Polysomnographic features of idiopathic central sleep apnea

Two patients with idiopathic central sleep apnea (ICSA), which is an uncommon condition, were recently encountered. This study examines the polysomnographic features of ICSA. The characteristic findings of ICSA are summarized as follows: (i) central apneas and hypopneas are progressively less frequent as sleep state deepens from stage 1 to stage 2 to stage 3 + 4 to stage REM (rapid eye movement); (ii) desaturation related to apneas and hypopneas is mild; and (iii) periodic breathing is commonly observed. However, the two patients demonstrated apparently different findings. It is suggested that the mechanisms underlying apnea and hypopnea in ICSA are heterogeneous.