A first hypoxic session will be performed to identify the subjects who will develop periodic ventilation. Only those who will exhibit periodic ventilation during sleep will continue the study. They will be prescribed either baclofen or placebo (double blind, randomized). The posology will be progressively increased (over approximately 10 days) to reach 20 mg 3 times a day, during 3 to 5 days. A second hypoxic session will be performed under this treatment. Then the posology will be decreased over 3 days and a complete weaning will be performed during 5 to 10 days. The same protocol will be repeated, either with baclofen or placebo (depending of the previous run) and a third hypoxic session will be performed. The posology will then be decreased over 3 days and the study will be considered ended for the subject after 2 more days of complete weaning.