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

Vennelle 2010.

Methods Randomised, blinded, cross‐over trial. Statistical analysis based on paired tests.
Participants N = 200 participants (154 M/46 F). Mean age 50; BMI 34.5 kg/m2; AHI: 33; ESS 14
Inclusion criteria: ESS > 10 or sleepiness while driving; AHI > 15 on PSG or > 25 apnoeas/hypopneas per hour on limited sleep study; age 18 to 75; CPAP naive
Exclusion criteria: neurological deficit compromising CPAP use; significant comorbidity; co‐existing narcolepsy/periodic limb movements; contraindication to CPAP
Interventions Fixed pressure versus variable pressure CPAP
Study duration: 2 x 6 weeks
Outcomes

  1. Machine usage (average hours used)

  2. Symptoms (ESS)

  3. QoL (SF‐36)

  4. Sleep latency

  5. Withdrawals

  6. Tolerablity

  7. Preference
Funding & conflicts of interest statements Quote: "This study was supported by a grant from ResMed, Poway, CA. Dr. Douglas is a shareholder in ResMed. The other authors have indicated no additional conflicts of interest. The study was proposed, designed and all analysis performed solely by the authors."
Notes  
Risk of bias
Bias Authors' judgement Support for judgement
Random sequence generation (selection bias) Low risk Quote: "Patients were randomized...using a randomization schedule of balanced blocks..."
Allocation concealment (selection bias) Low risk Quote: "Patients were randomized...by a worker otherwise uninvolved in the trial."
Blinding of participants and personnel (performance bias) 
 Machine usage, symptoms, quality of life, withdrawal, adverse effects Low risk Quote: "Patients were informed that 2 different methods of giving CPAP were to be assessed, but were not told which was the new method"
Quote: "None of the staff involved in data acquisition or analysis were aware of the mode of treatment the patient was receiving"
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: "The blinded staff member conducted the follow‐up assessments unaware of the type of CPAP the patient was using at the time of assessment."
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 High risk Quote: "Nineteen patients did not complete the study; at the time of dropout 9 of these were receiving fixed and 10 variable pressure CPAP"
Balanced drop out which could impact on machine usage and symptoms
Selective reporting (reporting bias) High risk Side effects were rated by the Edinburgh questionnaire but not reported.
Other bias Low risk No concerns identified