Neutrophils in reexpansion pulmonary edema

This study investigated the possible contribution of neutrophils to development of reexpansion pulmonary edema (RPE) in rabbits. Rabbits' right lungs were collapsed for 7 days and then reexpanded with negative intrathoracic pressure for 2 h before study, a model that creates unilateral edema in the reexpanded lungs but not in contralateral left lungs. Two hours after lung reexpansion, significant increases in lavage albumin concentration (17-fold), percent neutrophils (14-fold), and total number of neutrophils (7-fold) recovered occurred in the reexpanded lung but not in the left. After 2 h of reexpansion increased leukotriene B₄ was detected in lavage supernatant from right lungs (335 ± 33 pg/ml) compared with the left (110 ± 12 pg/mg, P < 0.01), and right lung lavage acid phosphatase activity similarly increased (6.67 ± 0.35 U/l) compared with left (4.73 ± 0.60 U/l, P < 0.05). Neutropenia induced by nitrogen mustard (17 ± 14 > neutrophils/μl) did not prevent RPE, because reexpanded lungs from six neutropenic rabbits were edematous (wet-to-dry lung weight ratio 6.34 ± 0.43) compared with their contralateral lungs (4.97 ± 0.04, P < 0.01). An elevated albumin concentration in reexpanded lung lavage from neutropenic rabbits (8-fold) confirmed an increase in permeability. Neutrophil depletion before reexpansion did not prevent unilateral edema, although neutrophils were absent from lung sections and alveolar lavage fluid from neutropenic rabbits.