Impact of rapid ascent to high altitude on sleep.

PURPOSE: Sleep disturbance at high altitude is common in climbers. In this study, we intended to evaluate the effect of rapid ascent on sleep architecture using polysomnography (PSG) and to compare the differences between subjects with and without acute mountain sickness (AMS). METHODS: The study included 40 non-acclimatized healthy subjects completing PSG at four time points, 3 days before the ascent (T0), two successive nights at 3150 m (T1 and T2), and 2 days after the descent (T3). All subjects were transported by bus from 555 to 3150 m within 3 h. AMS was diagnosed using self-reported questionnaire of Lake Louise score. RESULTS: Twenty of 40 (50%) subjects developed AMS. At high altitude, awakening percentages increased in AMS group but changed insignificantly in non-AMS group. Arousal index and apnea/hypopnea index (AHI) increased irrespective of AMS. The increases of AHI were more evident in non-AMS group than in AMS group. Compared to subjects without AMS, those with AMS had significantly lower sleep efficiency, lower central apnea index, and longer latencies to sleep and rapid eye movement (REM) sleep at T1 and lower REM sleep percentages at T1 and T2. Subjects with older age and lower minimum arterial oxygen saturation during sleep at sea level were prone to develop AMS. CONCLUSIONS: Higher AHI did not cause more frequent awakenings and arousals at high altitude. Central sleep apneas were observed in non-AMS but not in AMS group. Subjects unacclimatized to acute hypobaric hypoxia might have delayed and less REM sleep.

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 2h. 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. METHODS: Patients who visited the sleep centre at a tertiary medical centre between January and December 2008, for symptoms related to sleep disorders (sleepiness, snoring, sleep disturbance), and who completed full-night PSG, were evaluated for this study. Full-night PSG data were processed to obtain partial-night PSG data, from which AHI were computed as a reference for diagnosing severe OSA. Full-night and partial-night PSG data obtained over different recording times (expressed as x-h PSG, where xONL001831140 =1-6) were compared using receiver operating characteristic (ROC) curve analysis. The diagnostic validity of 2-h PSG with different AHI cut-off points (25/h to 45/h) was also calculated. RESULTS: Data from 198 PSG recordings was processed. For 2-h PSG, an AHI cut-off point of 30/h gave the highest accuracy of 90.9%. Comparing areas under the ROC curves (AUC), 2-h PSG (AUC=0.97) was as good as 2.5-h PSG (AUC=0.977, P=0.057) and 3-h PSG (AUC=0.978, P=0.125), but was better than 1.5-h PSG (AUC=0.955, P=0.016). CONCLUSIONS: Partial-night PSG is effective for diagnosing severe OSA. If there is an unabridged PSG recording indicating an AHI of ≥30/h for 2h, severe OSA can be diagnosed and PAP titration initiated.

Craniofacial abnormalities in Chinese patients with obstructive and positional sleep apnea.

BACKGROUND: Obstructive sleep apnea (OSA) is a common disorder characterized by recurrent episodes of a complete or partial collapse of the upper airway during sleep. Traditionally, the disease is diagnosed by overnight polysomnography. Studies have shown correlation between parameters of cephalometry and severity of sleep apnea. We wish to determine the variable of craniofacial dimensions in the upper airway that contribute to OSA, and to investigate the significance of craniofacial measurements in positional and non-positional sleep apnea patients. METHODS: From July 2002 to June 2006, we studied 84 males and 15 females who came to the sleep center because of daytime sleepiness. All the participants underwent overnight polysomnography and lateral cephalograms, performed by an experienced technician. RESULTS: Craniofacial measurements of gnathion-gonion, anterior superior hyoid to mandibular plane (MP-H), posterior nasal spine (PNS) to the velum tip (SPL), widest point of the soft palate (SPW), and the product of PNS to the velum tip and widest point of the soft palate (product of soft palate (SPP)=SPL x SPW) were positively related to the apnea/hypopnea index (AHI). The velum tip to the pharyngeal wall parallel to the Frankfurt horizontal (PAS) was negatively related to the AHI. We further divided the study subjects into 4 groups according to AHI value (group 1, AHI<5; group 2, 5 or=30). Age, body mass index (BMI), neck circumference (NC), distances of PAS, SPL, SPW, SPP and angle of sella-nasion-infradentale (SNB) were significantly different depending on the degree of severity of sleep-disordered breathing (SDB). Patients who were older, with a high BMI and longer MP-H distance, had more daytime sleepiness (Epworth sleepiness scale, ESS). Furthermore, lower AHI values and longer PAS measurements were found in the positional sleep apnea group when compared to the non-positional sleep apnea group. After adjusting for confounding factors of age, BMI and NC, we found that BMI, MP-H distance and PAS measurement were correlated with severity of OSA. CONCLUSIONS: Cephalometry could be a useful and inexpensive clinical tool to evaluate Chinese patients with OSA. MP-H and PAS should be measured in Chinese patients with OSA. MP-H was correlated with ESS. The PAS measurement was narrower in non-positional OSA patients compared to positional OSA patients.

