Cerebrovascular regulatory capacity is essential for maintaining brain stability. Most previous studies have focused on middle-aged and elderly populations, where regulation depends on vasodilation with reduced resistance and elevated blood pressure—the pressure-dependent mechanism. Whether this paradigm applies to younger individuals remains unclear. Given the rising prevalence of cardiovascular and cerebrovascular risks in young adults, elucidating youth-specific mechanisms is of great importance. In this study, standardized breath-holding was used to induce hypercapnia in 52 young volunteers (23.67 ± 1.77 years). Hemodynamic parameters of both middle cerebral arteries (blood pressure, heart rate, and flow velocity) were measured at rest and during hypercapnia. The breath-holding index (BHI), reflecting cerebrovascular regulatory capacity, was calculated, and a hemodynamic model was applied to derive resistance variation coefficient (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">$R_{v}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>R</mi> <mi>v</mi> </msub> </math></EquationSource> </InlineEquation>), diameter variation coefficient (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$D_{v}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>D</mi> <mi>v</mi> </msub> </math></EquationSource> </InlineEquation>), and compliance (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$C$</EquationSource> <EquationSource Format="MATHML"><math> <mi>C</mi> </math></EquationSource> </InlineEquation>), forming a multiparametric framework. In total, 104 unilateral datasets underwent multilevel statistical analysis. Two regulatory patterns were identified: pressure-dependent (n = 72) and pressure-independent (n = 32). The pressure-independent group showed greater dilation (<InlineEquation ID="IEq4"> <EquationSource Format="TEX">$D_{v}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>D</mi> <mi>v</mi> </msub> </math></EquationSource> </InlineEquation>: 1.4222 vs. 1.2817, p < 0.05) and more stable blood pressure (1.4271 vs. 5.3937 mmHg, p < 0.05), achieving comparable cerebrovascular regulatory capacity (<InlineEquation ID="IEq5"> <EquationSource Format="TEX">${\text{BHI}}$</EquationSource> <EquationSource Format="MATHML"><math> <mtext>BHI</mtext> </math></EquationSource> </InlineEquation>: 1.3327 vs. 1.3907, p > 0.05) via enhanced compliance. Strong correlations were observed between rest and task states for blood pressure, heart rate, and flow velocity (all r > 0.85, p < 0.001). The proposed pressure-independent mechanism challenges the conventional paradigm, highlights individual variability, and offers new insights into cerebrovascular regulatory capacity under hypercapnia.

Compliance-mediated pressure-independent cerebrovascular regulation: a distinct novel mechanism in youth

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2026年3月22日

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Zijie Wang,
Youjun Liu,
Hao Sun,
Tengfei Li,
Liyuan Zhang,
Guangfei Li,
Binxu Yang,
Yanjun Gong,
Bao Li

摘要

Cerebrovascular regulatory capacity is essential for maintaining brain stability. Most previous studies have focused on middle-aged and elderly populations, where regulation depends on vasodilation with reduced resistance and elevated blood pressure—the pressure-dependent mechanism. Whether this paradigm applies to younger individuals remains unclear. Given the rising prevalence of cardiovascular and cerebrovascular risks in young adults, elucidating youth-specific mechanisms is of great importance. In this study, standardized breath-holding was used to induce hypercapnia in 52 young volunteers (23.67 ± 1.77 years). Hemodynamic parameters of both middle cerebral arteries (blood pressure, heart rate, and flow velocity) were measured at rest and during hypercapnia. The breath-holding index (BHI), reflecting cerebrovascular regulatory capacity, was calculated, and a hemodynamic model was applied to derive resistance variation coefficient ( $R_{v}$ $R_{v}$ ), diameter variation coefficient ( $D_{v}$ $D_{v}$ ), and compliance ( $C$ $C$ ), forming a multiparametric framework. In total, 104 unilateral datasets underwent multilevel statistical analysis. Two regulatory patterns were identified: pressure-dependent (n = 72) and pressure-independent (n = 32). The pressure-independent group showed greater dilation ( $D_{v}$ $D_{v}$ : 1.4222 vs. 1.2817, p < 0.05) and more stable blood pressure (1.4271 vs. 5.3937 mmHg, p < 0.05), achieving comparable cerebrovascular regulatory capacity ( ${\text{BHI}}$ $BHI$ : 1.3327 vs. 1.3907, p > 0.05) via enhanced compliance. Strong correlations were observed between rest and task states for blood pressure, heart rate, and flow velocity (all r > 0.85, p < 0.001). The proposed pressure-independent mechanism challenges the conventional paradigm, highlights individual variability, and offers new insights into cerebrovascular regulatory capacity under hypercapnia.