TNF-alpha in bronalvelar lavage of rabbits with acute pulmonar lesion and portection ventilation and prone position.

Abstract

Mechanical ventilation (MV) is essential support in severe lung injury and acute respiratory distress syndrome (ARDS). Due to high mortality rates in ARDS, additional therapeutic strategies to MV have been developed and associated with protective ventilation treatment (PMV). The prone positioning during ventilation is a strategy in combination with protective mechanical ventilation. It can improve gas exchange by redistribution of O2 to the dorsal lung areas, lung perfusion, ventilation/perfusion ratio, homogenization of tidal volume distribution, alveolar recruitment, redirection of compressive forces exerted by the weight of the heart on the lungs, tissue oxygenation and secretion removal. This study will investigate the effect of the prone position and protective MV on TNF-alpha concentration in bronchoalveolar lavage, oxygenation, inflammatory process and pulmonary histology by comparing it with the supine position in an experimental model of acute lung injury induced in rabbits. For this experiment, 20 randomly grouped rabbits will compose two groups: 1) animals undergoing protective MV in the supine position for lung injury (MVS, n = 10), 2) animals undergoing protective MV in the prone position for lung injury (VMP, n = 10). Acute lung injury will be induced by repeated lung lavage with saline warmed to 38 ÚC and 30 mL/kg. The animals will remain on mechanical ventilation for four hours, being closely monitored in terms of ventilatory and hemodynamics during all this time. The outcomes will be pathophysiological indexes of acute lung injury: TNF-alpha concentration in bronchoalveolar lavage, gas exchange and oxygenation, histology of lung tissue and number of polymorphonuclear cells in the bronchoalveolar lavage.