Quantifying the Magnitude of Pharyngeal Obstruction During Sleep Using Airflow Shape

Rationale Non-invasive quantification of the severity of pharyngeal airflow obstruction would enable recognition of obstructive versus central manifestation of sleep apnoea, and identification of symptomatic individuals with severe airflow obstruction despite a low apnoea-hypopnoea index (AHI). Objectives Here we provide a novel method that uses simple airflow- versus -time (“shape”) features from individual breaths on an overnight sleep study to automatically and non-invasively quantify the severity of airflow obstruction without oesophageal catheterisation. Methods 41 individuals with suspected/diagnosed obstructive sleep apnoea (AHI range=0–91 events·hr −1 ) underwent overnight polysomnography with gold-standard measures of airflow (oronasal pneumotach, flow ) and ventilatory drive (calibrated intraoesophageal diaphragm EMG, drive ). Obstruction severity was defined as a continuous variable ( flow:drive ratio). Multivariable regression used airflow shape features (inspiratory/expiratory timing, flatness, scooping, fluttering) to estimate flow:drive 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). Measurement and Main Results Gold-standard obstruction severity ( flow:drive ) varied widely across individuals independent of AHI. A multivariable model (25 features) estimated obstruction severity breath-by-breath (R 2 =0.58 versus gold-standard, p 2 =0.69, p Conclusions The severity of pharyngeal obstruction can be quantified non-invasively using readily-available airflow shape information. Our work overcomes a major hurdle necessary for the recognising and phenotyping of patients with obstructive sleep disordered breathing.