Tuesday, February 10, 2015

Study group discussion: JVP during inspiration

Systolic BP decreases in inspiration.....then what about JVP? It also decreases...But I'm not getting how?

During inspiration, there is increased negative pressure in the thorax..therefore the venous blood is forced to enter the heart. Hence the JVP reduces because the suction effect is more. But the venous blood supply to the heart reduces..that is via the pulmonary veins. Resulting in a reduced cardiac output. And reduced systolic. The left side of the heart I mean.

During inspiration a negative pressure is created which sucks the blood into the heart. That's why blood from the veins goes into the heart, the pressure or the JVP decreases (less volume).

Conditions where you dont see fall in blood pressure or JVP during inspiration?

Cardiac tamponade
Constrictive pericarditis
Restrictive cardiomyopathy

Yes, when the heart can't fill up blood!

*someone had a confusion on rise or fall in JVP in tamponade, this was explained by Sakkan*

Most kussmaul sign is positive in cardiac tamponade. That is paradoxical rise in JVP in inspiration.

In cardiac tamponade.. Due to increased external pressure on the right side of heart..the blood can't enter during inspiration. This leads to rise in JVP.

This also leads to bulging of the interventricular septum Upon the left ventricle. This decreases the preasure more than the normal fall of 10 mm of Hg.

Related to this.. Cardiac tamponade has a classical triad..called becks traid. That is silent chest, increased JVP and reduced BP.

Muffled heartsound.
Yeah cause the pericardial fluid accumulation dampens the sounds.

Yeah JVP will be elevated in cardiac tamponade! Thanks for a nice explanation.

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