A comparison of the Invos 3100 and the Critikon 2020 near-infrared spectrophotometers as monitors of cerebral oxygenation

Assessment of cerebral oxygenation using near-infrared spectroscopy in intensive care is increasing. We compared the ability of the Invos 3100 and the Critikon 2020 monitors to produce stable and consistent readings of regional cerebral oxygen saturation in resting volunteers. Failure to obtain any stable reading with the Critikon occurred in eight out of 18 subjects (44.4%) and with the Invos in three out of 15 subjects (20%). The Critikon showed a significantly higher failure rate in male subjects (p = 0.0011). Differences in recorded values of cerebral oxygen saturation (Critikon - Invos) ranged from -4.7% to 12.6% and were significantly related to the average saturation level (p < 0.0001). The within-monitor variability was significantly higher for the Invos (p = 0.0124). Neither monitor is able to give stable and consistent readings over time, particularly in male subjects. The unacceptably high failure rate of the recently introduced Critikon 2020 will limit or prevent its clinical use.