Affiliation:
1. Mayo Clinic and Mayo Foundation, Section of Physiology, and Mayo Graduate School of Medicine, University of Minnesota Rochester, Minnesota 55901; Dr. Viles is now Resident in Pediatric Cardiology, Mayo Clinic, and he is also recipient of a Special Fellowship from the National Institute of Child Health and Human Development, Public Health Service.
Abstract
Isolated cat lungs perfused at constant flow (75 ml/min per kg total body weight) were ventilated with gases of varying CO
2
content (0 to 10%), 20% O
2
, and the balance N
2
. Tidal volume was constant, and airway pressure did not change. Left atrial pressure was held constant, and changes in pulmonary artery pressure (PPA) were taken to reflect changes in pulmonary vascular resistance. Progressive hypercapnia (Pco
2
= 0 to 60 mm Hg) resulted in an increase in PPA as pH decreased. Equivalent degrees of acidosis, produced by the infusion of 0.3 N lactic acid, resulted in a higher PPA. Changes in PPA produced by lactic acid were reversible with 0.89 M sodium bicarbonate. With Pco
2
constant, and pH changed by lactic acid or sodium bicarbonate infusion, PPA was higher in lungs ventilated with room air (Pco
2
= 0) than in those ventilated with 5 or 10% CO
2
(Pco
2
= 30 or 60 mm Hg) at the same hydrogen ion concentration of the perfusate. These findings can be explained by two opposing actions of CO
2
on pulmonary vessels: a dilator action due to the direct effect of CO
2
and a constrictor action caused by the increase in hydrogen ion concentration.
Publisher
Ovid Technologies (Wolters Kluwer Health)
Subject
Cardiology and Cardiovascular Medicine,Physiology
Cited by
80 articles.
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