Effects of Certain Broncho-Constricting Drugs on Intrapleural Pressure. ∗

Abstract

Report has previously been made 1 that following the administration to dogs of such typical broncho-dilating drugs as epinephrin and atropine, there is a definite increase in intrapleural pressure, i. e., intrapleural pressure becomes more positive than is normally the case. This was interpreted as being due to lessened suction on expansion of the chest because of lessened resistance to the movement of air in and out of the lungs as a result of broncho-dilatation. It naturally became of interest to determine by direct observation whether or not the corollary is also true, viz., that broncho-constriction is followed by the development of more negative intrapleural pressure than is normally present.

We employed the same dogs as had been used in our former experiments, and we had sufficient observations on normal intrapleural pressures in these animals to enable us to judge whether or not changes following drug administration were beyond normal diurnal variation. The technique used was the same as that previously described. 1

Following the subcutaneous injections of solutions of pilocarpine nitrate and physostigmine (eserine) salicylate, we found uniformly in 6 experiments with each drug that intrapleural pressure definitely became less, i. e., more negative. The experiments were made on 3 dogs, with intervals of a week or more between experiments. We were unable to draw definite conclusions following the administration of histamine or of arecoline because of marked disturbances in character of respiration and in the condition of the animal. Quantitative data from sample experiments may be found in Table I.