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Lung Function Tests

Performing Spirometry

February 15th, 2021


Correct spirometry technique is vital for collecting an accurate sample, and poor compliance with the test may result in a false positive or false negative result.
  • How to Perform

  • Attach the mouthpiece to spirometer
  • Ask the patient to breath in deeply
  • Ask the patient to blow into the spirometer as hard and as fast as possible, until there is no breath left
  • Encourage the patient to keep blowing out for at least six seconds
  • Repeat the procedure three times total, ensuring that the best two are within 100mL or 5% of each other
  • Calculate the predicted values based on the patient's sex, age and height
  • Calculate the percent predicted, based on the patient's results
  • Contraindications to Spirometry

  • Acutely unwell
  • Haemoptysis of unknown origin
  • Pneumothorax
  • Recent abdominal, thoracic or eye surgery
  • Recent MI
  • Thoracic or abdominal aneurysm
  • Contributors to Poor Readings

  • Incomplete inhalation prior to the test
  • Lack of effort on exhalation
  • Stopping exhalation early
  • Poor seal around the mouthpiece
  • Exhalation through the nose
  • Coughing
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