• Sleep Medicine and Psychophysiology
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• v.5 no.1
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• pp.103-110
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• 1998

Objectives : High co-morbidity of periodic limb movements during sleep(PLMS) and obstructive sleep apnea syndrome(OSAS) is well known and their incidences tend to increase in the elderly. Previous studies have inconsistently rep0l1ed increase or no change of periodic limb movement index(PLMI) by nasal continuous positive airway pressure(CPAP) in OSAS without analyzing possible variables affecting PLMI. We attempted to examine PLMI change evoked during CPAP titration and also factors affecting it in OSAS. Methods : Twenty-nine OSAS patients(M:F=26:3, mean age: $51.6{\pm}10.6\;yrs$) without other sleep disorders except for PLMS were selected, based on the nocturnal (baseline) polysomnograhy. Another night of noctumal polysomnography was performed for CPAP pressure titration. We compared between those two nights PLMI, mean and lowest $SaO_2$, and sleep variables. We also calculated PLMI differences between baseline and CPAP nights, named as delta PLMI (value of CPAP night PLMI minus value of baseline night PLMI). Correlations were calculated between delta PLMI and factors such as age, body mass index, applied CPAP pressure, baseline night values of respiratory disturbance index, mean and lowest $SaO_2$, and sleep parameter differences between baseline and CPAP nights. Results : Decrease of RDI(p<.01) and increase in mean and lowest $SaO_2$ (p<.05, p<.01) were observed during CPAP night. No sleep parameters showed significant change except for the decrease of total stage 1 sleep%(p<.01) during CPAP night. Ten out of 29 patients showed PLMI increase, while the other 19 patients showed either no change(n=14) or even PLMI decrease(n=5) during CPAP night. The 10 patients showing PLMI increase during CPAP night showed a significant positive correlation between delta PLMI and baseline night RDI(p<.05), which meant that PLMI increase was found to be more prominent in higher RDI patients than in lower RDI ones. There were no significant correlations between delta PLMI and other factors in the other 19 patients. Conclusions : We suggest that during the baseline night PLMS would have been underscored and/or masked due to the overlapping of PLMS and apneas/hypopneas or the arousals induced by apneas/hypopneas. Despite its still unknown mechanism, the CPAP application may unmask PLMS and increase PLMI in a subgroup of OSAS patients. It needs to be evaluated further whether the chronic CPAP use sustains the above finding.

• Tuberculosis and Respiratory Diseases
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• v.45 no.5
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• pp.1039-1046
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• 1998

Background: Sleep-related breathing disorders(SRBD) and periodic leg movements disorder(PLMD) are both common, and are considered as separate sleep disorders. However, both disorders show high comorbidity. SRBD and PLMD can result in excessive daytime sleepiness and insomnia due to frequent sleep fragmentation. So, it is very important to consider the presence of PLMD, when we are dealing with the diagnosis and management of SRBD. The objectives of this study were to determine the incidence of PLMD in patients with SRBD, and to describe any differences between patients with and without PLMD. Method: The authors reviewed the sleep recordings of 106 patients with a final diagnosis of SRBD(obstructive sleep apnea or upper airway resistance syndrome), who underwent full nocturnal polysomnography, including the monitoring of the anterior tibialis electromyogram. All sleep records were recorded and scored using the standard criteria. The data was analyzed by the student t-test. Result: 106 patients(M=76, F=30) were included in the analysis. Data revealed a mean age of $49.5{\pm}13.6$ years, a respiratory disturbance index(RDI) of $22.3{\pm}25.4$/hour sleep, a lowest oxygen saturation of $84.9{\pm}11.3%$, a maximal esophageal pressure of $-41.0{\pm}19.1cmH_2O$, and PLM index(PLMI) of $13.1{\pm}22.4$movements/hour sleep. Forty four percent(47 of 106 patients) had a PLMI of greater than 5 on this study. The mean age of the patients with PLMD was significantly higher than that of the patients without PLMD(p<0.005). Female patients with SRBD accompanied more PLMD(p<0.05). The apnea index of the patients with PLMD was significantly lower than that of the patients without PLMD(p<0.01). The percentage of stage 1 sleep in the patients with PLMD was significantly lower than that of the patients without PLMD(p<0.05). Conclusion: The prevalence of PLMD in the patients with SRBD was high at 44.3%. The patients with PLMD were older and had more high RDI in comparison to the patients without PLMD, which was consistent with previous findings. The authors recommend that more careful consideration of PLMD is required when diagnosing and treating SRBD.

