Objective: To probe further the role of neutrophil activation in the lung injury induced by mechanical ventilation.
Methods: Thirty-two normal Wistar rats were randomly divided into four groups: control group, low tidal volume group, conventional tidal volume group, and high tidal volume group. The counts of white blood cell (WBC) and neutrophil in bronchoalveolar lavage fluid (BALF) were carried out. The levels of protein and myeloperoxidase (MPO) activity in plasma and BALF were determined by biochemical methods respectively.
Results: The numbers of WBC and neutrophils, and the levels of protein and MPO activity in BALF were significantly increased in normal and high tidal volume groups than those in control and low tidal volume groups (P<0.05 or P<0.01, respectively). The levels of protein and MPO activity in BALF in high tidal volume group were markedly higher compared with normal tidal volume group (both P<0.01), but no statistical differences existed between the low tidal volume group and the control group (both P>0.05). There were no significant differences in the levels of protein and MPO activity in plasma among the four groups (P>0.05).
Conclusion: The recruitment and activation of neutrophils might play an important role in pathogenesis of the biotrauma induced by mechanical ventilation. MPO activity in BALF is a credible index in reflecting the activation of neutrophils. Measuring the level of protein in BALF is valuable to evaluate the extent of lung injury induced by mechanical ventilation.