Reference values of capillary blood saturation in neonates and its difference from pulse oximetry.

INTRODUCTION Haemoglobin saturation is an obligatory oxygen parameter in the assessment of neonatal oxygenation. Although, pulse oximetry is currently one of the major methods in the determination of haemoglobin saturation, capillary blood saturation is still present in the diagnostic process. As well known, haemoglobin saturation value of capillary blood is insufficiently accurate, but not as much as the difference in relation to the values determined by pulse oximetry. Until now published studies have reported that capillary samples are obtained according to a protocol by the principle of free blood outflow, which is practically almost unachievable in the neonate. OBJECTIVE Determination of the reference values of oxygen saturation (SCO2) and partial pressure (pcO2) of capillary blood by squeezing of the foot. The determination of difference between ScO2 and pulse oximetry (SpO2). METHODS In 134 term newborns, we determined SpO2. Subsequently, we measured the values of ScO2 and pcO2 from the same extremity. While withdrawing a capillary sample, we exerted multiple squeezing of the foot. The mean value of ScO2, pcO2, SpO2 and the difference between ScO2 and SpO2 were determined. RESULTS Mean ScO2 value was 80.5 +/- 8.5%, pcO2 was 48.2 +/- 11.4 mm Hg and SpO2 was 98 +/- 1.9%. The difference between ScO2 and SpO2 values was 17.5 +/- 8.6% (t = 23.568; p = 0.000). CONCLUSION There is a statistically highly significant difference between the values of ScO2 and SpO2. Having the knowledge of this difference can increase the accuracy of clinical evaluation and further diagnostics. Comparison in up-to-now conducted studies suggests that the squeezing of the foot for obtaining a capillary sample in relation to free blood outflow does not bear any significant influence on the resultant values of haemoglobin saturation.