Table 4 Change in daytime gas exchange, weight and subjective sleep quality following 3 months of positive pressure in the three treatment groups

Outcome	Change in CPAP group Mean (SD)	Change in BVS group Mean (SD)	Mean difference between treatments(95% CI)	p Value†
Paco₂(mm Hg)	−5.8 (8.4)*	−6.9 (6.7)*	1.04 (−4.5 to 6.6)	0.7
Awake Spo₂(%)	6 (3)*	8 (5)*	1.9 (−5. 2 to 1.3)	0.24
Bicarbonate (mmol/l)	−2.3 (8.5)*	−2.5 (2.5)*	0.2 (−4.2 to 4.6)	0.93
Weight loss (kg)	−4.9 (7.8)*	−5.6 (9.4)*	0.7 (−5.2 to 6.5)	0.82
Mean nightly therapy use (h)	5.8 (2.4)	6.1 (2.1)	0.33 (−1.8 to 1.2)	0.66
ESS	−6 (8)*	−9 (5)**	2.89 (−1.78 to 7.56)	0.21
PSQI	−1.93 (3.5)	−5.6 (3.9)**	3.67 (0.82 to 6.5)	0.013

BVS, bilevel ventilatory support; CPAP, continuous positive airway pressure; Paco₂, arterial carbon dioxide tension; Spo₂, oxygen saturation; ESS, Epworth Sleepiness Scale; PSQI, Pittsburgh Sleep Quality Index.
*p<0.05, **p<0.001, within group changes from baseline.
†p Value denotes mean difference between CPAP and BVS treatment groups using unpaired t tests.