The side-effects to CPAP treatment inventory: the development and initial validation of a new tool for the measurement of side-effects to CPAP treatment.

Continuous positive airway pressure (CPAP) is the treatment of choice for obstructive sleep apnoea syndrome (OSAS), but side-effects are common. No validated self-rating scale measuring side-effects to CPAP treatment exists today. The aim was to develop the side-effects to CPAP treatment inventory (SECI), and investigate the validity and reliability of the instrument among patients with OSAS. SECI was developed on the basis of: (1) in-depth interviews with 23 patients; (2) examination of the scientific literature and (3) consensus agreement of a multi-professional expert panel. This yielded 15 different types of side-effects related to CPAP treatment. Each side-effect has three sub-questions (scales): perceived frequency (a) and magnitude (b) of the side-effect, as well as its perceived impact on CPAP use (c). A cross-sectional descriptive design was used. A total of 329 patients with OSAS with an average use of CPAP treatment for 39 months (2 weeks to 182 months) were recruited. Data were collected with SECI, and obtained from medical records (clinical variables and data related to CPAP treatment). Construct validity was confirmed with factor analysis (principal component analysis with orthogonal rotation). A logical two-factor solution, the device subscale and symptom subscale, emerged across all three scales. The symptom subscale describing physical and psychological side-effects and the device subscale described mask and device-related side-effects. Internal consistency reliability of the three scales was good (Cronbach's α = 0.74-0.86) and acceptable for the subscales (Cronbach's α = 0.62-0.86). The satisfactory measurement properties of this new instrument are promising and indicate that SECI can be used to measure side-effects to CPAP treatment.