Fig. 4.
Valsalva maneuver. During the Valsalva maneuver, the patient is asked to blow and generate approximately 40 mm Hg of Valsalva pressure (VP) for 15 seconds while continuously monitoring HR and BP. In a healthy individual (A), the BP and pulse pressure initially decease because of the drop in venous return, but this hypotension triggers an increase in sympathoneurally mediated vasoconstriction. The BP starts to recover in late phase II (IIL). After release of VP (and with it increased venous return) the BP overshoots in phase IV (IV) before returning to baseline. A patient with nOH (B) might not be able to generate the appropriate sympathoneurally mediated vasoconstriction in response to the initial hypotension. Patients with nOH typically lack the late phase II BP recovery and the phase IV BP overshoot.