A 64-year-old man presents with acute onset severe shortness of breath, pink frothy sputum and orthopnoea. He has a history of ischaemic cardiomyopathy. On examination he is tachypnoeic, hypertensive at 180/100 mmHg, with bibasal crackles to the mid-zones. Which immediate intervention is most appropriate in the emergency department to treat his acute pulmonary oedema?