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

Objective: To investigate the effect of a single, vital capacity breath (vi tal capacity maneuver [VCM]), administered at the end of cardiopulmonary by pass (CPB), on pulmonary gas exchange in patients undergoing coronary arter y bypass graft surgery. Design: Prospective, randomized, double-blind study. Setting: University-affiliate 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 rec eived a VCM at the conclusion of CPB. Control patients received no VCM. Mea surements and Main Results: Intrapulmonary shunt (Q(S)/Q(T)) arterial oxygenation (PaO2), and alveolar-arterial oxygen gradients (P(A-a)O-2) were measured after ind uction of anesthesia, CPB, intensive care unit (ICU) arrival, and extubatio n. The duration of postoperative intubation was recorded for each group. O- S/Q(T) increased significantly 30 minutes after CPB in the control group (1 5.7 +/- 1.8% to 27.4 +/- 2.6%; p = 0.01). In the VCM group, a small decreas e in Q(S)/Q(T) occurred [16.1 +/- 2.0% to 14.9 +/- 2.0%). After ICU arrival and extubation, no significant difference in Q(S)/Q(T) existed between the 2 groups. With the exception of a higher P(A-a)O-2 in the control group at induction of anesthesia, no differences in PaO2 or P(A-a)O-2 were present between the 2 groups at any measurement interval. Patients who received a V CM 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 O-S/Q(T) from occurri ng in the operating room. Although a VCM did not influence pulmonary gas ex change in the ICU, its application in the operating room appears to exert a beneficial effect on tracheal extubation times after cardiac surgery. Copy right (C) 2001 by W.B. Saunders Company.