[Measuring human mucociliary clearance]

Using a new inhalation technique, it is possible to inject aerosol boluses of defined volume at any moment during inspiration into the inhaled air. Deposition of particles in different lung depths was achieved by holding the breath at end-inspiration. Particle clearance of the inhaled radioactively labelled particles was determined by measuring the radioactivity retained in the lungs as a function of time after inhalation. Even for shallow volumetric lung depths as small as 35 cm3 slow clearance of a significant fraction of the deposit has been observed.