Comparison of Impedance Cardiographic Measurements using Band and Spot Electrodes
University of North Carolina, Chapel Hill 27599. Psychophysiology
(Impact Factor: 2.99).
12/1992; 29(6):734-41. DOI: 10.1111/j.1469-8986.1992.tb02051.x
The comprehensive assessment of cardiac function using impedance cardiography has led to increasingly widespread use of the technique in psychophysiology. Disposable adhesive band electrodes have been the most widely used electrode type, but spot electrode configurations present attractive alternatives in terms of convenience and subject comfort. The present study was designed to evaluate whether one such spot electrode configuration yielded the same information as the more standard band electrodes for cardiac output and systolic time interval measurement. Male and female healthy adult subjects (N = 20) were tested. Comparisons between spot and band electrodes were made for the absolute magnitude of cardiac output and systolic time intervals, as well as for responses to the highly reproducible effects of bicycle exercise. Consistent with previous findings, systolic time interval measurements were unaffected by electrode type. However, for cardiac output measurements, differences between spot and band electrode measurements were found. Under resting conditions, the absolute magnitudes of cardiac output values measured using spot electrodes were smaller than for band electrodes. Subtle, yet significant differences were also found for cardiac output responses to exercise, with spot electrodes indicating greater increases in cardiac output than band electrodes. At the same time, anticipated gender differences found for cardiac output at rest and in response to exercise were unaffected by electrode type. Overall, these findings suggest that when comparing the results of studies that have utilized different impedance electrode types, it would be prudent to remain alert to the possibility of confounding influences.
Available from: David Amaral
- "Electrode sites on the animals were shaved with a battery-operated clipper, cleaned with gauze soaked in 70% ethanol, and allowed to air dry. Cardiac impedance electrodes were attached in a configuration identical to that used in humans  (placement on the notch of the clavicle and xyphoid process on the animal's front side, and ∼3 cm above and below the front electrodes on the back surface). ECG electrodes were attached in a modified lead II configuration. "
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ABSTRACT: Autonomic nervous system activity is an important component of affective experience. We demonstrate in the rhesus monkey that both the sympathetic and parasympathetic branches of the autonomic nervous system respond differentially to the affective valence of passively viewed video stimuli. We recorded cardiac impedance and an electrocardiogram while adult macaques watched a series of 300 30-second videos that varied in their affective content. We found that sympathetic activity (as measured by cardiac pre-ejection period) increased and parasympathetic activity (as measured by respiratory sinus arrhythmia) decreased as video content changes from positive to negative. These findings parallel the relationship between autonomic nervous system responsivity and valence of stimuli in humans. Given the relationship between human cardiac physiology and affective processing, these findings suggest that macaque cardiac physiology may be an index of affect in nonverbal animals.
Available from: Ruth Elaine Graves
- "valid and reliable (Sherwood et al., 1992). All other guidelines for impedance cardiography were followed per the committee report of the Society for Psychophysiological Research (Sherwood et al., 1990). "
Available from: Heath Demaree
- "Because dual electrodes were used, the upper-and lower-current electrodes were placed 41 mm above and below the voltage electrodes, respectively . The use of spot electrodes have been validated for the measurement of time-intervals derived from impedance cardiography, such as PEP (Sherwood et al., 1992). Signals were transduced using Biopac EL500 dual electrodes and amplified by Biopac EBI100C amplifiers set for a gain of 20 and using a low-pass filter of 100 Hz. "
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ABSTRACT: Relative to watching in a natural manner, people asked to suppress or exaggerate their facial response to a negative emotional stimulus experience greater activation of the sympathetic nervous system but report a similar subjective emotional experience. The present research extends prior research on response modulation in two important ways. First, discrete indicators of cardiac vagal and sympathetic control (respiratory sinus arrhythmia (RSA) and pre-ejection period (PEP), respectively) were included as dependent measures along with interbeat interval (IBI) and skin conductance (EDR). Second, to help generalize results across response-focused modulation techniques, participants suppressed, exaggerated, or exerted no control over their responses while watching a disgust-eliciting film (for control purposes, a fourth group was asked to watch a neutral film naturally). Response modulation was associated with significantly decreased PEP (increased cardiac sympathetic control) relative to those in the natural-watch conditions. All participants evidenced increased EDR while watching the disgusting clip, but facial modulation did not produce EDR reactivity beyond that of watching the disgusting film naturally. Exaggerators experienced decreased IBI during modulation (perhaps due to increased muscle contraction) whereas all other groups showed increased IBI (i.e., the orienting response). Neither emotional experience nor facial modulation reliably impacted RSA, respiration rate, or inspiratory depth.
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