Computational and Experimental Characterization of Flow in an Intubated Human Trachea ^†

The increased incidence of respiratory diseases in the recent past has resulted in a growing number of respiratory failures and dependence on mechanical ventilation. The death rates in patients under long-term ventilator therapy are seen to be as high as 62%, with mortality often attributed to secondary bacterial infections originating in endotracheal tube (ETT) assemblies. The ETT connects the ventilator to the trachea, and the parameters selected by the clinician play important roles in determining the airflow dynamics and mucus transport. This study considers the influence of ETT cuff geometry and ventilator cycling on tracheal airflow behavior, comparing Taperguard- and Microcuff-type designs with respect to Pressure-Controlled Ventilation (PCV) and Assisted Volume-Controlled Ventilation (VCV) modes. Three-dimensional Unsteady Reynolds Averaged Navier–Stokes (URANS) simulations in an idealized intubated trachea were performed and complemented by flow visualization and flow rate measurements for model validation. The simulation results show that both the cuff geometry and ventilation mode affect flow asymmetry of air flow in the trachea and consequently the wall shear stresses and secondary flow development. Specifically, the Taperguard-style cuff under PCV conditions generated substantially elevated wall shear stress values—nearly twice those observed for the same cuff operating in VCV mode. In contrast, the Microcuff configuration paired with VCV produced lower gas flow velocities and reduced shear stress levels, reaching only about 80% of the peak values associated with the Taperguard case. These differences highlight the combined influence of cuff geometry and ventilation strategy on local airway loading. These findings highlight the coupled impact of cuff design and ventilatory mode, and provide a pathway for understanding flow physics in intubated trachea towards improved respiratory care and mechanical ventilation practices.