Constanzo FRC compliance graph

[aspiringmd1015]

It states that in emphysema, at the original FRC value, tendency of lungs to collapse is less than tendency of chest wall to expand, so the forces are no longer balanced and the frc is set higher. I can't see this graphically though, I understood everything before but where does it show that the tendency of the lung to collapse is less than the tendency of the chest wall to expand at original FRC?


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[jqueb29]

It states that in emphysema, at the original FRC value, tendency of lungs to collapse is less than tendency of chest wall to expand, so the forces are no longer balanced and the frc is set higher. I can't see this graphically though, I understood everything before but where does it show that the tendency of the lung to collapse is less than the tendency of the chest wall to expand at original FRC?


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Think about it logically. FRC is determined by the balance of lung elastic recoil and chest wall expansion. In emphysema, you have destruction of alveolar walls. This destruction decreases the elastic recoil of the lungs. As a result of this decreased elastic recoil, the point where lung collapsing and chest wall expansion balance out (FRC) will be increased.

 

[aspiringmd1015]

That's fine, but graphically I can't see it


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