Journal of Applied Physiology, Vol 45, Issue 3 442-450, Copyright © 1978 by American Physiological Society
Effects of lung inflation on pulmonary arterial pressure in dogs with pulmonary edema
J. F. Murray
The effects of lung inflation from positive airway pressure (Paw) on
pulmonary arterial pressure (Ppa) and the slope deltaPpa/deltaPaw were
studied in normal dogs and dogs with pulmonary edema. Under base-line zone
2 conditions with the lungs perfused at constant flow (100 ml/kg per min)
and vascular pressures measured relative to pleural (atmospheric) pressure,
the slope deltaPpa/deltaPaw was nearly one (at Paw greater than or equal to
5 cmH2O). Pulmonary edema from high capillary pressure and oleic acid
caused deltaPpa/deltaPaw and Ppa to decrease at high lung volumes and Ppa
to increase at low lung volumes. These changes were not simulated by
vasoactive drugs (adenosine and norepinephrine) but were reproduced by
instilling dextran into the lungs and, in part, by occluding the right
intermediate bronchus. In pulmonary edema the increased Ppa at low lung
volumes is caused by the effects of decreases in the caliber of
extra-alveolar vessels, by trapped air or liquid raising alveolar pressure,
or by both; the decreased deltaPpa/deltaPaw and Ppa at high volumes is
caused mainly by nonuniform distribution of driving pressures and blood
flow.
