Computational fluid dynamics as an objective measure for assessing congenital tracheal stenosis: Proof-of-concept study.

Background: Conventional diagnostic assessment of congenital tracheal stenosis does not always closely correlate with clinical status, especially in asymptomatic children. Clinical decision making is often difficult in these circumstances. Computational fluid dynamics (CFD), in which computed tomography scans are reconstructed to map dynamic flow in the body, has shown promise as a tool for assessing airflow in children with congenital tracheal stenosis when traditional imaging modalities are limited. We sought to establish proof of this concept by applying CFD to congenital tracheal stenosis. Methods: A retrospective single-center cohort study was performed for patients with congenital tracheal stenosis treated with slide tracheoplasty. A total of 9 children (age 3 months-12 years; weight 3-42 kg) with tracheal stenosis were assessed, including 2 with isolated stenosis, 2 with stenosis with a left pulmonary artery sling, 2 with stenosis with tracheal bronchus, and 3 with stenosis with single lung. Preoperative and postoperative computed tomography scans were obtained retrospectively and then used to construct 3-dimensional tracheal models and assess airflow using CFD. The 3-dimensional tracheal geometries were segmented to extract centerlines and prepare inlet/outlet planes, a steady velocity was imposed at the inlet, and zero pressure was imposed at the outlets. Results: CFD simulations were successfully run to visualize velocity and pressure fields, which in turn were used to calculate pressure gradients across areas of obstruction and energy loss in the system. Postrepair velocities at the areas of maximum obstruction were lower than pre-repair velocities at the mid-trachea or carina for all 9 patients. Higher velocity, lower pressure, and increased wall stress corresponded to areas of stenosis across CFD simulations. Conclusions: Clinicians have limited functional data to inform decision making in the surgical repair of congenitally malformed tracheas. CFD using our methodology can virtually simulate flow in pre-repair and postrepair scenarios in several different malformations. The results of this study support CFD as a promising method for objectively assessing fluid dynamic metrics in congenital tracheal stenosis and correlating with clinical presentation and prognosis.