Fluid-structure interaction modelling of the upper airway with and without obstructive sleep apnea: a review

Obstructive sleep apnea (OSA) is a common respiratory disorder associated with the collapse of the upper airway during sleep. OSA may cause oxygen desaturation, arousals from sleep, and daytime sleepiness, in turn affecting quality of life. There is low success rate in existing OSA surgical treatments mainly due to heterogeneity of the OSA population and poor understanding of the mechanism of the upper airway collapse in each individual. However, advancements in computational simulation have led to some detailed structural modelling of the upper airway that may help to better understand its collapse mechanism in OSA. Alternative surgical treatment methods may be critically assessed with simulation prior to clinical adoption to provide personalized treatment insight for an OSA individual. This review summarizes the current literature related to the application of fluid structure interaction simulation for OSA analysis, with a focus on pharyngeal airway deformation mechanisms, airflow characteristics, and OSA surgical treatment efficacy; it also identifies the shortcomings of current models with suggestions for future studies. It is evident that the upper airway collapse mechanism, the anatomical factors affecting the location and timing of the collapse, and the association of the upper airway anatomical features with critical pressure (P_crit) are still lacking. Moreover, numerical simulation has been shown to be a great tool in OSA surgical treatment efficacy. Future studies incorporating the practice of virtual surgery may further support clinical decision-making.