Cerebral tissue oxygenation measured by two different probes: Challenges and interpretation

Abstract

Purpose: Cerebral tissue oxygenation (PbrO 2) is most frequently monitored using a Licox CC1.SB system (LX, Integra Neuroscience, France) but recently a new probe-the Neurovent-PTO (NV)-was introduced by a different manufacturer (Raumedic, Germany). There are no prospective data on how these probes compare in clinical routine. We therefore compared both probes in comatose patients suffering from traumatic brain injury (TBI) or subarachnoid haemorrhage (SAH) during dynamic changes of inspirational oxygen fraction (FiO 2) and mean arterial pressure (MAP). Methods: PbrO 2 in 11 patients was recorded continuously using an LX and NV probe placed side by side into the same cerebrovascular region. Once a steady baseline value was reached FiO 2 was increased by 20% for 10 min. Once the baseline values were re-established MAP was increased by 20 mmHg for 10 min. Evaluation was performed using a four-parameter logistic function and Bland-Altman analyses. Results: PbrO 2 values of both probes differed significantly at all times. The LX probe reacted significantly faster to changes in FiO 2 and MAP. Limits of agreement ranged between -32.1 and 20.0 mmHg. Mean LX values were 6.1 mmHg lower than NV values. Conclusions: Since the examined patient cohort was rather small, this study's results are preliminary. However, they suggest that LX and NV probes measure different PbrO 2 values in routine monitoring as well as during phases of dynamic changes in FiO 2 and MAP. These data therefore do not support the view that both probes can be used interchangeably. © 2011 Copyright jointly held by Springer and ESICM.