• Sleep Medicine and Psychophysiology
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• v.3 no.2
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• pp.32-42
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• 1996

Objectives : Upper airway resistance syndrome(UARS) is a sleep-related breathing disorder characterized by abnormal negative intrathoracic pressure during sleep. Abnormally increased negative intrathoracic pressure results in microarousal and sleep fragmentation which underlay UARS-associated complaints of daytime fatigue and sleepiness. Although daytime dysfunction in patients with UARS is comparable to that of sleep apnea syndrome, UARS has been relatively unnoticed in clinical setting. That is why UARS is apt to be excluded in diagnosing of sleep-related breathing disorders since its respiratory disturbance index and arterial oxygen saturation are within normal limits. The current study presents a summary of clinical and polysomnographic characteristics found in patients with UARS. The present study aims (1) to explore characteristics of patients diagnosed with UARS, (2) to characterize the polysomnographic findings of UARS patients, and (3) to enhance the understanding of UARS through those clinical and laboratory characteristics. Methods : This was a retrospective study of 20 UARS patients (male 15, female 5) and 30 obstructive sleep apnea (OSA) patients (male 21, female 9) at the Stanford Sleep Disorders Clinic. We diagnosed patients as having UARS when they met critenia, RDI < 5 characteristic findings of an elevated esophageal pressure($<-10\;cmH_2O$), frequent arousals secondary to an elevated esophageal pressure, and symptoms of daytime fatigue and sleepiness. We used polysomnographic value, which is standardized by Williams et al(1974), as normal control. Statiotical test were done with student t-tests. Results : (1) Mean age of UARS was $41.0\;{\pm}\;14.8$ years and OSA was $50.9\;{\pm}\;12.0$ years. UARS subject was significantly younger than OSA subject (p<0.05). (2) The total score of Epworth Sleepiness Scale (ESS) was UARS $9.7\;{\pm}\;6.3$ and OSAS $11.2\;{\pm}\;6.3$. There was no significant difference between two groups. (3) The mean body mass index was UARS $28.1\;{\pm}\;5.7\;kg/m^2$ and OSAS $32.9\;{\pm}\;7.0\;kg/m^2$. UARS had significantly lower meen body man index than OSAS subjects (p<0.05). (4) The polysomnographic parameters of UARS were not significantly different from those of OSA except RDI(p<0.001), $SaO_2$ (p<0.001) and slow wave sleep latency (p<0.05). (5) Compared with normal control, Total sleep time in UARS subjects was significantly shorter (p<0.001), sleep efficiency index was significantly lower (p<0.001), total awakening percentage was significantly higher (p<0.001), and sleep stage 1 (p<0.001) were significantly higher. (6) OSA patients showed poor sleep quality and distinct abnormal sleep architectures compared with normal control. Conclusions : Conclusions from the above results are as follows : (1) UARS patients were younger and had lower body mass index when umpared with OSA patients. (2) The quality of sleep and sleep architectures of the UARS and OSA patients are significantly different from those of normal control. (3) ESS scores and awakening frequencies of UARS are similar with those of OSA, suggesting that daytime dysfunction of UARS patients may be comparable to those of OSA patients. (4) The RDI and the $SaO_2$ which are important indicators in diagnosing sleep-related breathing disorders, of UARS subjects are close to normal value. (5) According to the the above results, we unclude that despite the absence of $SaO_2$ drops and the absence of an elevated number of apnea and hypopnea, subjects developed clinical complaints which were associated with laborious breathing, elevated Pes nadir, and frequently snoring. (6) Accordingly, we suggest including LIARS in the differential diagnosis list when sleep related breathing disorder is suspected clinically and overnight polysomnographic findings except snoring and frequent microarousal are within normal limits.

• Journal of Environmental Science International
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• v.6 no.6
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• pp.605-612
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• 1997

This study is to evaluate the overall NPP(Net Primary Productions distribution in the Korean Peninsula from the satellite data(NOAA/AVHRR). This has been done using the linear relationship between the natural vegetation condition and the NPP. The NPP of natural vegetation increases proportional to the annual net radiation(Rn), where radiative dorless Index(RDI) is a proportional constant connecting Rn to NPP. Normalized Difference Vegetation Index(NDVI) Is used for monitoring vegetation change, and INDVI (Integrated NDVI) for annual analysis. The INDVI has a close relation to .Rn and NPP. which can be used effectively for estimating NPP distribution of where the meteorological data Is unavailable such as North Korea. The NPP distribution of the Korean Peninsula was estimated based on the model.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.426-430
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• 2009

