EFFECTS OF THE VALSALVA MANEUVER ON CEREBRAL-CIRCULATION IN HEALTHY-ADULTS - A TRANSCRANIAL DOPPLER STUDY

Background and Purpose Knowledge is limited about the effects of the V alsalva maneuver on cerebral circulation because of the poor temporal resolution of traditional cerebral blood flow measurements. The purpos e of this study was to investigate changes in cerebral blood flow duri ng the Valsalva maneuver and to explore its potential use for the eval uation of cerebral autoregulation. Methods Using transcranial Doppler ultrasonography, we simultaneously recorded systemic arterial blood pr essure in the radial artery and flow velocities in both middle cerebra l arteries in 10 healthy adults during the Valsalva maneuver. Gosling' s pulsatility index was calculated for all phases of the Valsalva mane uver. Autoregulatory capacities were estimated from the change in cere brovascular resistance (flow velocity in relation ship to blood pressu re) during phase II and changes in the velocity-pressure relationship in phase IV relative to phase I. Results The characteristic changes in blood pressure (phases I to IV) were seen in all subjects, accompanyi ng distinct changes in cerebral blood flow velocity. The relative chan ges in mean velocity during phases II and IV were significantly ter th an those in mean blood pressure. Compared with the baseline value, vel ocity decreased by 35% in phase IIa, then rose by 56.5% in phase IV (c orresponding changes in blood pressure were -10.2% and +29.8%, respect ively). During phase II, the pulsatility and cerebrovascular resistanc e decreased by 19.9%. The increase in cerebral blood flow velocity in phase IV was significantly higher than in phase I (P < .0004), and the re was no corresponding significant difference in blood pressure. Conc lusions These results demonstrated that in healthy humans the Valsalva maneuver causes characteristic changes in systemic blood pressure as well as in flow velocity in the middle cerebral artery, reflecting the sympathetic and cerebral autoregulatory responses, respectively. Anal ysis of these changes may provide an estimate of autoregulatory capaci ty.