A 43-year-old woman is brought to the emergency department because of severe central chest pain, mild shortness of breath, and one episode of coughing up blood since waking up that morning. The pain worsens on inspiration, and she describes it as 8 out of 10 in intensity. Three months ago, she underwent a left modified radical mastectomy for invasive ductal carcinoma. Her temperature is 37.8°C (100.0 °F), pulse is 103/min, respirations are 20/min, and blood pressure is 102/74 mm Hg. Arterial blood gas drawn on room air shows an arterial partial pressure of oxygen (PaO₂) of 54 mm Hg and an arterial partial pressure of carbon dioxide (PaCO₂) of 26 mm Hg. Which of the following processes is most likely occurring in this patient?

Question

Quizplus · Accepted Answer

Eductional Objective: An acute ventilation/perfusion mismatch (eg, due to pulmonary embolism or pneumonia) causes hypoxemia and triggers hyperventilation. Because the removal of CO₂ is directly dependent on ventilation but the absorption of O₂ is capped by the high baseline saturation of hemoglobin, the hyperventilation response typically leads to respiratory alkalosis (low arterial partial pressure of carbon dioxide) with persistent hypoxemia.

A 43-Year-Old Woman Is Brought to the Emergency Department Because