Does the anatomic makeup of parenchymal lung strips affect
oscillatory mechanics during induced constriction.
Salerno, F. G., M. Dallaire, M. S. Ludwig.
Meakins-Christie Laboratories, Royal Victoria Hospital, McGill
University, Montreal, Quebec, CANADA
APStracts 2:0114A, 1995.
Parenchymal tissue strips have been used to investigate the mechanical
behavior of the lung parenchyma. We questioned whether the relative
amounts of alveolar (AW), blood vessel (BVW) and bronchial wall (BW)
would be important when the contractile response of parenchymal
strips from Sprague Dawley rats was studied. One group of strips was
cut from the subpleural edge and another from between 1 to 3 mm
proximal to the pleura. Strips were suspended in an organ bath filled
with Krebs solution (37 C degrees , pH=7.4) bubbled with 95%O2/5%CO2.
Resting tension (T) was set at 1.1 g and sinusoidal oscillations of
2.5% resting length (Lo) at a frequency of 1 Hz were applied.
Measurements of length (L) and T were recorded during baseline
conditions and after Acetylcholine (ACh, 10-3 M) was added to the
bath. Elastance (E), resistance (R) and hysteresivity ([theta], the
ratio of the energy dissipated to that conserved) were calculated.
Strips were fixed in formalin at a T of 1 g, histologic sections
prepared and the fractional area of AW, BVW and BW measured using
point counting. Significant differences were found between the two
groups of strips in the ACh response and in the anatomic makeup. The
magnitude of the changes of all the mechanical parameters were
correlated with the volume proportions of the different anatomic
constituents when all the strips were plotted together but not when
the subpleural strips were considered alone. We conclude that
subpleural parenchymal strips are a sound model of parenchymal lung
behaviour. When more proximal strips are studied, the amount of
bronchial wall may play an important role in determining the
hysteretic response.
Received 28 November 1994; accepted in final form 7 March 1995.
APS Manuscript Number A1205-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.