[Deposition of particles in the respiratory tract]

In order to appraise the site of deposition of an aerosol of particles in the airways, it is important to analyse the size distribution of the particles that form the aerosol by granule size range analysis. The three main different mechanisms involved in deposition of an aerosol are inertia impaction, sedimentation and brownian diffusion, and one or another predominates, according to the size of the inhaled aerosol. Finally, several factors may influence the deposition in the respiratory tract: anatomy of the airways, the respiratory method, the size range and the moisture content of the aerosol, smoking and respiratory pathology. Only by taking into account all these factors can an assessment be made of the deposition site in the airways of the inhaled particles.