Segregated signal averaging of sympathetic baroreflex responses in humans.
The goal of this study was to merge the methods currently used to assess beat-by-beat changes in muscle sympathetic nerve activity with a signal-averaging approach and overcome the inherent subjectivity and time-consuming nature of manual analysis of baroreflex-mediated sympathetic responses in humans. This is a retrospective study using data obtained during two prior studies [J. R. Halliwill, J. A. Taylor, and D. L. Eckberg. J. Physiol. (Lond.) 495: 279-288, 1996; C. T. Minson, J. R. Halliwill, T. Young, and M. J. Joyner. FASEB J. 13: A1044, 1999]. Beat-by-beat arterial pressure (Finapres device) and muscle sympathetic nerve activity (microneurography) were recorded in seven healthy, nonsmoking, normotensive subjects (2 men, 5 women) between the ages of 23 and 32 yr during arterial pressure changes induced by bolus injections of nitroprusside and phenylephrine. The muscle sympathetic nerve activity-diastolic pressure relationship was analyzed by both the traditional manual detection method and a novel segregated signal-averaging method. The results show the two analysis approaches are highly correlated across subjects (r = 0.914, P < 0. 05) and are in close agreement [slope for manual detection -6.17 +/- 0.91 (SE) vs. slope for segregated signal averaging -5.98 +/- 0.83 total integrated activity. beat(-1). mmHg(-1); P = 0.60]. However, a considerable time savings is seen with the new method (min vs. h). Segregated signal averaging as developed here provides a valid alternative to "by-hand" analysis of beat-by-beat changes in muscle sympathetic nerve activity that occur during dynamic baroreflex-mediated changes in sympathetic outflow. This approach provides an objective, rapid method to analyze nerve recordings.
Halliwill
J R
JR
Department of Anesthesiology, Mayo Clinic and Foundation, Rochester, Minnesota 55905, USA. halliwill.john@mayo.edu
D000328:Adult; D017704:Baroreflex / Q000502:physiology*; D001794:Blood Pressure / Q000502:physiology; D003971:Diastole; D004562:Electrocardiography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D012189:Retrospective Studies; D012815:Signal Processing, Computer-Assisted; D013223:Statistics as Topic; D013564:Sympathetic Nervous System / Q000502:physiology*