COPD exacerbation management, non-invasive ventilation indications

A 62-year-old man with COPD (FEV₁ 35% predicted) presents to the emergency department with acute dyspnea, wheezing, and a peak expiratory flow (PEF) of 120 L/min (baseline 300 L/min). Arterial blood gas shows pH 7.28, PaCO₂ 65 mmHg, PaO₂ 55 mmHg on room air. He is given oxygen, nebulized salbutamol, and ipratropium. After 1 hour, repeat ABG shows pH 7.32, PaCO₂ 62 mmHg, PaO₂ 88 mmHg. Which of the following is the most appropriate next step in management?