A 52-year-old woman with acute respiratory distress syndrome (ARDS) secondary to pneumonia is on volume-controlled ventilation with a tidal volume of 6 mL/kg ideal body weight, respiratory rate 18/min, PEEP 10 cm H₂O, and FiO₂ 0.8. Current ABG: pH 7.32, PaCO₂ 52 mmHg, PaO₂ 78 mmHg, HCO₃⁻ 24 mEq/L. Peak plateau pressure is 28 cm H₂O. She is adequately sedated and paralyzed. What is the most appropriate next step in management?