PSV allowed the patient to control his own frequency and therefore the circulating volume and minute volume. In this manner the PSV generated an adequate respiratory work and oxygen consumption of the respiratory muscles, diminishing fatigue and favoring re-training [12] . The combination of this modality with CPAP allowed to increase the functional residual capacity thus achieving a better oxygenation. This is owing to the increase in the number of effective alveolar units in gas exchange (alveolar recruitment). CPAP is able to offset the abnormal closing of the airway and the effect of the auto PEEP, noticing the beneficial effects when the level of inspiratory efforts to be developed during spontaneous breathing diminishes.