polysomnography

Polysomnography is a sleep study. It measures your sleep cycles and stages by recording brain waves (EEG), electrical activity of muscles, eye movement, breathing rate, blood pressure, blood oxygen saturation, and heart rhythm.

A specially trained health care provider will directly observe you while you sleep.

There are two states of sleep: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep.

REM sleep is associated with dreaming. Your body muscles (except your eyes and lungs) do not move during this stage of sleep.

NREM sleep has four stages distinguishable by EEG waves.

REM sleep alternates with NREM sleep approximately every 90 minutes. A person with normal sleep usually has four to five cycles of REM and NREM sleep during a night.