Guang-Ming Shiao

Effect of Rapid Ascent to High Altitude on Autonomic Cardiovascular Modulation

Background:Effect of acute hypobaric hypoxia on autonomic nervous activities remains unclear. We evaluated the effect of rapid ascent to high altitude on autonomic cardiovascular modulation and compared the differences between the subjects with and without acute mountain sickness (AMS). Method:Twenty-seven unacclimatized healthy subjects were included for this study. The sleep and study altitude (3180 m) was reached by car from low level (555 m) within 3 hours. The stationary spectral heart rate variability was measured 3 days before ascent (T0), 2 nights at high altitude (T1 and T2), and 2 days after descent (T3). AMS occurrence was evaluated by the Lake Louise score system. Results:At high altitude, RR intervals (RRI), standard deviation of RRI (SDRR), total power (TP), low-frequency power (LF), high-frequency power (HF), and normalized HF decreased significantly but normalized LF and LF/HF ratio increased significantly in subjects irrespective of AMS. AMS developed in 13 of 27 (48.1%) subjects. Compared with the data at T1, SDRR, TP, LF, and HF increased at T2 in AMS group but decreased in non-AMS group, and the differences in these variables (data at T2 minus data at T1) between the 2 groups showed statistical significance. Conclusions:After rapid ascent to high altitude, autonomic nervous activities were suppressed and sympathetic activity was relatively predominant. At high altitude, the discordant changes in SDRR, TP, LF, and HF may reflect varying capacity of acute hypobaric hypoxic adaptation between the subjects with and without AMS.

Sleep Apnea and Risk of Deep Vein Thrombosis: A Non-randomized, Pair-matched Cohort Study

BACKGROUND Patients with sleep apnea have been reported to be associated with increased prevalence of deep vein thrombosis (DVT) in some papers, which were criticized for either a small sample size or lack of a prospective control. Our study strived to explore the relationship of sleep apnea and the subsequent development of DVT using a nationwide, population-based database. METHODS From 2000 to 2007, we identified a study cohort consisting of newly diagnosed sleep apnea cases in the National Health Insurance Research Database. A control cohort without sleep apnea, matched for age, sex, comorbidities, major operation, and fractures, was selected for comparison. The 2 cohorts were followed-up, and we observed the occurrence of DVT by registry of DVT diagnosis. RESULTS Of the 10,185 sampled patients (5680 sleep apnea patients vs. 4505 control), 40 (0.39%) cases developed DVT during a mean follow-up period of 3.56 years, including 30 (0.53%) from the sleep apnea cohort and 10 (0.22 %) from the control group. Subjects with sleep apnea experienced a 3.113-fold (95% confidence interval, 1.516-6.390; P=.002) increase in incident DVT, which was independent of age, sex, and comorbidities. Kaplan-Meier analysis also revealed the tendency of sleep apnea patients toward DVT development (log-rank test, P=.001). The risk of DVT was even higher in sleep apnea cases who needed continuous positive airway pressure treatment (hazard ratio 9.575; 95% confidence interval, 3.181-28.818; P <.001). CONCLUSION Sleep apnea may be an independent risk factor for DVT.

Effect of large-volume paracentesis on pulmonary function in patients with cirrhosis and tense ascites

The effect of large-volume paracentesis on lung function was evaluated in 12 male patients with cirrhosis. All underwent pulmonary function tests including spirometry, plethysmography and single-breath carbon-monoxide diffusing capacity 1 day before and after paracentesis. The amount of ascitic fluid removed ranged from 3.6 to 131 (mean +/- SD, 7.4 +/- 3.01). After paracentesis, forced vital capacity, forced expiratory volume at 1 s, total lung capacity, functional residual capacity, inspiratory capacity, expiratory reserve volume, diffusing capacity and alveolar volume increased significantly. In contrast, Kco (diffusing capacity corrected by alveolar volume) decreased significantly. After paracentesis, the increase in diffusing capacity was highly correlated with lung volumes and the amount of removed ascitic fluid. Nevertheless, a significantly negative correlation was found between the change of Kco before and after paracentesis and that of lung volumes. The increase in lung volumes and ventilation to the lower lungs with unfavorable ventilation-perfusion matching might explain the discrepancy between changes in diffusing capacity and Kco after large-volume paracentesis. In conclusion, these results suggest that pulmonary function in patients with cirrhosis and tense ascites is partly improved by large-volume paracentesis. Large-volume paracentesis might be useful for symptomatic relief in selected patients with tense ascites.

