No influence of steady-state postural changes on cerebrovascular compliance in humans

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DOI

  • Alicia M Kells
    Western University, Ontario
  • M Erin Moir
    Western University, Ontario
  • Geoff B Coombs
    Western University, Ontario
  • Andrew W D'Souza
    Western University, Ontario
  • Stephen A Klassen
    Western University, Ontario
  • Baraa K Al-Khazraji
    Western University, Ontario
  • J Kevin Shoemaker
    Western University, Ontario

The aim of this study was to determine the effect of posture changes on vascular compliance in intracranial (brain) versus extracranial vascular beds (forearm). Eighteen young adults (nine females) performed a supine-to-seated-to-standing protocol involving 5 min of rest in each position. Continuous blood pressure, middle cerebral artery (MCA) blood velocity, and brachial artery blood velocity were recorded at each posture. Three to five consecutive steady-state cardiac cycles at each posture were analyzed by a four-element lumped parameter modified Windkessel model to calculate vascular compliance. Mean arterial pressure (MAP) increased from supine to seated (76(9) vs. 81(12) mmHg; P = 0.006) and from supine to standing (76(9) vs. 82(13) mmHg; P = 0.034). Mean blood flow was greater in the MCA relative to the forearm (forearm: 40(5) mL·min-1, MCA: 224(17) mL·min-1; main effect P < 0.001). Conversely, vascular resistance (forearm: 3.25(0.50) mmHg-1·mL·min-1, brain: 0.36(0.04) mmHg-1·mL·min-1; main effect P < 0.001) and compliance (forearm: 0.010(0.001) mL·min-1·mmHg-1, brain: 0.005(0.001) mL·min-1·mmHg-1; main effect P = 0.001) were greater in the forearm compared to the brain. Significant main effects of posture were observed with decreasing values in upright positions for mean blood flow (P = 0.001) in both vascular beds, but not for resistance (P = 0.163) or compliance (P = 0.385). There were no significant interaction effects between vascular bed and posture for mean flow (P = 0.057), resistance (P = 0.258), or compliance (P = 0.329). This study provides evidence that under steady-state conditions, posture does not affect cerebrovascular compliance.

Keywords

  • Humans, Female, Male, Cerebrovascular Circulation/physiology, Young Adult, Posture/physiology, Middle Cerebral Artery/physiology, Adult, Vascular Resistance/physiology, Blood Flow Velocity/physiology, Brachial Artery/physiology, Forearm/blood supply, Sitting Position, Supine Position/physiology, Blood Pressure/physiology, Compliance, Standing Position, Arterial Pressure
Original languageEnglish
Pages (from-to)1210-1216
Number of pages7
JournalApplied Physiology, Nutrition, and Metabolism
Volume49
Issue number9
Early online date4 Jul 2024
DOIs
Publication statusPublished - 1 Sept 2024
Externally publishedYes
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