Infective exacerbation of COPD with type 2 respiratory failure risk

Patient B-217, a 68-year-old man, presents with a 3-day history of worsening breathlessness, increased sputum production with purulent sputum, and wheeze. He is a current smoker with a 50 pack-year history. He has known COPD diagnosed five years ago, with an FEV1 of 45% predicted. Regular medications are tiotropium 18 micrograms once daily, salbutamol 100 micrograms as required, and simvastatin 40 mg at night. He has a history of penicillin allergy, which caused a severe rash. On examination, he is tachypnoeic with a respiratory rate of 28/min, heart rate 96/min, blood pressure 135/85 mmHg, temperature 37.8°C, oxygen saturation 88% on air. Chest auscultation reveals reduced air entry, widespread wheeze, and coarse crackles at the right base. Arterial blood gas on air: pH 7.32, PaCO2 7.8 kPa, PaO2 7.2 kPa, HCO3 28 mmol/L. Chest X-ray shows hyperinflation and right lower zone consolidation. Serum creatinine 1.2 mg/dL, eGFR 63 mL/min/1.73m². Liver function tests are normal. Weight 75 kg. He is not pregnant. The task is to prescribe the initial management in the emergency department, including oxygen therapy, nebulised bronchodilators, oral corticosteroid, and an oral antibiotic. For each prescription, specify drug, dose, frequency, and route of administration.