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Old 01-27-2012
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Lungs COPD and the Total Lung Capacity

Doing a UWorld question and was confused about this. In COPD the TLC and RV are increased, yet how is that RV/TLC is increased? UWorld does not give anything in explanation just that it is increased . I was thinking TLC/RV would be increased since TLC = all the lung capacities.
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Old 01-28-2012
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in COPD the main increase is in RV.... which in turn increases TLC....



yeah TLC would go up tooo..but remember things like FEV are going down too. but RV goes up much much more... as a PERCENTAGE OF THE ORIGINAL


hence the percentage increase in the numerator is more than the percentage increase in denominator... thus resulting in increased RV/TLC
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Old 01-28-2012
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the same concept applies for
1- FF= GFR/RPF...
hence in constriction of the afferent... GFR goes down.. but RPF goes down MORE... Hence NET FF INCREASES


2- in restrictive lung diseases...
FEV1/FVC increases. ... .. inspite of both decreasing..

n so on and so forth..
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Old 01-29-2012
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To add to the discussion- the first change to come is the FRC, then RV, and then TLC. Therefore, I guess temporality has a role to play in the changes in the ratios.
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Originally Posted by mbbs2010 View Post
in COPD the main increase is in RV.... which in turn increases TLC....



yeah TLC would go up tooo..but remember things like FEV are going down too. but RV goes up much much more... as a PERCENTAGE OF THE ORIGINAL


hence the percentage increase in the numerator is more than the percentage increase in denominator... thus resulting in increased RV/TLC
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Pathology-, Physiology-, Respiratory-

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