Abstract
Objective The aim of this article was to evaluate the correlation between the oxygen index
(OI) and the oxygen saturation index (OSI, measured by pulse oximetry and noninvasively)
in neonates with acute respiratory failure and to predict the OI from the OSI.
Study Design A retrospective cohort study was conducted in neonates requiring invasive mechanical
ventilation who had arterial blood gas between 2018 and 2019 at a neonatal intensive
care unit. The correlation between OI and OSI was analyzed by using the Pearson correlation
coefficient.
Results A total of 636 measurements from 68 neonates (35 preterm and 33 terms) were recruited
into the study. There was a strong correlation between the OI and the OSI (r = 0.90) in all neonates. The correlation between the OI and the OSI in persistent
pulmonary hypertension of the newborn, congenital cyanotic heart disease, and other
causes of respiratory failure also showed a strong correlation (r = 0.88, 0.93, and 0.88, respectively). The correlation was strong in neonates with
an oxygen saturation less than 85% (r = 0.88), those with oxygen saturation ranging from 85 to 95% (r = 0.87), and also in preterm and term infants (gestational age < 28, 28 − 34, 34 − 36,
and ≥37 weeks, r = 0.87, 0.92, 0.89, and 0.90, respectively). There were strong accuracy measures
of the OI for OI cutoffs of 5, 10, 15, and 20 (area under the curve > 0.85). The equation
relating the OI and OSI was represented by: OI = (2.3 × OSI) – 4.
Conclusion The OSI has a strong correlation with the OI, is a reliable assessor of the severity
of respiratory failure in neonates without arterial sampling, and has high accuracy
when the OI is less than 40.
Key Points
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OSI is calculated as (FiO2 × mean airway pressure × 100)/SpO2.
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OSI is as effective tool as OI for assessing the severity of pediatric acute respiratory
distress syndrome.
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OSI has a strong correlation with OI in neonatal respiratory failure.
Keywords
neonates - respiratory failure - oxygenation index - oxygen saturation index
