Dynamic Pressure–Flow Velocity Relationships in the Human Cerebral Circulation
| Autor: | William H. Gild, Gust H. Bardy, David W. Newell, Stephanie R. Lash, Rune Aaslid |
|---|---|
| Rok vydání: | 2003 |
| Předmět: |
Adult
Male Middle Cerebral Artery medicine.medical_specialty Ultrasonography Doppler Transcranial Electric Countershock Hemodynamics Blood Pressure Hyperemia Diastole Heart Rate medicine.artery Internal medicine Humans Medicine Radial artery Aged Advanced and Specialized Nursing Fibrillation Fourier Analysis Cardiac cycle business.industry Brain Reproducibility of Results Middle Aged Critical closing pressure Transcranial Doppler Forearm Blood pressure Flow velocity Cerebrovascular Circulation Anesthesia Radial Artery Ventricular Fibrillation Linear Models Cardiology Female Neurology (clinical) medicine.symptom Cardiology and Cardiovascular Medicine business Blood Flow Velocity |
| Zdroj: | Stroke. 34:1645-1649 |
| ISSN: | 1524-4628 0039-2499 |
| DOI: | 10.1161/01.str.0000077927.63758.b6 |
| Popis: | Background and Purpose— The pressure–flow velocity relationship in the cerebral circulation is characterized by the critical closing pressure (CCP), which is the pressure at which flow ceases, and the linear slope of a plot between pressure and flow velocity. It has been suggested, but not validated, that CCP can be determined from arterial blood pressure (ABP) and transcranial Doppler (TCD) recordings during the cardiac cycle. We studied a group of patients in whom ventricular fibrillation (VF) was induced. The time interval before defibrillation enabled calculation of CCP from data in which flow approached zero. These estimates were compared with values calculated before and after fibrillation and during regular heartbeats. Methods— TCD velocities and ABP in the radial artery were recorded before, during, and after 28 episodes of VF in 13 patients. CCPs were calculated by 3 different methods: (1) linear extrapolation from data during VF (gold standard); (2) linear extrapolation from normal heartbeat data; and (3) first harmonic Fourier filtering of normal heartbeat data. Results— The CCP during VF calculated from long diastoles was 32.9±11 mm Hg (mean±SD). The regular heartbeat estimate was 6.0±4.3 mm Hg lower ( P P =NS) lower than during VF. During hyperemia after defibrillation, the CCP decreased by 13.3 mm Hg, while velocity increased by 63%. The decrease in CCP could explain half of the increase in flow velocity during hyperemia. Conclusions— CCP can be accurately estimated from regular heartbeat data and is an important factor in regulation of the cerebral circulation. |
| Databáze: | OpenAIRE |
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