What SpO2 Tells You
Pulse oximetry estimates the percentage of hemoglobin saturated with oxygen. A normal reading is 95 to 100 percent. It is a useful trend tool, but it does not measure ventilation or the quality of oxygen delivery to tissues.
Common Sources of Error
Carbon monoxide binds to hemoglobin and can falsely produce a normal reading. Poor perfusion, cold extremities, nail polish, motion, and bright ambient light can also cause inaccurate values. Severe anemia may produce a normal saturation despite poor oxygen-carrying capacity.
Clinical Judgment
Always treat the patient, not the monitor. A patient with a normal SpO2 but significant respiratory distress still needs oxygen and close monitoring. In suspected carbon monoxide poisoning, give high-flow oxygen regardless of the displayed reading.