Search

High-frequency ventilation was investigated in a model of the central airways of a human lung cast enclosed in a spherical cavity (alveolí). The experiments were performed at high frequencies (5, 10, 15 and 20 Hz) and tidal volumes (50, 90 and 120 cm) less than the anatomical dead space volume. The efficiency of gas mixing in the model was assessed by measuring the decay of carbon dioxide concentration in the sphere during high-frequency mechanical ventilation. The experimental results were then compared with those obtained from simulations on a theoretical model based on a diffusional resistance concept which could take account of either turbulent, steady laminar or oscillatory laminar dispersion coefficients. Our results showed that the Taylor turbulent dispersion mechanism had a significant effect and could be the principal factor for the efficiency of gas mixing during high-frequency ventilation at small tidal volumes. [ABSTRACT FROM AUTHOR]