Ischemic preconditioning enhances recovery of isolated rat lungs after hypothermic preservation

Ischemic preconditioning, an endogenous protection mechanism, occurs in many organs, including lungs. The efficacies of differing ischemic durations in protecting the lung are unknown. We compared the ability of three preconditioning protocols to protect rat lungs during storage.

Function was measured in five groups of perfused, ventilated rat lungs. Group 1 lungs underwent control perfusion (60 minutes) without storage. Groups 2 through 5 underwent the following prestorage protocols: group 2, 20 minutes of perfusion; group 3, 10 minutes of perfusion, 5 minutes of cessation of ventilation and perfusion (ischemia), and 5 minutes of reperfusion; group 4, 5 minutes of perfusion, 10 minutes of ischemia, and 5 minutes of reperfusion; and group 5, 2 periods of 5 minutes of ischemia and 5 minutes of reperfusion. Lungs were then flushed with, and immersed (6 hours) in modified bicarbonate buffer (4 degrees C). Lung function was reassessed during 40 minutes of reperfusion (37 degrees C). Subsequently we examined preconditioning by stopping ventilation or perfusion separately.

After reperfusion, lungs in group 2 had a compliance of 0.015+/-0.002 mL/cm H2O (mean +/- SE, n = 10), significantly lower than lungs in group 1 (0.063+/-0.002 mL/cm H2O). Ischemic preconditioning was protective, with lungs in groups 3, 4, and 5 having compliances greater (p<0.05) than those in group 2. Preconditioning by cessation of ventilation alone was also effective.

Preconditioning attenuates deterioration in lung compliance on reperfusion to a degree dependent on the protocol used.