Control system analysis of visually evoked blood flow regulation in humans under normocapnia and hypercapnia.

摘要: Abstract Objective: Among other factors, the cerebral blood flow (CBF) is regulated in accordance to arterial CO 2 tension and cortical activity. The test commonly used measure vascular reserve capacity. Most functional imaging studies rely on activity-flow coupling (AFC). We aimed combine both challenges order increase insight into mechanisms of CBF regulation. Methods: Fifteen healthy students underwent a transcranial Doppler using visual stimulation paradigm: firstly under normocapnia secondly conditions hypercapnia. Hypercapnia was induced by breathing carbogene gas mixture 5% 95% O . entire time course velocity adaptation posterior artery (PCA) analyzed mathematically control system approach. Results: Resting velocities increased nearly 26% hypercapnia, whereas slight pressure (ABP) decrease Pourcelot–Pulsatility index (PI) were statistically not significant. From parameters which delay, rate time, gain, attenuation natural frequency, only parameter indicative for initial steepness increase, showed significant decrease, consistently peak systolic enddiastolic data. As concluded from unchanged gain absolute amount evoked same stimulus also 26%. Conclusion: Evaluated measurements hypercapnia seems influence AFC two ways: It decreases enhances stimulus.