Around one in three patients with OSAS is unable to continue with CPAP. The reasons for this are still poorly understood. Patients being assessed for Bariatric Surgery are informed that untreated OSAS can increase peri-operative risk. We investigated whether this information had an effect on CPAP use. Over a six month period we identified 22 obese patients (Mean BMI 49.3) with OSAS discovered during assessment for Bariatric Surgery (OSAS Bar). Over the same period we identified a group of 33 obese patients (Mean BMI 42.1) with OSAS referred through conventional pathways by General Practitioners and Hospital Doctors (OSAS Conv) not under consideration for Bariatric Surgery. OSAS was diagnosed by overnight pulse oximetry, clinical interview and Epworth Sleepiness Score (ESS) using established criteria.

Results There were more women than men in the OSAS Bar group (41%) than in the OSAS Conv group (18%). Apart from this the 2 groups (OSAS Bar vs OSAS Conv) were well matched prior to CPAP for: Age (Mean 51.2 vs 48.3, p = ns), >4% Oxygen Desaturation Index (Mean 31.9/hour vs 42.3/hour, p = ns) and ESS (Mean 12.8 vs 14.8, p = ns). By 6 weeks after Out-Patient CPAP initiation, 6(27%) of the OSAS Bar group and 7(21%) of the OSAS Conv group had stopped using CPAP. In the patients continuing with CPAP there was no difference between the two groups in hours of CPAP used per night as measured from the CPAP device clock: CPAP Bar (Mean 5, Range 1 8, hours), CPAP Conv (Mean 6, Range 1.5 8.5, hours) or in the ESS on CPAP: CPAP Bar (Mean ESS 6.8), CPAP Conv (Mean ESS 5.8).

Conclusion This group of obese patients with OSAS under assessment for Bariatric Surgery had similar CPAP use to obese patients with OSAS not considering surgical intervention. Information on peri-operative risk does not appear to be a motivator in overcoming whatever inhibiting factors prevent patients from using CPAP. Pre-operative assessment clinics should be aware that CPAP prescription does not necessarily mean that CPAP is being used.