POLYSOMNOGRAPHY

Abstract

Polysomnography (PSG) is the gold standard diagnostic test for several sleep disorders. It records , analyzes, & interprets multiple simultaneous physiologic characteristics during sleep. These parameters include brain waves, the oxygen level in the blood, heart rate and breathing, body position, as well as eye and leg movements, along with synchronized audiovisual monitoring. Moreover, in certain conditions, additional parameters may be included such as esophageal pH monitoring, esophageal manometry , and overnight blood pressure monitoring. The test is usually performed at a sleep disorders unit within a hospital or at a sleep disorders centre. Sleep architecture is largely divided into non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. NREM is further divided into three stages: N1, N2, and N3 : N3 being the deepest stage of sleep. REM sleep alternates with NREM sleep and a normal person usually has 4–6 cycles of REM and NREM sleep . Monitoring of the different sleep stages, sleep interruptions, movements, and the other respiratory and cardiac signals are clinically helpful for identifying the nature of patient’s sleep problems and assessing response to treatment. JMS 2015;18(2):165-166