The Airway Angle to Gravity

To compute the angle to gravity for each airway, we assumed gravity to be perpendicular to the trachea and laying on the plane defined by the trachea and the average vector of the two main bronchi. Typically, and considering the type of aerosol being modeled, three particle deposition mechanisms are used to calculate the deposition within the airways: diffusion, impaction, and sedimentation mechanisms. For example, the branch inclination to gravity is a critical parameter for the sedimentation mechanism in the case of submillimeter particles. The physiological difference in terrestrial locomotion between humans, who are bipedal, and rodents, which are quadrupedal, leads to different assumptions in the tracheobronchial region, for example, that the trachea is parallel to the force of gravity for humans and at 90° to gravity for rodents.