Breath stacking: patients were connected to a unidirectional valve coupled to artificial airway (tracheostomy), with bacteriological filter. The ventilator was coupled to the unidirectional valve to measure inspiratory volume mobilized in each cycle and a connection to adapt a manometer. The patient performed successive inspirations for a maximum period of 30 seconds or until unidirectional valve opening or volume increase was observed for 2 consecutive efforts. Ten cycles of the technique were performed, with an interval of 30 seconds.

Air stacking: the same system of monitoring and adaptation of the ventilometer and manometer was carried out. A manual resuscitator coupled to a unidirectional valve was used, both connected to the tracheostomy, with a filter interface. Slow and successive inspirations were performed through slow compression of the resuscitator until the maximum inspiratory pressure reached 40 cmH2O. Ten cycles of the technique were performed, with an interval of 30 seconds.

Patients were connected to a unidirectional valve coupled to artificial airway (tracheostomy), with bacteriological filter. The ventilator was coupled to the unidirectional valve to measure inspiratory volume mobilized in each cycle and a connection to adapt a manometer. The patient performed successive inspirations for a maximum period of 30 seconds or until unidirectional valve opening or volume increase was observed for 2 consecutive efforts. Ten cycles of the technique were performed, with an interval of 30 seconds.

Compliance was assessed through the occlusion maneuver at the end of inspiration, considering tidal volume, plateau pressure and PEEP. Three measurements were taken at each moment, the mean being used.

The total resistance of the respiratory system was evaluated through the occlusion maneuver at the end of the inspiration, considering the resistive pressure, measured by the difference between the maximum plateau pressure. Three measurements were taken at each moment, the mean being used.