Objective: Our aim was to define the relationship of PaO(2) and pulse oxygen saturation values during routine clinical practice and to evaluate whether pulse oxygen saturation values between 85% and 93% were associated with PaO(2) levels of <40 mmHg.
Methods: Prospective comparison of PaO(2) and pulse oxygen saturation values in 7 NICUs at sea level in 2 countries was performed. The PaO(2) measurements were obtained from indwelling arterial catheters; simultaneous pulse oxygen saturation values were recorded if the pulse oxygen saturation values changed <1% before, during, and after the arterial gas sample was obtained.
Results: We evaluated 976 paired PaO(2)/pulse oxygen saturation values in 122 neonates. Of the 976 samples, 176 (18%) from infants breathing room air had a mean pulse oxygen saturation of 93.9 +/- 4.3% and a median of 95.5%. The analysis of 800 samples from infants breathing supplemental oxygen revealed that, when pulse oxygen saturation values were 85% to 93%, the mean PaO(2) was 56 +/- 14.7 mmHg and the median 54 mmHg. At this pulse oxygen saturation level, 86.8% of the samples had PaO(2) values of 40 to 80 mmHg, 8.6% had values of <40 mmHg, and 4.6% had values of >80 mmHg. When the pulse oxygen saturation values were >93%, the mean PaO(2) was 107.3 +/- 59.3 mmHg and the median 91 mmHg. At this pulse oxygen saturation level, 39.5% of the samples had PaO(2) values of 40 to 80 mmHg and 59.5% had values of >80 mmHg.
Conclusions: High PaO(2) occurs very rarely in neonates breathing supplemental oxygen when their pulse oxygen saturation values are 85% to 93%. This pulse oxygen saturation range also is infrequently associated with low PaO(2) values. Pulse oxygen saturation values of >93% are frequently associated with PaO(2) values of >80 mmHg, which may be of risk for some newborns receiving supplemental oxygen.