Particle transport onto human airway surfaces.

Three domains can be distinguished for particle transport onto human airway surfaces: 1. thermodynamic domain. Particles are transported by diffusion. Deposition decreases with particle diameter, is independent of particle density, increases with inspiration time and should be independent of flow rate. 2. intermediate domain. Particles are transported by diffusion and gravitational sedimentation. Deposition is slightly dependent on particle diameter, particle density and flow rate and increases with inspiration time. Since particles are effectively collected by inertial impaction in the nose this domain disappears for nose-breathing. 3. aerodynamic domain. Particles are transported by gravitational sedimentation and by inertial impaction. Deposition increases with particle diameter, particle density, inspiration time and flow rate. For normal breathing this domain consists of three subdomains. 3.1. sedimentation domain. Particles aerodynamically smaller than 2 micrometers are deposited by gravitational sedimentation in the alveolar region. 3.2. impaction-sedimentation domain. Particles aerodynamically between 2 and 12 micrometers are deposited by inertial impaction in the extrathoracic airways, by gravitational sedimentation and inertial impaction in the bronchial airways and by gravitational sedimentation in the alveolar region. 3.3 impaction domain. Particles aerodynamically larger than 12 micrometers are deposited by inertial impaction predominantly in the extrathoracic and less in the bronchial airways.