• 대한의용생체공학회:의공학회지
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• 제15권3호
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• pp.265-274
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• 1994

This paper proposes a method of noninvasive reflectance light to measure the blood fractional volume (Vb) and oxygen saturation ($SO_2$) of biological tissue. We chose the red light of 660nm and infrared light of 880nm. In Vivo reflectance data were obtained by the physiological changes front the surface of the skin over the calf in human subject. The reflected light intensity from different layers within a biological tissue was measured by specially designed reflectometer to apply photon path diffusion model. The collected data represent the changes of blood (ractional volume and oxygen saturation at each reflected light wavelengths. The data evaluation was assessed by examining the slopes of the plotted indices for the changes in oxygen saturation and blood (ractional volume. The results presented in this paper claim that light reflectance can separately discriminate the change of blood volume and that of oxygenation in muscle and also in skin.

• 한국의학물리학회지:의학물리
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• 제10권1호
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• pp.9-15
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• 1999

혈액에서의 산소 포화도는 Hb와 HbO$_2$의 광학 스펙트라에서 흡수계수의 차이에 의해서 측정할 수 있다. 본 연구는 하지 조직에서 발생하는 말초혈관계 질환진단을 위하여 파장이 660nm 와 940nm의 LED를 이용하여 산소포화도를 측정하는 장치를 개발하였다. 산소측정장치는 광 탐촉자와 광 신호처리부, LED 구동회로, 컴퓨터와 인터페이스로 구성하고, 데이터의 수집과 분석을 위한 프로그램 을 개발하였다. 구현된 산소측정장치에 대한 임상적인 평가를 위하여 하지조직에서 운동 부하에 따른 실험을 하여 생체조직내 생리적변화에 따른 산소량의 변화를 측정하고, 기기의 성능을 평가하였다. 실험결과 생체조직내의 산소포화도는 광원과 검출기의 간격에 따라 측정이 가능함을 보여 주었다.

• 한국의학물리학회지:의학물리
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• 제7권1호
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• pp.25-35
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• 1996

혼탁한 물질인 생체조직에서 신진대사, 혈액확산, 혈중산소의 비침습적 측정에 관한 연구를 광을 이용한 방법으로 제시하였다. 생체조직내의 산소포화도와 혈액분량을 측정하기 위하여 660nm와 880nm 의 광파장을 이용하여 측정하였으며, 생체조직에서 얻은 광 세기의 데이터는 조직내의 깊은 곳에서 생리적인 변화를 나타낸다. 데이터의 평가는 혈액분량과 산소포화도의 변화에 대한 지수의 기울기로서 조사하여 평가하였다. 여기서 곡선으로 나타낸 지수는 각각의 파장에서 기준파장의 세기와 측정부위에서의 반사광의 세기를 비율에 의한 자연대수로 나타냈다. 장단지 근육에 대한 실험 결과에 따르면 산소의 지수는 운동중에 현저하게 변화를 보여 주었다.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.420-423
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• 1997

The oxygen saturation of blood can be measured by sensing the difference absorption in optical spectra of Hb and $HbO_2$, as the well known previous study. [1] In this study we developed the noninvasive tissue reflectance oximeter(TRO) using three kinds of LEDs which produce a peak spectral emission at a wavelength of 565, 660 and 940nm. And we tested the unction of the TR oximeter by comparing the output signals measured on normal tissue to measured on low oxygenated tissue. The results showed that oxygen saturation of blood and biological tissue can be monitored from the separation arrangement light source and detector.

• Archives of Plastic Surgery
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• 제40권5호
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• pp.505-509
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• 2013

Background The aim of this study was to collect important data on the time of oxygen saturation change in relation to skin flap color alteration using non-invasive pulse oximetry to evaluate its ability to provide continuous monitoring of skin flap perfusion. Methods An experimental study on the monitoring of blood perfusion of 20 tube-island groin flaps of 10 male New Zealand rabbits was performed using pulse oximetry. The animals were randomly assigned to one of two groups representing a blockage of either arterial or venous blood flow. The oxygen saturation change and clinical color alteration were monitored from the beginning of vessel clamping until the saturation became undetectable. The result was analyzed by the t-test using SSPS ver. 10.0. Results The mean times from the vessel clamping until the saturation became undetectable were $20.19{\pm}2.13$ seconds and $74.91{\pm}10.57$ seconds for the artery and vein clamping groups, respectively. The mean time of the clinical alteration from the beginning of vein clamping was $34.5{\pm}11.72$ minutes, while the alteration in flaps with artery clamping could not be detected until 2.5 hours after clamping. Conclusions The use of neonate-type reusable flex sensor-pulse oximetry is objective and effective in early detection of arterial and vein blockage. It provides real-time data on vessel occlusion, which in turn will allow for early salvaging. The detection periods of both arterial occlusion and venous congestion are much earlier than the color alteration one may encounter clinically.

