Introduction

The obstructive sleep apnea-hypopnea syndrome (OSA) is recognized predominantly by daytime somnolence and night-time snoring often in obese individuals (1,2). The diagnosis is confirmed by demonstrating a sufficient number of obstructive apneas (absence of airflow with continued respiratory effort) and/or obstructive hypopneas (reduction in airflow despite sufficient respiratory effort to produce normal airflow) (1). The daytime somnolence appears to result, in large part, from short, amnestic arousals that fragment and reduce the efficiency of sleep. OSA appears to affect about 4% of men and 2% of women between 30 and 60 years of age (3). OSA is associated with systemic hypertension, myocardial infarction, motor vehicle accidents, and cerebrovascular accidents (4-7).

Daytime somnolence is a nonspecific symptom and may be due to narcolepsy, insufficient sleep, and idiopathic hypersomnia among other conditions (2). In addition, snoring is a nonspecific finding; for example, 67% of obese patients [body mass index (BMI) > 30] who snored loudly (patient report) had OSA (8). The general non-specificity of daytime sleepiness and snoring requires objective measurement of apneas and hypopneas during sleep for confirmation of OSA.

In general, confirmation involves an overnight sleep study while monitoring a number of respiratory channels (nasal and oral airflow, chest wall and abdominal movement, and oximetry), sleep staging by electroencephalogram (EEG) (central and occipital electrodes usually referenced to the ear), electro-oculogram (right and left eye movement) and chin electromyogram, at least a one-lead electrocardiogram, as well as leg movements (bilateral anterior tibialis electrodes) which may also produce frequent arousals (9). The study is attended by a technician (polysomnographic or sleep technologist) to perform and observe the study, ensure quality and safety, and make needed interventions including application of the most frequently used therapy, continuous positive airway pressure (CPAP). This approach is called polysomnography (PSG).

The number of potential patients usually exceeds the number of sleep laboratory facilities capable of performing the test in a timely fashion. The labor intensity of the attendant, scoring and interpretation of the study, and cost of the space and equipment make PSG relatively expensive, typically costing $1000 or more per study (10).

To increase access to diagnosis and potentially reduce cost, there has been an effort to produce systems that incorporate part or all of the PSG but make it portable and ideally usable without an attendant technician. The ideal system would measure the minimum number of channels necessary, be self-contained and self-administered by the patient, be amenable to rapid and accurate scoring, and provide information that would confirm OSA with identical specificity and sensitivity to the PSG. This review will evaluate the ability of various methods to achieve this goal in adults.

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