The influence of a carbachol aersol on the tracheobronchial deposition of 99mTc tagged particles.

Abstract

The tracheobronchial deposition of inhaled 99mTc tagged teflon particles of 6 mum (specific density 2g/cm3) was determined in rabbits by comparing the particle content in free dissected parts of the tracheobronchial tree with that in the whole lung. There was a singificantly larger deposition of particles in the proximal parts of the airways in rabbits exposed to an aerosol of the bronchoconstrictor compound carbachol than in control rabbits exposed to distilled water alone. The resistance to insufflation of a constant volume of air increased during the exposure to the carbachol aerosol, indicating bronchoconstriction. There was reproducible interindividual differences in bronchoconstrictor response to the carbachol aerosol. They were attributed to interindividual differences either in deposition of carbachol or in bronchial muscle sensitivity to carbachol. It is concluded that bronchoconstriction might serve as a defensive measure in causing a more proximal deposition of inhaled particles.