• 대한의용생체공학회:의공학회지
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• 제44권6호
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• pp.450-464
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• 2023

Pulse oximetry, a non-invasive technique for evaluating blood oxygen saturation, conventionally depends on isolated measurements, rendering it vulnerable to factors like illumination profile, spatial blood flow fluctuations, and skin pigmentation. Previous efforts to address these issues through imaging systems often employed red and near-infrared illuminations with distinct profiles, leading to inconsistent ratios of transmitted light and the potential for errors in calculating spatial oxygen saturation distributions. While an integrating sphere was recently utilized as an illumination source to achieve uniform red and near-infrared illumination profiles on the sample surface, its bulkiness presented practical challenges. In this work, we have enhanced the pulse oximetry imaging system by transitioning illumination from an integrating sphere to a multi-wavelength LED configuration. This adjustment ensures simultaneous emission of red and near-infrared light from the same position, creating a homogeneous illumination profile on the sample surface. This approach guarantees consistent patterns of red and near-infrared illuminations that are spatially uniform. The sustained ratio between transmitted red and near-infrared light across space enables precise calculation of the spatial distribution of oxygen saturation, making our pulse oximetry imaging system more compact and portable without compromising accuracy. Our work significantly contributes to obtaining spatial information on blood oxygen saturation, providing valuable insights into tissue oxygenation in peripheral regions.

• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 동계학술발표회 논문집
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• pp.359-360
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• 2006

Functional photoacoustic tomography is a new non-invasive imaging modality, and it is emerging as a very practical method for imaging biological tissue structures by means of laser-induced ultrasound. Structures with high optical absorption, such as blood vessels, can be imaged with the spatial resolution of ultrasound, which is not limited by the strong light scattering in biological tissues. By varying wavelengths of the laser light and acquiring photoacoustic images, optical absorption spectrum of each image pixel is found. Since the biochemical constituents of tissues determine the spectrum, useful functional information like oxygen saturation ($SO_2$) and total haemoglobin concentration (HbT) can be extracted. In this study, as a proof-of-principle experiment, hypoxic brain tumor vasculature and traumatic brain injury (TBI) of small animal brain are imaged with functional photoacoustic tomography. High resolution brain vasculature images of oxygen saturation and total hemoglobin concentration are provided to visualize hypoxic tumor vasculature, and hemorrhage on the cortex surface by the TBI.

• Journal of Medicine and Life Science
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• 제18권1호
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• pp.20-23
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• 2021

Methemoglobin is generated by the oxidation of ferrous iron to ferric iron within a hemoglobin molecule. Methemoglobin is unable to bind and transport oxygen, resulting in methemoglobinemia, which can lead to fatal tissue hypoxia. The most common cause of methemoglobinemia is poisoning by oxidizing agents such as dapsone, benzocaine, and primaquine. However, methemoglobinemia can also be caused by normal dietary sources. We present two cases of methemoglobinemia that developed after a normal diet in two male patients. In this case report, the patients suddenly developed dyspnea and cyanosis after eating the same meal. They had no history of suspected poisoning, such as the use of drugs, exposure to chemicals, or gas inhalation. Their symptoms did not improve even after a high dose of oxygen was administered; further, an abnormal 'oxygen saturation gap' was observed. Because of CO-oximetry, the methemoglobin levels of the patients were 50.0% and 46.6%, respectively. We administered methylene blue (1 mg/kg), and the patients recovered completely without any complications. Emergency physicians should, therefore, be aware that methemoglobinemia can also be caused by normal dietary sources. In addition, if the source and route of contamination are unclear, an epidemiological investigation should be conducted.

