Upper Airway Flow Dynamics in Robin Sequence Infants: A 4-D Computed Tomography and Computational Fluid Dynamics Study*

Robin Sequence (RS) is a craniofacial condition characterized by undersized jaw, posteriorly displaced tongue, and resultant upper airway obstruction (UAO). It is potentially fatal and requires varying levels of treatment. Accurate assessment of UAO severity is essential for successful management and diagnosis, yet current evaluation has significant limitations and no quantitative measures of breathing resistance exist. In this study we combine 4-D CT and computational fluid dynamics (CFD) to quantify UAO severity and location in RS patients. Dramatic intrapopulation differences are found, with the ratio between most and least severe values of breathing resistance, energy loss, and peak velocity equal to 40:1, 20:1, and 6:1, respectively. The primary UAO is found either at the tongue base or the larynx, with tongue base obstructions causing a more energetic stenotic jet and greater breathing resistance. CFD-derived flow metrics are found to correlate well with the level of clinical respiratory support. Our results highlight the large intrapopulation variability, both in quantitative metrics of UAO severity and in the location and intensity of stenotic jets for RS. These results suggest that computed airflow metrics can provide an evidence-based structure for the management of RS.