Partitioning of lung tissue response and inhomogeneous airway constriction at the airway opening. Suki, B[acute]ela, Huichin Yuan, Qin Zhang, and Kenneth R. Lutchen. Department of Biomedical Engineering, Boston University, Boston, MA 02215
APStracts 3:0577A, 1996.
During a bronchial challenge much of the observed response of lung tissues is an artifactual consequence of inhomogeneous airway constriction. Inhomogeneities, in the sense of time constant inequalities, are an inherently linear phenomenon. Conversely, if lung tissues respond to a bronchoagonist, they become more nonlinear. Based on these distinct responses, we present an approach to separate real tissue changes from airway inhomogeneities. We developed a lung model that includes airway inhomogeneities in the form of a continuous distribution of airway resistances and nonlinear viscoelastic tissues. Since time domain data are dominated by nonlinearities while frequency domain data are most sensitive to inhomogeneities, we apply a combined time-frequency domain identification scheme. This model was tested with simulated data from a morphometrically based airway model mimicking gross peripheral airway inhomogeneities and shown capable of recovering all tissue parameters to within 15% error. Application to our previously measured data suggests that in dogs during histamine infusion, 1) the distribution of airway resistances increases widely and 2) lung tissues do respond, but less so than previously reported. This approach, then, is unique in its ability to differentiate between airway and tissue responses to an agonist from a single broadband measurement made at the airway opening. 

Received 20 May 1996; accepted in final form 4 December 1996.
APS Manuscript Number A477-6.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996