Patient-Specific Computational Fluid Dynamics and 4-D Computed Tomography Modeling of Airway Obstruction in Robin Sequence Infants

Robin Sequence is a congenital malformation where the underdeveloped jaw causes the tongue to be displaced back, leading to upper airway obstruction. There is no standard quantification of obstruction severity. This research presents airflow metrics based on patient-specific computational fluid dynamics (CFD). Peak velocity, pressure drop, work of breathing (WOB), and airflow resistance are computed as potential diagnosis tools. 4D computed tomography (4DCT) yields dynamic airway geometries that are integrated in the simulations with a mesh-morphing approach. Complete airway collapse is accurately simulated, overcoming limitations by using pressure, as opposed to flow or velocity at the inlet/outlet and a porous baffle interface to shut down flow at the onset of collapse. Region-specific and phase-specific WOB calculations reveal the airway regions' contributions to airflow resistance and indicate whether inspiratory or expiratory phases demand higher breathing effort. In a case of complete collapse, the daily WOB was ~700 J/day, with 44% coming from the oropharynx. Inspiration contributed 80% of total WOB. In contrast, in a less severe case, WOB is ~265 J/day, with 60% coming from the nasal cavity and nasopharynx. WOB is evenly distributed between inspiration and expiration. This study offers a novel framework for assessing severity and guiding surgical planning, improving over static-imaging-based CFD.