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Differential Systolic and Diastolic Regulation of the Cerebral Pressure-Flow Relationship During Squat-Stand Manoeuvres

  • Jonathan D. Smirl
  • Alexander D. Wright
  • Philip N. Ainslie
  • Yu-Chieh Tzeng
  • Paul van Donkelaar
Conference paper
Part of the Acta Neurochirurgica Supplement book series (NEUROCHIRURGICA, volume 126)

Abstract

Objective: Cerebral pressure-flow dynamics are typically reported between mean arterial pressure and mean cerebral blood velocity. However, by reporting only mean responses, potential differential regulatory properties associated with systole and diastole may have been overlooked.

Materials and methods: Twenty young adults (16 male, age: 26.7 ± 6.6 years, BMI: 24.9 ± 3.0 kg/m2) were recruited for this study. Middle cerebral artery velocity was indexed via transcranial Doppler. Cerebral pressure-flow dynamics were assessed using transfer function analysis at both 0.05 and 0.10 Hz using squat-stand manoeuvres. This method provides robust and reliable measures for coherence (correlation index), phase (timing buffer) and gain (amplitude buffer) metrics.

Results: There were main effects for both cardiac cycle and frequency for phase and gain metrics (p < 0.001). The systolic phase (mean ± SD) was elevated at 0.05 (1.07 ± 0.51 radians) and 0.10 Hz (0.70 ± 0.46 radians) compared to the diastolic phase (0.05 Hz: 0.59 ± 0.14 radians; 0.10 Hz: 0.33 ± 0.11 radians). Conversely, the systolic normalized gain was reduced (0.05 Hz: 0.49 ± 0.12%/%; 0.10 Hz: 0.66 ± 0.20%/%) compared to the diastolic normalized gain (0.05 Hz: 1.46 ± 0.43%/%; 0.10 Hz: 1.97 ± 0.48%/%).

Conclusions: These findings indicate there are differential systolic and diastolic aspects of the cerebral pressure-flow relationship. The oscillations associated with systole are extensively buffered within the cerebrovasculature, whereas diastolic oscillations are relatively unaltered. This indicates that the brain is adapted to protect itself against large increases in systolic blood pressure, likely as a mechanism to prevent cerebral haemorrhages.

Keywords

Cerebral blood flow Middle cerebral artery Cerebral autoregulation Cardiac cycle Transfer function analysis Blood pressure 

Notes

Conflicts of interest statement

We declare that we have no conflict of interest.

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Copyright information

© Springer International Publishing AG 2018

Authors and Affiliations

  • Jonathan D. Smirl
    • 1
  • Alexander D. Wright
    • 1
    • 2
    • 3
    • 4
  • Philip N. Ainslie
    • 5
  • Yu-Chieh Tzeng
    • 6
  • Paul van Donkelaar
    • 1
  1. 1.Sports Concussion Research Lab, School of Health and Exercise SciencesUniversity of British ColumbiaKelownaCanada
  2. 2.MD/PhD ProgramUniversity of British ColumbiaVancouverCanada
  3. 3.Southern Medical ProgramUniversity of British ColumbiaKelownaCanada
  4. 4.Experimental Medicine ProgramUniversity of British ColumbiaVancouverCanada
  5. 5.Centre for Heart, Lung and Vascular Health, School of Health and Exercise SciencesUniversity of British ColumbiaKelownaCanada
  6. 6.Cardiovascular Systems Laboratory, Centre for Translational PhysiologyUniversity of OtagoWellingtonNew Zealand

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