Effects of independent lung ventilation and lateral position on cytokine markers of inflammation after unilateral lung acid injury in dogs.

BACKGROUND AND OBJECTIVE

The aim of this study was to compare the effects of conventional ventilation, lateral (non-injured lung-dependent) position, asynchronous and synchronous independent lung ventilation on inflammatory markers in an animal model of unilateral lung acid injury.

METHODS

Twenty-eight dogs underwent unilateral endobronchial instillation with hydrochloric acid and randomly received (n = 7 in each group) conventional ventilation in the supine (group I) or lateral position (group II), and independent lung ventilation in asynchronous (group III) or synchronous (group IV) modes. Arterial blood gases and serum cytokine levels were assessed at baseline, and 5 min and 4 h after mechanical ventilation. At the end of the study, cytokine levels were measured in individual lung lavage fluid. In three animals per group, differential lung perfusion was detected using a dual-head gamma camera.

RESULTS

Unilateral acid injury alone worsened oxygenation as determined by the ratio of PaO(2) to fraction of inspired oxygen (PaO(2)/FiO(2)) and increased serum cytokine levels. Mean oxygenation (SD) was significantly preserved in group II, 338 (26); group III, 396 (28); and group IV, 395 (22) compared with group I, 173 (18) (all P < 0.01). Serum IL-8, left-lung lavage IL-8 and matrix metalloproteinase-9 levels were significantly lower in groups II-IV (all P < 0.05). Only group I showed significantly different left and right lung lavage fluid cytokine levels. Groups III and IV showed slightly decreased left lung perfusion. Cytokine levels and oxygenation were similar in groups III and IV.

CONCLUSIONS

In this model of unilateral lung acid injury, lateral position and independent lung ventilation preserved oxygenation and attenuated the inflammatory response in serum and injured lung BAL fluid.