Understanding cardiac physiology 005 – finding the bottleneck.

The cardiac ventricles may be underfilled due to many reasons.

The case I represent below has to do with the pulmonary vasculature being the bottleneck.

When pulmonary vasculature constricts, the LV does not get its fill of blood to generate an

appropriate blood pressure (an MAP > 60mmHg).


pictured above : everything is in fine working condition.

the alveoli are nice and patent – open abundant alveoli

oxygenating and ventilating.


pictured above : the initial insult >> some catastrophic

event causes a significant amount of alveoli to collapse.

(severe atelectasis >> a.k.a. ALI / ARDS).


pictured above : severe atelectasis leads to

HPV (hypoxic pulmonary vasoconstriction).

the aforementioned bottleneck (in the pulmonary



pictured above : now the RV cannot eject is normal volume

forward and therefore starts to distend and become dysmorphic

to the point of RV dysfunction.

This is where starting nitric oxide is thought to help RV strain >>

by dilating the pulmonary vasculature to decongest the RV

back into its proper place on the Starling Curve.


pictured above : and now, the LV does not have the appropriate

volume to generate forward flow to perfuse all of the body’s

vital organs.

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