The definitive diagnosis for the presence of sleep apnea is based on clinical evaluation during a sleep test and polysomnography (PSG). Nocturnal polysomnography is the most comprehensive examination and remains the one of choice for evaluating sleep breathing disorders. PSG consists of a night of recordings of various parameters for a period of at least 6 hours. This comprehensive test can diagnose several types of sleep disorders, including sleep apnea (obstructive) syndrome (OSAS), restless legs syndrome and narcolepsy.