Prediction of Intracranial Hypertension and Brain Tissue Hypoxia Utilizing High-Resolution Data from the BOOST-II Clinical Trial

Abstract

The current approach to intracranial hypertension and brain tissue hypoxia is reactive, based on fixed thresholds. We used statistical machine learning on high-frequency intracranial pressure (ICP) and partial brain tissue oxygen tension (PbtO2) data obtained from the BOOST-II trial with the goal of constructing robust quantitative models to predict ICP/PbtO2 crises. We derived the following machine learning models: logistic regression (LR), elastic net, and random forest. We split the data set into 70?30% for training and testing and utilized a discrete-time survival analysis framework and 5-fold hyperparameter optimization strategy for all models. We compared model performances on discrimination between events and non-events of increased ICP or low PbtO2 with the area under the receiver operating characteristic (AUROC) curve. We further analyzed clinical utility through a decision curve analysis (DCA). When considering discrimination, the number of features, and interpretability, we identified the RF model that combined the most recent ICP reading, episode number, and longitudinal trends over the preceding 30?min as the best performing for predicting ICP crisis events within the next 30?min (AUC 0.78). For PbtO2, the LR model utilizing the most recent reading, episode number, and longitudinal trends over the preceding 30?min was the best performing (AUC, 0.84). The DCA showed clinical usefulness for wide risk of thresholds for both ICP and PbtO2 predictions. Acceptable alerting thresholds could range from 20% to 80% depending on a patient-specific assessment of the benefit-risk ratio of a given intervention in response to the alert.

Keywords

• brain hypoxia
• intracranial hypertension
• prediction
• secondary brain injury
• traumatic brain injury