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spirometry user

This is a device that measures the amount and speed of air exhaled and from the lungs. The patient places the filtered mouthpiece between their teeth and tightly closed lips so no air leaks out. After a deep inhalation to completely fill the lungs with air , the patient exhales forcefully as hard and fast and as long as they can from the chest and diaphragm, holding the exhalation as long as possible as the device needs at least 6 seconds. The test is repeated until 3 tests that vary by no more than 150mls are obtained. This represents a valid and repeatable test. Because the test relies on a maximal forced exhalation, the accuracy is highly dependent on the patients understanding, co-operation and best efforts.

  • Used to assess lung causes of breathlessness such as asthma, emphysema, COPD.

  • Can be repeated after a dose of medication to measure its effect.

  • Differs from peak flow by measuring the entire exhalation, not just the peak.

  • If the initial test is normal it can be done after a challenge (hypertonic saline or histamine or methacholine).

  • To see if asthma can be triggered.

  • Obtained values are compared to predicted normals that depend on age, sex, height and race.

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Severity of Obstruction CORD

(FEV1/FVC < 70%)

  • FEV1 60-80% = mild

  • FEV1 40-59%=moderate

  • FEV1 <40% = severe

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