Background: In patients with obstructive sleep apnea, automatic continuous positive airway pressure machines (autoCPAP) are said to be capable of identifying various breathing abnormalities during sleep and to correct them by increasing progressively the positive pressure applied to the airway. Once breathing becomes normal, pressure slowly declines. AutoCPAP devices have never been tested in Phase I studies. The investigators hypothesised that normal breathing would not be recognised as such, and that pressure would increase even in a normal subject.

Material and Methods: We will submit one normal (confirmed with two polysomnographies, PSG) subject to a double blind study. Pairs of PSG will be performed on successive days once a week, one night with a 4 cm water fixed pressure CPAP device, previously shown not to disturb the subject's sleep and breathing, the other night with one of five well known autoCPAP devices programmed to work between 4 and 15 cm H2O pressure. The same mask and headgear will be used throughout the study. The subject and the physicians reading the tracings will ignore which device is being used on which night.

Inclusion Criteria:

• normal subject
• male and female
• age 18 to 65 years old

Exclusion Criteria:

• obstructive sleep apnea
• unable to sleep with a CPAP device