Evaluation of the Tracheal Stenosis Effects on Airway Resistance and Work of Breathing Using Computational Fluid Dynamics.

Background: Bronchoscopy is one of the most accurate procedures to diagnose airway stenosis which is an invasive procedure. However, a quick and noninvasive estimation of the percent area of obstruction (%AO) of the lumen is helpful in decision-making before performing a bronchoscopy procedure. We hypothesized that there is a relationship between %AO and tracheal resistance against fluid flow.

Materials and methods: By measuring airway resistance, %AO could be estimated before the procedure. Using computational fluid dynamics (CFD), this study simulates the fluid flow through trachea models with web-liked stenosis using CFD. A cylindrical segment was inserted into the trachea to represent cross-sectional areas corresponding to 20%, 40%, 60%, and 80% AO. The fluid flow and pressure distribution in these models were studied. Our CFD simulations revealed that the tracheal resistance is exponentially increased by %AO.

Results: The results showed a 130% and 55% increase in lung airway resistance and resistive work of breathing for an 80% AO, respectively. Moreover, a curve-fitted relationship was obtained to estimate %AO based on the measured airway resistance by body plethysmography or forced oscillation technique.

Conclusion: This pre-estimation is very useful in diagnostic evaluation and treatment planning in patients with tracheal stenosis.