The recovery of 1μm aerosol particles from large human airways

Aerosol particles with aerodynamic diameters (d ac ) of about 1.1 μm were inspired into human conducting airways by the bolus inhalation technique. Inhaling small volumes of aerosols (“20 cm 3 - boluses”) at the very end of a clean air inhalation these particles should only reach conducting human airways. Particle recoveries (RC) in the exhaled air after various periods of breath holding (t b ) were measured in front of the mouth with an aerosol laser photometer. Assuming that losses of the inhaled particles were caused by sedimentation during breath holding periods, the slope of the recovery function (RC(t b )) is a measure of the airway dimensions where the particles were located at end inhalation. This function can be estimated theoretically. By comparing bolus recovery data to model calculations, assuming different aerosol distributions in airway models, and both still and stirred settling, it could be shown that aerosol boluses inhaled to lung depths 3 do not reach alveolar airspaces during inhalation.