Aerosol Drug Therapy Practice Test

Inertial impaction happens when particles have enough momentum that they can’t perfectly follow the air as it changes direction at bends or branch points in the airways. When you inhale with a higher flow rate, the air moves faster, increasing the particle momentum and making it harder for larger particles to turn with the airstream. They end up striking the airway walls and depositing there, often in the upper airways rather than reaching deeper lungs. So a higher inspiratory flow rate favors inertial impaction. Lowering the flow rate reduces this effect because the air isn’t rushing as much, allowing particles to better follow the stream and pass deeper. Smaller particle size also reduces inertial impaction since tiny particles can follow the air more readily. Breath-holding tends to enhance deposition by sedimentation and diffusion rather than inertia, so it doesn’t specifically promote inertial impaction.