Effects of Bronchoconstriction on Elastic Properties of Excised Lungs and Bronchi

Abstract

Excised gas-free cat and dog lungs were filled with oxygenated Ringer-Locke''s solution in a bath at 37.5[degree]C. Pressure-volume curves obtained before and after the adition of acetylcholine (with physostigmine) and atropine to the fluid filling the lungs showed no effect of these drugs on the emptying curves, where dynamic effects were minimized. Measurement of intrapulmonary pressure at a constant lung volume under static conditions, showed a mean rise of pressure at equilibrium from 3.08 to 3.26 cm of water when acetylcholine and physostigmine were introduced into the bronchial tree. Subsequent addition of large doses of atropine lowered the pressure by an average of 0.32 cm of water or 10.8%. Isolated bronchial segments mounted in a Ringer-Locke''s bath at 37.5[degree]C showed no significant change in their length-tension characteristics upon addition of the drugs to the bath. Results indicate that the bronchial smooth mucle has little direct effect on lung elastic recoil. The effect of surface tension added to smooth muscle contraction in the production of bronchiolar closure and changes in lung compliance in vivo is discussed briefly.