Evaluation of sham-CPAP as a placebo in CPAP intervention studies.

CONTINUOUS POSITIVE AIRWAY PRESSURE (CPAP) IS THE PRIMARY MEDICAL TREATMENT FOR OBSTRUCTIVE SLEEP APNEA (OSA).1,2 NUMEROUS RANDOMIZED controlled trials (RCTs) have assessed the effectiveness of this treatment in patients with OSA.3 initial trials used either an oral placebo tablet 4–8 or conventional care9,10 for patients randomized to non-CPAP treatment. as noted by farree and colleagues, these studies failed to apply identical instrumental constraints to both treatment and non-treatment groups.11 in an effort to create a more appropriate placebo, farree and colleagues modified the CPAP apparatus so that pressure levels at the mask interface were < 1 cm H2o.11 comparing polysomnograms (PSGs) in patients with OSA recorded with and without sham-CPAP, the modified CPAP circuit had no effect on apnea-hypopnea index (AHI), a measure of OSA severity.11 sham-CPAP is currently the placebo intervention of choice in RCTs evaluating the effectiveness of CPAP treatment.12–15 although these studies uniformly report no difference in AHI on PSGS with and without sham-CPAP in patients randomized to the placebo intervention arm, no systematic evaluation in a large number of subjects has assessed the effect of sham-CPAP on multiple other PSG measures that might influence clinical outcomes. The primary purpose of this study was to perform a comprehensive evaluation of sham-CPAP effects on PSG outcomes in subjects with OSA. To make this comparison, we used data obtained from participants in the CPAP Apnea Trial North American Program (CATNAP), a multi-center, randomized, triple-blind study utilizing sham-CPAP as the placebo intervention. One of the secondary purposes of this study was to validate the placebo used in CATNAP.