Adverse effects of the high tidal volume during mechanical ventilation of normal lung in pigs.

INTRODUCTION: The "open lung concept" theory of mechanical ventilation is correct, but an unsuitable setting of the machine is not appropriate in children.

TYPE OF STUDY: This experimental study is a comparative, closed, randomized, double-blind study. The aim of the study was to verify the hypothesis that even a short-term high tidal volume during the course of mechanical ventilation damages the lung parenchyma as well as extra-pulmonary organs.

MATERIAL AND METHODS: The inappropriate strategy of mechanical lung ventilation was simulated on an animal model. The study was performed on 30 healthy white domestic piglets (25 kg). Using a random selection, the piglets with healthy lungs were ventilated for 120 minutes under general anaesthesia with two different strategies of mechanical ventilation, i.e. 15 animals achieving alveolar hyperinflation with a high tidal volume (14 ml.kg(-1)), and 15 animals according to the "lung protective strategy" principle. Lung tissue samples were examined morphologically using the blind test method, and the proinflammatory cytokines levels were assessed in the piglets' serum.

RESULTS: The study demonstrated that a high tidal volume during mechanical lung ventilation with permanent positive pressure after 120 minutes induced very important morphological and functional lung changes that unfavourably influenced blood circulation, reduced cardiac output and induced a systemic inflammatory reaction (Fig. 9, Ref. 11).