. 우선적으로 심장의 심박동을 연산량이 적은 Peak_detection에서 체크하여 전력소모를 줄이고 나오는 각 심실 및 심방의 Interval을 Disease_episode 에서 받는다. 여기서 5가지 심실 및 심방에 관한 질환들 (VF : Ventricular Fibrillation, VT : Ventricular Tachycardia, FVT : Fast Ventricular Tachycardia, FAT_AF : Fast Atrial Tachycardia/Atrial Fibrillation, AT_AF : Atrial Tachycardia AT_AF : Atrial Fibrillation)을 판별한 후 각 병증에 맞는 Therapy 값을 출력하게 하였다. 그 외에 남아있는 병증에 대해서도 Therapy가 저전력 및 성능향상 되도록 설계하였다. 기존에 적용되어 있는 Detection 기법에서는 각각의 병증에 대해서 각 Detection이 있어 VF와 VT 사이에 있는 FVT와 같은 병증을 치료할 때 FVT 같은 경우에는 VF와 VT사이에 있는 질병이기 때문에 FVT_VF 및 FVT_VT와 같이 각각의 Detection을 두어 전력 소모가 있었다. 심장에서는 여러 질병이 한번에 나을 수 없다는 것에 착안하여 (심박동 Interval에 의해 질병이 판단되므로) 다른 병증이지만 같은 진단 기준을 쓰는 Detection을 통합함으로써 하나의 모듈로 구성하여 Gate수를 줄이고 저전력을 구현하였다. 또한 병증을 판별하는 진단 기준 모듈 중 Onset_Criterion 재설계하여 좀더 성능 향상에 중점을 두었다.

• Journal of Chest Surgery
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• v.34 no.8
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• pp.591-596
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• 2001

Coronary artery bypass graft with cardiopulmonary bypass is a conventional method of operative revascularization of coronary artery disease. Because of many troubles of cardiopulmonary bypass such as systemic inflammatory reaction, mechanical trauma of blood components and coagulopathy, coronary artery bypass graft without cardiopulmonary bypass has been popularized. Material and Method: From March 1999 to September 2000, 35 patients under went CABG at our institution. Among them, 14 patients received CABG without the use of CPB and 21 patients under went CABG with the use of CPB. Mean operative time, mean postoperative tracheal intubation time, mean ICU stay, mean hospital stay, the amount of transfusion, postoperative use of inotropic agents, and postoperative changes of cardiac enzymes were compared in both groups. Result: There were differences between the CABG without CPB group and CABG with CPB group with regard to mean tracheal intubation time, the amount of transfusion and the elevation of postoperative cardiac enzymes(p<0.05). Conclusion: While CABG without CPB provided satisfactory results, more long term follow-up is required.

• Journal of Biomedical Engineering Research
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• v.16 no.2
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• pp.175-182
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• 1995

Despite the simplicity of processing, a conventional autocorrelation function (ACF) method for the precise determination of fetal heart rate (FHR) has many problems. In case of weak or noise corrupted Doppler ultrasound signal, the ACF method is very sensitive to the threshold level and data window length. It is very troublesome to extract FHR when there is a data loss. To overcome these problems, the high resolution pitch detection algorithm was adopted to estimate the FHR. This method is more accurate, robust and reliable than the ACF method. With a lot of calculation, however, it is impossible to process real time FHR estimation. This paper is presented a new FHR estimation algorithm for real time processing and studied the real time FHR monitoring system by high resolution pitch detection algorithm.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1999.11a
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• pp.227-232
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• 1999

본 논문은 음악 리듬의 비트간의 간격의 변화가 사람의 심박동 및 쾌적감에 미치는 영향을 평가하기 위하여 음악 리듬의 박자를 규칙적인 다섯 단계의 변화를 적용하여 평가했다. 평가 항목으로는 (1) LF성분에 많은 영향을 보이는 심박동의 전력스펙트럼 분석과 (2) S.D.법으로 심리적 평가항목을 수행하였다. 실험 결과는, 박자의 변동이 일정한 정박자 리듬에서는 생체에 특이한 변화가 나타나지 않았지만 박자의 변동이 변화하는 리듬에서는 LF성분이 증가함으로 긴장과 불안이 유발됨을 알 수 있었다. 추가적으로 심박변동의 스펙트럼 분석를 통하여 얻을 수 있는 LF와 HF 성분사이의 비를 조사함으로 심리학적 불안을 평가하는 가능성을 제안한다.

• Journal of the Korean Society of Radiology
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• v.5 no.1
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• pp.19-25
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• 2011

Photoplethysmogram(PPG) is the method to obtain the biomedical signal using the linear relationships between the blood volume for changing the cardiac contraction and relaxation and the amount of light for absorbing the hemoglobin in the blood. In this paper, we proposed the analyzed results which show the heart rate variability and the distribution of heart rate for before and after using PPG. Moreover, this paper designed and implemented the system based on personal computer to predict cardiovascular disease in advance using the analyzed results for the autonomic balance from taking the spectral analysis of heart rate and the state of the blood vessel for analyzing APG(acceleration plethysmogram).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.503-504
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• 2017

Recently, economic growth in the world has increased interest in healthy life, and the smart health care industry is growing. In the field of smart healthcare, wearable-type biometric information measurement technology has been highlighted due to the importance of IoT technology. The purpose of this study is to develop a wearable heart - rate monitoring system that can be applied to wearable health care and glove - type monitoring that enables convenient monitoring of heart rate during activity. For this purpose, a glove - type wearable health care system was developed and its performance was evaluated. Experimental results showed that the heartbeat monitoring was possible even in the presence of actual daily activities.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.1
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• pp.45-50
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• 2019

