Pulse Oximetry during Exercise

In the 1980's the pulse oximetry method was developed to measure the level of Oxygen in the blood, as a percentage saturation level (SaO2). The measurement of SaO2 by pulse oximeters is based on the same principles as for CO-oximeters, except pulse oximeters do not require taking a sample of arterial blood. Pulse oximetry involves simply placing a sensor on the skin, usually the earlobe or finger, and the measurement of the relative transdermal absorption of infra-red light by Hb and HbO2.

As pulse oximeters only use two wavelengths, it cannot measure the presence of any of the dyshaemoglobins. Some models assume the presence of a certain amount of dyshaemoglobins, while others do not factor these into their algorithm.

Compared to direct analysis of arterial blood, pulse oximetry provides a simple, non-invasive and cheaper alternative measure of SaO2. Other advantages of pulse oximetry are that it provides immediate results and rapid response, which are ideal for testing during exercise. However, the validity of the measurement of SaO2 by pulse oximetry has been questioned, and many studies have investigated this (such as Mengelkoch et al, 1994).

measuring VO2maxThere are many different models of pulse oximeters available, and many of these have been validated. The Ohmeda/Biox models are the most popular, and have therefore been mostly studied.

Pulse Oximetry Validation

Every model of pulse oximeter is potentially different in its accuracy. Although based on the same measurement principle, the algorithm used for calculation of SaO2 may vary. Also, wear and tear on the sensor probe may effect the light emitter and sensor. Therefore every individual machine is required to be validated. There have been many studies which have conducted comparisons of SaO2 measurement by a pulse oximeter to CO-oximeter measurements of arterial blood, however, comparing the results of these becomes difficult due to differences in protocols. Such differences include subject copulation and size, whether exercise is involved, sensor sites, pulse oximeter averaging periods, and the range of O2 saturations over which the comparisons are made.

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Disclaimer

The above information is presented as a general guide. The author and publisher take no responsibility for any possible consequences from any treatment, procedure, exercise, action or application of medication based on this information. See more: Disclaimer.