The purpose of this review is to examine the literature with respect to the value of pulse oximetry during exercise spo2 and look at some of its potential errors. Although the literature examining the accuracy of pulse oximetry is abundant, it is restricted to an examination of the pulse oximeter at rest, for example as a critical care monitor. There is far less information available regarding the capabilities of pulse oximeters during exercise and most of this work is limited to studies of normal subjects and elite athletes. This information is not necessarily generalisable to patients with cardiovascular or pulmonary pathology, although these patients often undergo exercise testing and training. An accurate measure of oxygen saturation is of particular importance in this patient group.
This review has demonstrated that different pulse oximeters have varying degrees of accuracy under exercise conditions, being more accurate in the higher saturation ranges and over-estimating in the lower ranges. Probe site location (ie finger, ear, forehead) is another variable and still appears to be a contentious issue although more recent literature seems to favour finger probes over ear probes.
There are other factors which can affect the accuracy of pulse oximeters. Skin colour has an effect in that saturation may be over-estimated with black people. High levels of carboxyhaemo- globin also cause over-estimations. Many oximeters have two modes (fast and slow) in which they can be used. For exercise, the fast mode seems to be more appropriate to ensure detection of any transient desaturations. Measurement of heart rate using pulse oximeters seems to be limited in the higher ranges. An under-estimation may be seen with heavy exercise. It is questionable how accurate the saturation reading is when heart rate levels are inaccurately estimated.