A 65-year-old man with known COPD presents with increasing shortness of breath, wheeze, and increased sputum volume and purulence over the past 3 days. He is normally managed with a LABA/LAMA combination inhaler. His oxygen saturations are 91% on air. He has no features of pneumonia on examination or chest X-ray. According to NICE NG115, what is the most appropriate management for his exacerbation?