Quantifying the magnitude of pharyngeal obstruction during sleep using airflow shape

• Published in: The European respiratory journal Vol. 54; no. 1; p. 1802262
• Main Authors: Mann, Dwayne L, Terrill, Philip I, Azarbarzin, Ali, Mariani, Sara, Franciosini, Angelo, Camassa, Alessandra, Georgeson, Thomas, Marques, Melania, Taranto-Montemurro, Luigi, Messineo, Ludovico, Redline, Susan, Wellman, Andrew, Sands, Scott A
• Format: Journal Article
• Language: English
• Published: England 01-07-2019
• Subjects: Aged; Female; Humans; Linear Models; Male; Middle Aged; Multivariate Analysis; Pharyngeal Diseases - etiology; Pharyngeal Diseases - physiopathology; Phenotype; Polysomnography - methods; Sleep Apnea, Obstructive - complications; Sleep Apnea, Obstructive - physiopathology
• ISSN: 0903-1936; 1399-3003
• DOI: 10.1183/13993003.02262-2018

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 severity of airflow obstruction without oesophageal catheterisation.
41 individuals with suspected/diagnosed obstructive sleep apnoea (AHI range 0-91 events·h
) underwent overnight polysomnography with gold-standard measures of airflow (oronasal pneumotach: "flow") and ventilatory drive (calibrated intraoesophageal diaphragm electromyogram: "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 ratio 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 (flow:drive ratio) varied widely across individuals independently of AHI. A multivariable model (25 features) estimated obstruction severity breath-by-breath (R
=0.58
gold-standard, p<0.00001; mean absolute error 22%) and the median obstruction severity across individual patients (R
=0.69, p<0.00001; error 10%). Similar performance was achieved using nasal pressure.
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 recognition and phenotyping of patients with obstructive sleep disordered breathing.