• Sleep Medicine and Psychophysiology
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• v.13 no.2
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• pp.45-51
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• 2006

Obstructive sleep apnea (OSA) syndrome disrupts normal sleep. However, there were few studies to evaluate the asymmetric distribution, the one of the important factors of normal sleep in OSA subjects. We hypothesized that asymmetry would be broken in OSA patients. 49 male subjects with the complaint of heavy snoring were studied with polysomnography. We divided them into two groups based on the apnea-hypopnea index (AHI) fifteen: 13 simple snoring group (SSN, average AHI $5.9{\pm}4.4$) and 32 OSA group (average AHI $47.3{\pm}23.9$). We compared split sleep variables between the first half and the second half of sleep within each group with paired t-test for the evaluation of asymmetry. Changes of sleep architecture of OSA were higher stage 1 sleep% (S1), total arousal index (TAI), AHI, and mean heart rate (HR) and lower stage 2 sleep% (S2), REM sleep%, and mean arterial O2 saturation (SaO2) than SSN subjects. SWS and wake time after sleep onset (WASO) were not different between two groups. In split-night analysis, OSA subjects showed higher S2, slow wave sleep% (SWS), spontaneous arousal index (SAI), and mean HR in the first half, and higher REM sleep% and mean SaO2 in the second half. Those were same pattern as in SSN subjects. Mean apnea duration and longest apnea duration were higher in the second half only in the OSA. No differences of AHI, ODI, WASO, and S1 were found between the first and the second half of sleep in both groups. TAI was higher in the first half only in the SSN. SWS and WASO seemed to be influenced sensitively by simple snoring as well as OSA. Unlike our hypothesis, asymmetric distributions of major sleep architecture variables were preserved in OSA group. Losing asymmetry of TAI might be related to pathophysiology of OSA. We need more studies that include large number of subjects in the future.

• Sleep Medicine and Psychophysiology
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• v.19 no.2
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• pp.77-83
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• 2012

Objectives: Recent studies have reported a correlation between obstructive sleep apnea syndrome (OSA) and depression. In attempt to verify the suggestion that eveningness is related to depression, we examined the effect of morningness-eveningness on their depressive mood in patinets with OSA. Methods: The examination was based on the medical records and polysomnography reports of 211 OSA patients. Information was gathered from the patients who filled out the H$\ddot{o}$rne and Ostberg questionnaire (HOQ), profile of mood states-Korean version (K-POMS), and Epworth sleepiness scale (ESS). We compared mean values of K-POMS total, subscales of K-POMS, ESS, and OSA severity variables among the 3 morningness-eveningness groups (morningness, eveningness, and neither groups). Partial correlation analysis was performed between variables and ANCOVA was performed among the 3 groups after adjustment with age and weight. Results: There were significant negative correlations between HOQ and the followings : K-POMS total, POMS-T (tension-anxiety), POMS-D (depression-dejection), POMS-A (anger-hostility), POMS-F (fatigue-inertia), POMS-C (confusion-bewilderment), spontaneous arousal index, average O2 saturation. There were significant positive correlations between HOQ and the followings : POMS-V (vigor-activity), apnea-hypopnea index, respiratory arousal index, snore time. There were significant negative correlations between POMS-D and the followings : HOQ, POMS-V, stage 1 sleep (%), AHI, TAI (total arousal index), oxygen desaturation index, respiratory arousal index, neck circumference, average O2 desaturation, snore time (%). There were significant positive correlations between POMS-D and K-POMS total, POMS-T, POMS-A, POMS-F, POMS-C, sleep latency, stage 2 sleep (%), heart rate, spontaneous arousal index. There were significant differences in K-POMS total, POMS-T, POMS-D, POMS-F, POMS-C, spontaneous arousal index among the three HOQ groups in ANCOVA. Conclusion: The depressive correlates of OSA patients might be affected, not by excessive daytime sleepiness or OSA severity indexes, but by eveningness circadian characteristics. It would be important to take into account the morningness-eveningness tendency when we manage the depressive mood of OSA patients.

