Function of each lung of dogs during intermittent positive-pressure breathing

¹ Mayo Clinic and Mayo Foundation, Rochester, Minnesota

The distribution of tidal air and nonshunted blood flow to each lung, the elimination of CO₂ from each lung, and Paco₂ were measured in ten anesthetized and paralyzed dogs during intermittent positive-pressure breathing in the supine position and before and after thoracotomy in the lateral decubitus position. Ventilation via a divided tracheal airway (Wright-Lategola) at a constant rate and a constant volume (±5%) with 65% oxygen in nitrogen was provided by a Bird ventilator. Reduction of total CO₂ elimination and increase of ratio of total physiologic dead space to tidal volume were observed after thoracotomy. Mean percentages of total ventilation and blood flow to, and CO₂ elimination from, the right lung were about 58% in the supine position. When the right or left lung became dependent in the lateral decubitus position, its proportional ventilation and CO₂ elimination decreased. After thoracotomy was made on the superior nondependent side, further reductions were noted and blood flow to the dependent lung also decreased. Proportional CO₂ elimination was more dependent on alveolar ventilation than on the ratio of ventilation to perfusion.

Key Words: air • blood • thoracotomy • CO₂ elimination • ventilation, alveolar • ventilation, ratio to perfusion • tidal volume • blood flow • perfusion, ratio of ventilation

Submitted on July 5, 1963