Dynamic cerebral autoregulation during repeated squat-stand maneuvers

Jurgen A H R Claassen, Benjamin D. Levine, Rong Zhang

Research output: Contribution to journalArticlepeer-review

113 Scopus citations

Abstract

Transfer function analysis of spontaneous oscillations in blood pressure (BP) and cerebral blood flow (CBF) can quantify the dynamic relationship between BP and CBF. However, such oscillation amplitudes are often small and of questionable clinical significance, vary substantially, and cannot be controlled. At the very low frequencies (<0.07 Hz), coherence between BP and CBF often is low (<0.50) and their causal relationship is debated. Eight healthy subjects performed repeated squat-stand maneuvers to induce large oscillations in BP at frequencies of 0.025 and 0.05 Hz (very low frequency) and 0.1 Hz (low frequency), respectively. BP (Finapres), CBF velocity (CBFV; transcranial Dopp-ler), and end-tidal CO 2 (capnography) were monitored. Spectral analysis was used to quantify oscillations in BP and CBFV and to estimate transfer function phase, gain, and coherence. Compared with spontaneous oscillations, induced oscillations had higher coherence [mean 0.8 (SD 0.11); >0.5 in all subjects at all frequencies] and lower variability in phase estimates. However, gain estimates remained unchanged. Under both conditions, the "high-pass filter" characteristics of dynamic autoregulation were observed. In conclusion, using repeated squat-stand maneuvers, we were able to study dynamic cerebral autoregulation in the low frequencies under conditions of hemodynamically strong and causally related oscillations in BP and CBFV. This not only enhances the confidence of transfer function analysis as indicated by high coherence and improved phase estimation but also strengthens the clinical relevance of this method as induced oscillations in BP and CBFV mimic those associated with postural changes in daily life.

Original languageEnglish (US)
Pages (from-to)153-160
Number of pages8
JournalJournal of applied physiology
Volume106
Issue number1
DOIs
StatePublished - Jan 2009

Keywords

  • Blood pressure
  • Cerebral blood flow
  • Transcranial doppler ultrasonography
  • Transfer function analysis

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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