Sleep Apnea and Risk of Retinal Vein Occlusion: A Nationwide Population-Based Study of Taiwanese

PURPOSE To explore the relationship of sleep apnea and the subsequent development of retinal vein occlusion (RVO). DESIGN A retrospective nonrandomized, matched-control cohort study using the Taiwan National Health Insurance Research Database. METHODS From 1997 through 2007, we identified newly diagnosed sleep apnea cases in the database. A control group without sleep apnea, matched for age, gender, and comorbidities, was selected for comparison. The 2 cohorts were followed up, and the occurrence of RVO was observed. RESULTS Of the 35 634 sampled patients (5965 sleep apnea patients vs 29 669 controls), 52 (0.15%) experienced RVO during a mean follow-up period of 3.72 years, including 13 (0.22%, all branch RVO) from the sleep apnea cohort and 39 (0.13%, 39 branch RVO and 10 central RVO) from the control group. Kaplan-Meier analysis revealed the tendency of sleep apnea patients toward RVO development (P = .048, log-rank test). Patients with sleep apnea experienced a 1.94-fold increase (95% confidence interval, 1.03 to 3.65; P = .041) in incident RVO, which was independent of age, gender, and comorbidities. CONCLUSIONS Sleep apnea may be an independent risk factor for RVO.

The effects of high-fat and high-carbohydrate diet loads on gas exchange and ventilation in COPD patients and normal subjects.

Reducing the CO2 production (VCO2) is a plausible means to lower the ventilatory demand in the treatment of patients with COPD. The purpose of this study was to examine the effects of high-fat and high-carbohydrate (high-CHO) diet loads on gas exchange and ventilation in the COPD patients and normal subjects. The percentage of changes in the averaged values of VCO2, O2 consumption (VO2), respiratory quotient (RQ), minute ventilation (VE), and end-tidal CO2 (ETCO2) measured by a mass spectrometer for 5 min every 30 min after the diet were compared between diets and between study subjects. Compared with the high-fat diet, the high-CHO diet can lead to significantly higher levels of VCO2, VO2, RQ, and VE in the COPD patients 30 to 60 min after the diet, and the differences can last for about 1.5 h. The comparison between COPD patients and normal control subjects also showed that the high-CHO diet load can result in significantly higher levels of VCO2, VO2, and VE, and significantly lower level of ETCO2 in the COPD patients, whereas the high-fat diet cannot. In addition, enhanced thermic effect of food within 150 min (TEF150) occurred in the COPD patients as compared with that of normal controls, and the increase in TEF150 occurred only with the high-CHO diet. This study suggested that a high-fat diet is more beneficial to the COPD patient than a high-CHO diet, and that the gas exchange and energy utilization of the COPD patients following a high-CHO diet might be different from that of normal control subjects.

Sleep apnea and risk of peptic ulcer bleeding: a nationwide population-based study.

OBJECTIVE Patients with sleep apnea sustain cessation of breath during sleep, leading to intermittent hypoxia, systemic inflammation, and sympathetic activation. These insults may contribute to initiation or progression of peptic ulcers. This retrospective matched-control cohort study explored the relationship of sleep apnea and subsequent development of peptic ulcer bleeding. METHODS From 2000 to 2009, patients with newly diagnosed sleep apnea were identified from the Taiwan National Health Insurance Research Database. A control group without sleep apnea, matched for age, gender, comorbidities, and medications, was selected for comparison. In both groups, subjects with history of peptic ulcer bleeding, nonspecific gastrointestinal bleeding, or malignancy were excluded. The 2 cohorts were followed up and observed for occurrence of peptic ulcer bleeding. RESULTS Of the 35,480 sampled patients (7096 patients with sleep apnea vs 28,384 controls), 84 (0.24%) experienced peptic ulcer bleeding during a follow-up period of 3.57±2.61 years, including 32 (0.45% of patients with sleep apnea) from the sleep apnea cohort and 52 (0.18% of control) from the control group (log-rank test, P<.0001). In comparison with subjects without development of peptic ulcer bleeding, those with peptic ulcer bleeding were older and had a higher percentage of sleep apnea, coronary artery disease, peptic ulcer, ischemic stroke, and medication for nonsteroidal anti-inflammatory drugs. By Cox regression analysis, sleep apnea, older age, and peptic ulcer history were independent predictors of peptic ulcer bleeding. Patients with sleep apnea experienced a 2.400-fold (95% confidence interval, 1.544-3.731; P<.001) higher risk for incident peptic ulcer bleeding after adjusting for other variables. CONCLUSIONS Sleep apnea may be an independent risk factor for peptic ulcer bleeding.

Therapeutic effects of diuretics and paracentesis on lung function in patients with non-alcoholic cirrhosis and tense ascites.

BACKGROUND/AIMS Ascites may cause or aggravate pulmonary dysfunction in patients with liver cirrhosis. Diuretics and paracentesis are the main therapies for ascites. The aim of the present study was to evaluate and compare the therapeutic effects of diuretics and large-volume paracentesis on lung function in 26 male patients with non-alcoholic cirrhosis and tense ascites. METHODS The patients were divided into two groups. Group A was composed of 13 subjects who were treated with diuretics including spironolactone (100-400 mg/day) and furosemide (80-320 mg/day). In group B, 13 subjects received large-volume paracentesis plus intravenous albumin (6-8 g/l ascites removed). Pulmonary function tests including spirometry, plethysmography, single-breath carbon-monoxide diffusing capacity (DLco) and arterial blood gases, were done 1 day before diuretic treatment and 1 day after termination of the study in group A patients, and 1 day before and after large-volume paracentesis in group B subjects. RESULTS Before treatment, the clinical and laboratory data were comparable between the two groups. After treatment, ventilatory function as evidenced by forced expiratory volume in 1 s, forced vital capacity, total lung capacity, functional residual capacity and expiratory reserve volume, and DLco increased significantly in both groups. Arterial PO2 and PCO2 increased significantly and AaPO2 (alveolar-arterial PO2 difference) decreased significantly in the subjects treated with diuretics. Nevertheless, paracentesis did not improve arterial blood gases. The changes in lung volumes, DLco and PaO2 after treatment (the data after minus those before treatment) were comparable, except that a significant decrease in AaPO2 was observed in the diuretic group. CONCLUSIONS Both diuretic therapy and large-volume paracentesis significantly improved the ventilatory function in patients with tense cirrhotic ascites. In terms of oxygenation improvement as evaluated by AaPO2, diuretic treatment may be superior to large-volume paracentesis.

