The utility of topographic EEG mapping in obstructive sleep apnea syndrome.

A study was undertaken to determine whether topographic brain mapping of standard EEG and cognitive evoked potentials would provide additional information for the detection of subtle brain abnormalities associated with obstructive sleep apnea. During nocturnal sleep, significant brain activity was detected in frontal regions not usually monitored with standard sleep recordings. Moreover, preliminary results suggest that total brain activity decreased in association with apneic events and depth of O2 desaturation. Also, component asymmetry in the P300 waveform observed in brain areas not typically recorded improved with treatment. We conclude that the use of topographic mapping adds important information to the study of brain function during sleep and sleep apnea.

Detection of respiratory events during NPSG: nasal cannula/pressure sensor versus thermistor.

Recording of respiratory airflow is an integral part of polysomnography (NPSG). It is conventionally monitored with a thermistor that measures temperature as a surrogate of flow. The subjectivity of interpreting hypopnea from this signal has prompted us to measure nasal airflow directly with a simple pneumotachograph consisting of a standard nasal cannula connected to a 2-cm H2O pressure transducer. We manually analyzed respiratory events using simultaneous thermistor and nasal cannula in 11 patients with obstructive sleep apnea syndrome (OSAS) and 9 with upper airway resistance syndrome (UARS). Definite events were scored separately for each signal when amplitude was <50% for >10 seconds. Events were also scored on the nasal cannula signal when the flattened shape of the signal suggested flow limitation, and these were tabulated separately. Definite events in one signal were tabulated by whether the other signal showed a definite event or not. In addition, nasal cannula events were compared to a more liberal thermistor criterion (any change in the signal for > or = 2 breaths). Visually, events were more easily recognized on the nasal cannula signal than on the thermistor signal. In OSAS, 1,873 definite thermistor events were detected. Of these, 99.1% were detected by nasal cannula, and 0.9% were missed. Of 3,541 definite nasal cannula events, 51.9% were detected by definite thermistor criteria; 75.0% were detected by liberal thermistor criteria; 25.0% were missed. In UARS, 123 definite thermistor events were detected. Of these, 89.4% were detected by nasal cannula and 10.6% were missed. Nine hundred and three nasal cannula events were detected. However, only 17.2% of these were detected by definite thermistor criteria; 38.6% were detected by liberal thermistor criteria; 61.4% were completely undetected by thermistor. When events identified on the nasal cannula by flow limitation alone were excluded, the thermistor detected 30.1% of events by definite criteria and 78.6% by liberal criteria, still leaving 21.4% completely undetected by the thermistor. We conclude that the nasal cannula reliably detects respiratory events seen by thermistor. Additional events (including some characterized only by flow limitation) that help define the UARS, were recognized by nasal cannula but often completely missed by thermistor. We propose that respiratory monitoring during NPSG with nasal cannula significantly improves event detection and classification over that with thermistor.

Interobserver agreement among sleep scorers from different centers in a large dataset.

STUDY OBJECTIVES: To evaluate epoch by epoch agreement in sleep stage assignment between scorers from different laboratories. DESIGN: N/A. METHODS: 62 NPSGs were selected for analysis from 3 sleep centers (38 diagnostic studies for sleep disordered breathing [SDB], 10 studies during CPAP titration, and 14 studies in subjects with no sleep related complaints or sleep pathology). The sleep recording montage consisted of at least 2 EEG leads, left and right EOG and a submental EMG. Scoring was performed manually by 5 experienced sleep technologists. No scorer had knowledge of any other scorers' results. Agreement was tabulated both for sleep stage distribution and on an epoch by epoch basis for the entire data set and the normal and SDB subsets. MEASUREMENTS AND RESULTS: The mean epoch by epoch agreement between scorers for all records was 73% (range 67-82%). Agreements were higher in the normal subset (mean 76%, range 65-85%) than in the SDB subset (mean 71%, range 65-78%). There was significant variability in agreement between records and between pairs of scorers. Overall, 75% of epochs had at least 4 of the 5 scorers in agreement on the sleep stage and 96% of epochs had agreement of at least 3 of the 5 scorers. CONCLUSIONS: The level of agreement in sleep stage assignment varies between scorers, by diagnosis, and by record. The level of agreement between laboratories is lower than what can be maintained between scorers within the same laboratory. This warrants caution when comparing data scored in separate laboratories. The lower agreement in SDB patients supports the generally held view that sleep fragmentation makes application of the R&K rules less reliable.

