Cerebrovascular Response to CO₂ during Moderate-intensity Exercise Measured by Performing Transcranial Doppler Ultrasonography

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Previous studies demonstrated that cerebral blood flow (CBF) changes during dynamic exercise and aphysiological basis for this observation may be explained by the tight control of CBF by arterial carbon dioxidetension (PaCO₂). This study examined whether the steady state of the middle cerebral artery blood flow velocity(MCAVmean) and PaCO₂could be observed during constant work rate cycling exercise and to investigate the cerebrovascular reactivity (CVR) to CO₂. Seven young volunteers performed a 10-min exercise session with constant workload using a cycle ergometer, with intensities corresponding to the level below the lactate threshold. Respiratory gas analysis and MCAVmean were measured simultaneously using the transcranial Doppler (TCD) method. PaCO₂was estimated (ePaCO₂) using the end-tidal pressure of CO₂(PETCO₂) and the tidal volume(VT). On-transient phase II of VO₂and the corresponding responses of MCAVmean and ePaCO₂ were investigatedsimultaneously with the monoexponential model. Since the responses in ΔMCAVmean or ePaCO₂had theovershoot phase within 3min in some cases, analysis for the fitted curves of the monoexponential model wasperformed during the first 5 min as well as during the total 10 min. CVR to CO₂during the dynamic cyclicexercise was 5.33 % mmHg-1 and 4.78 % mmHg⁻¹ in the 5-min and the 10-min analysis, respectively. In the5-min and the 10-min analysis, CVR to CO₂significantly correlated with the exercise intensity during the10-min bout (r² = 0.89 and 0.75, respectively). During the on-transient phase of dynamic exercise, CBF wouldbe influenced by PaCO₂and other factors such as the neuronal activation and cardiac output would also beinvolved in changing CBF.
法政大学スポーツ健康学部の論文

Cerebrovascular Response to CO₂ during Moderate-intensity Exercise Measured by Performing Transcranial Doppler Ultrasonography

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