Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Compliance
Systematic review	89 people 2 RCTs in this analysis	Duration of nightly use with bi-level positive airway pressure with CPAP Absolute results not reported	WMD –0.08 hours 95% CI –0.55 hours to +0.38 hours See further information on studies for methodological weaknesses		Not significant
Systematic review	16 people Data from 1 RCT	Patient preference 40% with bi-level positive airway pressure 40% with CPAP Absolute numbers not reported	Significance not assessed See further information on studies for methodological weaknesses
RCT	104 people with OSAHS (mean AHI about 40; see table 2 ) non-compliant with CPAP therapy (defined as using CPAP for less than 4 hours per night)	Compliance 90 days 25/51 (49%) with bi-level positive airway pressure 15/53 (28%) with CPAP	P = 0.03	Effect size not calculated	bi-level positive airway pressure