FCA1-0269

FCA1-0269

A 19-year-old woman presents to the emergency department. She complains of symptoms indicative of an acute exacerbation of known ‘brittle’ asthma. On history, she reveals her asthma is normally controlled using inhalers and she has never had an acute exacerbation requiring hospitalisation. On her admission into the ICU, further examination and diagnostic investigations are conducted. Her readings are: Physical state: Alert, anxious and non-cyanotic. Respiratory rate: 30 breaths/min, Pulse: 120 beats/min, Blood pressure: 150/90 mmHg, SPO2: 95% on air. Auscultation: Quiet breath sounds at both lung bases. What is the next most important step of investigation?