INTRODUCTION
orthostatic, traumatic brain injury, brain injury, Orthostatic, TBI, orthostatic intolerance
HEART, AUTONOMIC DYSFUNCTION
In the early phase after traumatic brain injury (TBI), autonomic control of cardiovascular function is often compromised (Laver et al., Orthostatic training by head‐up tilt has been increasingly accepted as an important first step of rehabilitation for patients with a low level of consciousness (Hernandez et al., Heart rate variability (HRV) is considered a biomarker of sympathetic‐parasympathetic balance within the autonomic nervous system (Malik et al., The mechanisms behind orthostatic intolerance and autonomic dysfunction in these patients are incompletely understood. Besides the effects of brain injury per se and sedation, immobilization may also play a role as seen in healthy persons confined to bed rest (Barbic et al., This study aimed to examine autonomic control of cardiovascular function and the response to head‐up tilt in patients with TBI, analyzed by position‐dependent changes in HRV. We hypothesized that in the early phase after TBI, (1) the short‐term HRV response to head‐up tilt is impaired, and (2) orthostatic training by head‐up tilt improves long‐term HRV.