In vivo measurements of oxyhaemoglobin saturation by a fiberoptic catheter. The effects of variations in pH and haematocrit.

The development of plastic fiberoptic catheters, cheaper and less fragile than glass ones, has enabled the more widespread use of oxyhaemoglobin saturation (SO2) monitoring. They allow direct determinations of SO2 to be made, using reflection spectrophotometry. The purpose of the present work was to evaluate the accuracy of SO2 measurements as provided by these catheters. The studies were performed in dogs, with large variations of SO2, acid-base balance and haematocrit levels.