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

Cerebrovascular hemodynamics during physical stress have,been sparsely inve stigated, mostly through risky invasive techniques. The aim of this study w as to determine the effect of ergometer stress on cerebrovascular hemodynam ics in humans using the non-invasive and thus clinically-applicable method of transcranial Doppler sonography (TCD) combined with simultaneous non-inv asive measurements of cardiovascular parameters. In eighteen healthy subjec ts (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, s ystolic, diastolic, mean CBFVs, pulsatility index (PI), heart rate, brat-to -beat blood pressure (BP) and transcutaneous p(CO2) were measured. The subj ects were supine with elevated trunk. Ergometry was performed by pedalling a Muhe-ergometer. In right volunteers, the procedure was repeated within th e next day to test the repeatability of the results. Heart rate increased s ignificantly during ergometry (from 65.2 +/- 11 to 105.3 +/- 12.3/min; P < 0.05). The systolic BP increased significantly slightly later during ergome try (from 118.9 +/- 8.6 to 141.6 +/- 17.9 mmHg; P < 0.05). Transcutaneous p (CO2) was initially within physiological ranges, but increased significantl y 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 i ncreased immediately and significantly at thr start of exercise (PI at rest 0.93 + 0.11; PI egometry 1.1 + 0.13 P < 0.05). The results were found to b e reproducible in the eight volunteers. The cerebrovascular changes during ergometer exercise may reflect the combined activation of the cerebrovascul ar autoregulative mechanisms (neurogenic, myogenic and metabolic). The TCD- ergometer test presented here is non-invasive and would seem to present a l ow 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. All rights reserved.