Cerebral Hemodynamics During the Valsalva Maneuver

Abstract

Background and Purpose— The aim of this study was to differentiate the mechanical effects of the Valsalva maneuver (VM) from the effects of changes in autonomic neural activity on cerebral hemodynamics in humans. Methods— Nine healthy subjects performed the VM before and after autonomic ganglionic blockade with trimethaphan. Blood pressure (BP) was measured in the radial artery with an indwelling catheter or at the finger by Finapres. Cerebral blood flow (CBF) velocity was measured in the middle cerebral artery with transcranial Doppler; end-tidal CO2 was measured by mass spectrometry. Results— Before blockade, during phase II of the VM, BP was reduced by 27% and CBF velocity was reduced by 33% (magnitude of changes during phase II divided by baseline measurements before the VM, P<0.05). Cerebrovascular conductance index (CVCI) increased by 21%. During phase IV, overshoot of CBF velocity was proportionately greater than that of BP (46% versus 30%). After blockade, during phase II, BP fell to a much greate...