Polysomnography also called a sleep study or PSG is a test used to diagnose sleep disorders. Polysomnography records your brain waves, the oxygen level in your blood, heart rate and breathing, as well as eye and leg movements during the study. You'll be asked to arrive at our sleep center in the evening so that the PSG test can record your nighttime sleep patterns. Polysomnography is occasionally done during the day as well to accommodate shift workers who habitually sleep during the day and to diagnose other disorders such as Narcolepsy. In addition to helping diagnose sleep disorders, polysomnography may be used to help adjust your treatment plan if you've already been diagnosed with a sleep disorder.