Polysomnography study is conducted in the independent sleep laboratory.
Before the studies, individuals are interviewed about their sleep characteristics and health history. They will have a brief general exam and neurological exam. Body habitus ( weight and height ) and neck size are recorded.
Polysomnography consists of continuous polygraphic recording from surface electrodes for electroencephalography, electroocculography( eye movements recording), electromyography, electrocardiography and transcutaneous oximetry( continuous measurement and recording of the blood oxygenation). Non invasive sensors for nasal air flow, oral air flow, abdominal and chest respiratory efforts is utilized.
Interpretation of the Polysomnography Data
Polysomnography records are scored for sleep, breathing, oxygenation, and movements in 30 second periods(EPOCHS).
Sleep data are staged ( stages 1 through 4 and REM sleep). This staging and recording is according to the system developed and and implamented by Rechtschaffen and Kales.
An abnormal breathing event during objectively measured sleep is defined according to the commonly used criteria for either compltete cessation of airfflow lasting 10 seconds or longer ( Apnea ) or a discernable reduction in respiratory air flow associatted with a decrease in oxygen saturation of 4 percent or more ( Hypopnea). The average number of episodes of apnea and hypopnea per hour of sleep ( Apnea Index ) also called RDI ( Respiratory Disturbance Index) is calculated as the summery measurement of sleep disorder breathing. The usual cut off point for abnormal score is ten or more apnea index or RDI.