# The Agreement Between Pulse Oximetry and Measured Arterial Oxygen Saturations in Postoperative Functionally Univentricular Patients

## TL;DR

Pulse oximeters overestimate blood oxygen levels in children with certain heart conditions, especially when oxygen is low, suggesting they shouldn't be relied on alone.

## Contribution

The study reveals that arterial oxygen saturation level—not race—is the main factor affecting pulse oximeter accuracy in univentricular heart patients.

## Key findings

- Pulse oximetry overestimates arterial oxygen saturation in univentricular patients, with bias increasing at lower saturation levels.
- Arterial saturation levels explain 50% of the variance in measurement bias, more than race or surgical procedure.
- Fontan physiology shows reduced overestimation by pulse oximetry compared to other procedures.

## Abstract

What are the main findings?
Pulse oximetry systematically overestimates arterial oxygen saturation in children with functionally univentricular circulation, with wide limits of agreement and worsening bias during hypoxemia.Arterial saturation level, rather than race, was the dominant determinant of measurement bias, with nonlinear overestimation increasing markedly at lower saturation ranges.

Pulse oximetry systematically overestimates arterial oxygen saturation in children with functionally univentricular circulation, with wide limits of agreement and worsening bias during hypoxemia.

Arterial saturation level, rather than race, was the dominant determinant of measurement bias, with nonlinear overestimation increasing markedly at lower saturation ranges.

What is the implication of the main finding?
In single-ventricle physiology, reliance on pulse oximetry alone may mask clinically significant hypoxemia, particularly when saturations fall below ~80%.Oxygen saturation values in congenital heart disease should be interpreted in a physiologic context, and confirmatory blood gas or adjunctive monitoring should be considered during clinical deterioration.

In single-ventricle physiology, reliance on pulse oximetry alone may mask clinically significant hypoxemia, particularly when saturations fall below ~80%.

Oxygen saturation values in congenital heart disease should be interpreted in a physiologic context, and confirmatory blood gas or adjunctive monitoring should be considered during clinical deterioration.

Background: Pulse oximetry is widely used to estimate arterial oxygen saturation, yet accuracy may vary for a number of reasons. Data on children with functionally univentricular circulation are limited. The primary aim of this study was to evaluate the agreement between arterial oxygen saturation measured by blood gas and pulse oximetry in children with functionally univentricular circulations. Methods: A retrospective analysis was performed of paired arterial blood gas and pulse oximetry oxygen saturation measurements following Norwood, Glenn, or Fontan procedures. Signed difference was defined as arterial oxygen saturation by blood gas—arterial oxygen saturation by pulse oximetry. Bland–Altman analyses, multivariable regressions, and generalized additive modeling were performed. Results: Mean bias was −4.9 percentage points, indicating pulse oximetry overestimated arterial saturation. The 95% limits of agreement were wide, from −20.7 to 10.8. The agreement was similar in Black and White patients. Fontan physiology demonstrated reduced overestimation by pulse oximetry by multivariable regression. Nonlinear modeling demonstrated more bias in agreement at lower arterial oxygen saturation levels, with arterial oxygen saturation levels explaining 50% of the variance. Conclusions: In functionally univentricular patients, pulse oximetry using the Nellcor MAXN-NS pulse oximeter (Medtronic, Dublin, Ireland) systematically overestimates arterial saturation, particularly in the setting of hypoxemia. Saturation level, rather than race, was the dominant determinant of bias.