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The Stroke Project

Cerebral autoregulation is the ability of the brain to maintain a steady blood inflow albeit the cerebral perfusion pressure or the arterial blood pressure is variable. It protects the brain against secondary insults. Patients with severe stonosis of the internal carotid artery with a disturbed autoregulation have a higher risk to suffer from stroke. A working autoregulation mechanism is essential for the further prognosis for patients that already suffer a stroke.

Aim of the Project

In order to support the medical diagnosis, the treatment of stenosis and the stroke therapy, timeseries algorithms to determine and monitor the dynamic cerebral autoregulation are developed. The following methods are used:

Correlation Coefficient Analysis:
The time-averaged correlation index of mean, systolic, and diastolic arterial blood pressure and the blood flow velocities in the brain arteries which can serve as a measure for the autoregulation mechanism of stenosis patients.

Transfer Function Analysis:
The basis of the transfer function analysis of cerebral autoregulation are auto and cross spectral estimates of the arterial blood pressure and the cerebral blood flow velocities and the respective cross spectra. Moreover, the coherence spectrum, the phase spectrum and the gain are estimated. Using data achieved during deep breathing (regular breathing at 6 per minute) and also during normal breathing, it is possible to detect malfunction in autoregulation by investigation of the phase shift between arterial blood pressure and cerebral blood flow velocity. We are currently developing a method which does not need the measurement of arterial blood pressure and we are also applying several parametric approaches for the spectral estimation.

CO2 Reactivity:
The capacity of the cerebrovascular reserve (CO2 reactivity) is determined by an inhalation of up to 7% CO2 enriched room air. In order to account for blood pressure influences we are using differential equations to model cerebral blood flow velocity as a function of CO2 and arterial blood pressure.

Continuous measurement:
We are working on adaptive measures for dynamic cerebral autoregulation which allow continuous monitoring. To this aim parametric approaches for spectral estimation are used.

NIRS:
Using near-infrared spectroscopy cerebral autoregulation can be investigated with higher spatial resolution. Further information on this project can be found on the NIRS-project page.

 

The Team

  1. Prof. Dr. Jens Timmer (Freiburg Center for Data Analysis and Modeling, Freiburg, Germany)
  2. Dr. Björn Schelter (Freiburg Center for Data Analysis and Modeling, Freiburg, Germany)
  3. Linda Sommerlade (Freiburg Center for Data Analysis and Modeling, Freiburg, Germany)
  4. Joachim Ortmann (Freiburg Center for Data Analysis and Modeling, Freiburg, Germany)
  5. Sebastian Rutsch (Department of Neurology, University Medical Center Freiburg, Germany)
  6. PD Dr. Matthias Reinhard (Department of Neurology, University Medical Center Freiburg, Germany)
For contact concerning this project, please send an e-mail to Linda Sommerlade

Publications

  • Reinhard M., Neunhoeffer F., Gerds T.A., Niesen W.-D., Buttler K.-J., Timmer J., Schmidt B., Czosnyka M., Weiller C., Hetzel A., 2010
    Secondary decline of cerebral autoregulation associates with worse outcome after intracerebral hemorrhage. Intensive Care Medicine 36, 264-271
  • Jachan M., Reinhard M., Spindeler L., Hetzel A., Schelter B., Timmer J., 2009
    Parametric versus nonparametric transfer function estimation of cerebral autoregulation from spontaneous blood-pressure oscillations. Cardiovascular Engineering 9, 72-82
  • Reinhard M., Gerds T.A., Grabiak D., Zimmermann P., Roth M., Guschlbauer B., Timmer J., Czosnyka M., Weiller C., Hetzel A., 2008
    Cerebral dysautoregulation and the risk of ischemic events in occlusive carotid artery disease. J. Neurology 255, 195-199
  • Reinhard M., Waldkircher Z., Guschlbaur B., Timmer J., Weiller C., Hetzel A., 2008
    Cerebellar autoregulation dynamics in humans. J. Cerebral Blood Flow Metabolism 28, 1605-1612
  • Reinhard M., Wihler C., Roth M., Harloff A., Niesen W.D., Timmer, J. Weiller C., Hetzel A., 2008
    Cerebral autoregulation dynamics in acute ischemic stroke after rtPA thrombolysis. Cerebrovasc. Dis. 26, 147-155
  • Reinhard M., Wehrle-Wieland E., Roth M., Niesen W.D., Timmer, J. Weiller C., Hetzel A., 2007
    Preserved dynamic cerebral autoregulation in the middle cerebral artery among persons with migraine. Exp. Brain Res. 180, 517-523
  • Reinhard M., Wehrle-Wieland E., Grabiak D., Roth M., Guschlbauer B., Timmer J., Weiller C., Hetzel A., 2006
    Oscillatory cerebral hemodynamics - the macro- vs. microvascular level. J. Neurol. Sci. 250, 103-109
  • Reinhard M.,Roth M., Guschlbauer B., Harloff A., Timmer J., Czosnyka M., Hetzel A., 2005
    Dynamical cerebral autoregulation in acute ischemic stroke assessed from spontaneous blood pressure fluctuations. Stroke 36(8), 1684-1689
  • Reinhard M., Roth M., Müller T., Guschlbauer B., Timmer J., Czosnyka M., Hetzel A., 2004
    Effect of carotid endarterectomy or stenting on impairment of dynamic cerebral autoregulation. Stroke, 35(6), 1381-1287
  • Reinhard M., Roth M., Müller T., Czosnyka M., Timmer J., Hetzel A., 2003
    Cerebral autoregulation in carotid artery occlusive disease assessed from spontaneous blood pressure fluctuations by the correlation coefficient index. Stroke, 34(9), 2138-2144
  • Reinhard M., Müller T., Roth M., Guschlbauer B., Timmer J., Hetzel A., 2003
    Bilateral severe carotid artery stenosis or occlusion - cerebral autoregulation dynamics and collateral flow patterns. Acta Neurochirurgica, 145(12), 1053-1060
  • Reinhard M., Müller T., Guschlbauer B., Timmer J., Hetzel A., 2003
    Dynamical cerebral autoregulation and collateral flow patterns in patients with severe carotid stenosis or occlusion. Ultrasound Med. Biol., 29(8), 1105-1113
  • Reinhard M., Müller T., Guschlbauer B., Timmer J., Hetzel A., 2003
    Transfer function analysis for clinical evaluation of dynamic cerebral autoregulation - a comparison between spontaneous and respitory-induced oscillations. Physiol Meas., 24(1),27-43
  • Müller T., Lauk M., Reinhard M., Hetzel A., Lücking C.H., Timmer J., 2003
    Estimation of delay times in biological systems. Ann Biomed Eng., 31(11):1423-39
  • Müller T., Reinhard M., Oehm E., Hetzel A., Timmer J., 2003
    Detection of very low frequency oscillations of cerebral hemodynamics is influenced by data detrending. Med. Biol. Eng. Comp., 41(1), 69-74
  • Reinhard M., Hetzel A., Lauk M., Lücking C.H., 2001
    Dynamic cerebral autoregulation testing as a diagnostic tool in patients with carotid artery stenosis. Neurological Research, 23, 55-63
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