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)
The critical closing pressure (CrCP) of the cerebral circulation indicates the value of arterial blood pressure (ABP) at which cerebral blood flow (CBF) approaches zero. Measurements in animals and in humans, have shown that the CrCP is significantly greater than zero. A simple mathematical model, incorporating the effects of arterial elasticity and active(More)
The contributions of beat-to-beat changes in mean arterial blood pressure (MABP) and breath-by-breath fluctuations in end-tidal CO2 (EtCO2) 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 EtCO2) had significant cross-correlations with CBFV but(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 intra- and inter-subject variabilities of the cerebral dynamic autoregulatory index (ARI) were studied in a group of 14 healthy subjects aged 23-51 years. An alternative index, derived from autoregressive-moving average (ARMA) modelling of the arterial blood pressure (ABP)-cerebral blood flow velocity (CBFV) dynamic relationship, named ARMA-ARI, is also(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)
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 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)
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)