A 58-year-old male with COPD (FEV₁ 28% predicted) on triple therapy (ICS-LABA-LAMA) presents with acute onset of increased dyspnea, purulent sputum, and fever (38.2°C) for 2 days. Chest X-ray shows new infiltrates in the right lower lobe. Sputum culture is pending. Arterial blood gas shows pH 7.32, PaCO₂ 58 mmHg, HCO₃⁻ 28 mEq/L, PaO₂ 62 mmHg on room air. What is the most appropriate immediate next step?