How are sleep stages determined in a polysomnographic study?

In a polysomnographic study, sleep stages are primarily determined by analyzing EEG patterns, muscle activity, and eye movements. During the study, electrodes are placed on the scalp to record the electrical activity of the brain (EEG), allowing technicians to identify unique waveforms associated with different sleep stages, such as REM and non-REM sleep. Additionally, monitoring muscle tone through electromyography (EMG) helps determine whether the body is in a state of active sleep or quiet sleep. Eye movements are recorded using electrooculography (EOG) to differentiate between the various sleep stages, particularly distinguishing REM sleep, where rapid eye movements are present.

Other methods listed, such as monitoring respiratory rate, heart rate, or physical movements, can provide valuable information about a patient's overall health or identify sleep disorders, but they do not specifically define sleep stages. The analysis of EEG, muscle activity, and eye movements is the gold standard for accurately classifying sleep states during a polysomnographic examination.