A 28-year-old woman presents to the emergency department with acute dyspnoea and wheeze. She has a history of asthma controlled with as-needed low-dose budesonide-formoterol. On arrival she is speaking in phrases, RR 30 breaths/min, pulse 120 bpm, SpO₂ 92% on room air, PEFR 45% predicted. What is the most appropriate initial bronchodilator regimen?