MSFinals-5753

MSFinals-5753

A 58-year-old man presents to the Emergency Department with increasing shortness of breath and cough for the last two days. The patient reports feeling fevers and chills and although he has a chronic cough, this has now become productive of yellow sputum over the last 36 hours. He denies chest pain. His past medical history is significant for chronic obstructive pulmonary disease (COPD) for which he has been prescribed various inhalers that he is not compliant with. He currently smokes 15 cigarettes per day and does not drink alcohol.
His observations and blood tests results are shown below:
Investigation Result Normal value
Temperature 36.9 °C
Blood pressure 143/64 mmHg
Heart rate 77 beats per minute
Respiratory rate 32 breaths per minute
Sp(O2) 90% (room air)
White cell count 14.9 × 109/l 4–11 × 109/l
C-reactive protein 83 mg/l 0–10 mg/l
Urea 5.5 mmol/l 2.5–6.5 mmol/l
Physical examination reveals widespread wheeze throughout his lungs without other added sounds. There is no dullness or hyperresonance on percussion of the chest. His trachea is central.
Which of the following is the most appropriate next investigation?