A 70-year-old man with COPD (FEV1 45% predicted) presents with increased breathlessness, increased sputum volume, and sputum purulence over the past 2 days. He normally uses a LAMA/LABA inhaler. His oxygen saturation is 90% on air. According to NICE NG114, what is the most appropriate initial management for this exacerbation in primary care?