When OSA is suspected, polysomnography is indicated to establish the diagnosis. Standardized overnight polysomnography performed in a sleep laboratory by a trained technician is recommended as the best diagnostic approach. Polysomnography involves recording electrophysiologic variables such as the brain activity EEG, eye movements (EOG), and chin muscle tone (EMG). This information allows sleep quantity and quality to be characterized. The electrocardiogram is also recorded. Standard measurements of respiration include recordings of chest displacement, nasal and oral airflow, and arterial oxyhemoglobin saturation. The number of apneas and hypopneas, their type and duration, and their sequelae, such as the amount of hypoxia and associated sleep fragmentation, can then be quantified. Periods of sustained hypoventilation may also be identified. By defining the type and severity of sleep-disordered breathing and associated sleep fragmentation, polysomnographic data help the clinician to develop a therapeutic plan. Polysomnography should also be used to assess the response to therapy in OSA patients.

There has been interest in developing simplified diagnostic techniques. Proposed approaches include home monitoring with oximetry or abbreviated polysomnographic montages. However, the sensitivity, specificity, and cost-effectiveness of such approaches require further study before recommendations can be made regarding their routine use.