Healthy lung tissue response to mechanical ventilation in an experimental porcine model.

The aim of this comparative study was to assess the impact of two different settings of tidal volume (Vt) on the function and morphology of the mechanically ventilated lungs during a 12-h period.A total of 32 animals were randomly divided into two groups. Group A included piglets ventilated with a Vt of 6 ml/kg and group B piglets ventilated with a Vt of 10 ml/kg. Lung functions and pulmonary mechanics were evaluated after 1 and 12 h of mechanical ventilation. Morphological changes of the lung tissue were evaluated at the end of the study.Twelve hours of lower Vt ventilation was associated with the development of respiratory acidosis but minimal histological changes. Higher Vt led to pronounced histological changes in terms of proliferation and apoptosis and a decrease of dynamic compliance, with a trend towards lower oxygenation during the study.Mechanical ventilation with a Vt of 6 ml/kg induces minimal histological lung parenchymal changes in terms of proliferation and apoptosis. Positive pressure mechanical ventilation with Vt of 10 ml/kg does not protect lung tissue and induces substantial proliferative and apoptotic changes within the lung parenchyma. Positive pressure mechanical ventilation with Vt of 10 ml/kg does not guarantee protection of healthy pulmonary tissue in the absence of a priming pulmonary insult.