Effect of NIV on sleep continuity. Sleep time spent in sleep bouts, short naps and long naps during NIV and spontaneous breathing. Average sleep time (expressed as % of total sleep time) spent in sleep bouts lasting less than 10 minutes, short naps (10 to 30 minutes) and long naps (>30 minutes) during NIV (white boxes) and during spontaneous breathing (SB) (gray boxes) in 24 patients. Bottom and top of boxes are 25th and 75th percentiles, respectively, middle lines are median, lower and upper whiskers are 10th and 90th percentile, respectively; * P <0.05, Wilcoxon signed Rank Test. NIV, non-invasive ventilation.