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Why is there increased Dead Space ventilation in COPD??

there is alveolar destruction without change in perfusion, shouldn't that cause decreased V/Q and more pulm 'shunting'???

silly doubt, but cant figure it out..

dead space=area of ventilation but no perfusion
alveolar destruction-->bullea-->full of air with relatively less perfusion
pulmonary shunt = area of perfusion but no ventilation like ARDS, pul edema

ohhhhh! thanks toha. i felt that it should be shunting bcz the total surface area is reduced, and a lesser amount of surface area is being perused by the original amount of blood, lowering the V/Q. what do u think?

just think of the the large amount of O2 in bullae not being consumed because no adequate surface area for exchanging it.

dilatation issue