Effect of Airway Hypocapnia on Mechanics of Breathing during Cardiopulmonary Bypass

Patterson, R. W. M.D.
Sullivan, S. F. M.D.
Malm, J. R. M.D.
Bowman, F. O. Jr. M.D.
Papper, E. M. M.D.

From the Departments of Anesthesiology and Surgery, College of Physicians and Surgeons, Columbia University and the Presbyterian Hospital, New York, New York.

Circulation 35(4):p I212-I216, April 1967.

Total cardiopulmonary bypass separates the lungs from the pulmonary arterial circulation. Continued ventilation with non CO₂-containing mixtures during bypass will result in airway hypocapnia. Airway hypocapnia results in decreased compliance, increased work of breathing, and increased resistance to air flow. Reversal of airway hypocapnia increased compliance one-third, decreased work of breathing 20%, and decreased air flow resistance approximately 40% when compared to the values obtained during the period of low airway CO₂. These changes in airway mechanics must be considered for pulmonary management during cardiac bypass.