• Sleep Medicine and Psychophysiology
• /
• v.4 no.2
• /
• pp.164-171
• /
• 1997

Introduction : Periodic limb movement disorder (PLMD) is shown to common in patients with OSA and may become evident or worsened when treated with nasal continuous positive airway pressure (CPAP). Whether this is due to im proved sleep continuity. adverse nocturnal body positioning, uncovered by CPAP, or due to the CPAP stimulus is still debat-ed. We hypothesized that the increase in PLM activity following CPAP is associated with more supine-sleeping tendencies when being treated with CPAP. In the present work, we compared differences in the PLMD index (PLMI) and sleeping position of patients with sleep disordered breathing before and after CPAP treatment. Method : We studied 16 patients (mean age 46 yr, 9M, 7F) with OSA (11 patients) or UARS (5 patients) who either had PLMD on initial polysomnogram (baseline PSG) or on nasal CPAP trial (CPAP PSG). All periodic leg movements were scored on anterior tibialis EMG during sleep according to standard criteria (net duration; 0.5-5.0 seconds, intervals; 4-90 seconds. 4 consecutive movements). Paired t-tests compared PLMD index (PLMI), PLMD-related arousal index (PLMD-ArI), respiratory disturbance index (RDI), and supine sleeping position spent with baseline PSG and CPAP PSG. Results : Ten patients (63%) on baseline PSG and fifteen patients (94%) on CPAP PSG had documented PLMD ($PLMI{\ge}5$) respectively with significant increase on CPAP PSG(p<0.05). Ten patients showed the emergence (6/10 patients) or substantial worsening (4/10 patients) of PLMD during CPAP trial. Mean CPAP pressure was $7.6{\pm}1.8\;cmH_2O$. PLMI tended to increase from baseline PSG to CPAP PSG, and significantly increase when excluding 2 outlier (baseline PSG, $19.0{\pm}25.8/hr$ vs CPAP PSG, $29.9{\pm}12.5/hr$, p<0.1). PLMD-ArI showed no significant change, but a significant decrease was detected when excluding 2 outlier (p<0.1). There was no significant sleeping positional difference (supine vs non-supine) on baseline PSG, but significantly more supine position (supine vs non-supine, p<0.05) on CPAP PSG. There was no significant difference in PLMI during supine-sleeping and nonsupine-sleeping position on both of baseline PSG and CPAP PSG. There was also no significant difference in PLMI during supine-sleeping position between baseline PSG and CPAP PSG. With nasal CPAP, there was a highly significant reduction in the RDI (baseline PSG, $14.1{\pm}21.3/hr$ vs CPAP PSG, $2.7{\pm}3.9/hr$, p<0.05). Conclusion : This preliminary data confirms previous findings that CPAP is a very effective treatment for OSA, and that PLMD is developed or worsened with treatment by CPAP. This data also indicates that supine-sleeping position is more common when being treated with CPAP. However, there was no clear evidence that supine position is the causal factor of increased PLMD with CPAP. It is, however, suggested that the relative movement limitation induced by CPAP treatment could be a contributory factor of PLMD.

• Journal of Biomedical Engineering Research
• /
• v.21 no.4
• /
• pp.391-401
• /
• 2000

Flow through compliant tubes with linear taper in wall thickness is numerically simulated by finite element analysis. For verification of the numerical method, flow through a compliant stenotic vessel is simulated and the results are compared to the existing experimental data. Steady two-dimensional flow in a collapsible channel with initial tension is also simulated and the results are compared with numerical solutions from the literature. Computational results show that as cross-sectional area decreases with the reduction in downstream pressure, flow rate increases and reaches the maximum when the speed index (mean velocity divided by wave speed) is near the unity at the point of minimum cross-section area, indicating the flow limitation or choking (flow speed equals wave speed) in one-dimensional studies. for further reductions in downstream pressure, flow rate decreases. The flow limitation or choking consist of the main reasons of waterfall effect which occurs in the airways, capillaries of lung, and other veins. Cross-sectional narrowing is significant but localized. When the ratio of downstream-to-upstream wall thickness is 2, the area throat is located near the downstream end. As this ratio is increased to 3, the constriction moves to the upstream end of the tube.

