Secondary flow augmentation during intermittent oscillatory flow in model human central airways

The efficiency of axial gas dispersion during ventilation with high-frequency oscillations (HFO) can be improved by manipulating the oscillatory flow waveform such that intermittent oscillatory flow occurs. To clarify the augmentation of axial gas transfer during intermittent oscillatory flow, we measured the axial and secondary velocity profiles during intermittent oscillatory flow through a model human central airway. We used a rigid model of human airways consisting of asymmetrical bifurcations up to third generation. Velocities in the axial and radial directions were measured with two-color laser-Doppler velocimetry. Secondary flow was accelerated at the beginning of the stationary period, particularly in the trachea, which resulted in enhanced gas transport during intermittent oscillatory flow.