Influence of Open-Heart Surgery on Respiratory Work

¹ Department of Surgery, State University of New York, Downstate Medical Center

1. The work of breathing, measured from pressure volume loops, was determined preoperatively and postoperatively in 20 patients following open-heart surgery for acquired valvular disease. In all patients the work of breathing was twice normal before operation.

2. Thirteen surviving patients had physiologically insignificant increase in the work of breathing on the first or second day following the operation. This change does not explain the respiratory difficulties experienced by these patients.

3. In seven fatal cases, the respiratory work increased an average of five times the preoperative value (ten times normal). In such patients, the excessive work of breathing produces a significant demand upon the cardiac output, and controlled mechanical ventilation is indicated in the post-operative period.