The nurse takes into consideration that carbon monoxide poisoning is often fatal because carbon monoxide:

A. binds with hemoglobin in place of oxygen: Carbon monoxide has a much higher affinity for hemoglobin than oxygen—approximately 200–250 times greater. When carbon monoxide binds to hemoglobin, it forms carboxyhemoglobin, which prevents oxygen from attaching and being transported to tissues. This leads to tissue hypoxia and cellular injury, which can be rapidly fatal if exposure is significant. B. is a respiratory depressant: Carbon monoxide does not directly depress the respiratory center in the brain. Respiratory function may remain normal, and the person may not sense hypoxia, which makes carbon monoxide poisoning particularly dangerous because symptoms can be subtle or delayed. C. is a pneumotoxic agent: Carbon monoxide is not directly toxic to lung tissue. Its harmful effects occur systemically due to impaired oxygen delivery, not due to damage to the pulmonary parenchyma. Lungs generally appear normal on examination, even in severe poisoning. D. interferes with expulsion of carbon dioxide: Carbon monoxide does not prevent the body from expelling carbon dioxide. Respiratory exchange of CO₂ continues normally, so hypercapnia is not typically a feature of carbon monoxide poisoning. The critical issue is oxygen deprivation, not CO₂ retention.