ABSTRACT
Substantial attention has been given to the study of the sleep apnea syndrome and similar or related syndromes such as snoring and sudden infant death syndrome. This attention has led to the development of new methods of investigation and multidisciplinary involvement. Polygraphy is a rather extensive method of investigation of the main physiological functions during sleep, especially neuro-cardio-respiratory ones. This requires a simultaneous recording of a great number of signals, through various techniques. Neurophysiological signals make a definition of sleep quality and quantity possible. The electroencephalogram is the main signal used to define sleep stages. It is collected by using AgCl electrodes attached to the scalp with collodion. The electrodes are set according to an international convention. The electromyogram (EMG) is used to assess the average muscular tone and obtain a more precise recognition of the sleep stages. This is collected through electrodes stuck on either side of the chin.
