A 72-year-old woman with acute pneumonia and sepsis is intubated in the ICU. Initial ventilator settings are: volume-controlled mode, tidal volume 6 mL/kg IBW, respiratory rate 16/min, FiO₂ 0.8. After 6 hours, her PaO₂ is 65 mmHg despite high FiO₂, and her peak inspiratory pressure is 48 cm H₂O with plateau pressure 42 cm H₂O. Chest X-ray shows bilateral infiltrates consistent with ARDS. She is deeply sedated and paralyzed. Her hemodynamics are stable. What is the most appropriate ventilation strategy at this point?