Pulse Oximetry Overestimates Oxyhemoglobin in Neonates with Critical Congenital Heart Disease.

BACKGROUND: Pulse oximetry is a key part of the clinical evaluation and management of neonates with congenital heart defects. In 2011, the US Department of Health and Human Services recommended use of routine pulse oximetry to screen for critical congenital heart disease (CCHD). Current studies suggest pulse oximetry overestimates arterial oxygen saturation in moderately hypoxemic pediatric patients. Based on variable hypoxemia in neonates with CCHD, concern exists that present pulse oximeter technology may overestimate measured oxyhemoglobin.
OBJECTIVES: To compare pulse oximetry and oxyhemoglobin values in NICU patients with known CCHD to evaluate the ability of pulse oximetry to reliably predict oxyhemoglobin accounting for potential confounding variables such as heart lesion, saturation range, total hemoglobin concentration, peripheral perfusion, and timing of measurements.
METHODS: This is a single-center retrospective study. Inclusion criteria were AHA-defined CCHD and umbilical artery blood gas-derived oxyhemoglobin with concurrent pulse oximetry recording during hours of life 0-72. Bland-Altman analysis and the concordance correlation coefficient were used to measure the internal consistency (agreement) between the two measurements.
RESULTS: 89 patients were evaluated with 599 paired arterial oxyhemoglobin and pulse oximetry recordings. 47% of all pulse oximetry values were ≥95% - the cutoff for CCHD screening. Pulse oximetry overestimated arterial oxyhemoglobin by a mean of 5.4% over all levels of oxygen saturation. Pulse oximetry overestimation was >3 in 65.4% of measurements, >6 in 41.2% of measurements, and >10 in 15.3% of measurements. Hour of life, total hemoglobin, and peripheral perfusion did not significantly affect the degree of overestimation.
CONCLUSIONS: Our results reinforce the concern that present pulse oximeters overestimate oxyhemoglobin values, contributing to some false-negative CCHD screens and potentially leading to unnecessary escalations in care of those patients with diagnosed CCHD. Improvements in pulse oximetry accuracy and precision in the neonate would benefit both screening and clinical care in the NICU.