Aerosol Drug Therapy Practice Test

The main concept is that particle inertia causes deposition when a particle can’t bend its path with the airflow around airway bends. Large or fast-moving particles carry momentum that keeps them moving in a straight line as the airstream curves at branch points in the airways. Because they can’t follow the turning flow, they strike the airway walls and deposit there. This is inertial impaction, and it is most impactful for bigger particles or higher flow rates, which is why upper airway deposition is common with these conditions. Sedimentation relies on gravity pulling particles down during slower or longer residence times, and Brownian diffusion involves random molecular motion that matters most for very small particles over time. Interception, meanwhile, happens when a particle following a streamline comes within a particle radius of a surface and is effectively “caught” by geometry, not primarily by inertia. So the mechanism driven by inertia—the straight-line tendency of heavier particles that prevents them from following curved airways—is inertial impaction.