Gozal 1997.

Methods	RCT. Cross‐over design. Duration: 3 nights within a 15‐day period.
Participants	Six participants with CF and moderate to severe lung disease and significant gas exchange abnormalities during sleep. Stable participants. Age mean (SD) [range]: 22.3 (4.7) [13 ‐ 28]. FEV₁% predicted mean (SD): 29.4% (3.4).
Interventions	Session 1: room air. Session 2: night‐time bilevel NIPPV with supplemental oxygen given via nasal mask.
Outcomes	TST; sleep latency; NREM; NREM %TST; REM min; REM %TST; undetermined % TST; total arousals; arousal index; SaO₂; TcCO₂.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Stated as randomised, methods not discussed.
Allocation concealment (selection bias)	Unclear risk	Not discussed.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Participants were obviously aware of the intervention being administered; however, all were reportedly unaware of the purpose of the trial with participants and sleep technicians blinded to the results until completion of the third night.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	2 participants dropped out due to non‐tolerance of NIV; it was not explicitly stated that intention‐to‐treat was not used, but results are based on the remaining 6 participants who completed the trial.
Selective reporting (reporting bias)	Low risk	All outcome measures were reported.
Other bias	Unclear risk	Methods of statistical analysis were described.