8 research outputs found

    A real-time device for converting Doppler ultrasound audio signals into fluid flow velocity

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    A Doppler signal converter has been developed to facilitate cardiovascular and exercise physiology research. This device directly converts audio signals from a clinical Doppler ultrasound imaging system into a real-time analog signal that accurately represents blood flow velocity and is easily recorded by any standard data acquisition system. This real-time flow velocity signal, when simultaneously recorded with other physiological signals of interest, permits the observation of transient flow response to experimental interventions in a manner not possible when using standard Doppler imaging devices. This converted flow velocity signal also permits a more robust and less subjective analysis of data in a fraction of the time required by previous analytic methods. This signal converter provides this capability inexpensively and requires no modification of either the imaging or data acquisition system

    Blood volume pulse (BVP) derived vagal tone (VT) between 5 and 7 years of age: A methodological investigation of measurement and longitudinal stability

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    The present study evaluated the possibility of collecting cardiac vagal tone data using a photoplethysmograph, and its stability and continuity in a longitudinal sample of early-school aged children. A method for the optical (i.e., blood volume pulse) estimation of heart rate was established in a pilot study. Then the longitudinal stability and continuity in photoplethysmograph-derived vagal tone was assessed in 114 children (56 girls) at three sessions between 5 and 7 years of age. Results indicate that this method possesses substantial measurement reliability and individual stability, as children report low intra-individual variation over time. Children also report a mean decrease in vagal tone from 5 to 7 years of age, consistent with increased attentional capacity. Overall, this suggests blood volume pulse estimation of vagal tone is both accurate and appropriate for naturalistic developmental research
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