Degree of Severity


  • 4) What is the degree of severity? This question can be answered for an obstructive problem. However, it cannot be answered for a restrictive problem. Degree of severity for restrictive is determined by the total lung capacity.
  • FEV1 < 65-80% mild obstruction
  • FEV1 < 50-65% moderate obstruction
  • FEV1 < 50% severe obstruction


  • 5) If a bronchodilator was administered and the test repeated, did the FEV1 or FVC improve (see interpretation guidelines above)?

Authored by William A. French. Medically reviewed by Dr. Barbara Erickson, PhD, RN, CCRN.

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