The minimum period of polysomnography required to confirm a diagnosis of severe obstructive sleep apnoea.

Background and objective:  To combine the diagnosis of OSA with titration of positive airway pressure (PAP), current guidelines recommend that split‐night polysomnography (PSG) be performed if an AHI of ≥40/h is recorded over 2 h. However, the diagnostic validity of partial‐night PSG is uncertain. This study aimed to test the validity of partial‐night PSG and to determine the optimum AHI cut‐off points.

Increased Morning Cortisol Level: Effect of Sleep Fragmentation or Stress Response to the Last Annoying Stimulus?

Fragmented sleep has great effects on daily life, including sleepiness, impaired cognitive function, decreased mood, and elevated BP. 1 3 In an excellent study in a recent issue of CHEST (January 2010), Stamatakis and Punjabi 4 show that two nights of nonspecifi c sleep fragmentation in healthy volunteers led to decreased insulin sensitivity and glucose effectiveness despite normal sleep duration. This study helps to elucidate the infl uence of sleep fragmentation per se on glucose metabolism without the confounding effect of sleep duration or hypoxic insult, as seen in the case of obstructive sleep apnea. The authors concluded that increased sympathetic activity and adrenocortical activity likely mediate the adverse effects of poor sleep quality, based on the fi nding of increased morning cortisol levels and increased sympathetic activity. They used auditory and mechanical stimuli to elicit EEG microarousals with a frequency of 30 events/h. If the stimuli failed, the subsequent stimulus got larger by increasing the tone volume of auditory stimuli or combining the two kinds of stimulus. In this study, most of the stimuli were effective, including the last one at the end of the sleep period, which was probably the largest stimulus in intensity. When a human is exposed to noxious or potentially noxious stimuli, there is an increased secretion of corticotropin and, consequently, a rise in the circulating cortisol. Approximately 90% to 95% of the cortisol in the plasma binds to plasma proteins, which slows the elimination of cortisol from the plasma. Therefore, cortisol has a relatively long half-life of 60 to 90 min and thus a lasting action. 5 An increased morning cortisol level (measured at 8:00 am in this study) may be the consequence of the last effective stimulus, elicited 1 or 2 h prior to measurement, rather than that of sleep fragmentation. As the authors stated, elevations of cortisol, even within the normal physiologic range, can decrease insulin sensitivity, enhance hepatic gluconeogenesis, and inhibit insulin secretion. 6 To settle this dispute, one additional night of nonfragmented sleep following the two nights of fragmented sleep is needed as a sleep-recovery period, as stated in some sleep deprivation studies. 7 9 In addition, one single stimulus is given near the end of the night, which is of the same intensity and timing as the last stimulus in the previous night of sleep fragmentation. If an elevated cortisol level is still observed in the coming morning (day 5), the disturbed glucose metabolism may not be attributed to the effect of sleep fragmentation. Besides, evening cortisol concentration following sleep deprivation was raised in sleep deprivation studies, reflecting an impairment of negative feedback control of the hypothalamopituitary-adrenal axis. 8 , 10 This fi nding was not observed in this study, suggestive of a different mechanism underlying sleep deprivation and sleep fragmentation, or just an unequal stress in intensity, which deserves further exploring.

Realization of a CORDIC-Based Plug-In Accelerometer Module for PSG System in Head Position Monitoring for OSAS Patients

Overnight polysomnography (PSG) is currently the standard diagnostic procedure for obstructive sleep apnea (OSA). It has been known that monitoring of head position in sleep is crucial not only for the diagnosis (positional sleep apnea) but also for the management of OSA (positional therapy). However, there are no sensor systems available clinically to hook up with PSG for accurate head position monitoring. In this paper, an accelerometer-based sensing system for accurate head position monitoring is developed and realized. The core CORDIC- (COordinate Rotation DIgital Computer-) based tilting sensing algorithm is realized in the system to quickly and accurately convert accelerometer raw data into the desired head position tilting angles. The system can hook up with PSG devices for diagnosis to have head position information integrated with other PSG-monitored signals. It has been applied in an IRB test in Taipei Veterans General Hospital and has been proved that it can meet the medical needs of accurate head position monitoring for PSG diagnosis.