Hysteresivity of the lung and tissue strip in the normal rat: effects of heterogeneities.
Sakai, Hiroaki, Edward P. Ingenito, Rene Mora, Senay Abbay, Francisco S. A.
Cavalcante, Kenneth R. Lutchen, and Béla Suki.
1Department of Biomedical Engineering, Boston University, Boston 02215; and
2Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital,
Boston, Massachusetts 02115
APStracts 8:0254A, 2001.
We measured lung impedance in rats in closed chest (CC), open chest (OC), and isolated
lungs (IL) at four transpulmonary pressures with an optimal ventilator waveform. Data
were analyzed with an homogeneous linear or an inhomogeneous linear model. Both
models include tissue damping and elastance and airway inertance. The homogeneous
linear model includes airway resistance (Raw), whereas the inhomogeneous linear model
has a continuous distribution of Raw characterized by the mean Raw and its SD. Lung
mechanics were compared with tissue strip mechanics at frequencies and operating
stresses comparable to those during lung impedance measurements. The hysteresivity (?)
was calculated as tissue damping/elastance. We found that 1) airway and tissue
parameters were different in the IL than in the CC and OC conditions; 2) SD of Raw was
lowest in the IL; and 3) ? in IL at low transpulmonary pressure was similar to ? in the
tissue strip. We conclude that ? is primarily determined by lung connective tissue, and its
elevated estimates from impedance data in the CC and OC conditions are a consequence
of compartment-like heterogeneity being greater in CC and OC conditions than in the IL.
Received 15 August 2000; accepted in final form 12 April 2001
APS Manuscript Number A826-0.
Article publication pending J Appl Physiol
ISSN 1080-4757 Copyright 2001 The American Physiological Society.
Published in APStracts on 18 June 2001