Journal of Applied Physiology, Vol 41, Issue 3 388-395, Copyright © 1976 by American Physiological Society
Distribution of pulmonary resistance: effects of gas density, viscosity, and flow rate
J. M. Drazen, S. H. Loring and R. H. Ingram Jr
Theoretical predictions of the distribution of inspiratory viscous pressure
loss were made for canine and human pulmonary airways for gases with
varying density and viscosity at different pulmonary flow rates. We
predicted that in canine or human airways when tracheal flow was turbulent,
most of the total calculated pressure loss would be in the first few
branchings of the bronchial tree; however when tracheal flow was nearly
laminar inspiratory pressure loss would be spread more uniformly along the
airways. To test these predictions an airway catheter was used to partition
total pulmonary resistance (RL) in five anesthetized dogs. On air the
catheter was positioned such that the mean resistance mouthward of the
catheter tip (Rc) at a flow of 0.5 1/s was 63% of RL. At the same catheter
position Rc was 87% of RL when the dogs were breathing a mixture of 80%
sulfur hexafluoride-20% oxygen and resistance was determined at 1.0 1/s. Rc
was 50% of RL when the dogs were breathing a mixture of 80% helium-20%
oxygen and resistance was determined at 0.25 1/s. Thus altering gas
physical properties and flow rates changed the distribution of pulmonary
resistance as predicted.
