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Chronic obstructive pulmonary disease - Management
When should I arrange spirometry, and how should I interpret the results?

  • Ensure that there is access to spirometry performed by an appropriately trained professional and supported by quality-control processes, and that the skills are available to interpret results.
    • Referral to a community or hospital spirometry service may be necessary.
  • Measure post-bronchodilator spirometry to confirm the diagnosis of chronic obstructive pulmonary disease (COPD).
    • Do spirometry 15–20 minutes after the person has inhaled salbutamol 200 micrograms delivered via a spacer device (terbutaline 500 micrograms may be an alternative). If ipratropium bromide is used, wait for 30 minutes before doing spirometry.
    • In COPD, the ratio of forced expiratory volume in 1 second to forced vital capacity (FEV1/FVC ratio) is less than 0.7.
      • Predicted normal values of FEV1 and FVC depend on age, height, and sex. These values may over diagnose COPD in elderly people and are not applicable in black and Asian populations.
      • The slow or relaxed vital capacity (SVC) may be used instead of FVC to calculate the ratio if either the SVC is higher than the FVC, or the person cannot perform a forced manoeuvre to full exhalation.
    • If the FEV1 is 80% predicted normal or greater, a diagnosis of COPD should be made only in the presence of respiratory symptoms, for example breathlessness or cough.
  • Assess the severity of airflow obstruction according to the reduction in FEV1 — see Assessment of severity.
  • Routine spirometric reversibility testing is not recommended unless COPD and asthma cannot be distinguished clinically (see Distinguishing COPD and asthma).
  • Repeat spirometry if the person has an exceptionally good response to treatment; reconsider the diagnosis if the FEV1/FVC ratio is 0.7 or greater at follow up.

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