Fundamental relationships between blood pressure and cerebral blood flow in humans
| Autor: | Gregory S. H. Chan, Braid A. MacRae, Philip N. Ainslie, Yu-Chieh Tzeng |
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| Rok vydání: | 2014 |
| Předmět: |
Male
Middle Cerebral Artery Blood velocity Ultrasonography Doppler Transcranial Physiology Hemodynamics Blood Pressure Cerebral autoregulation Hypercapnia Young Adult Physiology (medical) medicine.artery Homeostasis Humans Medicine business.industry Compliance (physiology) Blood pressure Cerebral blood flow Cerebrovascular Circulation Anesthesia Middle cerebral artery Female medicine.symptom business Blood Flow Velocity |
| Zdroj: | Journal of Applied Physiology. 117:1037-1048 |
| ISSN: | 1522-1601 8750-7587 |
| DOI: | 10.1152/japplphysiol.00366.2014 |
| Popis: | Cerebral blood flow responses to transient blood pressure challenges are frequently attributed to cerebral autoregulation (CA), yet accumulating evidence indicates vascular properties like compliance are also influential. We hypothesized that middle cerebral blood velocity (MCAv) dynamics during or following a transient blood pressure perturbation can be accurately explained by the windkessel mechanism. Eighteen volunteers underwent blood pressure manipulations, including bilateral thigh-cuff deflation and sit-to-stand maneuvers under normocapnic and hypercapnic (5% CO2) conditions. Pressure-flow recordings were analyzed using a windkessel analysis approach that partitions the frequency-dependent resistance and compliance contributions to MCAv dynamics. The windkessel was typically able to explain more than 50% of the MCAv variance, as indicated by R2 values for both the flow recovery and postrecovery phase. The most consistent predictors of MCAv dynamics under the control condition were the windkessel capacitive gain and high-frequency resistive gain. However, there were significant interindividual variations in the composition of windkessel predictors. Hypercapnia consistently reduced the capacitive gain and enhanced the low-frequency (0.04–0.20 Hz) resistive gain for both thigh-cuff deflation and sit-to-stand trials. These findings indicate that 1) MCAv dynamics during acute transient hypotension challenges are dominated by cerebrovascular windkessel properties independent of CA; 2) there is significant heterogeneity in windkessel properties between individuals; and 3) hemodynamic effects of hypercapnia during transient blood pressure challenges primarily reflect changes in windkessel properties rather than pure CA impairment. |
| Databáze: | OpenAIRE |
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