It is crucial to pay attention to the error codes in the results of any spirometry session. These can affect the results significantly and if the tests are not repeated to include any errors, the results may not reflect the state of the subject's lung capacity correctly.
1. Hesitant start
Spirometry is a test based on the maximal capacity of the lungs, so any delay such as a hesitation in the beginning can affect the results.
This error code will be given if the BEV value is less than 5% of FVC or if the BEV value is under 100 ml. A maneuver showing this error should not be used as a figure to evaluate FEV1 by the operator.
In this case, the subject should be instructed to blow out faster.
2. Slow start
This error happens when the subject starts the maneuver too slowly. If the PEF rise time is more than 150 ms, this error code will be given.
In this case, the subject should be instructed to blow out immediately.
3. No plateau (Early termination)
This error will show if there is a lack of full exhalation - if there's less than 0.025 L of expiration in the last second, or if the expiration time is less than 15 s.
The subject should be instructed to keep blowing out until there is no air left in the lungs in this case.
4. Hesitation at max volume
This error will be given out if the subject waits more than 2 seconds to exhale after taking the deepest breath possible.
In this case, the subject should be instructed to blast out immediately after they inhaled the maximum amount they can.
5. Incomplete inspiration prior to FVC
This error means that the subject did not breathe in to their full capacity before the FVC maneuver.
The subject should be instructed to breathe in until they cannot anymore, to ensure they inhaled a full breath.
6. Slow filling
This error shows that the subject did not breathe in as fast as they should have and is given out if the FIF25-75 value is less than 2 L/s.
In this case, the subject should breathe in faster before starting to blast out.
7. Obstructed mouthpiece
If there is any kind of object (the subject's finger/hand for example) that is blocking the airway, this error code will come up.
The object should be removed and the maneuver should be repeated.
This error code means that there was a cough detected during the testing.
A cough during the first second of the maneuver can affect the measured FVC value and the FVC from such a maneuver is not acceptable or usable. The subject should repeat the maneuver in this case. However, the FEV1 may be acceptable.
9. Glottis closure
If the airflow during exhalation suddenly ceases before the lungs are completely emptied, this error will show. This would mean that the subject may have closed their vocal cords (glottis closure) or held their breath.
Glottis closure may be involuntary and should be documented, but if the subject held their breath, the operator must instruct them to keep blowing out until the lungs are empty.
- "Spirometry Quality Assurance: Common Errors and Their Impact on Test Results", National Institute for Occupational Safety and Health, 2012.
- "Standardisation of spirometry", European Respiratory Journal, 2005.
- "Spirometry: step by step", Breathe - ERS Journals, 2012.
- "Standardization of Spirometry 2019 Update". An Official American Thoracic Society and European Respiratory Society Technical Statement, 2019.