Physiology Philes: Valsalva Manoeuvre

aka BSCC Physiology 001

The Valsalva Manoeuvre is an example of a tactic that demonstrates a basic cardiovascular physiologic feedback loop. The purpose of it is to induce vagal firing from the cardiovascular control centre in the medulla, in order to slow the heart rate, and interrupt the rapid ventricular rate in a supraventricular tachycardia.

The video takes us through the manoeuvre – we start with an increase in transmural pressure in the aorta, and the initial baroreceptor reflex causing an initial slowing of the heart, through afferents to the medulla and a reduction in sympathetic outflow and increased vagal firing. We then follow the fall in venous return and thus cardiac output as a result of the sustained intrathoracic pressure increase, which stimulates a reverse and increase in sympathetic outflow. When the manoeuvre finishes, after about 10 seconds,  and blood rushes back into the great vessels, with added sympathetic peripheral vasoconstriction, the sudden increase in stretch at the aortic arch and carotid sinus again caused profound vagal outflow, at this point hopefully slowing down the AV node conduction enough to stop the SVT.

We then look at the best way of performing this in the clinical setting…


References


BSCC Basic Science in Clinical Context 700 2

Basic Science

in Clinical Context

Emergency physician. Lives for teaching and loves clinical work, but with social media, she is like the syndromic cousin in the corner who gets brought out and patted on the head once in a while | Literary Medicine | @eleytherius | Website |

One comment

  1. Thanks Michelle for a clear explanation. Like you,I’ve been doing it with pt supine/ head-down. EMRAP recently (October 2020) reviewed a study looking at a slightly modified valsalva where the subject is semi-reclined initially (when they strat the manoevre) then laid flat/ head down when they finish exhaling against resistance, to maximally fill neck vessels and further accentuate the response- they found a reduced need for rescue meds. I’m keen to try it next time. Interested in your thoughts?

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.