A 56-year-old man is thrown violently against the steering wheel of his truck during a motor vehicle crash. On arrival to 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? Select one: a. b. C. d. e. Tachycardia Pulse volume Breath sounds Pulse pressure Jugular venous pressure