Penetration of an aerosol, produced by film atomization, through the carinal bifurcation

We have measured the size of spots produced by atomization of simulated biofilm particles from a tracheal tube. Draughtsman's ink was atomized from 8.5-mm i.d. Portex tracheal tubes, using an airflow of 1 litre s-1, and trapped on vertical acetate sheets. The spots produced by these particles were compared with the spot size after entrainment and dissemination from an ink-lined tracheal tube through a bifurcating tracheobronchial tube towards a glass plate. Spot dimensions were measured by computer-assisted image analysis of a video image. The smallest particles observed on the acetate sheets were 4-17 microns in size. In the bifurcating tube experiment, large particles were deposited around the carinal bifurcation, but smaller particles traversed the bend. The smallest spot size observed (7 microns minimum; 17 microns median) corresponds to particles small enough to penetrate further into the lower respiratory tract. Travel via a tube similar to the carinal bifurcation suggests that fragments of biofilm entrained in the tracheal tube could be propelled deeper into the respiratory tract during the inspiratory phase of mechanical ventilation.