This study investigates the dynamics of cerebral autoregulation in 10 healthy volunteers under normocapnia, hypocapnia, and hypercapnia. Cerebral blood flow (CBF) was measured using transcranial Doppler, while arterial blood pressure (ABP) was monitored with a servo-cuff method. The results showed that CBF returned to pretest levels rapidly in hypocapnia (4.1 seconds), but more slowly in normocapnia and hypercapnia. The rate of regulation (RoR), defined as the normalized change in cerebrovascular resistance per second, was 0.38, 0.20, and 0.11/sec in hypocapnia, normocapnia, and hypercapnia, respectively. There was a strong inverse correlation between RoR and PaCO₂, indicating that cerebral autoregulation is significantly influenced by vascular tone. Cerebral autoregulation is a homeostatic mechanism that maintains CBF despite changes in cerebral perfusion pressure (CPP). It is controlled by cerebrovascular resistance (CVR) and is most effective within a CPP range of 50–170 mm Hg. The study highlights the importance of measuring autoregulatory responses with high time resolution, as previous methods have limited this capability. Recent advancements allow noninvasive measurement of autoregulatory responses, which is crucial for understanding and managing patients with cerebral vascular disease. The study found that autoregulatory responses varied significantly with PaCO₂ levels. In hypocapnia, autoregulation was very rapid, with CBF returning to control levels within 1.9 seconds. In normocapnia, the response was slower, with a half-maximal response at 3.4 seconds. In hypercapnia, the response was delayed, with a half-maximal response at 5.2 seconds. These findings suggest that autoregulation is highly dependent on vascular tone and PaCO₂ levels. The study also demonstrated that the rate of regulation (RoR) was significantly affected by PaCO₂. In hyperventilation (hypocapnia), RoR was higher (0.38/sec) compared to normocapnia (0.20/sec), while in hypercapnia, RoR was lower (0.11/sec). These results indicate that autoregulation is more effective in hypocapnia and less effective in hypercapnia. The study's findings have important clinical implications, as they suggest that autoregulation is significantly influenced by PaCO₂ and vascular tone. This information could be useful in the diagnosis and management of patients with cerebral vascular disease. The study also highlights the importance of noninvasive methods for measuring autoregulatory responses, as they provide valuable insights into cerebral autoregulation without the need for invasive procedures.This study investigates the dynamics of cerebral autoregulation in 10 healthy volunteers under normocapnia, hypocapnia, and hypercapnia. Cerebral blood flow (CBF) was measured using transcranial Doppler, while arterial blood pressure (ABP) was monitored with a servo-cuff method. The results showed that CBF returned to pretest levels rapidly in hypocapnia (4.1 seconds), but more slowly in normocapnia and hypercapnia. The rate of regulation (RoR), defined as the normalized change in cerebrovascular resistance per second, was 0.38, 0.20, and 0.11/sec in hypocapnia, normocapnia, and hypercapnia, respectively. There was a strong inverse correlation between RoR and PaCO₂, indicating that cerebral autoregulation is significantly influenced by vascular tone. Cerebral autoregulation is a homeostatic mechanism that maintains CBF despite changes in cerebral perfusion pressure (CPP). It is controlled by cerebrovascular resistance (CVR) and is most effective within a CPP range of 50–170 mm Hg. The study highlights the importance of measuring autoregulatory responses with high time resolution, as previous methods have limited this capability. Recent advancements allow noninvasive measurement of autoregulatory responses, which is crucial for understanding and managing patients with cerebral vascular disease. The study found that autoregulatory responses varied significantly with PaCO₂ levels. In hypocapnia, autoregulation was very rapid, with CBF returning to control levels within 1.9 seconds. In normocapnia, the response was slower, with a half-maximal response at 3.4 seconds. In hypercapnia, the response was delayed, with a half-maximal response at 5.2 seconds. These findings suggest that autoregulation is highly dependent on vascular tone and PaCO₂ levels. The study also demonstrated that the rate of regulation (RoR) was significantly affected by PaCO₂. In hyperventilation (hypocapnia), RoR was higher (0.38/sec) compared to normocapnia (0.20/sec), while in hypercapnia, RoR was lower (0.11/sec). These results indicate that autoregulation is more effective in hypocapnia and less effective in hypercapnia. The study's findings have important clinical implications, as they suggest that autoregulation is significantly influenced by PaCO₂ and vascular tone. This information could be useful in the diagnosis and management of patients with cerebral vascular disease. The study also highlights the importance of noninvasive methods for measuring autoregulatory responses, as they provide valuable insights into cerebral autoregulation without the need for invasive procedures.