Correlation between cerebral blood flow and oxygen saturation in patients with subarachnoid hemorrhage and traumatic brain injury

The INVOS cerebral oximeter and portable xenon enhanced CT (Xe/CT) scan are two commonly used diagnostic devices in patients who have experienced neurologic insults such as traumatic brain injury and subarachnoid hemorrhage. While the INVOS device is a relatively inexpensive, non-invasive measure of cerebral blood oxygen saturation, Xe/CT is a more complex costly diagnostic test that is the current gold standard for assessing cerebral perfusion in patients in the neurosciences intensive care unit (NSI) at the University of New Mexico Hospital. The purpose of this research was to investigate a possible relationship between these two diagnostic devices that might enable clinicians to better determine the appropriate timing and necessity of Xe/CT scans by evaluating trends in cerebral oximetry. The research was conducted in the University of New Mexico Hospital NSI over 18 months, with 25 imaging studies being collected from among 22 patients. Computer generated cortical segments obtained from the Xe/CT scans were correlated to INVOS cerebral oximeter pad placement on each patient's forehead, and the values were then compared using Spearman correlation coefficients. In this study, no statistically significant relationship between the devices was found although expansion of the study to a greater number of patients may uncover such a relationship.