Journal of Applied Physiology, Vol 65, Issue 6 2446-2452, Copyright © 1988 by American Physiological Society
Airway resistance measured in liquid-trapped guinea pig lungs by micropuncture
Y. L. Lai, S. Ganesan and S. J. Lai-Fook
Pharmacology and Toxicology Division, College of Pharmacy and Biomedical Engineering, Wenner-Gren Research Laboratory, University of Kentucky, Lexington 40546.
We studied the relationship between bronchoconstriction and the degree of
trapping in saline-filled lungs isolated from guinea pigs postmortem after
rapid exsanguination. Airway resistance was measured in nine lungs, and in
five lungs the site of airway narrowing was located radiographically.
Animals were anesthetized with pentobarbital sodium, degassed by O2
absorption, then rapidly exsanguinated when O2 absorption was almost
complete. Liquid trapping was assessed from the pressure-volume behaviour
measured in saline-filled lungs. During a slow deflation from maximum
volume, alveolar liquid pressure (Palv) was measured by the
micropipette-servonulling method, airway opening pressure (Pao) by a strain
gauge, and flow rate (Q) by weighing a reservoir connected to the airway.
Airway resistance (Raw) was calculated at different lung volumes from the
relationship: Raw = (Palv-Pao)/Q. In untreated lungs, Raw and fluid
trapping were relatively high, and severe bronchoconstriction occurred at
the level of the main stem and lobar bronchi. Nifedipine infusion reduced
Raw 40-fold and decreased trapping. Raw was further reduced 10-fold and
fluid trapping was minimal in lungs pretreated with nifedipine before
exsanguination. Results suggest a close association between
bronchoconstriction and fluid trapping in guinea pig lungs.
