What is the purpose of using a pulse oximeter during a sleep study?

Using a pulse oximeter during a sleep study primarily serves to measure blood oxygen saturation levels. This is crucial in assessing a patient's respiratory status during sleep. The device works by passing a light through a relatively translucent part of the body, such as a fingertip or earlobe, and then measuring the amount of light absorbed by the oxygenated and deoxygenated hemoglobin in the blood.

Monitoring blood oxygen saturation is essential in sleep studies, particularly for identifying conditions such as sleep apnea, where intermittent breathing can lead to drops in oxygen levels. By providing continuous data on how well oxygen is being delivered to the body's tissues, clinicians can make informed decisions about diagnosis and treatment for sleep-related breathing disorders.

While the other choices address different physiological measurements—such as brain activity, heart rate variability, and muscle tone—they do not pertain to the specific functionality of a pulse oximeter, which is exclusively focused on measuring oxygen levels in the blood.