Time Series Analysis of Invasive Brain Tissue Oxygen Tension and near Infrared Spectroscopic Cerebral Oxygen Saturation: a Canadian High Resolution-traumatic Brain Injury (CAHR-TBI) Study

Introduction: Brain tissue oxygen tension (PbtO2) has emerged as a vital monitoring modality in the management of moderate/severe traumatic brain injury (TBI) patients. Limitations of this modality include its invasive nature and the small volume of brain tissue examined. Near infrared spectroscopy (NIRS) based modalities provide a non-invasive means of evaluating cerebral oxygen content, through regional cerebral oxygen saturation (RSO2), with improved spatial resolution. However, comparisons of PbtO2 and RSO2 in the literature have been limited to grand mean correlation analysis. Through advanced time series analysis, a better understand the relationship between these modalities may be obtained.

Methods: Utilizing prospectively collected high-resolution physiologic data from the CAnadian High Resolution TBI (CAHR-TBI) Research Collaborative database collected between 2016 and 2022 a retrospective multi-institution cohort study was performed. The cohort included adult moderate/severe TBI patients admitted to the Intensive Care Unit (ICU) with PbtO2 and RSO2 monitoring. Advanced times series analysis was used to examine the autocorrelative structure of PbtO2 and RSO2 signals as well as model PbtO2 signals based on RSO2.

Results: A total of 20 TBI patients met the study inclusion criteria. Times series methods were utilized to examine the relationship between PbtO2 and RSO2 signals beyond grand mean correlation analysis. This represents the first such attempt at leveraging advanced signals processing techniques to quantify the relationship between these modalities.

Conclusion : Times series analysis allows for a more complete understanding of the relationship between PbtO2 and RSO2 in the setting of moderate/severe TBI patients. Such analysis has the potential help elucidate the role of RSO2, relative to PbtO2, in the management of moderate/severe TBI.