Effect of Unilateral Carbon Dioxide Breathing on Pulmonary Blood Flow

¹ From the Department of Surgery, University of North Carolina, Chapel Hill, North Carolina

The effect of breathing increased concentrations of carbon dioxide was studied in dogs. Each lung was independently ventilated with the chest open. The pulmonary artery pressure was recorded and blood flow determined for each lung by the Fick principle during room air breathing. After this control period, increased concentrations of carbon dioxide were substituted for room air in one lung and the above determinations repeated. In all but 2 of 11 animals the pulmonary vascular resistance fell in the CO₂ lung and the blood flow to this lung increased.