PARTICLE RECOVERY FROM HUMAN CONDUCTING AIRWAYS AFTER SHALLOW AEROSOL BOLUS INHALATION

Aerosol particles were delivered into human conducting airways by inhaling small volumes of aerosols (''boluses'') at the end of a clean air inhalation. Particle recovery (RC) in the exhaled air after various periods of breathholding (t(b)) was measured in front of the mouth with a laser photometer. Inspired and expired flowrates were measured with a pneumotachograph. Aerosol particles with aerodynamic diameters (d(ae)) between 2 and 5.5 mum were used for these measurements. Particles reaching regions of small airspaces are deposited more efficiently than those located in larger conducting airways at the end of inhalation. With different theoretical models the aerosol recovery was calculated assuming various axial aerosol distributions in the airways. Comparing the theoretically-obtained recovery results with the experimental data for a healthy male subject, it is shown that less than 2% of particles from shallow aerosol boluses reached the airways of the investigated subject with diameters < 1 mm during inhalation.