Night-to-night variability of obstructive sleep apnoea

In current clinical practice, diagnosis and exclusion of obstructive sleep apnoea (OSA) is based on a single sleep study. The aim of this study was to assess night-to-night variability of OSA to evaluate the current practice. 77 patients previously diagnosed with OSA randomised to continuous positive airway pressure (CPAP) withdrawal within four trials performed nightly pulse oximetry over two weeks off CPAP. The main outcome of interest was the coefficient of variation (CV) of the oxygen desaturation index (ODI) as marker of night-to-night variability in OSA. OSA was categorised according to conventional thresholds using ODI (no OSA: <5/h, mild 5-15/h, moderate 15-30/h and severe OSA >30/h). High night-to-night variability of OSA was evidenced by a CV of ODI of 31.1% (SD16.5). Differences in ODI >10/h between nights were found in 84.4% and shifts in OSA severity stages in 77.9% of patients. The probability of missing moderate OSA in a random night was up to 60%. Variability was higher in less severe OSA. High night-to-night variability of OSA was evidenced by a CV of ODI of 31.1% (SD16.5). Differences in ODI >10/h between nights were found in 84.4% and shifts in OSA severity stages in 77.9% of patients. The probability of missing moderate OSA in a random night was up to 60%. Variability was higher in less severe OSA.