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Evaluation of Cerebral Blood Flow Autoregulation in the Rat Using Laser Doppler Flowmetry
Published on: January 19, 2020
Cerebral blood flow adaptation to chronic hypoxia
Haiying Zhou1, Gerald M Saidel, Joseph C LaManna
1Department of Biomedical Engineering, Case Western Reserve University, Cleveland 44106, USA.
Advances in Experimental Medicine and Biology
|February 23, 2008
Summary
Mild hypoxia initially boosts cerebral blood flow (CBF), but prolonged exposure normalizes it. Increased oxygen carrying capacity and brain stem PO2 signaling regulate CBF during chronic hypoxia.
Area of Science:
- Physiology
- Neuroscience
- Biophysics
Background:
- Hypoxia initially increases cerebral blood flow (CBF) to maintain oxygen delivery.
- With chronic hypoxia, CBF returns to baseline despite sustained tissue hypoxia.
- CBF regulation is linked to blood oxygen carrying capacity.
Purpose of the Study:
- To quantitatively analyze CBF control mechanisms during chronic hypoxia using a mathematical model.
- To investigate the roles of local PO2, blood viscosity, and neurogenic input.
- To test the hypothesis that increased brain stem PO2 signals CBF normalization.
Main Methods:
- Developed a mathematical model for O2 and CO2 transport and metabolism in blood and brain.
- Utilized a one-dimensional convection-dispersion model for capillary blood.
- Analyzed three potential CBF control mechanisms: tissue PO2, blood viscosity, and neurogenic input.
Main Results:
- Model simulations quantified the contributions of different control mechanisms over 4 days of hypoxia.
- Simulations showed increased arterial oxygen carrying capacity and decreased local metabolism contribute to normalized CBF.
- Results align with experimental data showing CBF normalization despite persistent cortical hypoxia (elevated HIF-1).
Conclusions:
- Increased brain stem PO2, resulting from enhanced oxygen carrying capacity and reduced metabolism, is the key signal for CBF normalization during chronic hypoxia.
- The study provides quantitative insights into the interplay of physiological factors regulating cerebral blood flow under hypoxic stress.
- Mathematical modeling effectively elucidates complex physiological responses to hypoxia.
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