A male client who weighs 75 kg is being mechanically ventilated. His ventilator settings are as follows: Assist control Rate 10 PEEP +5 Tidal volume 550 FIO2 40% His ABG reveals: pH 7.41 CO2 39 HCO3 24 paO2 49 Which one of the following adjustments would you expect the respiratory therapist to make first?