Search results for "heartbeat"
showing 9 items of 39 documents
Optical multichannel monitoring of skin blood pulsations for cardiovascular assessment
2004
Time resolved detection and analysis of the skin back-scattered optical signals (reflection photoplethysmography or PPG) provide rich information on skin blood volume pulsations and can serve for cardiovascular assessment. The multichannel PPG concept has been developed and clinically verified in this work. Simultaneous data flow from several body locations allows to study the heartbeat pulse wave propagation in real time and to evaluate the vascular resistance. Portable two- and four-channel PPG monitoring devices and special software have been designed for real-time data acquisition and processing. The multi-channel devices were successfully applied for cardiovascular fitness tests and fo…
Recognition of Cardiac Arrhythmia by Means of Beat Clustering on ECG-Holter Recordings
2012
The follow-up of some cardiac diseases may be achieved by ECG-holter record analysis. A heartbeat clustering method can be used to reduce the usually high computational cost of such Holter analysis. This study describes a method aimed at cardiac arrhythmia recognition based on this approach, by means of unsupervised inspection of morphologically similar heartbeat groups. Singular Value Decomposition (SVD) is used as the feature selection method since the complexity increases exponentially with the number of features. A modification of the k-means algorithm was developed for centroid computation, taking into account heartbeat length changes. Experimental set consisted of ECG records from the…
Determination of Death in Execution by Lethal Injection in China.
2018
Abstract:Since 1997, execution in China has been increasingly performed by lethal injection. The current criteria for determination of death for execution by lethal injection (cessation of heartbeat, cessation of respiration, and dilated pupils) neither conform to current medical science nor to any standard of medical ethics. In practice, death is pronounced in China within tens of seconds after starting the lethal injection. At this stage, however, neither the common criteria for cardiopulmonary death (irreversible cessation of heartbeat and breathing) nor that of brain death (irreversible cessation of brain functions) have been met. To declare a still-living person dead is incompatible wi…
Distinctive body perception mechanisms in high versus low symptom reporters: A neurophysiological model for medically-unexplained symptoms.
2020
Abstract Objective The neurophysiological processes involved in the generation of medically-unexplained symptoms (MUS) remain unclear. This study tested three assumptions of the perception-filter model contributing to MUS: (I.) increased bodily signal strength (II.) decreased filter function, (III.) increased perception. Methods In this cross-sectional, observational study, trait MUS were assessed by a web-based survey (N = 486). The upper and lower decile were identified as extreme groups of high (HSR; n = 29; 26 women; Mage = 26.0 years) and low symptom reporters (LSR; n = 29; 21 women; Mage = 28.4 years). Mean heart rate (HR) and heart rate variability (HRV), and cortisol awakening respo…
Dual channel photoplethysmography studies of cardio-vascular response to the body position changes
2005
The dual-channel photoplethysmography studies of physiological responses during 3-stage orthostatic test were performed. Clear differences in heartbeat rate, pulse wave transit time and blood pressure variations of healthy volunteers and diabetic patients have been observed.
Metodi Chemiometrici per la sintesi razionale di Nanowires di ZnO per l'elettronica su Circuiti
2019
I nanowires di ZnO (ZnO NWs) rappresentano uno dei materiali 1D di maggiore interesse per lo sviluppo di sensori e/o trasduttori, date le loro ot time proprietà piezoelettriche e semiconduttive1 . Tuttavia, la sintesi chimica di ZnO NWs ad alto “aspect ratio” da soluzione acquosa a basse temperature stemi elettronici completi. Recentemente abbiamo sviluppato2 un metodo per il controllo razionale della sintesi di nanowires di ZnO (Figura 1) su supporti conduttivi in rame per la realizzazione di nanotrasduttori...
Behavioral Inhibition Underlies the Link Between Interoceptive Sensitivity and Anxiety-Related Temperamental Traits
2017
Interoceptive sensitivity is a biologically determined, constitutional trait of an individual. High interoceptive sensitivity has been often associated with proneness to anxiety. This association has been explained by elevated autonomic responsiveness in anxious individuals. However, in a heartbeat discrimination task (discrimination of heartbeats’ simultaneity to an external stimulus) low cardiac responsiveness has accompanied enhanced performance. The relation between these factors seems task dependent, and cannot comprehensively explain the link between interoceptive sensitivity and anxiety. We explored for additional explanatory factors for this link. More specifically, we studied which…
Cardiac cycle and respiration phase affect responses to the conditioned stimulus in young adults trained in trace eyeblink conditioning
2022
Rhythms of breathing and heartbeat are linked to each other as well as to rhythms of the brain. Our recent studies suggest that presenting the conditioned stimulus during expiration or during the diastolic phase of the cardiac cycle facilitates neural processing of that stimulus and improves learning an eyeblink classical conditioning task. To date, it has not been examined whether utilizing information from both respiration and cardiac cycle phases simultaneously allows even more efficient modulation of learning. Here we studied whether the timing of the conditioned stimulus to different cardiorespiratory rhythm phase combinations affects learning trace eyeblink conditioning in healthy you…
CA3–CA1 long‐term potentiation occurs regardless of respiration and cardiac cycle phases in urethane‐anesthetized rats
2023
Breathing and heartbeat synchronize to each other and to brain function and affect cognition in humans. However, it is not clear how cardiorespiratory rhythms modulate such basic processes as synaptic plasticity thought to underlie learning. Thus, we studied if respiration and cardiac cycle phases at burst stimulation onset affect hippocampal long-term potentiation (LTP) in the CA3–CA1 synapse in urethane-anesthetized adult male Sprague–Dawley rats. In a between-subjects design, we timed burst stimulation of the ventral hippocampal commissure (vHC) to systole or diastole either during expiration or inspiration and recorded responses throughout the hippocampus with a linear probe. As classic…