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Lung Function Tests
Lung Function Tests

Performing Spirometry



  • 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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