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

• Tuberculosis and Respiratory Diseases
• /
• v.46 no.6
• /
• pp.803-810
• /
• 1999

Background : The patient's work of breathing(WOBp) during assisted ventilation may vary according to many factors including ventilatory demand of the patients and applied ventilatory setting by the physician. Pressure-controlled ventilation(PCV) which delivers gas with decelerating flow may better meet patients' demand to improve patient-ventilator synchrony compared with volume-controlled ventilation(VCV) with constant flow. This study was conducted to compare the difference in WOBp in two assisted modes of ventilation, PCV and VCV with constant flow. Methods : Ten patients with respiratory failure were included in this study. Initially, the patients were placed on VCV with constant flow at low tidal volume($V_{T,\;LOW}$)(6-8 ml/kg) or high tidal volume($V_{T,\;HIGH}$)(10-12 ml/kg). After a 15 minute stabilization period, VCV with constant flow was switched to PCV and pressure was adjusted to maintain the same tidal volume($V_T$) received on VCV. Other ventilator settings were kept constant. Before changing the ventilatory mode, WOBp, $V_T$, minute ventilation($V_E$), respiratory rate(RR), peak airway pressure (Ppeak), peak inspiratory flow rate(PIFR) and pressure-time product(PTP) were measured. Results : The mean $V_E$ and RR were not different between PCV and VCV during the study period. The Ppeak was significantly lower in PCV than in VCV during $V_{T,\;HIGH}$. HIGH ventilation(p<0.05). PIFR was significantly higher in PCV than in VCV at both $V_T$ (p<0.05). During $V_{T,\;LOW}$ ventilation, WOBp and PTP in PCV($0.80{\pm}0.37\;J/min$, $164.5{\pm}74.4\;cmH_2O.S$) were significantly lower than in VCV($1.06{\pm}0.39J/mm$, $256.4{\pm}107.5\;cmH_2O.S$)(p<0.05). During $V_{T,\;HIGH}$ ventilation, WOBp and PTP in PCV($0.33{\pm}0.14\;J/min$, $65.7{\pm}26.3\;cmH_2O.S$) were also significantly lower than in VCV($0.40{\pm}0.14\;J/min$, $83.4{\pm}35.1\;cmH_2O.S$)(p<0.05). Conclusion : During assisted ventilation, PCV with decelerating flow was more effective in reducing WOBp than VCV with constant flow. But since individual variability was shown, further studies are needed to confirm these results.

• Tuberculosis and Respiratory Diseases
• /
• v.52 no.4
• /
• pp.346-354
• /
• 2002

Background : Dyspnea and a limitation in exercise performance are important cause of disability in patients with chronic obstructive pulmonary disease(COPD). A depleted nutritional state is a common problem in patients with a severe degree of chronic airflow limitation. This study was carried out to assess the factors determining the maximum exercise capacity in patients with COPD. Methods : The resting pulmonary function, nutritional status, and maximum exercise performance was assessed in 83 stable patients with moderate to severe COPD. The nutritional status was evaluated by bioelectrical impedance analysis. Maximum exercise performance was evaluated by maximum oxygen uptake($VO_2max$). Results : Among the 83 patients, 59% were characterized by nutritional depletion. In the depleted group, a significantly lower peak expiratory flow rate(p<0.05), Kco(p<0.01) and maximum inspiratory pressure(p<0.05), but a significantly higher airway resistance(p<0.05) was observed. The maximum oxygen uptake and the peak oxygen pulse were lower in the depleted group. The $VO_2max$ correlated with some of the measures of the body composition : fat-free mass(FFM), fat mass(FM), body mass index(BMI), intracellular water index(ICW index), and pulmonary function : forced vital capacity(FVC), forced inspiratory vital capacity(FIVC), diffusion capacity(DLCO) : or maximum respiratory pressure : maximum inspiratory pressure(PImax), maximum expiratory pressure(PEmax). Stepwise regression analysis demonstrated that the FFM, DLCO and FIVC accounted for 68.8% of the variation in the $VO_2max$. Conclusion : The depletion of the FFM is significant factor for predicting the maximum exercise performance in patients with moderate to severe COPD.

• Journal of Chest Surgery
• /
• v.30 no.12
• /
• pp.1159-1166
• /
• 1997

For Improvement of lung preservation, many tripes of preservation solution were developed and tested. The aim of this study was to compare the effect of the most frequently used extracellular type pieservation solution (Low Potassium Dextran, LPD) with a newly developed trehalose containing extracellular type preservation solution(ET-Kyoto, ETK) on postischemic lung function. Twelve New-Zealand white rabbit lungs were harvested and studied on an isolated, blood-perfused model of lung function after 4 hours of cold ischemia at $10^{\circ}C$ In group I (n=6), lungs were preserved with 100 mL/kg of LPD solution; in group II(n=6), lungs were preserved with 100 mL/kg of ETK solution. A few minutes before flushing with preservation solutions, 20$\mu\textrm{g}$ of PGEI were injected into main pulmonary artery. Functions of the preserved lung were compared with PO2, PA pressure, t acheal air pressure, and drylwet ratio. The pulmonary efferent blood oxygen tension at the end of the 60-minute reperfusion period was higher in group II compacted with group I(486.5 $\pm$ 80.3 mmHg versus $432.5\pm82.9$ mmHg at FiO2 1.0, p-value = NS). The mean pulmonary arterial pressure was similar in both $groups.(33.7\pm2.2$ mmHg versus $35.5\pm2.0$ mmHg, p-value : NS). The peak inspiratory airway pressure was significantly lower in group 11(8.010.6 mmHg versus 11.8 $\pm$ 1.4 mmHg, p-value=0.02) The water content of the lung was lower in group II $(70.2\pm6.9%$ versus 78.5 $\pm6.1%),$ but not significant. These data demonstrate that a newly-developed trehalose-containing ET-Kyoto solution yield equal or slightly superior lung function after reperfusion compared with LPD solution.