• Tuberculosis and Respiratory Diseases
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• v.48 no.6
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• pp.956-963
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• 2000

Backgrounds : Obstructive sleep apnea syndrome(OSA) can divided into two groups, positional(PP) and non-positional(NPP) obstructive sleep apnea syndrome, according to the body position while sleeping. In this study, we evaluated the differences of anthropometric data and polysomnographic recordings between the two types of sleep apnea syndrome. Materials : Fifty patients with OSA were divided two groups by Cartwright's criteria. The supine respiratory disturbance index (RDI) was at least two times higher than the lateral RDI in the PP group, and the supine RDI was less than twice the lateral RDI in the NPP group. This patients underwent standardized polysomnographic recordings. The anthropometric data and polysomnographic data were analyzed, statistically. Results : Of all 50 patients, 30% were found to be positional OSA. BMI was significantly higher in the PP group(p<0.05). Total sleep time was significantly longer in the PP group (350.6$\pm$28.2min, 333.3$\pm$46.0min, (p<0.05). Sleep efficiency was high in the PP group(89.6$\pm$6.4%, 85.6$\pm$9.9%, p<0.05). Deep sleep was significantly higher and light sleep was lower in the PP group than in the NPP group but no difference was observed in REM sleep between the two groups. Apnea index(AI) and RDI were significantly lower( 17.0$\pm$10.6, 28.5$\pm$13.3, p<0.05) and mean arterial oxygen saturation was higher in the PP group(92.7$\pm$1.8%. p<0.05) than in the NPP group. Conclusion : Body position during sleep has a profound effect on the frequency and severity of breathing abnormalities in OSA patients. A polysomnographic evaluation for suspected OSA patients must include monitoring of the body position. Breathing function in OSA patients can be improved by controlling their obesity and through postural therapy.

• Journal of Korean Society of Forest Science
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• v.89 no.3
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• pp.323-334
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• 2000

This study was carried out to investigate the effects of geological and topographical features on landslide and land-creep at the twenty four surveyed sites of Kyungpook province. According to the results obtained, it was concluded that continuous heavy rainfall was one of the primary factors to occur landslide and land-creep. Most of the landslides occurred in the past were concentrated in the granite and granitic gneiss zones, while land-creeps were mainly occurred in the mud-stone zones. Therefore, it was thought that the physical properties such as soil texture, solid phase, moisture contents, density, hardness and porosity rate of weathered granite and granitic gneiss could affect the occurrence of landslide and land-creep. Due to the holding of sand contents in the upper soil layers of weathered granite and granitic gneiss, rainfall could infiltrate into the soil easily. While lower soil layers contained much quantity of clay and silt contents, those soils saturated with rainfall cause to lose viscosity and shear strength. Therefore, it was seemed that landslide was occurred more easily and the saturation of those soils was made much easily by bed rocks under those soils. Landslide and land-creep are slided into lower place by gravitation and slope degree factors. Therefore, prediction of landslide occurrence is very difficult because landslide is occurred abruptly, and physical properties of the soil have to be understood and checking the existence of bed rocks under the soils is not easy, on the other hand, land-creep is progressed very slowly. Therefore, it was suggested that in a degree creeping could be protected by removing of several causing factors.

• Sleep Medicine and Psychophysiology
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• v.21 no.1
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• pp.14-20
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• 2014

Objectives: Several studies suggest that nocturia may be related to obstructive sleep apnea syndrome (OSAS). The mechanism by which OSAS develops nocturia has not been determined. The present study aimed to determine the prevalence of nocturia among adults with OSAS and to identify factors that may be predictive in this regard. Methods: Retrospective review of clinical and polysomnographic data obtained from patients evaluated at the sleep clinics of the St. Paul's Hospital between 2009 and 2012. The urinary symptoms were assessed on the basis of the International Prostate Symptom Score (IPSS). Pathologic nocturia was defined as two or more urination events per night. OSAS was defined as apnea-hypopnea index (AHI) ${\geq}5$. A multivariate analysis using logistic regression was performed to examine the relationship between polysomnographic variables and the presence of pathologic nocturia, while controlling for confounding factor. Results: A total of 161 men >18 years of age (mean age $46.7{\pm}14.1$), who had been referred to a sleep laboratory, were included in the present study. Among these, 27 patients with primary snoring and 134 patients with obstructive sleep apnea were confirmed by polysomnography. Nocturia was found in 53 patients with OSAS (39.6%) and 8 patients with primary snoring (29.6%). The AHI was higher in patients with nocturia than in those without nocturia (p=0.001). OSAS patients with nocturia had higher arousal index (p=0.044), and lower nadir oxyhemoglobin saturation (p=0.001). Multiple regression analysis showed that age (${\beta}$=0.227, p=0.003), and AHI (${\beta}$=0.258, p=0.001) were associated with nocturia, and that the presence of pathologic nocturia was predicted by age (OR 1.04 ; p=0.004) and AHI (OR 1.02 ; p=0.001). Conclusion: Nocturia is common among patients with OSAS. The strongest predictors of nocturia are age and AHI in patients with OSAS.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.638-647
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• 2007