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.

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.

Associations between submicrometer particles exposures and blood pressure and heart rate in patients with lung function impairments.

OBJECTIVE: The objective of this study was to evaluate whether submicrometer particle is associated with elevated blood pressure (BP) and heart rate (HR). METHODS: We measured ambulatory systolic BP (SBP), diastolic BP (DBP), and HR using a portable BP monitoring system and number concentrations of submicrometer particle with a size range of 0.02 to 1 microm (NC0.02-1) by a P-TRAK Ultrafine Particle Counter for 10 patients with lung function impairments. RESULTS: We found NC0.02-1 exposures at 1- to 3-hour moving averages were associated with the elevation of SBP, DBP, and HR. There were 1.4 to 3.4-mm-Hg increases in SBP, 1.4 to 2.2-mm-Hg increases in DBP, and 0.3 to 3.5-beats/min increases in HR for 10,000 particles/cm increases in NC0.02-1 at 1- to 3-hour moving averages. CONCLUSIONS: Exposures to submicrometer particles were associated with short-term increases in BP and HR in patients with lung function impairments.

Personal exposure to submicrometer particles and heart rate variability in human subjects.

We conducted a study on two panels of human subjects--9 young adults and 10 elderly patients with lung function impairments--to evaluate whether submicrometer particulate air pollution was associated with heart rate variability (HRV). We measured these subjects' electrocardiography and personal exposure to number concentrations of submicrometer particles with a size range of 0.02-1 microm (NC0.02-1) continuously during daytime periods. We used linear mixed-effects models to estimate the relationship between NC0.02-1 and log10-transformed HRV, including standard deviation of all normal-to-normal intervals (SDNN), square root of the mean of the sum of the squares of differences between adjacent NN intervals (r-MSSD), low frequency (LF, 0.04-0.15 Hz), and high frequency (HF, 0.15-0.40 Hz), adjusted for age, sex, body mass index, tobacco exposure, and temperature. For the young panel, a 10,000-particle/cm3) increase in NC0.02-1 with 1-4 hr moving average exposure was associated with 0.68-1.35% decreases in SDNN, 1.85-2.58% decreases in r-MSSD, 1.32-1.61% decreases in LF, and 1.57-2.60% decreases in HF. For the elderly panel, a 10,000-particle/cm3 increase in NC0.02-1 with 1-3 hr moving average exposure was associated with 1.72-3.00% decreases in SDNN, 2.72-4.65% decreases in r-MSSD, 3.34-5.04% decreases in LF, and 3.61-5.61% decreases in HF. In conclusion, exposure to NC0.02-1 was associated with decreases in both time-domain and frequency-domain HRV indices in human subjects.

Sleep disruption in spinocerebellar ataxia type 3: a genetic and polysomnographic study.

BACKGROUND: Sleep structure disruption and rapid eye movement (REM) sleep behavior disorders (RBD) have been previously reported in patients with neurodegenerative diseases. However, similar studies have rarely been quantitatively conducted in type 3 spinocerebellar ataxia (SCA3). METHODS: Fifteen patients with SCA3 and 16 healthy controls were recruited and evaluated by clinical history, International Cooperative Ataxia Rating Scale (ICARS), Epworth sleepiness scale (ESS), and polysomnography. RESULTS: Patients with SCA3 had reductions in sleep efficiency and percentage of REM sleep, which were negatively correlated with the severity of ataxia as evaluated by ICARS. REM sleep reduction occurred regardless of the presence of RBD, and severe reduction of REM sleep may significantly disturb the assessment of RBD. CONCLUSION: Poor sleep efficiency and REM sleep aberrations are the characteristics of sleep structure disruption in SCA3 as the disease progresses. The incidence of respiratory disturbance during sleep or excessive daytime sleepiness was not significantly higher in SCA3 patients than controls.

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.

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.

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.