Influence of Positive End-Expiratory Pressure Ventilation on Survival During Severe Hemorrhagic Shock

Study objective Although a moderate positive end-expiratory pressure (PEEP) level is widely recommended, it is unknown whether moderate PEEP during mechanical ventilation has adverse effects during severe hemorrhagic shock. Therefore, the purpose of our study was to evaluate the effects of 0 cm H 2 O PEEP versus 5 cm H 2 O PEEP versus 10 cm H 2 O PEEP on short-term survival in a porcine model of severe hemorrhagic shock. Secondary study endpoints were hemodynamic variables and blood gases. Methods Twenty-four anesthetized pigs were bled approximately 45 mL/kg, randomized into 3 groups, and then ventilated with 0, 5, or 10 cm H 2 O PEEP. Survival rates were compared using Kaplan-Meier methods with log rank (Mantel Cox) comparison of cumulative survival by treatment group. Results Seven of 8 0 cm H 2 O PEEP animals survived the 120-minute study period, but 8 of 8 5 cm H 2 O PEEP animals died within 30 minutes, and 8 of 8 10 cm H 2 O PEEP animals were dead within 20 minutes ( P 2 O PEEP prevented a further reduction of mean arterial blood pressure and cardiac output. When compared with the 0 cm H 2 O PEEP group, end-tidal CO 2 declined in the 5 cm H 2 O PEEP and 10 cm H 2 O PEEP animals. Compared with the 0 cm H 2 O PEEP animals, those ventilated with 5 or 10 cm H 2 O PEEP had higher lactate levels after 10 minutes. Conclusion When compared with pigs ventilated with either 5 or 10 cm H 2 O PEEP, those ventilated with 0 cm H 2 O PEEP during untreated, severe hemorrhagic shock had significantly improved short-term survival.