Fig. 3

A–D Relationship between CPP and UL-PRx, stratified by age and GOSE. The combined plot illustrates a comparative analysis of ultra-low-pressure reactivity index (UL-PRx) dynamics in patients with traumatic brain injury, specifically examining the relationship between cerebral perfusion pressure (CPP) and UL-PRx. The plot is divided into four quadrants, each focusing on different patient groups based on Glasgow Outcome Scale Extended (GOSE) scores and age categories. The upper left quadrant examines autoregulation patterns for GOSE 1–4 patients aged 16 years or younger, while the upper right quadrant examines patients older than 16 years. The lower left quadrant provides insights into UL-PRx dynamics for GOSE 5–8 patients aged 16 years or younger, while the lower right quadrant examines the same for those aged 16 years or older. Each bar represents the mean UL-PRx value for specific CPP groups, with error bars indicating 95% confidence intervals. In the top panels, patients with poorer GOSE scores show a trend toward higher UL-PRx values, both in the pediatric and adult populations. Conversely, the lower panels, representing patients with higher CPP and positive results, show a trend toward values close to or predominantly negative UL-PRx