If the SpO₂ reading is much different from the measured HbO₂, what should be considered?

Dyshemoglobinemia refers to the presence of abnormal hemoglobin in the blood, which can lead to discrepancies between the peripheral capillary oxygen saturation (SpO₂) reading obtained from pulse oximetry and the actual amount of oxygen bound to hemoglobin (HbO₂) measured through arterial blood gas analysis. This condition can occur due to various factors, including carbon monoxide poisoning, methemoglobinemia, or other hemoglobin variants that can interfere with the light absorption characteristics used by oximeters to determine saturation levels.

When a healthcare provider observes a significant difference between the SpO₂ reading and the measured HbO₂, it becomes essential to consider dyshemoglobinemia as a potential cause. This is because standard pulse oximetry, which is designed to measure oxygen saturation based on the properties of normal hemoglobin, may not accurately reflect the patient's true oxygenation status in the presence of abnormal hemoglobin types.

While proper sensor attachment, normal perfusion, and patient movement are also important factors to ensure accurate pulse oximetry readings, they do not directly relate to the interpretation of discrepancies in SpO₂ and HbO₂ measurements in the context of hemoglobin abnormalities. Proper sensor attachment is critical; however, if the sensor