Evaluation of the OSM2 hemoximeter.

The linearity and repeatability of measurements of total haemoglobin concentration ([Hb]) and oxygen saturation (So2) by the OSM2 oximeter have been studied. Standard deviations (SD) of measurements from linearity were as follows: [Hb], 4.2 g . litre-1; So2, 1.14 to 1.08% between zero and 100% saturation. Reproducibility by a single operator was within SD 1.1 g . litre-1 for [Hb] and 0.32% for So2, and between operators the means of 5 measurements had SD 0.42 g . litre-1 for [Hb] and 0.19% for So2, suggesting little if any extra variation from one operator to another. Foetal haemoglobin behaved as adult haemoglobin, but carboxyhaemoglobin caused a systematic and reproducible error in So2 measurement, from which HbCO concentration can be derived.