polysomnography

Polysomnography is the comprehensive, attended overnight test that watches the whole body sleep at once. The name says it: poly (many) somno (sleep) graphy (recording). A web of sensors is placed on the scalp, face, chest, abdomen, and a finger, and across the night they capture a coordinated picture of brain waves, eye movements, muscle activity, breathing, airflow, and blood oxygen.

Several channels work together. Electrodes on the scalp record the electroencephalogram to stage sleep and detect arousals; sensors track eye and chin movements to identify REM sleep; a flow sensor and belts around the chest and abdomen distinguish whether reduced airflow comes with continued breathing effort (obstructive) or without it (central); a pulse oximeter logs oxygen; and additional leads can monitor heart rhythm, leg movements, and body position.

This breadth is its strength. Polysomnography can diagnose and grade obstructive and central sleep apnea, separate them, reveal Cheyne–Stokes respiration, quantify oxygen desaturation, and uncover other sleep disorders such as periodic limb movements. It is the reference standard against which simpler home tests are measured, and it is preferred when the picture is complex or when central apnea or another disorder is suspected.

Its drawbacks are practical: it requires an overnight stay in a sleep laboratory, is more costly and less convenient than home testing, and the unfamiliar setting can disturb sleep, sometimes giving a less representative night. For straightforward suspected obstructive apnea, a home sleep apnea test is often a reasonable first step, with full polysomnography reserved for unclear or higher-risk cases.