What is the Valsalva Maneuver?
The Valsalva maneuver is one of the most important clinical physiological tests for autonomic failure. It consists of blowing against a resistance for several seconds, then relaxing. The instant a person begins to blow, the sudden increase in chest and abdominal pressure forces blood out of the chest and down the arms. This increases blood pressure briefly (phase I). Soon afterwards, the amount of blood ejected by the heart with each beat (stroke volume) plummets, because the straining decreases entry of blood from the veins into the heart. Blood pressure progressively falls (phase II). The brain senses this fall and a rapid decrease in outflow in the parasympathetic nervous system to the heart. The increase in nerve traffic leads to more release of norepinephrine, which tightens blood vessels throughout the body. When the patient relaxes at the end of the maneuver (phase III), briefly, the blood pressure falls, but then blood rushes back into the chest and within a few heartbeats, the
