Effect of dynamic cerebral autoregulation of cerebral blood flow regulation during cold pressor test.

The cold pressor test (CPT) is a clinical stress test commonly used to evoke acute pressor and respiratory responses, accompanied by increased sympathetic nerve activity. Cerebral blood flow (CBF) is well-preserved during CPT despite elevated arterial blood pressure (ABP), but the underlying mechanisms remain unclear. We hypothesized that dynamic cerebral autoregulation (dCA) contributes to this CBF preservation, preventing overperfusion under stress-induced hypertension. Thirty-seven healthy volunteers performed CPT for 3 min, while ABP, middle cerebral artery mean velocity (MCA Vmean), and end-tidal carbon dioxide partial pressure (PETCO2) were measured. CPT significantly increased ABP (p < 0.001) and decreased PETCO2 (p = 0.032), whereas MCA Vmean remained unchanged (p = 0.976), resulting in a significant decrease in cerebrovascular conductance index (CVCi) (p < 0.001). The CPT-induced relative change in CVCi was significantly associated with the low-frequency (LF) phase (p < 0.001). Notably, the CPT-induced decrease in PETCO2 was significantly associated with the decreases in MCA Vmean (p < 0.001) and in %CVCi (p = 0.009). These findings suggest that dynamic cerebral autoregulation, as well as the respiratory response (change in PETCO2), plays a key role in maintaining CBF during CPT-induced elevations in ABP. Furthermore, individual differences in dCA and respiratory responses may account for variability in cerebrovascular responses to acute pressor stimuli.