Ronney B. Panerai

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Assessment of cerebral autoregulation is an important adjunct to measurement of cerebral blood flow for diagnosis, monitoring or prognosis of cerebrovascular disease. The most common approach tests the effects of changes in mean arterial blood pressure on cerebral blood flow, known as pressure autoregulation. A 'gold standard' for this purpose is not(More)
Short-term regulation of cerebral blood flow (CBF) is controlled by myogenic, metabolic and neurogenic mechanisms, which maintain flow within narrow limits, despite large changes in arterial blood pressure (ABP). Static cerebral autoregulation (CA) represents the steady-state relationship between CBF and ABP, characterized by a plateau of nearly constant(More)
BACKGROUND AND PURPOSE Assessment of cerebral autoregulation has been traditionally performed with static changes in arterial blood pressure. Newer dynamic methods require the induction of sudden drops in arterial blood pressure with the sudden release of bilateral thigh cuffs. An alternative method is proposed, based on the spontaneous variability of(More)
Transcranial Doppler ultrasound (TCD) can measure cerebral blood flow velocity in the main intracranial vessels non-invasively and with high accuracy. Combined with the availability of non-invasive devices for continuous measurement of arterial blood pressure, the relatively low cost, ease-of-use, and excellent temporal resolution of TCD have stimulated the(More)
The contributions of beat-to-beat changes in mean arterial blood pressure (MABP) and breath-by-breath fluctuations in end-tidal CO/sub 2/ (EtCO/sub 2/) as determinants of the spontaneous variability of cerebral blood flow velocity (CBFV) were studied in 16 normal subjects at rest. The two input variables (MABP and EtCO/sub 2/) had significant(More)
Arterial pCO2 is known to influence cerebral autoregulation but its effect on the dynamic relationship between mean arterial blood pressure (ABP) and mean cerebral blood flow velocity (CBFV), obtained from spontaneous fluctuations in ABP, has not been established. In 16 normal subjects, ABP was measured non-invasively (Finapres), CBFV was estimated with(More)
The Valsalva maneuver (VM), a voluntary increase in intrathoracic pressure of approximately 40 mmHg, has been used to examine cerebral autoregulation (CA). During phase IV of the VM there are pronounced changes in mean arterial blood pressure (MABP), pulse interval, and cerebral blood flow (CBF), but the changes in CBF are of a much greater magnitude than(More)
BACKGROUND AND PURPOSE The baroreceptor reflex arc is important in the short-term regulation of the cardiovascular system, and small studies have reported impaired cardiac baroreceptor sensitivity (BRS) after acute stroke. However, the prognostic significance of impaired BRS is uncertain. METHODS One hundred twenty-four patients underwent simultaneous ECG(More)
The cerebral circulation shows both structural and functional complexity. For time scales of a few minutes or more, cerebral blood flow (CBF) and other cerebrovascular parameters can be shown to follow a random fractal point process. Some studies, but not all, have also concluded that CBF is non-stationary. System identification techniques have been able to(More)
The passive relationship between arterial blood pressure (ABP) and cerebral blood flow velocity (CBFV) has been expressed by a single parameter [cerebrovascular resistance (CVR)] or, alternatively, by a two-parameter model, comprising a resistance element [resistance-area product (RAP)] and a critical closing pressure (CrCP). We tested the hypothesis that(More)