Predicting cerebral blood flow response to orthostatic stress from resting dynamics: Effects of healthy aging

K. Narayanan, James J. Collins, Jason Hamner, Seiji Mukai, Lewis A. Lipsitz

Research output: Contribution to journalArticle

31 Scopus citations

Abstract

The transfer function relating arterial pressure (AP) to cerebral blood flow velocity (CBFV) during resting conditions has been used to predict the CBFV response to hypotension. We hypothesized that this approach could predict the CBFV response to posture change in elderly individuals if impaired autoregulation allowed changes in AP to be passively transferred to CBFV. AP (Finapres) and CBFV (middle cerebral artery transcranial Doppler) were measured in 10 healthy young (age 24 ± 1 yr) and 10 healthy elderly (age 72 ± 3 yr) subjects during 5 min of quiet sitting and 1 min of active standing while breathing was paced at 0.25 Hz. Transfer functions between AP and CBFV changes during sitting were estimated from each full waveform in both low-frequency (LF; 0.05 - 0.2 Hz) and heartbeat-frequency (HBF; 0.7 - 1.4 Hz) ranges. The impulse-response function was used to compute changes in CBFV during posture change. The LF transfer function did not predict orthostatic changes in CBFV in either group, suggesting normal cerebral autoregulation. In the HBF range, the prediction was high in elderly (R = 0.65 ± 0.23) but not young subjects (R = 0.19 ± 0.35; P < 0.003, young vs. elderly). Thus rapidly acting regulatory mechanisms that reduce the transmission of beat-to-beat changes in AP to CBFV may be engaged during posture change in young but not elderly subjects.

Original languageEnglish (US)
Pages (from-to)R716-R722
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume281
Issue number3 50-3
DOIs
StatePublished - Jan 1 2001

Keywords

  • Autoregulation
  • Hypotension
  • Pulsatility
  • Transfer function
  • Vascular stiffness

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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