Days after surgical fixation of a fractured femur, a client suddenly reports chest pain and difficulty in breathing. The nurse suspects that the client had a pulmonary embolus. Which action should the nurse take first?

Choice C is correct because providing supplemental oxygen is the first action that the nurse should take for a client who has a suspected pulmonary embolus. A pulmonary embolus is a life-threatening condition that occurs when a blood clot travels to the lungs and blocks the blood flow, causing hypoxia and respiratory distress. The nurse should administer oxygen to improve the client's oxygenation and prevent further complications.

Choice A is incorrect because notifying the healthcare provider is not the first action that the nurse should take for a client who has a suspected pulmonary embolus. The nurse should notify the healthcare provider after providing supplemental oxygen and assessing the client's vital signs and symptoms.

Choice B is incorrect because preparing a continuous heparin infusion per protocol is not the first action that the nurse should take for a client who has a suspected pulmonary embolus. Heparin is an anticoagulant that can prevent further clot formation and reduce the risk of recurrence, but it does not dissolve existing clots or improve oxygenation. The nurse should prepare a heparin infusion after obtaining a prescription from the healthcare provider and confirming the diagnosis with diagnostic tests.

Choice D is incorrect because bringing the emergency crash cart to the bedside is not the first action that the nurse should take for a client who has a suspected pulmonary embolus. The emergency crash cart contains equipment and medications that can be used in case of cardiac arrest or other emergencies, but it does not address the immediate need of oxygenation. The nurse should bring the emergency crash cart to the bedside after providing supplemental oxygen and assessing the client's condition.