Quantifying the magnitude of pharyngeal obstruction during sleep using airflow shape

Non-invasive quantification of the severity of pharyngeal airflow obstruction would enable recognition of obstructive central manifestation of sleep apnoea, and identification of symptomatic individuals with severe airflow obstruction despite a low apnoea-hypopnoea index (AHI).Here we provide a novel method that uses simple airflow--time ("shape") features from individual breaths on an overnight sleep study to automatically and non-invasively quantify the of airflow obstruction without oesophageal catheterisation.41 individuals with suspected/diagnosed obstructive sleep apnoea (AHI range=0-91 events·hr) underwent overnight polysomnography with gold-standard measures of airflow (oronasal pneumotach, ) and ventilatory drive (calibrated intraoesophageal diaphragm EMG, ). Obstruction severity was defined as a continuous variable ( ratio). Multivariable regression used airflow shape features (inspiratory/expiratory timing, flatness, scooping, fluttering) to estimate in 136 264 breaths (performance based on leave-one-patient-out cross-validation). Analysis was repeated using simultaneous nasal pressure recordings in a subset (N=17).Gold-standard obstruction severity () varied widely across individuals independent of AHI. A multivariable model (25 features) estimated obstruction severity breath-by-breath (R=0.58 gold-standard,