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Old 04-11-2012
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Lungs Why Oxygen does not improve pulmonary shunt?

Why doesnt giving 100% oxygen improve PO2 in shunts/airway obstruction? its not like both lungs are collapsed or airways of both the lungs get obstructed!?
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Old 04-11-2012
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When they say Shunt/Obstruction, I think they are talking about a MAJOR one (unlike the physiological shunt) In shunting, the blood frm right side of the heart goes to the left side of the heart WITHOUT being oxygenated ... so even if u give 100% oxygen, that oxygen WILL NOT reach the shunted blood! .. when the shunted blood mixes with the normal oxegenated blood the Po2 and hence the SaO2 goes down.
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Old 04-12-2012
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Thatīs right.
Shunt means extreme degree of ventilation perfusion mismatch caused by thebypassed deoxygenated/venous blood from the ventilated alveoli and its mixing with oxygenated blood that has already flowed through the ventilated alveoli.

Ultimate effect is the reduced PO2, PaO2 and CaO2.
Notably, significant rise in PaCO2 only occurs when the shunt is > 60%.
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Old 08-21-2012
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I THINK intrapulmonary shunt is a consequence for the decreased ventilation, so when there is complete airway obstruction, V =zero, V/Q will be zero, and blood will be shunted to the venous side in this case without oxygenation, and hence 100% O2 will not change the situation, because the airway is obstructed.

let me know guys if I have a wrong understanding, please.
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