Compliance-Mediated Pressure-Independent Cerebrovascular Regulation: A Distinct Novel Mechanism in Youth

Cerebral blood flow (CBF) regulation 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) was calculated, and a hemodynamic model was applied to derive resistance variation (\(\:{R}_{v}\)), diameter variation (\(\:{D}_{v}\)), and compliance (\(\:C\)), 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 (\(\:{D}_{v}\): 1.4222 vs. 1.2817, P < 0.05) and more stable blood pressure (1.4271 vs. 5.3937 mmHg, P < 0.05), achieving comparable CBF regulation (\(\:BHI\): 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 CBF regulation under hypercapnia. These findings have implications for early diagnosis and personalized interventions in cerebrovascular disorders.