Transcranial Doppler sonography-ergometer test for the non-invasive assessment of cerebrovascular autoregulation in humans

Cerebrovascular hemodynamics during physical stress have been sparsely investigated, mostly through risky invasive techniques. The aim of this study was to determine the effect of ergometer stress on cerebrovascular hemodynamics in humans using the non-invasive and thus clinically-applicable method of transcranial Doppler sonography (TCD) combined with simultaneous non-invasive measurements of cardiovascular parameters. In eighteen healthy subjects (six women, twelve men; 29.3 ± 4.6 years old) left midcerebral artery blood flow velocities (CBFVs) were continuously monitored using TCD during 3 min at rest, 3 min during ergometry and 3 min recovery. Simultaneously, systolic, diastolic, mean CBFVs, pulsatility index (PI), heart rate, beat-to-beat blood pressure (BP) and transcutaneous p(CO₂) were measured. The subjects were supine with elevated trunk. Ergometry was performed by pedalling a Muhe-ergometer. In eight volunteers, the procedure was repeated within the next day to test the repeatability of the results. Heart rate increased significantly during ergometry (from 65.2 ± 11 to 105.3 ± 12.3/min; P < 0.05). The systolic BP increased significantly slightly later during ergometry (from 118.9 ± 8.6 to 141.6 + 17.9 mmHg; P < 0.05). Transcutaneous p(CO₂) was initially within physiological ranges, but increased significantly after a delay during the 3rd min of cycling (from 39.7 ± 3.7 to 41.1 ± 4.7 mmHg; P < 0.05). MFV started to rise significantly after 1 min of the exercise period (from 59.6 + 10.9 to 68.3 + 13.9 cm/s; P < 0.05). PI increased immediately and significantly at the start of exercise (PI at rest 0.93 + 0.11; PI ergometry 1.1 + 0.13; P < 0.05). The results were found to be reproducible in the eight volunteers. The cerebrovascular changes during ergometer exercise may reflect the combined activation of the cerebrovascular autoregulative mechanisms (neurogenic, myogenic and metabolic). The TCD-ergometer test presented here is non-invasive and would seem to present a low risk for patients who are judged fit enough for mild exercise. The test may contribute to the detection of cerebrovascular abnormalities in various diseases. (C) 2000 Elsevier Science B.V.