Table 1

Ventilatory pattern distribution versus classification schema and predictive equations used. Classification 1 included spirometry only (FEV1/FVC vs FEV1/FVCLLN). Classification 2 partitioned ventilatory impairments based on FEV1/FVC versus FEV1/FVCLLN, FVC versus FVCLLN and TLC versus TLCLLN (observed vs lower limit of normal, LLN)

ClassificationReference equationsNormalObstructionRestrictionMixedSmall airway disease (SAD)
Classification 1
(spirometry only, %)
NHANES III39.4
GLI42.6
Classification 2
(spirometry + lung volumes, %)
NHANES III27.648.419.74.2
GLI28.249.717.24.9
  • NHANES III, National Health and Nutrition Examination Survey 3.