Effects of Airway Branching Patterns on Particle Deposition in the Lungs

Abstract

Abstract Humans have relatively symmetrical bifurcations of their tracheobronchial airways, while all commonly used experimental animals have lung airways which branch in a highly asymmetric manner. Differences in airway sizes and branching result in major differences in particle deposition patterns and efficiencies within bronchial airways. Comparative studies have been performed in this laboratory on aerosol recovery during breath holding in humans in vivo, and in excised lungs of humans and donkeys in relation to their airway morphometry. Other studies compared particle deposition in humans in vivo and in excised human and dog lungs for particles of the same intrinsic mobility when suspended in air, mixtures of O2 and He, and O2 and SF6. Additional comparisons are based on in vivo measurements of tracheobronchial deposition in donkeys and humans. Both aerosol probe and morphometric measurements show that peripheral airspace sizes are substantially smaller in donkeys than humans. While donkeys have larger central airways, they have greater tracheobronchial deposition related to their greater deposition in small conductive airways. Particle deposition in humans in vivo and in excised human lungs is affected by carrier gas composition. However, deposition in excised dog lungs is not affected, apparently owing to the interspecies differences in airway branching patterns.