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Diagnosis of Obstructive Sleep Apnea Syndrome
Diagnostic Evaluation of Obstructive Sleep Apnea Syndrome
During polysomnography, episodes of apnea (cessation of breathing lasting for 10 seconds or longer) and hypopnea (decreased rate and depth of breathing lasting 10 seconds or longer) are recorded. The number of apnea/hypopnea episodes per hour of sleep is calculated and is expressed as the apnea-hypopnea index (AHI). The AHI is the basis for determining whether or not a patient has OSAS. The AHI scores for patients with OSAS can range from a minimum of 5 to a maximum of 30 or higher. In general, patients with severe OSAS have higher AHI scores than those with mild or moderate OSAS. Most experts agree that an AHI score of 5 or higher in patients with excessive daytime sleepiness is sufficient to establish the diagnosis of OSAS. For a variety of reasons, it is not always possible to make a diagnosis of OSAS with a single polysomnography and, for some patients, the sleep test may have to be repeated on a second night.
