A 74-year-old man with COPD presents with a 4-day history of increased dyspnoea, cough and change in sputum from white to green. He is febrile at 38.2 °C, respiratory rate 28 breaths/min, and oxygen saturation 90 percent on 2 L/min nasal oxygen. Chest examination shows diffuse wheeze, and there is no consolidation on chest radiograph. What is the most appropriate management regarding antibiotics?