When medical professionals want to evaluate your sleep, they turn to polysomnography, a big ol' Hellenic compound that means "sleep study."
A patient arrives at the clinic ready to doze the better part of a night in a space that feels like a budget motel room. The standard apparatuses used to build a complete sleep profile are:
• Electroencephalogram (EEG), which measures brain activity by way of electrodes stuck to the scalp (and other areas of the head), charts cortical electrical activity -- that is, the electrical impulses of neurons in the brain close to the skull.
• Electrooculogram (EOG) measures electrical activity around the eyes in order to determine rapid-eye movement (REM) sleep, a stage very different from other sleep stages, marked by sharp fluctuations in brain activity and vivid dreaming.
REM sleep interrupts non-REM sleep, which itself undulates between light and deep sleep, about every 90 minutes. A normal night's sleep might see four cycles of REM and non-REM sleep.
• Electrocardiogram (EKG) measures cardiac activity; there's not a ready connection between heart activity and sleep normalcy except that a heart condition could affect sleep.
• Plethysmograph belts go around the chest and stomach and measure the muscular effort of breathing.
• Pulse oximetry determines changes in blood oxygen levels that often correspond with sleep apnea and other respiratory problems. The instrument clips onto a fingertip or an earlobe.
• Electromyogram (EMG) measures muscle activity typically in the legs to check for periodic limb movement disorder (PLMD).
• Video feed and sound intercom: Most rooms are outfitted with an intercom whereby clinicians see movement and listen for moderate or profound snoring.
Medical professionals draw on all of this data to assess patients' sleep. They consider something called "sleep onset latency," the time it takes to fall asleep, as well as sleep efficiency, the ratio of sleep to total minutes in bed. They're considering heartbeat, leg muscle contractions, breathing irregularities and oxygen saturation, and sudden shifts in brain activity (often followed by shifts in a sleep state).
-- Bobby Ampezzan
ActiveStyle on 02/15/2016