Fig. 1.
A graphical display (pressure–time curve, flow–time curve, and volume–time curve) of ventilator strategies in the two experimental groups. A showed the ventilator strategy in biphasic positive airway pressure (BIPAP) minus spontaneous breathing (SB) group. Animals’ SB efforts were fully depressed. Therefore, BIPAP was equal to pressure-controlled ventilation. B showed the ventilator strategy in BIPAP plus SB. SB efforts were regained. Mandatory rate was reduced to allow unsupported SB (red region in flow–time curve) occurring during each mechanical cycle phase and was carefully adjusted to maintain minute ventilation of unsupported SB at 10–50% of total minute ventilation. The other ventilator settings were maintained the same in both groups.