Influence of a vital capacity maneuver on pulmonary gas exchange after cardiopulmonary bypass

Abstract

Objective: To investigate the effect of a single, vital capacity breath (vital capacity maneuver [VCM]), administered at the end of cardiopulmonary bypass (CPB), on pulmonary gas exchange in patients undergoing coronary artery bypass graft surgery. Design: Prospective, randomized, double-blind study. Setting: University-affiliated hospital. Participants: Forty patients scheduled for elective coronary artery bypass graft surgery and early tracheal extubation. Interventions: Patients were randomized to 1 of 2 groups. VCM patients received a VCM at the conclusion of CPB. Control patients received no VCM. Measurements and Main Results: Intrapulmonary shunt (QS/QT), arterial oxygenation (PaO2), and alveolar-arterial oxygen gradients (P(A-a)O2) were measured after induction of anesthesia, CPB, intensive care unit (ICU) arrival, and extubation. The duration of postoperative intubation was recorded for each group. QS/QT increased significantly 30 minutes after CPB in the control group (15.7 ± 1.8% to 27.4 ± 2.6%; p = 0.01). In the VCM group, a small decrease in QS/QT occurred (16.1 ± 2.0% to 14.9 ± 2.0%). After ICU arrival and extubation, no significant difference in QS/QT existed between the 2 groups. With the exception of a higher P(A-a)O2 in the control group at induction of anesthesia, no differences in PaO2 or P(A-a)O2 were present between the 2 groups at any measurement interval. Patients who received a VCM were extubated earlier than the control group (6.5 ± 2.1 hours v 9.4 ± 4.2 hours; p = 0.01). Conclusion: The use of a VCM prevented an increase in QS/QT from occurring in the operating room. Although a VCM did not influence pulmonary gas exchange in the ICU, its application in the operating room appears to exert a beneficial effect on tracheal extubation times after cardiac surgery. Copyright © 2001 by W.B. Saunders Company