Which signs point to carbon monoxide poisoning and what is the ED treatment protocol?

• A. Headache, dizziness, confusion; pulse oximetry may be falsely normal; treat with 100% oxygen; consider hyperbaric oxygen for severe cases
• B. Chest pain is the only symptom; treat with aspirin
• C. Pulse oximetry is always accurate; treat with oxygen only if chest pain
• D. CO poisoning cannot occur without fire exposure

Answer: (A)

Carbon monoxide poisoning causes a decrease in oxygen delivery to tissues because CO binds tightly to hemoglobin, forming carboxyhemoglobin and shifting the oxygen delivery curve. That’s why headaches, dizziness, and confusion are common early signs, along with weakness, nausea, and sometimes fainting.

Pulse oximetry can be misleading here because standard devices can’t distinguish carboxyhemoglobin from oxyhemoglobin, so a normal reading does not rule out CO poisoning. In the ED, the priority is to give 100% oxygen right away to displace CO from hemoglobin and speed its elimination, typically via a tight-sealing non-rebreather mask or other high-flow delivery. If symptoms are severe or there are neurologic signs, metabolic acidosis, myocardial involvement, or in a pregnant patient, hyperbaric oxygen therapy is considered because it more rapidly lowers carboxyhemoglobin levels and can reduce ongoing injury.

Always remove the person from the exposure, monitor vital signs and neurologic status, and obtain co-oximetry (carboxyhemoglobin level) and ABG as part of the assessment, with ECG to check for arrhythmias. The statements that CO poisoning presents only with chest pain, that pulse oximetry is always accurate, or that it cannot occur without a fire exposure are not correct. CO exposure can come from sources like car exhaust or faulty furnaces and often presents with nonspecific symptoms.