Aerosol Bolus Transport Through a Hollow Airway Cast by Steady Flow in Different Gases

TLDR: In this paper, the authors measured the transport of aerosol through the airways of a hollow cast of a canine tracheobronchial tree, and found that the aerosol particles were fastest in the gas of highest kinematic viscosity (helium), and slowest in a gas of lowest kinematics viscoelasticity (sulfur hexafluoride).

Abstract: Transport of aerosol through the airways of a hollow cast of a canine tracheobronchial tree was measured for steady flow in different gas mixtures. A small bolus of 0.5-μm aerosol particles was inserted as a tracer of convective motion in the flow at the entrance of the trachea, and particles were collected and counted as they arrived at a flow-balanced sampling bag at a peripheral segment of the cast. Transport was fastest in the gas of highest kinematic viscosity (helium), and slowest in the gas of lowest kinematic viscosity (sulfur hexafluoride). This is consistent with the lubrication theory that describes an axial core in the divergent flow field of the bronchial tree. The finer core in helium transports the particles at a greater velocity to distal airways. Transport of gases through the in vivo respiratory tract should also be influenced by these fluid mechanics of convection resembling Poiseuille flow that is substantially modified according to lubrication theory. As predicted by some other invest...