3rd August 2020

A 62-year-old male with a history of chronic obstructive pulmonary disease (COPD) presents to hospital with shortness of breath

A 62-year-old male with a history of chronic obstructive pulmonary disease (COPD) presents to hospital with shortness of breath. He states that he is not able to walk as far as previously and wakes frequently at night coughing and struggling to breathe. He has never had any chest pain. 

For the patient above, please select the SINGLE most useful INVESTIGATION likely to be performed INITIALLY to gain a diagnosis. Select ONE option from the list above.