A 72-year-old woman with COPD is admitted to the ICU following an acute exacerbation with hypercapnic respiratory failure (pH 7.25, PaCO₂ 72 mmHg, PaO₂ 55 mmHg on room air). She is intubated and initially placed on volume-controlled assist-control (VC-AC) mode with a set rate of 14 breaths/min and tidal volume of 450 mL. After 4 hours, repeat ABG shows pH 7.32, PaCO₂ 62 mmHg. However, the peak inspiratory pressure (PIP) has risen from 28 to 42 cm H₂O, and the patient is fighting the ventilator. The ICU team is concerned about barotrauma and ventilator-induced lung injury (VILI). Which ventilation mode would be most appropriate to switch to at this point?