In this study, we present the evaluation chart for assessing the applicability of $CO_2$ flooding method to oil reservoirs. The evaluation chart consists of four categories as source availability, miscibility, applicability and injecting method of miscible flooding. The applicability of reservoir and oil in the chart has basic items of the properties such as oil gravity, viscosity, oil saturation, reservoir temperature and permeability, and these are quantitatively graded. Meanwhile, for additional items of $CO_2$ purity, reservoir thickness and formation dip, they are graded as "highmediumlow". In the case of evaluating the injection method of either continuous injection or WAG ($CO_2$), the qualitative decision will be made according to formation dip, vertical permeability, reservoir thickness, etc. The recommended score in the chart was assigned by utilizing 51 oil producing fields which $CO_2$ flooding is successfully being applied. The evaluation chart developed in this work has been applied to the Captain oil producing field located in Scotland as well as to the Onado oil field of Venezuela, which Korean oil companies have participated in. For the Captain field, the reservoir quality in terms of permeability and porosity is considered to be very excellent to flow the oil. The oil in captain field contains heavier component of $C_{21+}$ as 54%. Therefore, this heavy oil could be immiscibly displaced, hence the evaluating result with the basis of immiscible criteria shows that $CO_2$ immiscible flooding in this field could be properly applied. In the case of Onado oil producing field, since the estimated minimum miscibility pressure is lower than the reservoir pressure, it was assessed that the Onado field would be efficiently conducted for $CO_2$ miscible flooding.

• Journal of the Korean Magnetics Society
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• v.19 no.3
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• pp.89-93
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• 2009

Amorphous $Ge_{1-x}Mn_x$ semiconductor thin films grown by low temperature vapor deposition were annealed, and their electrical and magnetic properties have been studied. The amorphous thin films were $1,000{\sim}5,000\;{\AA}$ thick. Amorphous $Ge_{1-x}Mn_x$ thin films were annealed at $300^{\circ}C$, $400^{\circ}C$, $500^{\circ}C$, $600^{\circ}C$ and $700^{\circ}C$ for 3 minutes in high vacuum chamber. X-ray diffraction analysis reveals that as-grown $Ge_{1-x}Mn_x$ semiconductor thin films are amorphous and are crystallized by annealing. Crystallization temperature of amorphous $Ge_{1-x}Mn_x$ semiconductor thin films varies with Mn concentration. Amorphous $Ge_{1-x}Mn_x$ thin films have p-type carriers and the carrier type is not changed during annealing, but the electrical resistivity increases with annealing temperature. Magnetization characteristics show that the as-grown amorphous $Ge_{1-x}Mn_x$ thin films are ferromagnetic and the Curie temperatures are around 130 K. Curie temperature and saturation magnetization of annealed $Ge_{1-x}Mn_x$ thin films increase with annealing temperature. Magnetization behavior and X-ray analysis implies that formation of ferromagnetic $Ge_3Mn_5$ phase causes the change of magnetic and electrical properties of annealed $Ge_{1-x}Mn_x$ thin films.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.11
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• pp.9-18
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• 2003

Two configurations of Film Bulk Acoustic Wave Resonators with acoustic quater-wave bragg reflector layers are theoretically analyzed using equivalent circuits and the difference of their characteristics are discussed. We compare the characteristics of λ/2 mode to those of ideal FBAR with top and bottom electrode contacting air and the characteristics of λ/4 mode to those of ideal FBAR with top electrode contacting air and bottom electrode clamped. We assume that the piezoelectric film is ZnO, the electrode is A1 and the substrate is Si, ABCD parameters are extracted and input impedance is calculated by converting the equivalent circuit from Mason equivalent circuits to the simplified equivalent circuits that ABCD parameters are extracted possible, From the variation of resonance frequency due to the change of thickness of reflector layers and the variation of electrical Q due to the change of mechanical Q of reflector layers, it is confirmed that the reflector layer just under the bottom electrode have the greatest effect on the varation of resonance frequency and electrical Q. It is shown that the number of reflector layers required for the saturation of electrical Q decreases with the increase of the impedance ratio of reflector layers and electrical Q of λ/2 mode is larger than that of λ/4 mode, Electromechanical coupling factor is independent of the number of layers, The impedance ratio of reflector layers becomes larger as the electromechanical coupling factor becomes larger, The electromechanical coupling factor of the two mode are smaller than those of ideal FBARs because of the trapping of acoustic energy in the reflector layers, The insertion loss of the ladder filter decreases with the increase of the number of reflector layers but the bandwidth is not affected much by the number of reflector layers, As the impedance ratio of reflector layers becomes larger the insertion loss becomes smaller and the bandwidth becomes wider, In our analysis of the two mode, characteristics of λ/2 mode appear to be slightly more favorable than that of λ/4 mode

