Case Three - Diagnose

Patient Chart

History

MN is a 20-year-old male who was transported to the ED by EMS because of an episode of sudden shortness of breath experienced at his place of employment. Physical assessment reveals a muscular young adult male in moderate respiratory distress. There is no evidence of trauma. Respiratory rate 32, temperature 98.7o F, SpO2 (on room air) 91%. His recent history is that he had a sudden onset of shortness of breath immediately after lifting several heavy boxes at work.

Which of the following is the most appropriate diagnostic test to perform at this time?