 Obstructive Sleep Apnea Syndrome OSAS is a common condition that leads to daytime sleepiness and loss of vigilance and, in addition, increased risk of cardiovascular events. The most effective treatment consists in ventilation by mask with continuous positive airway pressure CPAP, that prevents collapse of the upper airway. However the degree of collapsibility of the pharynx may vary in relation to position, sleep stage, or alcohol or sedative consumption. Thus, CPAP treatment invented in 1981 has evolved with the development of more sophisticated equipment that permits adapted variations in pressure levels autoCPAP with the objective adjusted pressure to avoid airways obstruction with minimal pressure. 