Pulse oximetry will not accurately assess arterial oxygenation in carbon monoxide toxicity because?

Pulse oximetry measures the saturation of oxygen in the blood by using light absorption characteristics of oxyhemoglobin and deoxyhemoglobin. In cases of carbon monoxide toxicity, the presence of carbon monoxide in the blood competes with oxygen for binding sites on hemoglobin. However, pulse oximeters cannot differentiate between oxyhemoglobin and carboxyhemoglobin (the compound formed when carbon monoxide binds to hemoglobin). This inability to distinguish means that if carbon monoxide is present, the pulse oximeter may inaccurately indicate normal or near-normal oxygen saturation levels, failing to provide an accurate assessment of arterial oxygenation in such cases. It is crucial for first responders and healthcare professionals to recognize this limitation in pulse oximetry when assessing patients for carbon monoxide poisoning.