Particle Deposition of Inhaled Aerosol Boluses in the Upper Human Airways

An inspired aerosol bolus of a defined volume injected at the end of an inhalation of particle free air was used to study particle losses and airway dimensions of the tracheo-bronchial tree. The penetration of the bolus into the lungs, the expired reserve volume, ERV, and the breathing posture were varied. From experiments with different breath-holding times after inhalation an effective airway diameter, DA, was evaluated for a preset bolus penetration. With decreasing ERV and increasing penetration the determined DA decreases. The lying posture of the subject yielded a smaller DA than the sitting position. Effective airway diameters greater than 2 mm were found if the volumetric penetration of the bolus maximum is less than 50 cm3.