Marshall 2008.

Methods	Randomised, single‐blind, parallel group trial
Participants	N = 19 participants (15 M/4 F). Mean age: 47; AHI: 78; ESS: 14 Inclusion criteria: severe OSA (AHI > 30; or symptomatic and AHI > 20) Exclusion criteria: other significant medical disorders
Interventions	C‐Flex versus fixed CPAP Study duration: 4 weeks
Outcomes	Machine usage (average hours used) Symptoms (ESS)
Funding & conflicts of interest statements	Quote: "None of the authors have had any financial relationships with Respironics Inc., who are the manufacturers of the device tested. Respironics International Inc., through their New Zealand suppliers Care Medical, provided six C‐Flex machines for the purposes of this trial."
Notes	Information on randomisation available from study authors
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The sequence of allocation to treatment was determined by sleep technicians randomly picking one of a set of pre‐prepared opaque envelopes containing the treatment allocation."
Allocation concealment (selection bias)	Low risk	Quote: "An urn with 2 differently coloured paper clips was prepared. One clip was blindly withdrawn, and its corresponding treatment noted on a folded piece of paper in an opaque envelope which was then sealed. The clip was then replaced in the urn along with another coloured clip, which represented the other treatment. This was repeated until 20 envelopes had been produced. Because a number of patients who did not meet the entry requirements, were randomised and then withdrawn from the study, a further 5 envelopes were subsequently prepared using the same method. This method leads toward roughly equal group sizes whilst maintaining unpredictability of sequence and sample sizes."
Blinding of participants and personnel (performance bias) Machine usage, symptoms, quality of life, withdrawal, adverse effects	High risk	Study personnel would have been aware of treatment group allocation.
Blinding of participants and personnel (performance bias) AHI, blood pressure, treatment pressure	Low risk	These outcomes unlikely to be affected by awareness of treatment group.
Blinding of outcome assessment (detection bias) Machine usage, symptoms, quality of life, withdrawal, adverse effects	Low risk	Quote: "Measurements of sleepiness and reaction times were undertaken by an investigator blinded to treatment allocation; patients were blinded to treatment allocation."
Blinding of outcome assessment (detection bias) AHI, blood pressure, treatment pressure	Low risk	These outcomes unlikely to be affected by awareness of treatment group allocation
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "Whilst all 19 patients were included in the primary analysis under the intention‐to‐treat principle due to missed appointments only 17 patients are included in the Epworth analysis." This is a low rate of attrition.
Selective reporting (reporting bias)	Low risk	All outcomes reported
Other bias	Low risk	No concerns identified