Compared with CTRL, FLUTTER improved sputum production (P<.001), respiratory system static compliance (P = .02), peak expiratory flow (P = .048), expiratory flow at 75% of tidal volume (P = .005), and arterial PO(2)-to-inspired oxygen concentration ratio (P<.001). Respiratory resistance, heart rate, and mean arterial pressure remained unaltered during the interventions (P>.05).