A 56-year-old man is thrown violently against the steering wheel of his truck during a motor vehicle crash. On arrival in the emergency department, he is diaphoretic and complaining of chest pain. His blood pressure is 60/40 mm Hg, and his respiratory rate is 40 breaths per minute. Which of the following best differentiates cardiac tamponade from tension pneumothorax as the cause of his hypotension?
a) Equalization of right and left ventricular pressures
b) Elevated central venous pressure (CVP)
c) Pulsus paradoxus
d) Hyperresonance to percussion on the affected side