Uncontrolled Circulation: Nonzero Pºhorax In our model of the uncontrolled circu

Question

Uncontrolled Circulation:

Nonzero Pºhorax In our model of the uncontrolled circulation, we also neglected Pºhorax. Fix this by changing the equations of the right and left hearts and the pulmonary compliance to the following:

QR = (FCR)(Pºv - Phorax) = KR (Pºv - Phorax)

QL = (FCL)(Pºv - Phorax) = KL(Pov – Phorax)

Vea = Cpa(Poa - Phorax) Vov = Cov(Pov - Phorax).

Here Phorax is a (negative) parameter and the volumes are understood to mean eaccess volumes as in the foregoing exercise. Solve the equations of the improved model and plot Q and Pºv as functions of Phorax for Phorax < 0.

Explanation / Answer

In the given model Pthorax is negative, hence, Psv turns negative. As a result the systemic veins of the heart are subjected to a partial collapse as they invade the thorax region. This partial collapse does not allow Psv to fall below zero. This results in a resistance Rc amongst the right auricle and the systemic waves.

Therefore, Psv = 0

QsRc = Psv - Pra = 0 - Pra

The right heart equation is replaced by

Qr = (FCr) (Pra - Pthorax) = Kr(Pra - Pthorax)

Here, Pra takes the place of Psv.

Rc = Resistance of partially collapsed veins

Pra = Rpressure in the right auricle.

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