Characterization of the bias between oxygen saturation measured by pulse oximetry and calculated by an arterial blood gas analyzer in critically ill neonates

Continuous monitoring of oxygenation with pulse oximetry is the standard of care for critically ill neonates. A better understanding of its measurement bias compared to arterial oxygen saturation could be helpful both for the clinician and researcher. Towards that end, we examined the electronic database from a large neonatal ICU. From a 24-month period we identified 23,032 paired SpO 2 -SaO 2 measurements from 1,007 infants who were receiving supplemental oxygen during mechanical ventilation. We found that SpO 2 was consistently higher than SaO 2 . The size of the bias was fairly constant when SpO 2 was between 75-93%, above which it dropped steadily. The median size of this bias was 1% SpO 2 during hyperoxemia (SpO 2 97-100%) with a median variation of 1.3% above and below. During periods of hypoxemia (SpO 2 75-85%) and normoxemia (SpO 2 89-93%) the bias was approximately 5% SpO 2 , with a median variation of 5% above and below.