Carbon Monoxide Exposure is a toxic gas reducing oxygen delivery.

• A. Toxic gas reducing oxygen delivery
• B. High voltage injury
• C. Radiation exposure
• D. Inhalation injury

Answer: (A)

Main concept: Carbon monoxide exposure reduces oxygen delivery by binding to hemoglobin and impairing its ability to carry and release oxygen.

Carbon monoxide binds to hemoglobin with far greater affinity than oxygen, forming carboxyhemoglobin and dramatically reducing the blood’s capacity to transport oxygen. This decreases the overall oxygen content available to tissues. The remaining oxygen-holding sites become harder to unload at the tissue level because the dissociation curve shifts to the left, so even when the partial pressure of oxygen is normal, tissues can become hypoxic. Pulse oximetry can be misleading in this situation, often showing a normal reading because it cannot distinguish carboxyhemoglobin from oxyhemoglobin; accurate assessment requires co-oximetry. While other scenarios involve inhalation or injury, the statement is specifically describing the mechanism by which a toxic gas—carbon monoxide—directly reduces oxygen delivery.