Is PbrO2 pressure reactivity index (ORx) dependent on the type of oxygen probe? An in vivo study

Abstract

Objective: To evaluate if ORx is dependent on the type of brain tissue O2 (PbrO2) probe in an in vivo setting. Methods: In eight German landrace pigs two types of probes were implanted simultaneously in the same cerebral hemisphere. All pigs underwent hepatectomy and received neuromonitoring until death. A LICOX® probe CCI.S, representing a Clarke type electrode, was compared with a Raumedic Neurovent PTO, representing an optode. Data were sampled at 50 Hz. Average values were calculated every 30 s. Cerebral perfusion pressure (CPP) was averaged over 30 s. ORx was calculated for each probe. To increase the signal to noise ratio of the ORx, the ORx values, which had been assessed every minute, were averaged over 1 h. Results: The overall measurement time was 145.1 h (8,703 data pairs). Despite a mean difference of 6.2 mmHg (p < 0.0001) in the measured values of PbrO2, the mean ORxlicox was 0.139, mean ORxraumedic 0.146 (p = 0.2098). Correlation coefficient of ORx values assessed every minute and every hour was 0.52 and 0.58 respectively. Conclusion: Despite this significant difference in absolute values of P brO2 the derived mean ORx values were not different. Similar to the established Licox system, the Raumedic system seems to enable a valid ORx recording. © 2012 Springer-Verlag/Wien.