The effects of positive end-expiratory pressure in alveolar recruitment during mechanical ventilation in pigs.

PURPOSE

To evaluate the effects of alveolar recruitment based on mean airway pressure (MAP) on pig lungs submitted to thoracotomy through blood gas exchange and hemodynamic parameters.

METHODS

Twelve pigs weighting approximately 25 Kg were intubated and ventilated on volume controlled ventilation (tidal volume 10 ml/Kg, respiratory rate 16 min, FiO2 1.0, inspiratory:expiratory ratio 1:2, PEEP 5 cmH2O). The animals were then randomized into two groups: control and left lateral thoracotomy. The PEEP was increased at each 15-minute intervals to reach a MAP of 15, 20 and 25 cmH2O, respectively. Hemodynamic, gas exchange and respiratory mechanic data were measured immediately before each PEEP change.

RESULTS

There were no significant differences between both groups in all parameters analyzed (P=1.0). The PaO2, PaCO2, MAP, PAP and plateau pressure were significantly worse at MAP of 25 cmH2O, when compared with the other values of MAP (P=0.001, P=0.039, P=0.001, P=0.016 e P=0.027, respectively). The best pulmonary performance according to the analyzed parameters was observed at MAP of 20 cmH2O.

CONCLUSION

PEEP adjusted to MAP of 20 cmH2O resulted in best arterial oxygenation, without compromising the venous return, as opposed to MAP of 25 cmH2O, which caused deterioration of gas exchange, hemodynamics and respiratory mechanic.