본 연구에서는 ADCP 측정자료를 효율적으로 활용할 수 있도록 ADCP 이동측정법 자료의 후처리 프로그램을 개발하였다. 먼저, 측정된 ensemble과 방위별 유속으로 표시되던 단면유속분포를 한 눈에 알아볼 수 있도록 좌표를 정리하고 주흐름방향 유속을 출력하는 등, Sontek과 RDI 자료 취득 소프트웨어의 ascii 파일을 사용자가 쉽게 알아보고 가공할 수 있도록 변형하였다. 또한, 기존 ADCP 사용과 관련하여 발표된 screening 및 smoothing 기법을 적용하여 유효한 유속자료를 선별하고 단면의 평균 흐름에 근접한 유속자료를 제공하도록 하였다. 멱함수를 이용한 외삽으로 측정불가역의 유속 및 유량을 추정하였으며, 총 53개 측정자료의 유량을 추정한 결과 ADCP 소프트웨어가 제공하는 유량과 평균 1.33 %의 오차를 보였다. 마지막으로, 정리된 ADCP 자료로부터 하천의 주요 수리학적 특성을 추정하도록 하여 하천단면을 횡단하는 간단한 ADCP 측정만으로도 많은 시간과 노력을 들여 측정하던 하천의 특성을 신속히 파악할 수 있도록 하였다.

• Structural Engineering and Mechanics
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• v.43 no.2
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• pp.225-237
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• 2012

This paper presents an experimental investigation of the flexural behavior of square hollow steel section (HSS) beams subjected to pure bending. Totally six unfilled and nine ultra high performance concrete (UHPC)-filled HSS beams were tested under four-point bending until failure. The effects of the steel tube thickness, the yield strength of the steel tube and the strength of concrete on moment capacity, curvature, and ductility of UHPC-filled HSS beams were examined. The performance indices named relative ductility index (RDI) and strength increasing factor (SIF) were investigated with regard to different height-to-thickness ratio of the specimens. The flexural strengths obtained from the tests were compared with the values predicted by Eurocode 4, AISC-LRFD and CIDECT design codes. The results showed that the increase in the moment capacity and the corresponding curvature is much greater for thinner HSS beams than thicker ones. Eurocode 4 and AISC-LRFD predict the ultimate moment capacity of the all UHPC-filled HSS beams conservatively.

• IEMEK Journal of Embedded Systems and Applications
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• v.18 no.2
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• pp.59-65
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• 2023

Currently, polysomnography is essential to diagnose sleep-related breathing disorders. However, there are several disadvantages to polysomnography, such as the requirement for multiple sensors and a long reading time. In this paper, we propose a system for predicting the severity of sleep-related breathing disorders at home utilizing measurable elements in a wearable device. To predict severity, the variables were refined through a three-step variable selection process, and the refined variables were used as inputs into three machine-learning models. As a result of the study, random forest models showed excellent prediction performance throughout. The best performance of the model in terms of F1 scores for the three threshold criteria of 5, 15, and 30 classified as the AHI index was about 87.3%, 90.7%, and 90.8%, respectively, and the maximum performance of the model for the three threshold criteria classified as the RDI index was approx 79.8%, 90.2%, and 90.1%, respectively.

• Sleep Medicine and Psychophysiology
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• v.9 no.1
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• pp.24-33
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• 2002

Objectives: Nasal continuous positive airway pressure (CPAP) corrected elevated blood pressure (BP) in some studies of obstructive sleep apnea syndrome (OSAS) but not in others. Such inconsistent results in previous studies might be due to differences in factors influencing the effects of CPAP on BP. The factors referred to include BP monitoring techniques, the characteristics of subjects, and method of CPAP application. Therefore, we evaluated the effects of one night CPAP application on BP and heart rate (HR) reactivity using non-invasive beat-to-beat BP measurement in normotensive and hypertensive subjects with OSAS. Methods: Finger arterial BP and oxygen saturation monitoring with nocturnal polysomnography were performed on 10 OSAS patients (mean age $52.2{\pm}12.4\;years$; 9 males, 1 female; respiratory disturbance index (RDI)>5) for one baseline night and another CPAP night. Beat-to-beat measurement of BP and HR was done with finger arterial BP monitor ($Finapres^{(R)}$) and mean arterial oxygen saturation ($SaO_2$) was also measured at 2-second intervals for both nights. We compared the mean values of cardiovascular and respiratory variables between baseline and CPAP nights using Wilcoxon signed ranks test. Delta ($\Delta$) BP, defined as the subtracted value of CPAP night BP from baseline night BP, was correlated with age, body mass index (BMI), baseline night values of BP, BP variability, HR, HR variability, mean $SaO_2$ and respiratory disturbance index (RDI), and CPAP night values of TWT% (total wake time%) and CPAP pressure, using Spearman's correlation. Results: 1) Although increase of mean $SaO_2$ (p<.01) and decrease of RDI (p<.01) were observed on the CPAP night, there were no significant differences in other variables between two nights. 2) However, delta BP tended to increase or decease depending on BP values of the baseline night and age. Delta systolic BP and baseline systolic BP showed a significant positive correlation (p<.01), but delta diastolic BP and baseline diastolic BP did not show a significant correlation except for a positive correlation in wake stage (p<.01). Delta diastolic BP and age showed a significant negative correlation (p<.05) during all stages except for REM stage, but delta systolic BP and age did not. 3) Delta systolic and diastolic BPs did not significantly correlate with other factors, such as BMI, baseline night values of BP variability, HR, HR variability, mean SaO2 and RDI, and CPAP night values of TWT% and CPAP pressure, except for a positive correlation of delta diastolic pressure and TWT% of CPAP night (p<.01). Conclusions: We observed that systolic BP and diastolic BP tended to decrease, increase or remain still in accordance with the systolic BP level of baseline night and aging. We suggest that BP reactivity by CPAP be dealt with as a complex phenomenon rather than a simple undifferentiated BP decrease.

