In bullous emphysema the air spaces are > 1 cm in diameter.

If the bullae are not significantly ventilated then lung mechanics and carbon monoxide transfer reflect properties of non-bullous lung.

The characteristic abnormality in bullous emphysema is a large difference between lung volumes measured by body plethysmography / radionucleotide techniques and helium equilibrium. Whole body plethysmography is superior for lung volume analysis to helium diffusion

Static lung compliance is increased

the ratio of FEV1/FVC is decreased

TLCO is decreased and KCO (which is TLCO / alveolar volume) is also reduced.