Dynamic changes of cerebral oxygenation measured by brain tissue oxygen pressure and near infrared spectroscopy

The aim of this study was to find out whether a correlation exists between changes in brain tissue oxygen pressure (ti-pO2) and hemoglobin oxygenation (HbO2) measured by near-infrared spectroscopy. We studied 10 patients with severe head injury. A ti-pO2 monitoring device was introduced in the frontal white matter as soon as possible after administration. Additionally a NIRS sensor was placed at the forehead. All data were recorded simultaneously. Changes of the ti-pO2 curve were defined as events with the following criteria: > 10% change from the baseline value, > 3 min duration, clearly not an artifact. 137 events were found with a mean change of ti-pO2 of 8.3 +/- 10.2 mmHg. In 77.4% we observed a corresponding change of the HbO2. In 7 patients we found a good correlation (r > 0.7) between change ti-pO2 and change HbO2. In 3 patients the correlation was poor. The reason for poor correlation might be poor signal quality of the NIRS sensor or inhomogenous distribution of ischemic areas in the whole brain. We conclude that under the condition of a stable NIRS signal and a diffuse brain lesion, changes of ti-pO2 are well reflected by NIRS.