Fiberoptic measurement of arterial oxygen saturation in premature and term neonates

BACKGROUND: Non-invasive oxygen monitoring with pulse oximetry or transcutaneous monitoring has gained widespread use in neonatology. Different factors like arterial hypotension, peripheral vasoconstriction and edema adversely affect the accuracy of both methods. To ensure reliable monitoring of oxygen saturation in critically ill patients we measured oxygen saturation with a fiberoptic catheter via umbilical artery. METHODS: In ventilated premature infants (FiO2 > 0.4) a 4F-fiberoptic catheter (Oximetrix)-3, Abbott) was inserted to the descending aorta (Th 6-8). Simultaneously pulse oximetry (SaPO2) was performed with the Ohmeda Biox 3700. To compare the reliability of both methods, blood was analysed for arterial partial oxygen pressure (PaO2), fetal hemoglobin (HbF) and arterial oxygen saturation (SaO2) by complete co-oximetry (Radiometer Copenhagen OSM3) as reference. RESULTS: In 10 premature infants (median gestational age 30.5 weeks; median birth weight 1360 g) oxygen saturation was measured with the fiberoptic catheter (SaFO2) over a total period of 935 hours. In all, 137 blood samples were analysed for arterial saturation (SaO2) by co-oximetry. The mean difference between the SaO2 and SaFO2 was -1.89% (+/- 1.53); the mean difference between SaO2 and the values obtained by pulse oximetry (SaPO2) was -3.09% (+/- 2.33). The SaFO2 results correlated closely with the co-oximetry values (r = 0.97; p < 0.0001). CONCLUSION: In critically ill patients, if non-invasive oxygen monitoring fails, a fiberoptic catheter offers the possibility of continuous and reliable measurement of oxygen saturation.