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. 2019 Dec 2;2019(12):CD003531. doi: 10.1002/14651858.CD003531.pub4

Ryan 2009.

Methods Randomised, parallel group trial
Participants N = 125 participants (116 M/9 F). Age: 48; BMI: 35 kg/m2; AHI: 36; ESS: 12.5
Inclusion criteria: AHI > 10, CPAP‐naive, successful nasal CPAP titration study, adequate nasal breathing
Exclusion criteria: Bi‐PAP or supplemental oxygen; malignant disease; psychiatric disease; regular use of narcotics; sedatives or psychoactive substances
Interventions Standard (dry) CPAP versus CPAP with heated humidification versus CPAP with nasal steroid spray
Study duration: 4 weeks
Outcomes

  1. Machine usage (average hours used and % nights used)

  2. Quality of life (SF‐36)

  3. Symptoms (ESS)

  4. Tolerability (nasal symptoms measured by MiniRQLQ)
Funding & conflicts of interest statements Quote: "This was not an industry supported study. The authors have indicated no financial conflicts of interest."
Notes  
Risk of bias
Bias Authors' judgement Support for judgement
Random sequence generation (selection bias) Low risk Block randomisation was used to randomise patients to different treatment groups
Allocation concealment (selection bias) Low risk Randomisation occurred centrally
Blinding of participants and personnel (performance bias) 
 Machine usage, symptoms, quality of life, withdrawal, adverse effects High risk Quote: "However, patients were not blinded, since blinding would be difficult to achieve and requiring the use of placebo humidification, which has also been a limitation of previous studies."
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 High risk Although the investigators administering questionnaires and downloading data from the devices were blinded to the treatment arm, participants rating symptoms and other subjective outcomes would have been aware of the treatment group.
Blinding of outcome assessment (detection bias) 
 AHI, blood pressure, treatment pressure Low risk These outcomes unlikely to be affected by awareness of treatment group.
Incomplete outcome data (attrition bias) 
 All outcomes Unclear risk Quote: "All analyses were undertaken using the intention‐to‐treat principle"
Quote: "Of the 123 patients participating in the study, 112 subjects (91%) completed the trial... Of the 10 patients wishing to discontinue
 CPAP, 5 were randomized to dry treatment, 2 were commenced on additional nasal steroid, and 3 were started on additional humidification [p = 0.207])Quote: "
For dichotomous outcomes the difference in drop out was low and unlikely to affect the size or direction of effect. For machine usage and symptom scores dropouts may have influenced the results.
Selective reporting (reporting bias) Low risk All outcomes reported
Other bias Low risk No concerns identified