Carboxyhemoglobin Determined in Neonatal Blood with a CO-Oximeter Unaffected by Fetal Oxyhemoglobin

Measurements of carboxyhemoglobin (COHb) for clinical purposes are routinely made with CO-oximeters. How-ever, fetal hemoglobin (HbF) interferes with this spectro-photometric method. The manufacturer (Ciba Corning Di-agnostics) of a new CO-oximeter (CCD 270) claims that COHb measurements with this instrument are insignifi-cantly affected by HbF. We examined this claim through CO-oximeter analysis of cord blood/adult blood mixtures and compared the results with those obtained by gas chromatography (GC). We also studied the influence of oxygen and bilirubin concentrations. Measurements of COHb with CCD 270 were significantly lower than the GC measurements, but the differences were not clinically im-portant. Linear regression analysis of HbF and COHb measurements (n = 68) showed significant correlation (