FALSE LOW PULSE OXIMETRY READING ASSOCIATED WITH THE CONCOMITANT USE OF A PERIPHERAL-NERVE STIMULATOR AND AN EVOKED-POTENTIAL STIMULATOR

One of the sources of error In pulse oximetry readings is associated w ith an abnormal signal-to-noise ratio. The pulse oximeter distinguishe s the light absorbance of arterial blood fi om that of other absorbers by differentiating between a constant component and a pulsating compo nent. The pulsating component is most exclusively the result of arteri olar bed pulsations. Because pulse oximetry is based on the assumption that arterial blood is the only pulsatile absorber, any other fluctua ting phenomenon could constitute a source of error. We report a case i n which a low pulse oximetry reading was associated with concomitant u se of a pulse oximeter and a peripheral nerve stimulator on the same a rm. Further tests conducted using a nerve stimulator and a sensory evo ked potential stimulator with different amplitudes and frequencies con firmed the association and delineated the relationship between frequen cy and amplitude of stimulation and the degree of artificial desaturat ion. A theoretical explanation for this phenomenon is presented. (C) 1 997 by Elsevier Science Inc.