• Tuberculosis and Respiratory Diseases
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• v.45 no.2
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• pp.404-415
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• 1998

Background: Sleep apnea syndrome, which occurs in 1~4 % of the adult population, frequently has different cardiovascular complications such as hypertension, ischemic heart disease, cardiac arrythmia as well as sleep-wake disorder such as excessive daytime hypersomnolence or insomnia. Mortality and vascular morbidity are reported to be significantly higher in sleep apnea syndrome patients than in normal population. According to the recent studies, autonomic dysfunction as well as hypoxemia, hypercapneic acidosis, and increased respiratory effort, may playa role in the high prevalence of cardiovascular complications in patients with sleep apnea syndrome. However the cause and mechanism of autonomic neuropathy in patients with sleep apnea syndrome are not well understood. We studied the existence of autonomic neuropathy in patients with sleep apnea syndrome and factors which influence the pathogenesis of autonomic neuropathy. Method: We used the cardiovascular autonomic neuropathy(CAN) test as a method for evaluation of autonomic neuropathy. The subjects of this study were 20 patients who diagnosed sleep apnea syndrome by polysomnography and 15 persons who were normal by polysomnography. Results: Body mass index and resting systolic blood pressure were higher in sleep apnea group than control group. Apnea index(Al), respiratory disturbance index(RDI) and snoring time percentage were significantly higher in sleep apnea group compared with control group. But there were no significant differences in saturation of oxygen and sleep efficiency in two groups. In the cardiac autonomic neuropathy test, the valsalva ratio was significantly low in sleep apnea group compared with control group but other tests had no differences between two groups. The CAN scores and corrected QT(QTc) interval were calculated significantly higher in sleep apnea group, but there were no significant correlations between CAN scores and QTc interval. There were no significant data of polysomnography to correlate to the CAN score. It meant that the autonomic neuropathy in patients with sleep apnea was affected by other multiple factors. Conclusion: The cardiovascular autonomic neuropathy test was a useful method for the evaluation of autonomic neuropathy in patients with sleep apnea syndrome and abnormalities of cardiovascular autonomic neuropathy were observed in patients with sleep apnea syndrome. However, we failed to define the factors that influence the pathogenesis of autonomic neuropathy of sleep apnea syndrome. This study warrants futher investigations in order to define the pathogenesis of autonomic neuropathy in patients with sleep apnea syndrome.

• Tuberculosis and Respiratory Diseases
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• v.49 no.6
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• pp.715-723
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• 2000

Background : Obstructive sleep apnea syndrome (OSAS) affects systemic blood pressure and cardiac function. The development of cardiovascular dysfunction including the changes of systemic blood pressure and cardiac rhythm, suggests that recurrent hypoxia and arousals from sleep may increase a sympathetic nervous system activity. Continuous positive airway pressure (CPAP) therapy has been found to be an effective treatment of OSAS. However, only a few studies have investigated the cardiovascular and sympathetic effects of CPAP therapy. We evaluated influences of nasal CPAP therapy on the cardiovascular system and the sympathetic activity in patients with OSAS. Methods : Thirteen patients with OSAS underwent CPAP therapy and were monitored using polysomnography, blood pressure, heart rate, presence of arrhythmia and the concentration of plasma catecholamines, before and with CPAP therapy. Results: The apnea-hypopnea index (AHI) was significant1y decreased (p<0.01) and the lowest arterial oxygen saturation level was elevated significantly after applying CPAP (p<0.01). Systolic blood pressure tended to decrease after CPAP but without statistical significance. Heart rates during sleep were not significantly different after CPAP. However, the frequency and number of types of arrhythmia decreased and sinus bradytachyarrhythmia disappeared after CPAP. Although there was no significant difference in the level of plasma epinephrine concentration, plasma norepinephrine concentration significantly decreased after CPAP (p<0.05). Conclusion : CPAP therapy decreased the apnea-hypopnea index, hypoxic episodes and plasma norepinephrine concentration. In addition, it decreased the incidence of arrhythmia and tended to decrease the systemic blood pressure. These results indicate that CPAP may play an important role in the prevention of cardiovascular complications in patients with OSAS.