A 28-yeаr-оld femаle (55-kg IBW) is being mechаnically ventilated with VC-CMV, f = 14/min, VT = 700 mL. The patient has nо histоry of pulmonary disease. The resulting ABG values are: pH 7.55, PaCO2 27 mm Hg, HCO3- 23 mEq/L. The most appropriate action to take is which of the following?