What is the most reliable test to diagnose carbon monoxide poisoning?

What is the most reliable test to diagnose carbon monoxide poisoning?

• A. Pulse oximetry
• B. Venous or arterial co-oximetry
• C. ABG with carboxyhemoglobin
• D. Chest X-ray

Answer: (B)

Measuring how much carbon monoxide is bound to hemoglobin is the only way to truly confirm poisoning, because CO masks oxygen delivery without changing the basic oxygen tension right away. Co-oximetry does this by using multiple wavelengths to distinguish carboxyhemoglobin from oxyhemoglobin and other forms of hemoglobin, giving a precise carboxyhemoglobin percentage. This makes it the most reliable diagnostic test. Pulse oximetry isn’t trustworthy in this setting because it can’t tell CO-bound hemoglobin apart from normal oxyhemoglobin, so it often shows a normal or falsely reassuring oxygen saturation despite significant CO exposure. Chest X-ray doesn’t diagnose CO poisoning at all. An arterial blood gas can show oxygen tension and acid-base status, but it doesn’t quantify CO bound to hemoglobin unless a co-oximeter is used. Co-oximetry can be performed on either arterial or venous blood.

Measuring how much carbon monoxide is bound to hemoglobin is the only way to truly confirm poisoning, because CO masks oxygen delivery without changing the basic oxygen tension right away. Co-oximetry does this by using multiple wavelengths to distinguish carboxyhemoglobin from oxyhemoglobin and other forms of hemoglobin, giving a precise carboxyhemoglobin percentage. This makes it the most reliable diagnostic test.

Pulse oximetry isn’t trustworthy in this setting because it can’t tell CO-bound hemoglobin apart from normal oxyhemoglobin, so it often shows a normal or falsely reassuring oxygen saturation despite significant CO exposure. Chest X-ray doesn’t diagnose CO poisoning at all. An arterial blood gas can show oxygen tension and acid-base status, but it doesn’t quantify CO bound to hemoglobin unless a co-oximeter is used. Co-oximetry can be performed on either arterial or venous blood.