This test is used as a brief assessment of lung function, specifically in the context of obstructive airway diseases.

Performing the Test

  1. Ask the patient to take a deep breath in and then out as fast as possible with their mouth open
  2. Listen over the trachea with diaphragm of stethoscope and time the expiration phase
  3. Aim for 3 consistent readings during assessment

Expiratory time is prolonged in obstructive airway diseases. Patients > 60 y.o. are twice as likely to have COPD when forced expiratory time is > 6-8 s.


  1. Bickley LS. The thorax and lungs. In: Bickley LS, Szilagyi PG. Bates' Guide to Physical Examination and History Taking. 10th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009:283-321.