Large-scale ensemble averaging of ambulatory impedance cardiograms.
Impedance cardiography has been used increasingly to measure human physiological responses to emotional and mentally engaging stimuli. The validity of large-scale ensemble averaging of ambulatory impedance cardiograms was evaluated for preejection period (PEP), interbeat interval, and dZ/dt(min) amplitude. We tested whether the average of "classical" 60-sec ensemble averages across periods with fixed activity, posture, physical load, social situation, and location could be accurately estimated from a single large-scale ensemble average spanning these entire periods. Impedance and electrocardiograms were recorded for about 24-h from 21 subjects. Recordings were scored by seven raters, using both methods for each subject. Good agreement (average intraclass correlation coefficient was .91) between both ensemble averaging methods was found for all three cardiac function measures. The results indicate that for unambiguous ambulatory impedance cardiograms, large-scale ensemble averaging is valid, which makes measuring prolonged changes in cardiac sympathetic activity by measuring ambulatory PEP feasible even in large epidemiological samples.
Riese
Harriëtte
H
Department of Biological Psychology, Vrije Universiteit, Amsterdam, The Netherlands. h.riese@psy.vu.nl
Groot
Paul F C
PF
van den Berg
Mireille
M
Kupper
Nina H M
NH
Magnee
Ellis H B
EH
Rohaan
Ellen J
EJ
Vrijkotte
Tanja G M
TG
Willemsen
Gonneke
G
de Geus
Eco J C
EJ
D000204:Activity Cycles / Q000502:physiology*; D000328:Adult; D000704:Analysis of Variance; D002307:Cardiography, Impedance / Q000295:instrumentation / Q000379:methods*; D015716:Electrocardiography, Ambulatory / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D015588:Observer Variation; D012016:Reference Values; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D012890:Sleep / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology*