[Hypersomnia. Sleep apnea syndrome and somnolence]

A RECENTLY DEFINED SYNDROME: Sleep apnea syndrome is defined as 5 episodes of apnea or 10 episodes of hyopnea per hour of sleep; the cardinal symptom is excessive diurnal somnolence. Two factors could explain sleep apnea syndrome: hypoxemia and fragmented sleep. ROLE OF HYPOXEMIA: Early studies focused on hypoxemia, but few took into account the effect of subjective complaints of somnolence. Further investigations based on objective measurements introduced a certain degree of complexity distinguishing between sleepiness and the capacity for voluntary vigilance. FRAGMENTARY SLEEP: More recent work has demonstrated the important role played by perturbed sleep rhythm and particularly the effect of short repeated periods of vigilance fragmenting sleep. It has been suggested that finer fragmentation exists but non-documented on electroencephalograms. SIMPLE AND EFFECTIVE TREATMENT: The relative contribution of hypoxemia and fragmented sleeping patterns is still a topic of debate, but the clinical strategy is simple and based on the results of a therapeutic test with continuous positive pressure ventilation. There is an improvement both in hypoxemia and sleep pattern which resolves the problem of excessive diurnal somnolence in most cases.