PENETRATION OF AN AEROSOL, PRODUCED BY FILM ATOMIZATION, THROUGH THE CARINAL BIFURCATION

We have measured the size of spots produced by atomization of simulate d biofilm particles from a tracheal tube. Draughtsman's ink was atomiz ed 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 th ese particles were compared with the spot size after entrainment and d issemination from an ink-lined tracheal tube through a bifurcating tra cheobronchial tube towards a glass plate. Spot dimensions were measure d by computer-assisted image analysis of a video image. The smallest p articles observed on the acetate sheets were 4-17 mum in size. In the bifurcating tube experiment, large particles were deposited around the carinal bifurcation, but smaller particles traversed the bend. The sm allest spot size observed (7 mum minimum; 17 mum median) corresponds t o particles small enough to penetrate further into the lower respirato ry tract Travel via a tube similar to the carinal bifurcation suggests that fragments of biofilm entrained in the tracheal tube could be pro pelled deeper into the respiratory tract during the inspiratory phase of mechanical ventilation.