Protective ventilation attenuates postoperative pulmonary dysfunction in patients undergoing cardiopulmonary bypass

Objective: To ascertain if protective ventilation can attenuate the damagin g postoperative pulmonary effects of cardiopulmonary bypass (increases in a irway pressure, decreases in lung compliance, and increases in shunt). Design: Prospective, randomized clinical trial. Setting: Single university hospital. Participants:Twenty-five patients undergoing elective coronary artery bypas s graft procedure and early extubation. Interventions:Thirteen patients received conventional mechanical ventilatio n (CV; respiratory rate, 8 breaths/min; tidal volume, 12 mL/kg; fraction of inspired oxygen [F1O2]. 1.0; positive end-expiratory pressure [PEEP], +5), and 12 patients received protective mechanical ventilation (PV; respirator y rate, 16 breaths/min; tidal volume, 6 mL/kg; F1O2, 1.0; PEEP, +5). Periop erative anesthetic and surgical management were standardized. Various pulmo nary parameters were determined twice perioperatively: 10 minutes after int ubation and 60 minutes after arrival in the intensive care unit. Measurements and Main Results: The mean postoperative increase in peak airw ay pressure in group CV was significantly larger than the mean postoperativ e increase in peak airway pressure in group PV (7.1 v 2.4 cm H2O; p < 0.001 ). Group CV experienced significant postoperative increases in plateau airw ay pressure (p = 0.007), but group PV did not (p = 0.644). The mean postope rative decrease in dynamic lung compliance in group CV was significantly la rger than the mean postoperative decrease in dynamic lung compliance in gro up PV (14.9 v 5.5 mL/cm H2O; p = 0.002). Group CV experienced significant p ostoperative decreases in static lung compliance (p = 0.014), but group PV did not (p = 0.645). Group CV experienced significant postoperative increas es in shunt (15.5% to 21.4%; p = 0.021), but group PV did not (18.4% to 21. 2%; p = 0.265). Conclusions:Data indicate that protective ventilation decreases pulmonary d amage caused by mechanical ventilation in normal and abnormal lungs. The re sults of this investigation indicate that protective ventilation may also h elp attenuate the postoperative pulmonary dysfunction (increases in airway pressure, decreases in lung compliance, and increases in shunt) commonly se en in patients after exposure to cardiopulmonary bypass. Copyright (C) 2000 by W.B. Saunders Company.