Zopiclone effects on breathing at sleep in stable chronic obstructive pulmonary disease.

More than half of patients with chronic obstructive pulmonary disease (COPD) experiences sleep-related problems and about one fourth uses hypnotics regularly. We explored what the effect zopiclone, a commonly used hypnotic, had on nocturnal gas exchange and the apnea/hypopnea frequency in stable COPD. Randomized crossover study of 31 (ten males) inpatients at a pulmonary rehabilitation hospital, median age 64 years, of which 20 had a forced expiratory volume first second <50% of predicted. Subjects investigated in randomized order of either baseline sleep or intervention with 5 mg zopiclone by polysomnography including transcutaneous measurement of carbon dioxide pressure increased (ΔPtcCO₂). Zopiclone increased the mean ΔPtcCO₂ from baseline both in rapid eye movement (REM) sleep, non-REM sleep, and even in stage N0 (awake after sleep onset) with a mean (SD) of 0.25 (0.40) kPa, 0.22 (0.32) kPa, and 0.14 (0.27) kPa, respectively. Subjects with sleep hypoventilation as defined by the American Academy of Sleep Medicine increased from 6 subjects (19%) to 13 subjects (42%) (P = 0.020). REM sleep minimum oxygen saturation (minSpO₂) did not change significantly from baseline median (interquartile range [IQR]) minSpO₂ 81.8 (12.1) % to zopiclone sleep median (IQR) minSpO₂ 80.0 (12.0) % (P = 0.766). Interestingly, zopiclone reduced the number of apneas/hypopneas per hour (AHI) in subjects with overlap (AHI ≥ 15) with a median difference (IQR) of -8.5 (7.8) (N = 11, P = 0.016). In stable COPD, zopiclone moderately increases the mean ΔPtcCO₂ without changing minSpO₂ at night and reduces AHI in overlap (COPD and obstructive sleep apnea) subjects.