Air trapping + low diffusion capacity (KCO) - anyone else dealt with this combination?

My doctor referred me to a specialist clinic at a hospital - either to start biologic treatment for severe asthma, or to work up something other than asthma. But what I actually have is constant dyspnea and trouble exhaling, and neither of those really fits the typical asthma picture.

👉 FVC normal every time (107-109% predicted)

FEV1/FVC consistently reduced: 69-72% (should be ~82-84%)

Minimal response to bronchodilator

👉 Full plethysmography (Aug 2026) - this is the one that changed things:

- TLC 123% predicted (lungs bigger than average)

- RV 178% predicted (a lot of trapped air after exhaling)

- RV/TLC 145% of predicted

👉 DLCO, same day, good quality test:

- TLCO 84% predicted

- KCO 67% predicted - this is the one that stood out most, well below normal even accounting for lung size

VA 123% predicted