[indian]

I can't seem to understand why do we have decreases blood flow while the case is clearly f.b obstruction
I've seen three questions in Kaplan, UW, and USMLE consult all of them chose a decreased blood flow in a case of foreign body obstruction

would appreciate if you help me with that!

 

[lee-usmle]

Hypoxic Vasoconstriction

It's hypoxic vasoconstriction that explains why we have decreased blood flow to underventilated lung areas.
Decreased alveolar oxygen pressure causes reflex vasoconstriction in the pulmonary capillaries and so decreased blood flow to the area.

This happens not only in pathologic states but also under normal physiology where underventilated areas get less blood thereby minimizing the ventilation/perfusion mismatch and so returning the V/Q ratio towards the normal value of 0.8

 

[Sabio]

It's the pulmonary hypoxic vasoconstriction that is responsible for the development of pulmonary hypertension in the chronic obstructive airway diseases

We'll have chronic vasoconstriction so increased resistance so pulmonary hypertension and so later on the development of corpulmonale