ACCURACY OF PULSE OXIMETRY DURING HYPOXEMIA

To determine the accuracy of four pulse oximeters during mild and mode rate arterial hypoxemia, we produced stepwise arterial blood desaturat ion in 25 healthy, nonsmoking volunteers by adjusting the inhaled oxyg en concentration. At plateaus of <80%, 85% to 90%, 90% to 95%, and 95% to 100%, pulse oximetry saturation (SpO(2)) was measured with the fou r different monitors: Dinamap Plus Model 8700, Oxyshuttle, Ohmeda 3700 , and MiniOx IV. Arterial blood samples were analyzed with a co-oximet er and the arterial oxyhemoglobin saturation (SaO(2)) was compared wit h the SpO(2) readings at each plateau. Significant deterioration in th e accuracy of pulse oximeters was observed as SaO(2) decreased. In 14 instances of hypoxemia (SaO(2) < 90%), subjects exhibited SpO(2) value s greater than 90%. In conclusion, the accuracy of pulse oximetry dete riorates as hypoxemia worsens. Confirmation of arterial blood oxyhemog lobin saturation by co-oximetry is necessary when precise determinatio n of arterial oxyhemoglobin level is critical.