• Tuberculosis and Respiratory Diseases
• /
• v.50 no.5
• /
• pp.540-548
• /
• 2001

Backgrounds : Because ventilator-induced lung injury is partly dependent on the intensity of vascular flow, we hypothesized that hypothermia may attenuate the degree of such an injury through a reduced cardiac output. Methods : Twenty-seven male Sprague-Dawley rats were randomly assigned to normothermia ($37{\pm}1^{\circ}C$)-injurious ventilation (NT-V) group (n=10), hypothermia ($27{\pm}1^{\circ}C$)-injurious ventilation (HT-V) group (n=10), or nonventilated control group (n=7). The two thermal groups were subjected to injurious mechanical ventilation for 20 min with peak airway pressure 30 cm $H_2O$ at zero positive end-expiratory pressure, which was translated to tidal volume $54{\pm}6\;ml$ in the NT-V group and $53{\pm}4\;ml$ in the HT-V group (p>0.05). Results : Pressure-volume (P-V) curve after the injurious ventilation was almost identical to the baseline P-V curve in the HT-V group, whereas it was shifted rightward in the NT-V group. On gross inspection, the lungs of the HT-V group appeared smaller in size, and showed less hemorrhage especially at the dependent regions, than the lungs of the NT-V group. [Wet lung weight (g)/body weight (kg)] ($1.6{\pm}0.1$ vs $2.4{\pm}1.2$ ; p=0.014) and [wet lung weight/dry lung weight] ($5.0{\pm}0.1$ vs $6.1{\pm}0.8$ ; p=0.046) of the HT-V group were both lower than those of the NT-V group, while not different from those of the control group($1.4{\pm}0.4$, $4.8{\pm}0.4$, respectively). Protein concentration of the BAL fluid of the HT-V group was lower than that of the NT-V group($1,374{\pm}726\;ug/ml$ vs $3,471{\pm}1,985\;ug/ml$;p=0.003). Lactic dehydrogenase level of the BAL fluid of the HT-V group was lower than that of the NT-V group ($0.18{\pm}0.10\;unit/ml$ vs $0.43{\pm}0.22\;unit/ml$;p=0.046). Conclusions : Hypothermia attenuated pulmonary hemorrhage, permeability pulmonary edema, and alveolar cellular injuries associated with injurious mechanical ventilation, and preserved normal P-V characteristics of the lung in rats.

• Tuberculosis and Respiratory Diseases
• /
• v.45 no.4
• /
• pp.813-822
• /
• 1998

Background: Extubation is recommended to be performed at minimum pressure support (PSmin) during the pressure support ventilation (PSV). In field, physicians sometimes perform additional 1 hr T-piece trial to the patient at PSmin to reduce re-intubation risk. Although it provides confirmation of patient's breathing reserve, weaning could be delayed due to increased airway resistance by endotracheal tube. Methods: To investigate the effect of additional 1 hr T-piece trial on weaning outcome, a prospective study was done in consecutive 44 patients who had received mechanical ventilation more than 3 days. Respiratory mechanics, hemodymic, and gas exchange measurements were done and the level of PSmin was calculated using the equation (PSmin=peak inspiratory flow rate $\times$ total ventilatory system resistance) at the 15cm $H_2O$ of pressure support. At PSmin, the patients were randomized into intervention (additional 1 hr T-piece trial) and control (extubation at PSmin). The measurements were repeated at PSmm, during weaning process (in cases of intervention), and after extubation. The weaning success was defined as spontaneous breathing more than 48hr after extubation. In intervention group, failure to continue weaning process was also considered as weaning failure. Results: Thirty-six patients with 42 times weaning trial were satisfied to the protocol. Mean PSmin level was 7.6 (${\pm}1.9$)cm $H_2O$. There were no differences in total ventilation times (TVT), APACHE III score, nutritional indices, and respiratory mechanics at PSmin between 2 groups. The weaning success rate and re-intubation rate were not different between intervention group (55% and 18% in each) and control group (70% and 20% in each) at first weaning trial. Work of breathing, pressure time product, and tidal volume were aggravated during 1 hr T-piece trial compared to those of PSmin in intervention group ($10.4{\pm}1.25$ and $1.66{\pm}1.08$ J/L in work of breathing) ($191{\pm}232$ and $287{\pm}217$cm $H_2O$ s/m in pressure time product) ($0.33{\pm}0.09$ and $0.29{\pm}0.09$ L in tidal volume) (P<0.05 in each). As in whole, TVT, and tidal volume at PSmin were significantly different between the patients with weaning success ($246{\pm}195$ hr, $0.43{\pm}0.11$ L) and the those with weaning failure ($407{\pm}248$ hr, $0.35{\pm}0.10$L) (P<0.05 in each). Conclusion : There were no advantage to weaning outcome by addition of 1 hr T-piece trial compared to prompt extubation to the patient at PS min.

