Relationship Between Cerebral Pulsatility Index and Vasodilatory Responsiveness to a Hypercapnic Challenge

Authors

Hannah E. Nagib, The University of Texas at ArlingtonFollow
John Kolade, University of Texas at ArlingtonFollow
James E. Brown, University of Texas at ArlingtonFollow
Sajjad S. Moradi, University of Texas at ArlingtonFollow
R Matthew Brothers, University of Texas at ArlingtonFollow

Abstract

Cerebral vascular function/health is critical for the precise matching of cerebral blood flow and thus oxygen/substrate delivery and the metabolic demands of the brain. Cerebral pulsatility index (PI) reflects cerebral vascular resistance and compliance, and therefore provides a measure of cerebral vascular stiffness. A higher PI indicates augmented stiffness and is associated with risk for/prevalence of advanced atherosclerosis and poor cerebral vascular autoregulation, both of which can predispose individuals to various detrimental conditions including stroke and reduced neurocognitive function. Cerebral vascular function/health is also often assessed by the vasodilatory response to a hypercapnic stimuli with higher responses being associated with better health while reduced responses are associated with poorer health outcomes including increased risk for the aforementioned cerebral vascular and neurocognitive diseases/conditions. However, to our knowledge the relationship between PI and the subsequent vasodilatory response to a hypercapnic stimuli remains unknown. PURPOSE: The purpose of this study was to examine the effects of a hypercapnic challenge on vasodilatory responsiveness and cerebral pulsatility index. METHODS: Data is presented from 69 healthy individuals (50 female. Age: 25±9 yrs; BMI: 25±5 kg/m²). Continuous measures of heart rate, beat-to-beat blood pressure, end-tidal carbon dioxide concentration (PETCO₂), and middle cerebral artery blood velocity (MCAv) were assessed throughout the duration of data collection. Cerebral vascular function was indexed as PI ((MCAV systolic – MCAv diastolic)/MCAv mean) and cerebral vasodilatory responsiveness (% increase in cerebral vascular conductance (CVCi) slope) during 4-min of breathing a 6% carbon dioxide gas mixture (%CVCi/ΔPETCO₂). RESULTS: PI during normocapnia was 0.78±0.16. During the hypercapnic stimuli PETCO₂ was increased by 11±2 mmHg and cerebral vasodilator responsiveness assessed as %CVCi slope was 2.9±1.2 %/mmHg. There was not a significant relationship between PI and %CVCi slope (R²=0.018, p=0.13). CONCLUSION: These preliminary data indicate that cerebral vascular stiffness as indexed by PI does not have a primary effect on cerebral vasodilatory responsiveness to a hypercapnic stimuli.

Recommended Citation

Nagib, Hannah E.; Kolade, John; Brown, James E.; Moradi, Sajjad S.; and Brothers, R Matthew (2025) "Relationship Between Cerebral Pulsatility Index and Vasodilatory Responsiveness to a Hypercapnic Challenge," International Journal of Exercise Science: Conference Proceedings: Vol. 2: Iss. 17, Article 166.
Available at: https://digitalcommons.wku.edu/ijesab/vol2/iss17/166