The Valsalva maneuver is a test that you can perform on yourself at this very moment. Simply close your glottis and strain down hard for 20 seconds while palpating your radial pulse.
What happens?
The normal response to the Valsalva maneuver is as follows.
- The high intrathoracic pressure decreases venous return, causing an abrupt drop in cardiac output after several seconds.
- The normal autonomic response to the decreased output is twofold: peripheral vasoconstriction and tachycardia.
- Despite this compensatory mechanism, the blood pressure dwindles; this decrease causes the pulse to become feeble.
- After release the cardiac output is suddenly restored, causing an abrupt increase in blood pressure due to the temporary increase in peripheral vascular resistance.
- Increased blood pressure in turn triggers a reflex bradycardia (slowing), that is transient and somewhat delayed.
Finally, the normal state returns.
Responses (4) and (5) disappear with many forms of heart disease.