Modeling and simulation of conducting airways during continuous high-frequency oscillation therapy.

Abstract

Continuous high-frequency oscillation (CHFO) is used clinically as an adjunct for airway clearance and lung expansion, yet its pressure and shear distribution within human conducting airways remains poorly quantified. To better understand these flow mechanics, we created a patient-specific, CT-derived airway model (nasal and oral cavity to the 13th lung generation) and performed transient RANS simulations with k-ω SST turbulence closure on a 7.75 million cell hybrid mesh. A slow-breathing waveform was combined with 3 Hz oscillatory pressure input representative of a MetaNeb® system, and two therapeutic settings were compared: A standard CHFO mode and a high-pressure CHFO mode. We analyzed instantaneous and phase-averaged velocity, static pressure, wall shear stress, area-averaged pressure, time-averaged pressure and wall-normal force. The results show that anatomy fixes "hot spots" of mechanical loading: A persistent laryngeal jet generates local static-pressure minima and elevated shear, while the broader nasal-pharyngeal cavities carry the highest global wall-normal forces. In addition, distal generations experience tightly phase-locked pressures with modest proximal-to-distal gradients within the modeled conducting airways, indicating limited axial attenuation of oscillatory forcing over the resolved G0-G13 airway segment. Switching to high-pressure CHFO uniformly elevates mean and RMS airway pressures, increases wall-normal forces by ∼15-30% and extends exposure to values greater than 25 cmH₂O, yet pre65serves the spatial hierarchy of pressure and shear. These findings describe how CHFO-representative forcing reshapes pressure, shear, and wall-normal loading within the resolved rigid-wall conducting-airway model, from more phasic loading under standard CHFO to more tonic loading under high-pressure CHFO, while preserving an anatomy-defined spatial hierarchy within the model.