An Evaluation of the Accuracy of the Physio-Control Lifestat 1600 Pulse Oximeter in Measuring Arterial Oxygen Saturation

Abstract

This study evaluated the accuracy of the SaO₂ measured by the Physio-Control Lifestat 1600 Pulse Oximeter. Method: We evaluated the accuracy of this oximeter in the SaO₂ range of 75-100% in 9 normal, healthy, Caucasian volunteers, who had blood-sampling catheters placed in their radial arteries. Hypoxemia was produced by a rebreathing technique, normoxemia by having the subjects breathe room air, and hyperoxemia by having them breathe supplemental oxygen. After the subject's SaO₂ stabilized at the desired level, a pulse oximeter SaO₂ reading was taken and a simultaneously drawn arterial blood sample was analyzed on an IL282 CO-Oximeter for SaO₂, carboxyhemoglobin (COHb), and methemoglobin (metHb). Results: In the 114 data sets collected, the mean (± SD) Physio-Control SaO₂ was 87.9 ± 6.6% and the mean IL282 SaO₂ was 88.2 ± 6.4% (significantly different: P = 0.03). The mean COHb was 2.5 ± 0.5%, and the mean metHb was 0.5 ± 0.2%. There was a 0.97 correlation between the Physio-Control and the IL282-SaO₂ values. The limits of agreement for the Physio-Control SaO₂ were ± 3%. That is, the Physio-Control SaO₂ tended to be within 3 percentage points of the IL282 SaO₂. Conclusions: Although the difference between the mean SaO₂ values produced by the pulse oximeter and the CO-Oximeter was statistically significant, we consider it too small to be clinically important. When COHb and metHb levels are low, as they were in this normal population, the Physio-Control Lifestat 1600 Pulse Oximeter is acceptably accurate in the SaO₂ range of 75-100%.