False low pulse oximetry reading associated with the concomitant use of a peripheral nerve stimulator and an evoked-potential stimulator

• Published in: Journal of clinical anesthesia Vol. 9; no. 7; pp. 591 - 596
• Main Authors: Keidan, Ilan, Sidi, Avner, Gravenstein, Dietrich
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-11-1997
• Subjects: Electric Stimulation - adverse effects; Electric Stimulation - instrumentation; evoked potential stimulators; Evoked Potentials, Somatosensory - physiology; False Positive Reactions; Humans; Intraoperative Period; Male; Middle Aged; nerve stimulators; Oximetry - adverse effects; Oximetry - instrumentation; Oxygen - blood; Peripheral Nerves - physiology; pulse monitors; Equipment; evoked potential stimulators; nerve stimulators; pulse monitors
• ISSN: 0952-8180; 1873-4529
• DOI: 10.1016/S0952-8180(97)00152-9

One of the sources of error in pulse oximetry readings is associated with an abnormal signal-to-noise ratio. The pulse oximeter distinguishes the light absorbance of arterial blood from that of other absorbers by differentiating between a constant component and a pulsating component. The pulsating component is almost exclusively the result of arteriolar bed pulsations. Because pulse oximetry is based on the assumption that arterial blood is the only pulsatile absorber, any other fluctuating phenomenon could constitute a source of error. We report a case in which a low pulse oximetry reading was associated with concomitant use of a pulse oximeter and a peripheral nerve stimulator on the same arm. Further tests conducted using a nerve stimulator and a sensory evoked potential stimulator with different amplitudes and frequencies confirmed the association and delineated the relationship between frequency and amplitude of stimulation and the degree of artificial desaturation. A theoretical explanation for this phenomenon is presented.