Effect of Positive End-Expiratory Pressure After Porcine Unilateral Left Lung Transplant

Objectives: To evaluate the effects of 2 different levels of positive end-expiratory pressure on pigs who had unilateral lung transplants. Materials and Methods: A left lung transplant was performed in 12 pigs. The animals were randomized into 2 groups based on positive end-expiratory pressure: group 1 (5 cm H2O) and group 2 (10 cm H2O). Hemodynamics, gas exchange, and respiratory mechanics were measured before and after surgery. Cytokines, oxidative stress, and histologic scores were assessed in the lung tissue of each pig. Results: Pigs in group 2 exhibited a significantly higher mean heart rate (P = .006), static compliance (P = .001), lower mean arterial pressure (P = .003), and airway resistance (P = .001) than did pigs in group 1. There were no postoperative differences between the groups in concentrations of thiobarbituric acid reactive substances, superoxide dismutase, and interleukin 8. At the end of the observation period, pigs in group 2 had higher levels of thiobarbituric acid reactive substances (P = .001) and interleukin 8 (P = .05), and pigs in group 1 had higher levels of superoxide dismutase (P = .05) than they did at baseline. Conclusions: After unilateral lung transplant, higher positive end-expiratory pressure was associated with improved respiratory mechanics, a negative effect on hemodynamics, a stronger inflammatory response, and increased, production of reactive oxygen species, but no effect on gas exchange.