Diffusion-based model of pulse oximetry: in vitro and in vivo comparisons.

A model of pulse oximetry is developed based on the three-dimensional photon diffusion theory. To test the applicability of the model, an in vitro assay was developed. Three different scattering levels and six different relative dye concentrations were analyzed. Average percent errors of 13.9% were obtained over the full range of the study. An in vivo clinical study of two pulse oximeter probes with different spectral characteristics was compared with results estimated by the model. The model correctly predicted the changes in pulse oximeter response resulting from the wavelength changes. A x(2) test gave a probability of 20% that the model fit the data. These results demonstrated the utility of the photon diffusion theory for the modeling of tissue optics.