Criteria for judging severity of Obstruction:

• For observed FEV1/FVC
  • Severe <40%
  • Moderately severe 40-60%
  • Mild 60-75%
• For % predicted FEV1
  • Severe <40%
  • Moderately severe 40-60%
  • Mild 60-80%

  Our patient:

  • Observed FEV1/FVC 34
  • %Pred FEV1 13

  He would be considered to have severe obstructive defect.