Parenteral vs. inhaled atropine: density dependence of maximal expiratory flow.
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.
D000328:Adult; D001285:Atropine / Q000008:administration & dosage*; D005540:Forced Expiratory Flow Rates; D006801:Humans; D007263:Infusions, Parenteral; D008168:Lung / Q000502:physiology*; D008448:Maximal Expiratory Flow Rate; D011312:Pressure; D012115:Residual Volume; D014109:Total Lung Capacity; D014797:Vital Capacity
D001285:Atropine