Physical factors affecting deposition of aerosols

The major processes which influence deposition of dmg particles in the respiratory tract are, as illustrated in Fig. 9.44, 

When a particle contacts the walls of the airways it is removed from the airstream this process can occur during inspiration or expiration of a single breath, or later if the particle has been transferred to unexhaled lung air. Deposition increases with duration of breath holding and depth of breathing, hence the instmctions to patients to breathe deeply when using their inhalers. 

As flowing air moves in and out, inertial forces within the nasopharyngeal chamber and at the points of branching of the airways, or wherever the direction of flow changes, result in the collision of particles with 

The next sections present a more detailed account of deposition in the airways. 

The aerodynamic diameter of a particle, d, is related to the particle diameter (d) and density ip) by the equation 

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