ACCURACY OF PULSE OXIMETRY DURING INTENSE EXERCISE UNDER SEVERE HYPOXIC CONDITIONS

There is a growing need to measure arterial oxygen saturation with a n on-invasive method during heavy exercise under severe hypoxic conditio ns. Although the accuracy of pulse oximetry has been challenged by sev eral authors, it has not been done under extreme conditions. The purpo se of this study was to evaluate the accuracy of a pulse oximeter (Sat lite, Datex, Finland) during exercise under hypoxic conditions where a rterial oxygen saturation was below 75%, simulating exercise at extrem e altitude. Ten healthy nonsmoking men performed two exercise studies of 30 min under normoxia and under hypoxia on two consecutive days. Th e exercise intensity was 80% of maximal O-2 consumption of (V) over do t O-2max. Arterial oxygen saturation measured by pulse oximetry was co rrected (SpO2[corr]) according to previously published equations and w as compared to arterial oxygen saturation (SpO2) in blood samples take n simultaneously from the radial artery. Reference arterial saturation values ranged from 57.2 to 97.6% for the whole data set. This data se t was split according to low (SaO2 less than or equal to 75%) and high (SaO2 > 75%) SaO2 values. The error of pulse oximetry (SpO2[corr] -Sa O2) was 2.05 (0.87)% [mean (SD)] and 1.80 (1.81)% for high and low SaO 2 values, respectively. SpO2[corr] and SaO2 were highly correlated (r = 0.93, SEE = 1.8) for low values. During high-intensity constant work load under severe hypoxic conditions, once corrected, pulse oximetry p rovides an estimate of SaO2 with a mean error of 2%. Thus, the correct ion previously described for SpO2 values above 75% saturation applies also to SpO2 values in the range of 57-75% during exercise under hypox ic conditions.