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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)
Motor stimulation induces a neurovascular response that can be detected by continuous measurement of cerebral blood flow (CBF). Simultaneous changes in arterial blood pressure (ABP) and Pa(CO(2)) have been reported, but their influence on the CBF response has not been quantified. Continuous bilateral recordings of CBF velocity (CBFV), ABP, and end-tidal(More)
Cognitive and/or sensorimotor stimulations of the brain induce increases in cerebral blood flow that are usually associated with increased metabolic demand. We tested the hypothesis that changes in arterial blood pressure (ABP) and arterial Pco(2) also take place during brain activation protocols designed to induce hemispheric lateralization, leading to a(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)
The objective of the study was to test the hypothesis that dynamic cerebral pressure-autoregulation is associated with the outcome of patients with severe head injury and to derive optimal criteria for future studies on the predictive value of autoregulation indices. Repeated measurements were performed on 32 patients with severe head injury. Arterial blood(More)
Dynamic cerebral autoregulation (CA) describes the transient response of cerebral blood flow (CBF) to rapid changes in arterial blood pressure (ABP). We tested the hypothesis that the efficiency of dynamic CA is increased by brain activation paradigms designed to induce hemispheric lateralization. CBF velocity [CBFV; bilateral, middle cerebral artery(More)
Neural activation induces changes in cerebral blood flow velocity (CBFV) with separate contributions from resistance-area product (V(RAP)) and critical closing pressure (V(CrCP)). We modeled the dependence of V(RAP) and V(CrCP) on arterial blood pressure (ABP), end-tidal CO(2) (EtCO(2)), and cognitive stimulation to test the hypothesis that V(RAP) reflects(More)
Abstract PaCO2 affects cerebral blood flow (CBF) and its regulatory mechanisms, but the interaction between neurovascular coupling (NVC), cerebral autoregulation (CA), and cerebrovascular reactivity to CO2 (CVR), in response to hypercapnia, is not known. Recordings of cerebral blood flow velocity (CBFv), blood pressure (BP), heart rate, and end-tidal CO2(More)
This study aimed to compare the response of metabolic-induced cerebral hemodynamic changes measured using transcranial Doppler (TCD) ultrasonography during passive, active and motor imagery paradigms, and associated peripheral hemodynamic responses. Continuous recordings of bilateral cerebral blood flow velocity (CBFv), blood pressure, heart rate and(More)
Cerebral blood flow velocity (CBFv) changes to sensorimotor and cognitive paradigms have been used to assess the integrity of haemodynamic responses, though the reproducibility of these responses has not been properly assessed. Continuous recordings of blood pressure, end-tidal CO(2), heart rate and bilateral CBFv were obtained during 60s of active, passive(More)