Journal of Applied Physiology, Vol 75, Issue 4 1497-1501, Copyright © 1993 by American Physiological Society
Effect of isoproterenol on peripheral airway pressure-diameter behavior
L. E. Olson
Department of Veterinary Physiology and Pharmacology, Ohio State University, Columbus 43210-1092.
I radiographically evaluated the pressure-diameter relationships of
peripheral airways (average diameter approximately 2 mm at total lung
capacity) in a collaterally ventilating lung segment in 22 caudal dog lung
lobes. Eleven lobes were studied when freshly excised, and 11 lobes were
studied after being rinsed with 0.5% isoproterenol. Airways within the
segment (intrasegmental) and a control region of similarly sized airways
external to the segment were studied. Radiographs were taken when airway
opening pressure (Pao) equaled pressure in the segment (Ps) (homogeneous
case) and when Pao was 5, 10, or 15 cmH2O greater than Ps (nonhomogeneous
case). Airway diameter was calculated as a fraction of the diameter at Pao
= Ps = 25 cmH2O. The response of intrasegmental airways to increases in
pressure in the homogeneous case (Ps = Pao) and nonhomogeneous case (Ps
> Pao) differed between freshly excised and isoproterenol-rinsed lobes.
I conclude that dilating peripheral airways by decreasing bronchomotor tone
limits the extent to which they can respond to a regional increase in
alveolar pressure.
