Abstract
In the paper a pulse oximetry model is developed using an approach which combines both theoretical and empirical modelling. The optical properties of whole blood are measured as a function of cuvette depth by transmission spectrophotometry using red (660 nm) and infra-red (950 nm) light-emitting diodes as light sources. Twersky's theoretical model gives the best fit to the experimental data. A simple theoretical model which takes into account the nonlinear relationship between optical density and cuvette depth is then used to obtain an expression for the R:IR ratio, which relates the measurement of transmission at the two wavelengths. The R:IR ratio is found to be more or less independent of cuvette depth (SD=0·14 at 100 per cent SaO2). To validate the predictions of the theoretical model, the results of a previous experiment in which the relationship between SaO2 and the R:IR ratio was recorded using a flexible cuvette are used. The experimental values are found to lie within one standard deviation from the theoretical curve relating SaO2 and the R:IR ratio. It is argued that a reasonably accurate model for pulse oximetry which is based on whole blood and not haemoglobin solutions has been developed.
Similar content being viewed by others
References
Anderson, N. M. andSekelj, P. (1965) Studies on the light transmission of non-hemolysed whole blood. Determination of oxygen saturation.J. Lab. & Clin. Med.,63, 153–166.
Anderson, N. M. andSekelj, P. (1967) Light absorbing and scattering properties of non-haemolysed blood.Phys. in Med. & Biol.,12, 173–184.
Anderson, R. R. andParrish, J. A. (1981) The optics of human skin.J. Invest. Dermatol.,77, 13–19.
de Kock, J. P. (1991) Pulse oximetry: theoretical and experimental models. D. Phil. Thesis, University of Oxford.
de Kock, J. P. andTarassenko, L. (1991)In vitro investigation of the factors affecting pulse oximetry.J. Biomed. Eng.,13, 61–66.
Dorrington, K. L., Ralph, M. E., Bellhouse, B. J., Gardaz, J. -P. andSykes, M. K. (1985) Oxygen and CO2 transfer of a polypropylene dimpled membrane lung with variable secondary flows. —Ibid.,,7, 89–99.
Ishimaru, A. (1978)Wave propagation and scattering in random media, vol. 1. Academic Press.
Janssen, F. J. (1972) A study of the absorption and scattering factors of light in whole blood.Med. & Biol. Eng.,10, 231–240.
Johnson, C. C. (1970) Near infrared propagation in blood.J. Assoc. Adv. Med. Instrm.,4, 22–27.
Kramer, K., Elam, J. O., Saxton, G. A. andElam, W. N. (1951) Influence of oxygen saturation, erythrocyte concentration and optical depth upon the red and near-infrared light transmittance of blood.Am. J. Physiol.,165, 229–246.
Kubelka, P. andMunk, F. (1931) Ein Betrag zur Optik der Farbanstriche.Z. Techn. Phys.,12, 593–601.
Lipowsky, S., Usami, S., Chien, S. andPittman, R. N. (1980) Haematocrit determination in small bore tubes from optical density measurements under white light illumination.Microvasc. Res.,20, 51–70.
Loewinger, E., Gordon, A., Weinred A. andGross, J. (1964) Analysis of a micromethod for transmission oximetry of whole blood.J. Appl. Physiol.,19, 1179–1184.
Mendelson, Y. andKent, J. C. (1989) Variations in optical absorption spectra of adult and fetal haemoglobins and its effect on pulse oximetry.IEEE Trans.,BME-36, 844–848.
Payne, J. P. andSeveringhaus, J. W. (Eds.) (1986)Pulse oximetry. Springer Verlag, New York.
Severinghaus, J. W. andNaifeh, K. H. (1987) Accuracy of response of six pulse oximeters to profound hypoxia.Anesthesiol.,67, 551–558.
Shimada, Y., Yoshiya, I., Oka, N. andHamaguri, K. (1984) Effects of multiple scattering and peripheral circulation on arterial oxygen saturation measured with a pulse-type oximeter.Med. & Biol. Eng. & Comput.,22, 475–478.
Shockley, W. (1962) Diffusion and drift of minority carriers in semiconductors for comparable capture and scattering mean free paths.Phys. Rev.,125, 1570–1576.
Steinke, J. M. andShepherd, A. P. (1986) Role of light scattering in whole blood oximetry.IEEE Trans.,BME-33, 294–301.
Takatani, S., Cheung, P. W. andErnst, E. A. (1980) A noninvasive tissue reflectance oximeter—an instrument for measurement of tissue hemoglobin oxygen saturationin vivo.Ann. Biomed. Eng.,8, 1–15.
Twersky, V. (1962) Multiple scattering of waves and optical phenomena.J. Opt. Soc. Am.,52, 145–171.
Twersky, V. (1970a) Interface effects in multiple scattering by large, low refracting absorbing particles. —Ibid.,,60, 908–914.
Twersky, V. (1970b) Absorption and multiple scattering by biological suspensions. —Ibid.,,60, 1084–1093.
van Assendelft, O. W. (1970)Spectrophotometry of haemoglobin and its derivatives. Royal Vangorcum Ltd., Assen, The Netherlands.
Wilson, B. C. andAdam, G. (1983) A Monte Carlo model for the absorption and flux distribution of light in tissue.Med. Phys.,10, 842–830.
Wukitsch, M. W., Petterson, N. T., Tobler, D. R. andPologe, J. A. (1988) Pulse oximetry: analysis of theory, technology, and practice.J. Clin. Monit.,4, 290–301.
Yoshiya, I., Shimada, Y. andTanaka, K. (1980) Spectrophotometric monitoring of arterial oxygen saturation in the fingertip.Med. & Biol. Eng. & Comput.,18, 27–32.
Zdrojkowski, R. J. andPisharoty, N. R. (1970) Optical transmission and reflection of blood.IEEE Trans.,BME-17, 122–128.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
de Kock, J.P., Tarassenko, L. Pulse oximetry: Theoretical and experimental models. Med. Biol. Eng. Comput. 31, 291–300 (1993). https://doi.org/10.1007/BF02458049
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF02458049