Polysomnography is a noninvasive and painless test that allows the study of sleep stages (REM and non-REM) and its various modifications. It is indicated to diagnose possible disorders such as obstructive sleep apnea, narcolepsy, excessive sleepiness, restless legs syndrome or sleep terrors, among others. Overall, polysomnography is done at night, in specialized centers or at home, and while the patient sleeps, placing electrodes on your chin, scalp and the outer edge of the eyelids, other monitors in the chest. The system records different variables: the blood pressure, EEG activity, eye, muscle, heart and lung. It measures the time it takes the patient to fall asleep and duration of different sleep stages. A specialist observes from another room, the person being tested while sleeping and a polygraph records and stores the information of the different physiological signals, which will then be performed for diagnosis. The sleep period could also be recorded on video for later analysis.