RESUMEN
Experiments were performed to consider the use of conventional neonatal ventilators with assisted expiratory mechanism using ventilatory high frequency strategies. Gas exchange, hemodynamic state, and lung injury were also assessed. Twenty Albino Wistar rats, undergoing and acute lung lesion through physiological solution wash of the lungs were studied. Afterward, they were distributed into four groups according to the different ventilator strategies, based on the different pressure changes and the tidal volume, the baseline lung volume and the respiratory frequency. Group I, High Frequency Ventilation, with high baseline lung volumes (HFVh); group II, Conventional Mechanical Ventilation, with high baseline lung volume (CMVh), group III, High Frequency Ventilation, with low baseline lung volume (HFV1) and group IV Conventional Mechanical Ventilation, with low baseline lung volume (CMV1). Significant differences were found between group I (HFVh) and groups II (CMVh), III (HFV1) and IV (CMV1) as regards pO2, Artery/Alveolar relation to O2 (a/A), pCO2, arterial blood pressure and histopathologic lung lesion. The hypothesis concerning the decisive role of the baseline lung volume maintainence to minimize progressive damage caused by mechanical ventilation on a previously injured lung while attending ventilatory strategies that generate little pressure and volume cyclical changes was confirmed. We conclude that, high frequency mechanical ventilation is possible through conventional neonatal respirators with assisted expiratory mechanism.