查看文章

We investigated whether dynamic cerebral autoregulation is affected by exhaustive exercise using transfer-function gain and phase shift between oscillations in mean arterial pressure (MAP) and middle cerebral artery (MCA) mean blood flow velocity (V_mean). Seven subjects were instrumented with a brachial artery catheter for measurement of MAP and determination of arterial Pco₂ (Pa_CO2) while jugular venous oxygen saturation (Sv_O2) was determined to assess changes in whole brain blood flow. After a 10-min resting period, the subjects performed dynamic leg-cycle ergometry at 168 ± 5 W (mean ± SE) that was continued to exhaustion with a group average time of 26.8 ± 5.8 min. Despite no significant change in MAP during exercise, MCA V_mean decreased from 70.2 ± 3.6 to 57.4 ± 5.4 cm/s, Sv_O2 decreased from 68 ± 1 to 58 ± 2% at exhaustion, and both correlated to Pa_CO2 (5.5 ± 0.2 to 3.9 ± 0.2 kPa; r = 0 …