Breathing during sleep in patients with nocturnal desaturation

The mechanisms leading to hypoxemia during sleep in patients with respirato ry failure remain poorly understood, with few studies providing a measure o f minute ventilation ((V) over dotI) during sleep. The aim of this study wa s to measure ventilation during sleep in patients with nocturnal desaturati on secondary to different respiratory diseases. The 26 patients studied had diagnoses of chronic obstructive pulmonary disease (COPD) (n = 9), cystic fibrosis (CF) (n = 2), neuromusculoskeletal disease (n = 4), and obesity hy poventilation syndrome (OHS) (n = 11). Also reported are the results for se ven normal subjects and seven patients with effectively treated obstructive sleep apnea (OSA) without desaturation during sleep. Ventilation was measu red with a pneumotachograph attached to a nasal mask. In the treated patien ts with OSA and in the normal subjects, only minor alterations in (V) over dotI were observed during sleep. In contrast, mean (V) over dotI for the gr oup with nocturnal desaturation decreased by 21% during non-rapid-eye-movem ent (NREM) sleep and by 39% during rapid-eye-movement (REM) sleep as compar ed with wakefulness. This reduction was due mainly to a decrease in tidal v olume ((V) over dotT). Hypoventilation was most pronounced during REM sleep , irrespective of the underlying disease. These data indicate that hypovent ilation may be the major factor reading to hypoxia during sleep, and that r eversal of hypoventilation during sleep should be a major therapeutic strat egy for these patients.