santaclara
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a pulmonogist working on the diffusing lung capcity with relation of Hb level. at level 8 mg /dl, the lung diffusind capcity will
A) decrease
B) increase
C) no reation with Hb level
D) difficult to say
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| mani
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C) no reation with Hb level
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| santaclara
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how "c"?
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| BumbleB
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Lowering the Hb will lower the ammount of O2 delivered to the alveoli ("the perfusion"). But the diffusion - that is the rate at which the O2 can enter into the RBC's will only be affected by 3 thing: 1) the thickness of the alveoli, 2) the material composing the alveoli (like scar tissue vs. healthy tissue). 3) the surfaca area of the alveoli
Check out the fick's equation for more info.
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| santaclara
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hey BumbleB this means u think that answer is "c".
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| mani
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diffusion is independent of Hb level
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| BumbleB
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C sounds right
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| santaclara
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well i also post this Q on other website also and here is the reply.
It will decrease and the answer is "A".
The reason is simple
Diffusion depends on the
A:directly pressure difference of diffusing substance on two sides of membrane
B:Area of the membrane(directly)
C:Thickeness of the membrane (indirectly)
D iffusion Co-efficient
Here Pressure difference is problem.
Diffusing capacity is measured with CO which after crossing pulmonary membrane combines with Hb immediately giving Pressure "0" in blood.So in other words More Hb ,more capturing capacity of CO,less Hb ,less capturing capacity.
So if Hb is increased as in PRV (high Hct) DLCo is inreased ,and if Hb is decreases as in this condition DLCO is decreased.
Remember this is only for CO diffusion not for diffusion for other gases.
By the way the other condition which can increase DLCo is Bronchial Asthma attack,why ?? I do not know but possibly due to increased Lung surface due to stretch.(last sentence ,just additional information
i thinkalso this is the correct discription.
thanx.
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| mani
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i would disagree with this. As is given in this explanation as well, the main factor here is pressure difference ie partial pressure of CO, P(CO). As CO binds quickly with Hb its pressure in the blood is always zero for all practical purposes. So whether the Hb increases or decreases it wouldnt affect the diffusion as P(CO) depends on the amount of CO dissolved in blood, not the one attached to Hb.
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