Introduction Newborns (NBs) breathing room air (RA) have normal SpO2 of 95 to 100% but keeping SpO2 95 to 100% in NB breathing FiO2 > 0.21 can cause hyperoxia. In 2003 and 2006, we reported that SpO2 85 to 95% is associated with less morbidity. There is concern that these SpO2 levels may cause persistent or intermittent hypoxemia.
Objective To evaluate PaO2 at different SpO2 levels in NBs with arterial catheters.
Methods Prospective comparison of PaO2 and SpO2 in stable NB in six NICUs located at sea level in two countries. PaO2 was obtained for clinical indications; simultaneous SpO2 was recorded at the time of the arterial gas. Comparisons were made only in stable NBs if the SpO2 changed < 1% before, during and after the collection of the sample. Statistics: Chi-square, Fishers, bivariate and multivariate analysis.
Results 674 paired SpO2 values in 85 NBs; 20% of the samples when NBs in RA. GA and BW: 30.5 ± 5.3 w and 1,516 ± 910 g. NBs in RA: Mean and median SpO2 were 94.6% ± 4.3 and 96% (73-100%); with SpO2 85 to 93%, mean PaO2 was 59.4 ± 15.9 mm Hg. When SpO2 > 93%, mean PaO2 was 72.7± 24.7 mm Hg. NBs breathing FiO2 > 0.21: (a) With SpO2 85 to 93%, mean PaO2 was 60 ± 16.7 mm Hg, median 56 mm Hg (29-112); PaO2 of 40 to 80 mm Hg in > 79% of samples, and PaO2 < 40 mm Hg in 5%. (b) With SpO2 > 93%, mean PaO2 was 122.7 ± 62.9 mm Hg, median 110 mm Hg (38-438) (p ≤ .001 vs infants with SpO2 85-93%); 72% of the PaO2 values were > 80 mm Hg and 27% between 40 and 80 mm Hg.
Conclusions NBs breathing FiO2 > 0.21: (1) Normoxemia is much more frequent with SpO2 85 to 93% than with SpO2 > 93%; (2) SpO2 85 to 93% avoids abnormally high PaO2 and is infrequently associated with low PaO2; (3) SpO2 > 93% is associated with hyperoxia, which may be of risk in some NBs receiving FiO2 > 0.21.
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