Which polysomnographic variable measures oxygen saturation levels?

Pulse oximetry is the correct choice for measuring oxygen saturation levels. This non-invasive technique uses light sensors placed on a patient's finger or earlobe to assess the oxygen saturation of hemoglobin in the blood. The device emits light wavelengths that pass through the blood and measures the amount of oxygenated versus deoxygenated hemoglobin, providing a percentage reflecting the oxygen saturation levels.

This measurement is crucial in sleep studies, particularly in evaluating conditions like sleep apnea, where patients may experience fluctuations in oxygen saturation levels during sleep. Monitoring these levels helps in assessing the severity of respiratory disturbances that occur.

Other options, while important in polysomnographic studies, do not measure oxygen saturation. Electroencephalography focuses on recording electrical activity in the brain, electromyography measures muscle activity, and capnometry evaluates the concentration of carbon dioxide in exhaled air. Each serves a distinct purpose within the sleep study framework, but none provide direct measurements of oxygen saturation like pulse oximetry does.