Relationship between heterogeneous changes in airway morphometry and lung resistance and elastance

Lutchen, Kenneth R., and Heather Gillis. Relationshipbetween heterogeneous changes in airway morphometry and lung resistanceand elastance. J. Appl. Physiol.83(4): 1192-1201, 1997.We present a dog lung model to predictthe relation between inhomogeneous changes in airway morphometry andlung resistance (RL) andelastance (EL) for frequenciessurrounding typical breathing rates. TheRL andEL were sensitive in distinctways to two forms of peripheral constriction. First, when there is alarge and homogeneous constriction, theRL increases uniformly over thefrequency range. The EL israther unaffected below 1 Hz but then increases with frequencies up to5 Hz. This increase is caused by central airway wallshunting. Second, the RL andEL are extremely sensitive to mild inhomogeneous constriction in which a few highly constricted ornearly closed airways occur randomly throughout theperiphery. This results in extreme increases in the levelsand frequency dependence of RLand EL but predominantly attypical breathing rates (<1 Hz). Conversely, theRL andEL are insensitive to highly inhomogeneous airway constriction that does not produce any nearly closed airways. Similarly, alterations in theRL andEL due to central airway wallshunting are not likely until the preponderance of the peripheryconstricts substantially. The RLand EL spectra are far moresensitive to these two forms of peripheral constriction than toconstriction conditions known to occur in the central airways. On thebasis of these simulations, we derived a set of qualitative criteria toinfer airway constriction conditions from RL andEL spectra.