Identification of movement artefact by the Nellcor N-200 and N-3000 pulse oximeters

Objectives. The Nellcor N-3000 pulse oximeter is designed to be able to identify signal artefact related to movement of the body part to which the probe is attached. It may therefore provide a reliable means of monitoring arterial oxyhemoglobin saturation (SpO₂) in awake, moving patients. This study compared the Nellcor N-3000 and N-200 pulse oximeters in terms of their ability to identify readings associated with movement, in a group of volunteers making standardized movements. Methods. Thirty-six volunteers were studied. Volunteers breathed room air throughout the study. SpO₂ of each volunteer was monitored by both a Nellcor N-200 and a Nellcor N-3000 simultaneously on both hands. Volunteers made a series of five standardized movements, each lasting one minute, with each hand during the monitoring session, while SpO₂ and oximeter status were recorded from all four oximeters. The mean SpO₂ reading was calculated during each movement. SpO₂ readings which the oximeter identified as being associated with movement, pulse search not locked, sensor not attached, or break in communications were excluded from analysis. Results. The N-3000 rejected from 17 to 78% of readings taken during movement, compared to 0 to 2% with the N-200. Although the remaining readings of both types of oximeters were subject to some movement artefact, which led to spuriously low SpO₂, this was significantly less with the N-3000. Conclusions. The Nellcor N-3000 pulse oximeter is able, to some extent, to identify movement artefact. It should offer an advantage over the N-200 when monitoring moving patients.