Impulse response analysis of baroreceptor sensitivity .
Panerai, Ronney B., Martin A. James, and John F. Potter.
Division of Medical Physics, Faculty of Medicine, University of
Leicester, Leicester Royal Infirmary, Leicester LE1 5WW, and Division
of Medicine for the Elderly, Faculty of Medicine, University of
Leicester, Glenfield Hospital, Leicester LE3 9QP, UK
APStracts 3:0549H, 1996.
The impulse response function (IRF) can express the dynamic
relationship between systolic arterial pressure (SAP) and pulse
interval (PI) and, consequently, represents an alternative method to
assess baroreceptor sensitivity (BRS) in humans. Five normotensive
and 13 hypertensive subjects (age 68 +/- 5 years, range 60-74) were
studied at rest in the supine position during baseline conditions and
following injections of phenylephrine and sodium nitroprusside. SAP
and PI signals were derived from multiple 5 min. noninvasive
recordings of arterial blood pressure (Finapres) and the ECG.
Standard estimates of BRS were obtained by the slopes of transient
changes in SAP and PI following the injection of phenylephrineand
nitroprusside (BRSPE and BRSSNP) and by spectral analysis ([alpha]
index). Impulse responses were obtained by the inverse Fourier
transform of the transfer function between PI and SAP. The temporal
pattern of the IRF was characterized by a main peak at t = 0,
preceded by a 'trough' at t = -1 s. A mathematical model of the
baroreflex suggests that the peak value of IRF is linearly related to
the BRS. The peak value and its smoothed version were shown to be
significantly correlated to [alpha], BRSPE and BRSSNP and
significantly reduced in the hypertensive group during the three
stages of the protocol. We suggest that IRF might be the ideal method
to assess BRS because it does not require any subjective pre
-selection of data segments or spectral bands.
Received 20 May 1996; accepted in final form 3 December 1996.
APS Manuscript Number H456-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996