Dynamic characteristics of cerebrovascular reactivity or ventilatory response to change in carbon dioxide

The study investigated the dynamic characteristics of cerebrovascular carbon dioxide reactivity and the central respiratory chemoreflex in nine healthy young subjects, both at rest and during exercise. Using frequency domain analysis, it was found that the transfer function gain from end-tidal partial pressure of CO2 to cerebral blood flow or ventilation decreased in the high frequency range, and this pattern was consistent during exercise. Notably, the cut-off frequency for cerebrovascular CO2 reactivity was higher than that for the central respiratory chemoreflex, indicating variability in these systems across different frequency ranges. These findings suggested that traditional methods might not fully capture the time response properties of these systems, highlighting the need for dynamic assessment.