Journal of Applied Physiology, Vol 53, Issue 2 392-396, Copyright © 1982 by American Physiological Society

ARTICLES

Parenteral vs. inhaled atropine: density dependence of maximal expiratory flow

J. W. Weiss, E. R. McFadden Jr and R. H. Ingram Jr

Using forced vital capacity maneuvers, we measured maximal expiratory flow rates (Vmax) and static elastic recoil pressures of the lung [Pst(L)] using quasi-static maneuvers in normal nonsmoking human subjects who were breathing air and after a washing of 80% helium-20% oxygen before and after both inhaled and intravenously administered atropine sulfate. By both routes there were equivalent increases in Vmaxair but different effects on density dependence (DD) of Vmax (DD = ratio of VmaxHeO2 to Vmaxair) and on Pst(L). At 30% of vital capacity, DD decreased from an average of 1.47 to 1.32 (P less than 0.01, paired t test) after inhaled drug and did not change after parenteral administration [1.44 vs. 1.48 (P greater than 0.2)]. After inhalation Pst(L) did not change, but after parenteral administration Pst(L) significantly decreased. We interpret these findings to indicate a predominantly large-airway effect with the inhalation route and a more uniform dilatation after the parenteral dose. These results contrast with beta-adrenergic dilatation following which small-airway effects predominate regardless of route of administration.