• Journal of Chest Surgery
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• 제13권2호
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• pp.85-91
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• 1980

Extracorporeal circulation by hemodilution technique has been currently used with its clinical safety and good peripheral tissue perfusion in open heart surgery. There is no doubt that $O_{2}$ carrying capacity of the blood is disturbed by decreased hemoglobin level resulting from hemodilution of the circulating blood. From the view point of the blood gas exchange, these experimental studies were undertaken to determined the sate limit of hemodilution in the condition of cardiopulmonary bypass with a constant perfusion flow rate. Twelve adult mongrel dogs weighing 10 to 13 Kg. were anesthetized with pentobarbital and then respiration was controlled with Harvard volume respirator using room air. The cardiopulmonary by pass was performed by use of Sarns heart lung machine (console 5000, 5 head and 2 roller pumps) and Travenol pediatric bubble oxygenator. The perfusion rate during bypass was maintained at a constant rate of 80 ml/min/Kg of body weight. The ratio of oxygen gas flow to blood flow was kept in 3 to 1 constantly. International hemodilution was attained by serial blood withdrawals and immediate infusion of equal volumes of diluants composed of Ringer's lactate, 5% dextrose in water and 25% mannitol solution, proportionally 60%, 30%, and 10%. Arterial and venous blood samples were obtained between 15 and 20 minutes following each hemodilution. Hematocrits and hemoglobin values, $PO_{2}$, $PCO_{2}$ and pH were measured. Oxygen and carbon dioxide contents oxygen consumption and carbon dioxide elimination were calculated groups according to different hematocrit values and the correlations were evaluated. Result were as follows. 1. the arterial $O_{2}$ tension and $O_{2}$ saturation were maintained at the physiological level irrespective of the hematocrit value. 2. The venous $O_{2}$ tension and $O_{2}$ saturation showed a tendency to decline with the decrease in hematocrit value and positive correlation between them (r = +0.49, r = +0.76), The mean values of venous $O_{2}$ tension and $O_{2}$ saturation, however, were not decreased when the hematocrit levels were lower than 20%. 3. The arterial $O_{2}$ content declined lineally in proportion to the fall of hematocrit level with a positive correlation between them (r = +0.95). 4. The venous $O_{2}$ contents were decreased gradually as the hematocrit value decreased with positive correlation between them ( r =+0.89). The trend of diminution of venous $O_{2}$ content, however, was became low according to progressive decrease of hematocrit level. 5. Systemic oxygen consumption was in higher range than $O_{2}$ requirement of basal metabolism when the hematocrit value was above 20%, but abruptly decreased when the hematocrit value became to below 20%. 6. The arterial $CO_{2}$ tension and $CO_{2}$ content showed trend of increasing with progressive decrease of hematocrit value but exhibited a rather broad range and there was no relationship between those value and the hematocrit value. 7. The venous $CO_{2}$ tension and $CO_{2}$ content have also no correlation with change of Ht. value but related directly to those value of arterial blood with positive correlation between them (r = +0.78, r = +0.95_. 8. A-V difference of $CO_{2}$ content and $CO_{2}$ elimination wasnot significantly influenced by Ht. value. From the results, we obtained that feasible limit in inteneional hemodilution is above the hematocrit value of 20% under the given experimental condition.

• Journal of Oral Medicine and Pain
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• 제47권3호
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• pp.135-143
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• 2022

Purpose: This study aimed to evaluate polysomnographic and cephalometric characteristics of patients with OSA according to obesity level based on the World Health Organization (WHO) Asian-Pacific BMI criteria. Methods: One hundred and thirty-one consecutive patients with obstructive sleep apnea (OSA) were evaluated using standard level 1 polysomnography and cephalometric analyses. The subjects were categorized into normal, overweight and obese groups according to the WHO Asian-Pacific BMI criteria. Respiratory indices and cephalometric parameters were compared among groups. Results: The 131 patients consisted of 111 males and 20 females, with a mean age of 44.1±12.4 years. The mean value of BMI was 25.3±3.4 kg/m² for all subjects, 20.6±2.2 kg/m² for normal (n=27), 24.0±0.5 kg/m² for overweight (n=33) and 27.6±2.2 kg/m² for obese (n=71). The obese group had a significantly higher apnea-hypopnea index (AHI) and respiratory arousal index and lower oxygen saturation level than the normal group (p<0.05). Total AHI, mean oxygen saturation level and respiratory arousal index were significantly correlated with BMI (p<0.001). A longer soft palate and anterior position of the hyoid bone were significantly correlated with BMI level (p ≤0.05). Conclusions: Obese patients have a higher risk of compromised craniofacial skeletal features and soft tissue structures, and severe OSA than non-obese patients.