• Sleep Medicine and Psychophysiology
• /
• v.18 no.2
• /
• pp.87-94
• /
• 2011

Objective: OSAS (obstructive sleep apnea syndrome) is a common disorder and its consequences are often serious. It is important to detect the disorder early in the course for proper treatment. This study is to grasp the snoring clinic visitors' knowledge level of OSAS. Method: One hundred and seventy-nine visitors at the of snoring clinic of Seoul National University Hospital were surveyed by questionnaire about reasons of visit and knowledge of treatment methods of snoring and OSAS, diagnostic method, OSAS-related symptoms, and complications. Results: Most of the respondents (89.4%) "have already heard about OSAS" and the major sources of information was the mass media (58.1%) such as television and radio. More than half (60.3%) were aware that snoring is closely related to OSAS. More than half (59.8%) recognized that a nocturnal polysomnograpy was necessary for proper diagnosis. Two thirds (67%) of the respondents noted surgery as a treatment for snoring. More than half (55.9%) answered that they would follow the doctor's advice on the treatment choice. Only 12.3% of respondents "have heard about nCPAP". No one chose nCPAP (nasal continuous positive airway pressure) as a treatment for either snoring or OSAS. About one third (34.6%) of the respondents were aware that OSAS is related to hypertension. Only 12.8% noted that OSAS is related to diabetes mellitus. Conclusion: Visitors at the snoring clinic were found to have substantially limited knowledge of health risks and proper treatments of OSAS. We suggest that it is crucially important to educate patients and offer easy-to-understand information on snoring and OSAS. We predict that provision of educaiton and information to patients and general public will faciliate the diagnosis and treatment of snoring and OSAS and reduce the related disorders such as hypertension, stroke, and diabetes mellitus.

• Sleep Medicine and Psychophysiology
• /
• v.12 no.1
• /
• pp.32-38
• /
• 2005

Objectives: Obstructive sleep apnea syndrome (OSAS) has drawn increasing attention as medical community has become to be aware of its co-morbidities and complications, especially cardiovascular complications and excessive daytime sleepiness with accident proneness. As of now, polysomnography is the standard tool to diagnose sleep apnea and estimate the treatment validity. However, its being rather expensive and inconvenient, alternate diagnostic tools have been proposed including wrist actigraphy. So far, actigraphies have been adopted usefully to field-survey sleep apnea prevalence. In this study, we attempted in a sleep laboratory setting to assess the supplemental value of actigraphy in diagnosing OSAS. Methods: This study was done at the Division of Sleep Studies, the Seoul National University Hospital. Thirty-seven clinically suspected cases of OSAS underwent the one-night polysomnography, simultaneously wearing an actigraphy on non-dominant wrist. We analyzed the data of 27 polysomnographically-proven OSAS patients (male：female 20： 7；age $47.6{\pm}12.9$ years old；age range 23 to 72 years) with no other sleep disorders. We calculated RDI (respiratory disturbance index) from the polysomnography data and FI (fragmentation index) from the actigraphy data. Pearson correlation was calculated in order to compare FI with RDI and to evaluate the supplemental diagnostic value of the actigraphy. Results: Mean total sleep time on polysomnography was $401.4{\pm}57.8\;min$ (range of 274.0 to 514.1 min). Mean RDI was $21.7{\pm}20.4/hour$. Mean FI was $21.9{\pm}13.0/hour$. RDI and FI showed significant correlation (r=0.55, p<0.01). Conclusions: Wrist actigraphy in OSAS patients generates a comparable outcome to polysomnography, in measuring the nocturnal sleep fragmentation. The actigraphy could be used supplementally in inpatients, outpatients, and field survey subjects, if polysomnography is unavailable or impossible. In follow-ups related with nasal CPAP (continuous positive airway pressure), upper airway surgery, and oral appliance in OSAS patients, the actigraphy might play a more dominant role in the future.