The association of sleep-disordered breathing and sleep symptoms with quality of life in the Sleep Heart Health Study.

This study assessed the extent to which sleep-disordered breathing (SDB), difficulty initiating and maintaining sleep (DIMS), and excessive daytime sleepiness (EDS) were associated with impairment of quality of life (QoL) using the SF-36. Participants (n=5,816; mean age=63 years; 52.5% women) were enrolled in the nation-wide population-based Sleep Heart Health Study (SHHS) implemented to investigate sleep-disordered breathing as a risk factor in the development of cardiovascular disease. Each transformed SF-36 scale was analyzed independently using multiple logistic regression analysis with sleep and other potential confounding variables (e.g., age, ethnicity) included as independent variables. Men (11.6%) were significantly more likely to have SDB compared to women (5.6%), while women (42.4%) were significantly more likely to report DIMS than men (32.5%). Vitality was the sole SF-36 scale to have a linear association with the clinical categories of SDB (mild, moderate, severe SDB). However, individuals with severe SDB indicated significantly poorer QoL on several SF-36 scales. Both DIMS and EDS were strongly associated with reduced QoL even after adjusting for confounding variables for both sexes. Findings suggest 1) mild to moderate SDB is associated with reduced vitality, while severe SDB is more broadly associated with poorer QoL, 2) subjective sleep symptoms are comprehensively associated with poorer QoL, and 3) SF-36 mean score profiles for SDB and sleep symptoms are equivalent to other chronic diseases in the U.S. general population.

Sleep habits of Long Island Rail Road commuters.

STUDY OBJECTIVES: We addressed the issue of how commuting affects sleep habits, and its association with general health and potential sleep disorders in individuals on a large, U.S. commuter rail system. DESIGN: Postage-paid mail back questionnaires were distributed to commuters over 6 consecutive weekdays. The questionnaire incorporated previously validated questions regarding sleep habits. SETTING: Questionnaires were dispensed at 15 different rail stations. PARTICIPANTS: 21,000 commuters accepted the questionnaire. MEASUREMENTS AND RESULTS: Data was analyzed by total group and length of commute. A total of 4715 (22%) questionnaires were returned. Over 50% of the sample reported difficulty with sleep and wakefulness while only 3% sought professional help. Sleep apnea was suspected in 4.2% of male and 1% of female respondents and was associated with increased reports of excessive daytime sleepiness, and history of hypertension, diabetes and obesity. Total nocturnal sleep time was significantly less in those subjects with long commutes. Seventy percent of respondents reported napping during the commute. Length of commute was associated with hypertension. CONCLUSION: Commuting long distances negatively impacts one's ability to capture adequate sleep. Data suggests that there may be significant numbers of respondents with unrecognized sleep disorders which further impact on general health.

Health-related quality of life effects of modafinil for treatment of narcolepsy.

OBJECTIVE: To evaluate the burden of illness of narcolepsy and assess the health-related quality-of-life (HQL) effects of oral modafinil, a wake-promoting therapy for excessive daytime sleepiness associated with narcolepsy. METHODS: Subjects with narcolepsy enrolled in a nine-week, placebo-controlled, double-blind study and were randomized to placebo, modafinil 200 mg, or modafinil 400 mg. After the study, consenting subjects received modafinil in a 40-week open-label extension. A self-administered HQL questionnaire consisting of the 36-Item Short Form Health Survey (SF-36) and supplemental narcolepsy-specific scales was given to subjects at baseline, study endpoint, and several open-label timepoints. RESULTS: 481 subjects completed a baseline and double-blind endpoint HQL assessment. Compared to population norms, baseline HQL scores reflected substantial burden in vitality, social functioning, and performing usual activities. At study endpoint, subjects in the 400 mg modafinil group had significantly higher scores than placebo for 10 of the 17 HQL scales. The 400 mg modafinil group had more energy, fewer difficulties performing usual activities, fewer interferences with social activities, improved psychological well-being and higher productivity, attention and self-esteem compared to placebo subjects (p<.05). The positive treatment effects were sustained over the open-label extension. CONCLUSION: Modafinil significantly improves health-related quality of life in narcolepsy.

Relative occurrence of flow limitation and snoring during continuous positive airway pressure titration.

