A 56-year-old man presents after an industrial accident where the patient's chest was pinned between heavy machinery. On exam you note an obese man; blood pressure is $150 / 80 \mathrm{mmHg}$, heart rate is 90 beats per minute, and respiration rate is 24 breaths per minute. He is complaining of left anterior neck and chest discomfort as well as dysphagia. On exam, the patient has swelling and tenderness along the left clavicular area and over the sternum, with pain exacerbated upon movement of the left shoulder. A chest x-ray (CXR) reveals no fractures or pneumothorax, but the patient continues to complain of pain and difficulty swallowing. What is the MOST appropriate next diagnostic step?
(A) Oral challenge and discharge with appropriate follow-up.
(B) Left shoulder radiographs.
(C) CT of the chest.
(D) End-expiratory CXR.