Effect of non-invasive mechanical ventilation on sleep and nocturnal ventilation in patients with chronic respiratory failure

Background - Chronic respiratory failure (CRF) is associated with nocturnal hypoventilation. Due to the interaction of sleep and breathing, sleep qual ity is reduced during nocturnal hypoventilation. Noninvasive mechanical ven tilation (NMV), usually performed overnight, relieves symptoms of hypoventi lation and improves daytime blood gas tensions in patients with CRE The tim e course of the long term effect of NMV on sleep and breathing during both spontaneous ventilation (withdrawing the intervention) and NMV was investig ated in patients with CRF due to thoracic restriction. Methods - Fifteen consecutive patients (13 women) of mean (SD) age 57.9 (12 .0) years with CRF due to thoracic restriction were included in the study. During the one year observation period four polysomnographic studies were p erformed: three during spontaneous breathing without NMV - before initiatio n of NMV (T0) and after withdrawing NMV for one night at six months (T6) an d 12 months (T12-) - and the fourth during NMV after 12 months (T12+). Dayt ime blood gas tensions and lung function were also measured. Results - Spontaneous ventilation tin terms of mean oxygen saturation) prog ressively improved (from T0 to T12-) during both REM sleep (24.8%, 95% CI 1 2.9 to 36.9) and NREM sleep (21.5%, 95% CI 12.4 to 30.6), Sleep quality dur ing spontaneous ventilation also improved in terms of increased total sleep time (26.8%, 95% CI 11.6 to 42.0) and sleep efficiency (17.5%, 95% CI 5.4 to 29.6) and decreased awakenings (54.0%, 95% CI 70.3 to 37.7). Accordingly , REM and NREM, sleep stages 3 and 4 significantly improved. However, the m ost significant improvements in both nocturnal ventilation and sleep qualit y were seen during NMV at 12 months. Conclusions - After long term NMV both spontaneous ventilation during sleep and sleep quality in patients with CRF due to thoracic restriction showed evidence of progressive improvement compared with baseline after withdrawal of NMV for a single night at six and 12 months. However, the greatest impr ovements in nocturnal ventilation and sleep were achieved during NMV at 12 months.