OBJECTIVES: To examine the relative temporal appearance of flow limitation and snoring during continuous positive airway pressure (CPAP) titration, compare their sensitivity as indicators of airway obstruction, and assess their relative utility as feedback variables for automatic titration of CPAP. DESIGN: Retrospective review of data. SETTING: University teaching hospital. PATIENTS: Fifty-three patients diagnosed as having obstructive sleep apnea or upper airway resistance syndrome undergoing CPAP titration. MEASUREMENTS AND RESULTS: We used a prototype automatic CPAP device that adjusts pressure in response to apnea, snoring, and/or flow limitation. The present study takes advantage of the frequent automatic decreases in pressure from a therapeutic level, as well as any technician-initiated decreases in pressure. We tabulated, for each pressure decrease of >0.4 cm H2O, the occurrences of snoring alone, flow limitation alone, or simultaneous appearance of both. Of 2,177 automatic pressure decreases, 64% resulted in flow limitation alone, 8% in snoring alone, and 22% in the simultaneous occurrence of both. Overall, 86% of decreases resulted in flow limitation alone or were simultaneous with snoring, whereas 30% of decreases resulted in snoring alone or were simultaneous with flow limitation. In 10 of 35 patients, snoring alone occurred in > 10% of the pressure decreases. In all but 5 of 133 manual pressure decreases, flow limitation developed at or above the pressure at which snoring developed. CONCLUSIONS: While detection of snoring occasionally provided additional information, overall flow limitation was the earliest indicator of obstruction during decreases in CPAP.

Obstructive sleep apnea and body weight.

A patient with obstructive sleep apnea was monitored five times during three years while his weight fluctuated within a range of 26 kg. The number of apneas per hour of sleep varied from 59.6 at 111 kg of weight to 3.1 at 85 kg. The relation between apneas per hour of sleep and body weight was a logarithmic function. A modest decrease in weight was thus associated with a disproportionally larger decrease in the rate of apneas. Typical SaO2 levels during the apneic episodes also had a logarithmic relation with body weight. Apnea-related sinus bradycardia and sinus tachycardia were only present at the highest weight. The results suggested that dieting and weight loss lead to an improvement in sleep apnea and related sequelae.

Clinical diagnosis of pediatric obstructive sleep apnea validated by polysomnography.

The decision to perform tonsillectomy and adenoidectomy for treatment of pediatric obstructive sleep apnea syndrome is often made on a clinical basis without formal polysomnography. To examine the accuracy of the clinical diagnosis of pediatric obstructive sleep apnea syndrome, we prospectively evaluated 30 children with obstructive symptoms by a standardized history, physical examination, and review of a tape recording of breathing during sleep. On the basis of this clinical evaluation, patients were divided into three predictive groups: (1) definite obstructive sleep apnea syndrome, (2) possible obstructive sleep apnea syndrome, and (3) unlikely to have obstructive sleep apnea syndrome. Nocturnal polysomnography was used to determine the presence or absence of true sleep apnea. Ten of 18 (55.6%) patients predicted clinically to have definite obstructive sleep apnea syndrome had positive nocturnal polysomnographies. Two of six (33.3%) patients predicted to have possible obstructive sleep apnea syndrome had positive nocturnal polysomnographies. One of six (16.7%) patients predicted to be unlikely to have obstructive sleep apnea syndrome had a positive nocturnal polysomnography. Six nocturnal polysomnographies negative by conventional criteria were suspicious for apnea, but considering these positive for obstructive sleep apnea syndrome did not improve the specificity of the clinical prediction. Our results show that clinical assessment of obstructive sleep apnea syndrome in children is sensitive (92.3%) but not specific (29.4%) for making the diagnosis of obstructive sleep apnea syndrome as compared with nocturnal polysomnography and may contribute to the decision to obtain nocturnal polysomnography in specific circumstances.

Auditory event-related potentials and brain dysfunction in sleep apnea.

Auditory event-related potentials (ERPs) were recorded from 14 subjects with obstructive sleep apnea (OSA) before and after treatment with nasal continuous positive airway pressure (nCPAP). After 2 nights of treatment, there was dramatic improvement in the sleep patterns of the OSA patients, improvements in measures of apnea severity and oxygenation, and decrease in daytime sleepiness. The results of neuropsychological tests of a broad range of cognitive functions failed to confirm the patients' subjective reports of improvement in psychological functioning after treatment. The latencies of the N2 and P3 components were significantly prolonged prior to treatment, and there was a trend towards smaller N2 and P3 amplitude in the apneic subjects. The latency of P3 (but not N2) changed with treatment, decreasing almost to normative values. The results suggest that ERPs may be useful in documenting neural dysfunction in patients with OSA, in evaluating treatment efficacy, and possibly in determining the causes of the daytime symptoms of OSA.