Coupled processes of tissue oxygenation and fluid flow in biphasic vocal folds

Fluid-structure interaction (FSI) between the glottal airflow and the poroelastic tissue of the vocal folds (VFs) causes the VFs to vibrate, resulting in voice production. Prior experimental studies have reported that biological transport processes within the VF tissue play a crucial role in disease initiation and localized lesions. Particularly, it has been observed that physiological conditions during phonation influence the interstitial flow within the tissue and the associated oxygen partial pressure, which corresponds with dysfunctions such as intermittent hypoxia. The goal of this research is to develop a multiphysics computational methodology that investigates oxygen transport characteristics within the VFs. By considering transient glottal airflow and a biphasic description for the tissue, this coupled framework combines an FSI model with a mass transport model to quantify key features contributing to VF oxygenation. The Navier-Stokes equations represent the aerodynamics in the larynx, while linear elasticity for tissue dynamics is considered. Additionally, oxygen transport is simulated using the advection-diffusion-reaction equation, and the interstitial flow is solved via the Brinkman equation. Physiological parameters such as oxygen metabolic consumption, subglottal lung pressure, and tissue permeability coefficient are varied; and their contribution to oxygen supply as well as to the liquid dynamics within the VF are quantified. It is found that filtration velocity is directly proportional to subglottal pressure and tissue permeability. Oxygen flow is also found to be inversely related to reaction rate, directly related to permeability, and not noticeably affected by subglottal pressure. The findings provide insight into the VF oxygenation pathways and the potential link with some pathological states such as hypoxia and localized lesions.