The Stealth Station Image Guidance System may interfere with pulse oximetry

PURPOSE: Interference on pulse oximetry can come from many sources. We found an additional source of interference from the Stealth Station. This article gives an overview of sources of pulse oximeter interference so that clinicians can better prevent them.Technical features: This article discusses the infrared disturbances caused by the Stealth Station. The Stealth Station is a frameless stereotactic positioning system that utilizes a three dimensional location system to measure the position of the patient and the surgical tools, and to relate those positions to previously recorded imaging. To understand the disturbance caused by the Stealth Station, we discuss its operation and that of pulse oximeter monitors. Pulse oximeter interference can come from volume artifacts, electrical and light noise, and can be caused by issues related to the patient. Because the passive Stealth Station contains a strong infrared light source, interference caused by light is a likely reason for the interference we noted. Pulse oximeters rely on the time-variant light signal modulated by arterial volume variations in the finger. Although relatively immune to static light sources, pulse oximeters are extremely sensitive to time-varying light sources. The light emitted by the passive Stealth Station is time-varying at 4 Hz and this is causing the pulse oximeter to provide invalid results. Shielding can generally be used to stop the light from the Stealth Station from being picked up by the pulse oximeter sensor. CONCLUSION: Infrared light interference can be very common, but is easily dealt with if one is aware of it.