LED light can falsify pulse oximetry readings via the stroboscopic effect

Abstract

Because of its simplicity, pulse oximetry plays a ubiquitous role in neonatology. Its measurements are based on the absorption of light by hemoglobin. Ambient light can affect these values, therefore algorithms are designed to compensate for constant ambient light. Modern light-emitting diodes often flicker at a very high frequency. Such flickering ambient light can lead to significant measurement errors in saturation. To present a novel way in which light-emitting diodes influence the function of pulse oximeters and to demonstrate mathematically that a stroboscopic effect may well be responsible for this disturbance. Using publicly available data, a mathematical model of a pulse oximeter with a calibration curve and a proprietary measurement algorithm was created. This was used to simulate saturation measurements in flickering ambient light. To do this, photopletysmograms for red and infrared light at 98% oxygen saturation were mathematically superimposed on the light emission from an examination lamp used in the intensive care unit. From these results, presumable saturation measurements from a pulse oximeter were extrapolated. The light-emitting diodes in the examination lamp flicker at 207 Hz. The pulsating light from the light-emitting diodes causes superimposition of the photoplethysmogram due to the stroboscopic effect. With increasing brightness, the saturation dropped to 85% and the pulse rate to 108 bpm. The pulsed light of light-emitting diodes can distort pulse oximetry measurements. The stroboscopic effect leads to low saturation values, which can lead to the risk of blindness in premature infants due to excessive oxygenation.

Hospital Environmental Factors That Influence Peripheral Oxygen Saturation Measurements: A Cross-Sectional Study

“…In addition to light, other studies have considered the effect of flickering lights on SpO 2 measurements. This interruption has been shown to negatively affect SpO 2 readings due to the stroboscopic effect, with drops in saturation levels of up to 85% being observed [28].…”

“…This phenomenon is also observed in the case of light-emitting diode (LED) lamps. Blinking has been shown to negatively affect SpO 2 due to the stroboscopic effect, with drops to 85% [28]. Under operating room lights, standard light has been found to generate an overestimation of SpO 2 by 4% [29].…”