Bronchial Perfusion of Isolated Lung as a Method for Studying Pharmacologic Reactions of Bronchiolar Muscle.

Abstract

The methods for studying the changes of bronchiolar tone in intact animals are often complicated by changes in the circulation which make their interpretation uncertain. It would therefore be desirable to check them under conditions in which the circulation would be excluded, namely outside of the body. The use of ring preparations of tracheal or bronchial muscle for this purpose has not been altogether satisfactory, partly because these are confined to the trachea and larger bronchi which might react differently from the smaller bronchioles that play the major part in the bronchial reactions; and partly because it is difficult to reproduce the natural conditions of tension. These objections are avoided in the following method, which is based on measuring the rate of flow of a Locke solution through the bronchial tree, allowing the fluid to drain off by filtration.

The arrangement is shown diagramatically in Fig. 1. A Mariotte bottle (M) filled with Locke solution is connected with a Woulff bottle (W), also filled with Locke solution, which sits in a bath (B) regulated to keep the temperature of the solution at 39° to 40° C., as indicated by the thermometer (Th). The outflow passes to a tube (T). The upper limb of this is furnished with a short piece of rubber tubing (R) which may be closed by a screwclamp (S). The lower limb is connected with a cannula tied into the short stump of the trachea of the excised lung (L). This should be used either promptly after the death of the animal, or else after lying on ice.

In starting the experiment, the T tube is raised so that no fluid flows from the Mariotte bottle; the screwclamp (S) on the upper limb is opened, and the lung is attached to the lower limb. The T is then gradually lowered so that just enough liquid flows into the bronchi to distend the lung approximately to its normal size.