O008 The effect of flow limited breathing and endotypes on night to night variability of sleep apnoea severity

BACKGROUND: Obstructive sleep apnoea (OSA) is a condition involving repetitive collapse of the upper airway during sleep. The diagnosis and characterisation of OSA is based primarily off the apnoea-hypopnoea index (AHI) in a single-night sleep study. Recent data have demonstrated night to night variability (NNV) in OSA severity. Knowledge of which patients have more variable OSA would improve long-term risk stratification and management. However, patient and polysomnographic characteristics associated with high NNV have not been completely explored. This study aims to determine whether the pattern of flow limited breathing (FLB) and underlying endotypes of patients with OSA are predictive of those with high NNV in OSA severity. METHODS: 71 patients with OSA were identified from the placebo arm of randomized controlled trials testing novel OSA interventions. Each patient had undergone two sleep studies. Patient characteristics, medical history and data from both sleep studies were accessed. Sleep data were processed using established algorithms to quantify the degree of FLB as well as OSA endotypes. Differences between each night were analysed for agreement, and for change in the severity of OSA. PROGRESS TO DATE: Ethics approval has been obtained and data has been processed for statistical analysis. INTENDED OUTCOME AND IMPACT: It is expected that NNV will be high in those with mild to moderate OSA, and the pattern of FLB and endotypes across multiple nights will help predict those with more variable compared to stable disease.