An 84-kg (185-lb) 6-ft 1-in (185-cm) male is receiving mechanical ventilation by a volume-controlled ventilator in the assist/control mode on the following settings: 1) Mandatory rate 18/min, VT 650 mL, FIO2 0.4, PEEP 5 cm H2O. 2) ABGs:, pH 7.28, PaCO2 56 mm Hg, PO2 71 mm Hg, HCO3- 27 mEq/L, BE +3 mEq/L. Which of the following represents the most appropriate action?
A. increase FIO2 to 0.5
B. increase rate to 20
C. increase PEEP to 8 cmH2O
D. increase VT to 550