Normally, it is enough to have one night of sleep study to clearly diagnosis severe OSA in patients with sleep-disordered breathing and upper airway pathology. However, the others suffering from the severe OSA would not have been found and many with AHI variability would have been missed. .

Ahmadi et al. (2009) wanted to investigate AHI on two nights due to a concern with variability of the disorder and impact on clinical diagnosis. They conducted polysomnographies with 193 sleep clinic patients over two consecutive nights to analyze AHI variability. Anonymized records from five individuals with significant night-to-night AHI variability participated: the two-night tests from two patients were represented as four individual polysomnographies; the two-night tests for two others were represented as being obtained from two different sleep clinics; the last patient's results were shown as a two-night study. Twenty-two sleep experts at the Associated Professional Sleep Societies meeting diagnosed the...
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