Electronic versions

  • Saqib Saleem
    COMSATS Institute of Information Technology, Islamabad
  • Diana Vucina
    Clinical Hospital Center Split
  • Zoe Sarafis
    University of British Columbia
  • Amanda H X Lee
    University of British Columbia
  • Jordan W Squair
    University of Calgary
  • Otto F Barak
    University of Novi Sad
  • Geoff B Coombs
    University of British Columbia, Okanagan
  • Tanja Mijacika
    University of Split School of Medicine
  • Andrei V Krassioukov
    University of British Columbia
  • Philip N Ainslie
    University of British Columbia, Okanagan
  • Zeljko Dujic
    University of Split School of Medicine
  • Yu-Chieh Tzeng
    University of Otago
  • Aaron A Phillips
    University of Calgary

The capacity of the cerebrovasculature to buffer changes in blood pressure (BP) is crucial to prevent stroke, the incidence of which is three- to fourfold elevated after spinal cord injury (SCI). Disruption of descending sympathetic pathways within the spinal cord due to cervical SCI may result in impaired cerebrovascular buffering. Only linear analyses of cerebrovascular buffering of BP, such as transfer function, have been used in SCI research. This approach does not account for inherent nonlinearity and nonstationarity components of cerebrovascular regulation, often depends on perturbations of BP to increase the statistical power, and does not account for the influence of arterial CO2 tension. Here, we used a nonlinear and nonstationary analysis approach termed wavelet decomposition analysis (WDA), which recently identified novel sympathetic influences on cerebrovascular buffering of BP occurring in the ultra-low-frequency range (ULF; 0.02-0.03Hz). WDA does not require BP perturbations and can account for influences of CO2 tension. Supine resting beat-by-beat BP (Finometer), middle cerebral artery blood velocity (transcranial Doppler), and end-tidal CO2 tension were recorded in cervical SCI ( n = 14) and uninjured ( n = 16) individuals. WDA revealed that cerebral blood flow more closely follows changes in BP in the ULF range ( P = 0.0021, Cohen's d = 0.89), which may be interpreted as an impairment in cerebrovascular buffering of BP. This persisted after accounting for CO2. Transfer function metrics were not different in the ULF range, but phase was reduced at 0.07-0.2 Hz ( P = 0.03, Cohen's d = 0.31). Sympathetically mediated cerebrovascular buffering of BP is impaired after SCI, and WDA is a powerful strategy for evaluating cerebrovascular buffering in clinical populations.

Keywords

  • Adaptation, Physiological, Adult, Arterial Pressure, Blood Flow Velocity, Brachial Artery/physiopathology, Cerebrovascular Circulation, Female, Homeostasis, Humans, Male, Middle Aged, Middle Cerebral Artery/diagnostic imaging, Models, Cardiovascular, Predictive Value of Tests, Spinal Cord Injuries/diagnosis, Sympathetic Nervous System/physiopathology, Ultrasonography, Doppler, Transcranial/methods, Wavelet Analysis
Original languageEnglish
Pages (from-to)H1108-H1114
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume314
Issue number5
DOIs
Publication statusPublished - 1 May 2018
Externally publishedYes
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