[Noninvasive determination of oxygen saturation using pulse oximetry in pediatric cardiology]

Pulse oximetry is a relatively new noninvasive method to measure arterial oxygen saturation (SO2). We evaluated the reliability of a pulse oximeter (N-100, Nellcor/Drger, Lübeck) in single and continuous measurements of SO2. During cardiac catheterisation we compared pulse oximeter (puls.SO2) measurements to those in simultaneously taken arterial samples (art.SO2), and obtained 203 pair measurements in 85 patients, mostly newborns and infants; in 20 of them before and during the breathing of oxygen through a mask. We also have 67 pair measurements of capillary blood samples (kap.SO2) and puls.SO2. Continuous measurements with the pulse oximeter were carried out in 17 patients for up to 116 h. Our main results are: 1. In the puls.SO2 range of 66% to 100% the measurements with the pulse oximeter were accurate (r = 0.97, Syx = 2.1). Below 66% the puls.SO2 values were on average much higher than the art.SO2 values, with an increased variance. Intraindividual oxygenation changes before and during the breathing of oxygen were accurately measured. 2. Pulse oximetry is much more informative than kap.SO2 measurements, because its information about the SO2 before blood sampling (= resting value) and following SO2 changes during the painful procedure (= stress values). 3. Continuous measurements with the pulse oximeter are very simple and very reliable and are not associated with skin injury. Because the pulse oximeters responses rapid to oxygenation changes and does not need calibration it is very valuable in the assessment of therapeutic procedures in patients with cyanotic heart disease. We conclude that the pulse oximeter is a very important new diagnostic tool in pediatric cardiology.