1,721,045 research outputs found
Cerebral Blood Flow in Healthy Subjects with Different Hypnotizability Scores
No full textHypnotizability is a cognitive trait associated with differences in the brachial artery flow-mediated dilatation of individuals with high hypnotizability (highs) and low hypnotizability scores (lows). The study investigated possible hypnotizability-related cerebrovascular differences. Among 24 healthy volunteers, the Stanford Hypnotic Susceptibility Scale Form A identified 13 medium-to-lows (med-lows), 11 medium-to-highs (med-highs), and 1 medium hypnotizable. Hypnotizability did not influence the significant changes produced by the trail making task (TMT), mental arithmetic task (MAT), hyperventilation (HVT), and rebreathing (RBT) on heart rate (HR), arterial blood pressure (ABP), and partial pressure of end-tidal CO2 (PET CO2), but moderated the correlations between the changes occurring during tasks with respect to basal conditions (∆) in ABP and PET CO2 with middle cerebral artery flow velocity (MCAv). In HVT, med-lows exhibited a significant correlation between ∆MCAv and ∆PET CO2, and med-highs showed a significant correlation between ∆ABP and ∆MCAv. Cerebrovascular reactivity (CVR) and conductance (∆CVCi) were significantly correlated with ∆MCAv only in med-lows during HVT and RBT. For the first time, cerebrovascular reactivity related to hypnotizability was investigated, evidencing different correlations among hemodynamic variables in med-highs and med-lows
Il controllo fisiologico della circolazione cerebrale e possibile ruolo esercitato dal sistema ortosimpatico
No full textMulti-directional Assessment of Respiratory and Cardiac Pulsatility of the Inferior Vena Cava From Ultrasound Imaging in Short Axis
Full text linkThe pulsatility of the inferior vena cava (IVC) reflects the volume status of patients. It can be investigated by ultrasounds (US), offering an important non-invasive tool supporting fluid management. However, the method has limitations attributable to many confounding factors, e.g., related to IVC movements and non-regular shapes. Short- or long-axis views have been used, both having advantages and limitations in counteracting such confounding factors, depending on the specific condition. The aim of this study is to investigate IVC pulsatility in the different directions on the transverse plane and to assess its variability. Moreover, different components of this pulsatility (induced by either respiratory or cardiac activity) are investigated. The method is tested on 10 healthy patients, with large variations across them of IVC section (mean diameters in the range 1 cm to 3 cm), shape and pulsatility (average caval index [CI] ranging from approximately 20% to 70%). The average coefficient of variation of the CI estimated on 10 different directions was 13% (21% and 20% for the respiratory and cardiac components, respectively), with a range that was approximately 50% of the mean CI across different directions (approximately the same for the 2 different components). The minimum and maximum CI were found close to the directions of maximum and minimum IVC diameter, respectively. The investigation of IVC dynamics in the entire cross-section is crucial to obtain a more repeatable and reliable characterization of IVC pulsatility. The calculation of a CI based on the “equivalent” diameter (proportional to the square root of the IVC cross-sectional area) is encouraged
Influence of sympathetic innervation on cerebral microcirculation and on the morphology of its spontaneous oscillations: possible functional implications
No full textEffect of sympathetic activation on the morphology of cerebral blood flow spontaneous fluctuations: possible functional implications
No full textA further study on the sympathetically-induced reduction of stretch reflexes, in rabbit jaw closing muscles
No full textThe peripheral origin of tap-induced muscle contraction revealed by multi-electrode surface electromyography in human vastus medialis
Full text linkIt is well established that muscle percussion may lead to the excitation of muscle fibres. It is still debated, however, whether the excitation arises directly at the percussion site or reflexively, at the end plates. Here we sampled surface electromyograms (EMGs) from multiple locations along human vastus medialis fibres to address this issue. In five healthy subjects, contractions were elicited by percussing the distal fibre endings at different intensities (5-50 N), and the patellar tendon. EMGs were detected with two 32-electrode arrays, positioned longitudinally and transversally to the percussed fibres, to detect the origin and the propagation of action potentials and their spatial distribution across vastus medialis. During muscle percussion, compound action potentials were first observed at the electrode closest to the tapping site with latency smaller than 5 ms, and spatial extension confined to the percussed strip. Conversely, during tendon tap (and voluntary contractions), action potentials were first detected by electrodes closest to end plates and at a greater latency (mean ± s.d., 28.2 ± 1.7 ms, p < 0.001). No evidence of reflex responses to muscle tap was observed. Multi-electrode surface EMGs allowed for the first time to unequivocally and quantitatively describe the non-reflex nature of the response evoked by a muscle tap
Modeling of surface myoelectric signals, Part II : Model based signal interpretation
No full textIEEE TRANS. ON BIOMEDICAL ENG
Sympathetically-induced changes in the spindle affrent response to vibratory stimuli eliciting the TVR, in the rabbit jaw closing muscles
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