• Sleep Medicine and Psychophysiology
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• v.9 no.1
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• pp.34-40
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• 2002

Objectives: The gold standard for diagnosing obstructive sleep apnea syndrome (OSAS) is nocturnal polysomnography (NPSG). This is rather expensive and somewhat inconvenient, however, and consequently simpler and cheaper alternatives to NPSG have been proposed. Oximetry is appealing because of its widespread availability and ease of application. In this study, we have evaluated whether oximetry alone can be used to diagnose or screen OSAS. The diagnostic performance of an analysis algorithm using arterial oxygen saturation ($SaO_2$) base on 'dip index', mean of $SaO_2$, and CT90 (the percentage of time spent at $SaO_2$<90%) was compared with that of NPSG. Methods: Fifty-six patients referred for NPSG to the Division of Sleep Studies at Seoul National University Hospital, were randomly selected. For each patient, NPSG with oximetry was carried out. We obtained three variables from the oximetry data such as the dip index most linearly correlated with respiratory disturbance index (RDI) from NPSG, mean $SaO_2$, and CT90 with diagnosis from NPSG. In each case, sensitivity, specificity and positive and negative predictive values of oximetry data were calculated. Results: Thirty-nine patients out of fifty-six patients were diagnosed as OSAS with NPSG. Mean RDI was 17.5, mean $SaO_2$ was 94.9%, and mean CT90 was 5.1%. The dip index [4%-4sec] was most linearly correlated with RDI (r=0.861). With dip index [4%-4sec]${\geq}2$ as diagnostic criteria, we obtained sensitivity of 0.95, specificity of 0.71, positive predictive value of 0.88, and negative predictive value of 0.86. Using mean $SaO_2{\leq}97%$, we obtained sensitivity of 0.95, specificity of 0.41, positive predictive value of 0.79, and negative predictive value of 0.78. Using $CT90{\geq}5%$, we obtained sensitivity of 0.28, specificity of 1.00, positive predictive value of 1.00, and negative predictive value of 0.38. Conclusions: The dip index [4%-4sec] and mean $SaO_2{\leq}97%$ obtained from nocturnal oximetry data are helpful in diagnosis of OSAS. CT90${\leq}$5% can be also used in excluding OSAS.

• Tuberculosis and Respiratory Diseases
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• v.42 no.2
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• pp.206-217
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• 1995

Background: In patients with obstructive sleep apnea syndrome(OSAS), there are several factors increasing upper airway resistance and there is a predisposition to compromised respiratory function during waking and sleep related to constitutional factors including a tendency to obesity. Several recent studies have suggested a possible relationship between sleep apnea(SA) and systemic hypertension. But the possible pathophysiologic link between SA and hypertension is still unclear. In this study, we have examined the relationship among age, body mass index(BMI), pulmonary function parameters and polysomnographic data in patients with OSAS. And also we tried to know the difference among these parameters between hypertensive OSAS and normotensive OSAS patients. Methods: Patients underwent a full night of polysomnography and measured pulmonary function during waking. OSAS was diagnosed if patients had more than 5 apneas per hour(apnea index, AI). A careful history of previously known or present hypertension was obtained from each patient, and patients with systolic blood pressure $\geq$ 160mmHg and/or diastolic blood pressure $\geq$ 95mmHg were classified as hypertensives. Results: The noctural nadir of arterial oxygen saturation($SaO_2$ nadir) was negatively related to AI and respiratory disturbance index(RDI), and the degree of noctural oxygen desaturation(DOD) was positively related to AI and RDI. BMI contributed to AI, RDI, $SaO_2$ nadir and DOD values. And also BMI contributed to $FEV_1,\;FEV_1/FVC$ and DLco values. There was a correlation between airway resistance(Raw) and AI, and there was a inverse correlation between DLco and DOD. But there was no difference among these parameters between hypertensive OSAS and normotensive OSAS patients. Conclusion: The obesity contributed to the compromised respiratory function and the severity of OSAS. AI and RDI were important factors in the severity of hypoxia during sleep. The measurement of pulmonary function parameters including Raw and DLco may be helpful in the prediction and assessment of OSAS patients. But we could not find clear difference between hypertensive and normotensive OSAS patients.