A patient receiving volume-controlled continuous mandatory ventilation (VC-CMV) has the following ventilator settings: tidal volume (VT) 500 mL, respiratory rate (f) 12/min, FiO2 0.40, PEEP 5 cm H2O. ABG results show: pH 7.31, PaCO2 50 mm Hg, PaO2 80 mm Hg, HCO3 - 25 mEq/L. Which of the following ventilator changes are most appropriate? (Choose two.)