When PPG signal is used in mobile healthcare devices, the accuracy of the measured heartbeat decreases from the influence by the movement of the user. The reason is that the frequency band of the noise overlaps the frequency band of the PPG signal. In order to remove these same noises, the methods using frequency analysis method or application of acceleration sensor have been investigated and showed excellent performance. However, in applying these methods to low-cost healthcare devices, it is difficult to apply these methods because of much processing time and sensor's cost. In order to solve these problems, this study proposed the filter design method using an adaptive notch filter and the fuzzy inference system to extract more accurate heart rate in real time and evaluated its performance. As results, it showed better results than the other methods. Based on the results, when applying the proposed method to design the mobile healthcare device, it is possible to measure the heartbeat more accurately in real time.

• Science of Emotion and Sensibility
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• v.8 no.1
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• pp.47-54
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• 2005

This study is aimed to inspect how the different sensitivities in Behavioral activation system(BAS) and behavioral inhibition system(BIS) modulate on the properties of physiological responses stimulated by positive or negative affective sound. We measured the electroencephalogram(EEG) and electrocardiogram (ECG) of 32 students, consisted of four groups depending on the BAS and BIS sensitivities, during listening to meditation music or noise. The EEG was recorded at Fpl and Fp2 sites and Power spectral density(PSD) of HRV was derived from the ECG, and the power of HRV was calculated for 3 major frequency ranges(low frequency[LF], medium frequency and high frequency[HF]). After listening to music or noise, subjects reported the affect induced by the sound. For EEG, the power in the alpha band at Fp2, especially in the alpha-2 band(9.0-11.0 Hz) increased during the subjects listening to music, while the power at Fpl increased during noise. During listening to meditation music, there is a tendency that the left-sided activation in prefrontal cortex(PFC) is positively correlated with the difference of BAS(Z)-BIS(Z). During listening to noise, there is a tendency that the right-sided activation in PFC is dominant in case any of the sensitivity of BAS or BIS is high. For HRV, we found that the index of MF/(LF+HF), during listening to music, was higher significantly in the individuals with a low BIS but high BAS than in the individuals with a low sensitivity both BIS and BAS individuals. With high BIS, regardless of the BAS sensitivity, the difference of this index values was not significant. From these results we suggest that the physiological responses of different individuals in BAS and BIS react differently under the same emotionally provocative challenge.

• Journal of the Korean Society of Radiology
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• v.10 no.4
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• pp.285-290
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• 2016

The purpose of our study was to retrospectively evaluate the cause of a decreased calcium score of follow-up studies on coronary artery calcium scores (CACs) computed tomography (CT). The subjects were healthy 100 people(85 males $60.6{\pm}6.9$ years, 15 females $67.2{\pm}7.3$ years). The subjects decreased CACs were divided into 4 subgroups depending on Agatston classification, minimal (1-10), mild (11-100), moderate (101-400), severe (400<). As a result of decreased CACs were scan location disagreement 51%, motion artifact 26%, equipment changes 14%, operator mistakes 5%, input miss 2%, image loss 1%, arrhythmia 1%. In the mild group, the most common decreased CACs were 49 people. In the minimal group, the most significant variation reduction has occurred to 6 people. Scan location disagreement was considered a partial volume effects due to the scan starting position. It showed less than 100 CACs a high variation (19.7%) in more than 100 CACs, a lower variation (2.2%), these could be seen that the variation range is different that can be tolerated according to the calcification score. Motion artifact factor was found in 26%, which is so closely related to the preceding tests that affect the higher heart rate like this pulmonary function test, exercise stress test.

• Sleep Medicine and Psychophysiology
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• v.7 no.1
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• pp.43-50
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• 2000

Objectives: Obstructive sleep apnea syndrome(OSAS) is known to be associated with the changes of autonomic nervous system (ANS). Nasal continuous positive airway pressure(nCPAP) treatment was found to correct abnormal ANS changes in OSAS but it remains to be further clarified. We aimed to assess the effects of nCPAP on ANS manifested on electrocardiogram, using spectrum analysis in the subjects with OSAS. Methods: Digital polysomnography was performed in 18 patients with OSAS(mean age $43.7{\pm}16.6$ years ; 17 males, 1 female ; mean respiratory disturbance index (RDI) $48.6{\pm}20.9$) for one baseline and another CPAP nights. From each night, 300 continuous beats of ECGs without artifact were chosen from both stage 2 sleep and REM sleep and they were used for power spectrum analysis. We compared between baseline and CPAP nights the heart rate variability including VLF(very low frequency power), LF (low frequency power), HF(high frequency power), R-R means, R-R variance, and LF/HF ratio, using Wilcoxon signed ranks test. Results: In all patients, nCPAP proved to be effective in relieving apneas and snoring. During nCPAP night compared with baseline night, decreases in VLF(p<0.05), LF(p<0.01), and R-R variance(p<0.05) were found in stage 2 sleep, and decreased LF(p<0.05) was found in REM sleep. No significant differences in each sleep stage were found in other variables between the two nights. Conclusion: Our findings suggest that OSAS increases the activity of sympathetic nervous system and nCPAP application effectively decreases the activity. And nCPAP does not appear to influence the parasympathetic nervous activity in OSAS.