Impaired Cerebral Autoregulation during Head Up Tilt in Patients with Severe Brain Injury

PLoS One. 2016 May 11;11(5):e0154831. doi: 10.1371/journal.pone.0154831. eCollection 2016.


Early mobilization is of importance for improving long-term outcome for patients after severe acquired brain injury. A limiting factor for early mobilization by head-up tilt is orthostatic intolerance. The purpose of the present study was to examine cerebral autoregulation in patients with severe acquired brain injury and a low level of consciousness. Fourteen patients with severe acquired brain injury and orthostatic intolerance and fifteen healthy volunteers were enrolled. Blood pressure was evaluated by pulse contour analysis, heart rate and RR-intervals were determined by electrocardiography, middle cerebral artery velocity was evaluated by transcranial Doppler, and near-infrared spectroscopy determined frontal lobe oxygenation in the supine position and during head-up tilt. Cerebral autoregulation was evaluated as the mean flow index calculated as the ratio between middle cerebral artery mean velocity and estimated cerebral perfusion pressure. Patients with acquired brain injury presented an increase in mean flow index during head-up tilt indicating impaired autoregulation (P < 0.001). Spectral analysis of heart rate variability in the frequency domain revealed lower magnitudes of ~0.1 Hz spectral power in patients compared to healthy controls suggesting baroreflex dysfunction. In conclusion, patients with severe acquired brain injury and orthostatic intolerance during head-up tilt have impaired cerebral autoregulation more than one month after brain injury.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Brain / physiopathology*
  • Brain Injuries / physiopathology*
  • Cerebrovascular Circulation / physiology
  • Electrocardiography
  • Female
  • Hemodynamics
  • Homeostasis*
  • Humans
  • Male
  • Middle Aged
  • Tilt-Table Test*

Grant support

CGR received two grants for support in analysing data as well as drafting the manuscript. First grant from University hospital Glostrup, Denmark and second from the Danish Physical Therapy Association ( The funders had no role in study design, data collection and analysis, decision to publish, or preperation of the manuscript.