Physiology: Hemodynamics of a Valsalva maneuver

Normal physiology and cardiovascular hemodynamics changes during valsalva maneuver

0:24 Phase 1
3:48 Phase 2 (a+b)
6:36 Phase 3
8:27 Phase 4

In phase one doesnt decrease in radius of aoarta also increase afterload thus contribute to reduce stroke volume? (sahan isuru)

Yes, with decrease in radius of the aorta – aortic resistence increase and afterload increase. But the point here is that if LV works well ( no Heart Failure/ or any congenital defects), than it can push a massive amout of blood into Aorta even with hemodynamically insubstantial increase in Aortic resistence, without decrease in Stroke volume. ( heart has reserves and reflex regulation to provide this increase in contractility due to Anrep effect ( increase in contractility due to increase in afterload - there by it keeps Stroke volume and subsequently Blood pressure stable) and also due to the Bowditch reflex ( through increase in HR (staircase phenomenon ) – contractility increase. This effects compensate increased afterload – and provide increase in Blood pressure.
Another story - in Heart failure, or in case of peripheral vasculature.

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