Anderson 2003.

Methods	Randomised, crossover trial in which patients with OSA were assigned to receive CPAP treatment via a nasal mask and via an oral mask. Duration of study: 4 weeks in each arm, with no washout period (total of 8 weeks) Method of randomisation: Not stated. Allocation concealment: Used sealed envelopes, but unclear if opaque. Blinding of participants: Not possible to blind mask type; Participants were not made aware that compliance was being monitored Blinding of technicians: A qualified PSG technologist, who was blinded to mask sequence, analysed the diagnostic portion of the first study & each of the on‐treatment studies, at the final titrated pressures; Questionnaires were issued by the attending technician, not one of the investigators Blinding of investigators: Follow‐up phone calls were made by one on the investigators knowledgeable about the interfaces (this information was not available in publication, but obtained from author after request for further clarification) Withdrawals: 3 pts dropped out after randomisation ‐ 1 refused to use CPAP machine (nasal); 1 unable to tolerate nasal mask & switched to oral mask for continued therapy; 1 unable to tolerate oral mask & refused further treatment 1 pt was excluded from analysis because compliance data was unobtainable due to technical complications (oral) All pts who completed both arms of the trial were included in the analysis regardless of CPAP use. Intention to treat analysis: Not used
Participants	42 CPAP naïve pts recruited prior to polysomnography. 25 fulfilled criteria & all agreed to participate (nasal n = 13; oral n = 12). 21 pts analysed (nasal n = 11; oral n = 10) Recruited from consecutive pts referred to the Greenlane Hospital Sleep Disordered Breathing Unit (Hospital‐based sleep laboratory) Inclusion criteria: AHI > 20, ESS > 12, and at least 2 symptoms of OSA Exclusion criteria: previous CPAP therapy for OSA, coexisting COPD, coexisting sleep disorders, claustrophobia, gum or mouth disease, inability to communicate in English & no home telephone for communication Males/Females: Numbers not stated Age range: Not stated Mean age (SD): 46 (12) Mean BMI (SD): 43 (8) Baseline AHI (95% CI): 85 (69‐100)
Interventions	Nasal mask (Aclaim, Fisher & Paykel Healthcare; Sullivan Modular, Mirage or Ultramirage, Resmed) vs Oral mask (Oracle, Fisher & Paykel Healthcare) CPAP machine: Fisher and Paykel HC 201 with integrated heated humidification used in both arms Diagnostic study: Split‐night polysomnography for diagnosis and to determine CPAP requirements. At crossover, patients returned for second full‐night titration study with alternate interface. Therapeutic CPAP pressure: Minimum pressure required to eliminate all evidence of upper airway obstruction. Follow‐up telephone calls done 3 times during the first week & once a week thereafter to address issues of discomfort & ensure ongoing support
Outcomes	1) CPAP compliance ‐ recorded from hour meter of CPAP machine (run‐time) 2) Physiological parameters (e.g. arousals, apnoea‐hypopnoea index, sleep efficiency, minimum oxygen saturation) 3) CPAP side effects ‐ using posttreatment questionnaire containing 19 possible side effects with a 4‐point scale 4) Mask preference at end of the 8‐week trial 5) Epworth Sleepiness Scale 6) Symptoms ‐ 12‐item questionnaire with 4‐point Likert scale (0 = never to 3 = always); Patients rated the severity of: snoring, choking, breathing pauses, nocturnal awakenings, poor sleep quality, feeling unrefreshed on awakening, headaches, daytime sleepiness, concentration difficulties, decreased well‐being, daytime & evening napping
Notes	Further information regarding study quality and data obtained from author
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Described as randomised; other information not available
Allocation concealment (selection bias)	Unclear risk	Sealed envelopes. Not clear if opaque.
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Participants: Not possible to blind mask type; Participants were not made aware that compliance was being monitored. Technicians: A qualified PSG technologist, who was blinded to mask sequence, analysed the diagnostic portion of the first study & each of the on‐treatment studies, at the final titrated pressures; Questionnaires were issued by the attending technician, not one of the investigators Investigators: Follow‐up phone calls were made by one on the investigators knowledgeable about the interfaces (this information was not available in publication, but obtained from author after request for further clarification)
Incomplete outcome data (attrition bias) All outcomes	High risk	Withdrawals: 3 pts dropped out after randomisation ‐ 1 refused to use CPAP machine (nasal); 1 unable to tolerate nasal mask & switched to oral mask for continued therapy; 1 unable to tolerate oral mask & refused further treatment 1 pt was excluded from analysis because compliance data was unobtainable due to technical complications (oral) All pts who completed both arms of the trial were included in the analysis regardless of CPAP use.