COPD and errors in spirometry technique

Main features in COPD?

Chronic obstructive pulmonary disease COPD is an umbrella term for obstructive lung diseases characterized by chronic respiratory symptoms such as shortness of breath,  chronic cough, and increased sputum production) due to damage of the airways (bronchitis, bronchiolitis) and/or alveoli (emphysema) which cause persistent, often progressive, airflow obstruction that is not reversible.¹ In the UK an estimated 1.2 million people are living with diagnosed COPD – considerably more than the 835,000 the Department of Health estimated in 2011. In terms of diagnosed cases, this makes COPD the second most common lung disease in the UK, after asthma. The number of people who have ever had a diagnosis of COPD has increased by 27% in the last decade, from under 1,600 to nearly 2,000 per 100,000. This could mean more undiagnosed cases are being diagnosed and the disease is becoming more common however changes in record-keeping could also be a factor².

Prevalence of COPD in workers

 The overall statistics for the prevalence of COPD in workers in the UK are difficult to pinpoint, however, the HSE states that 21.9 million working days across the population were lost due to COPD between 1994 – 1995⁷ . COPD in workers tends to gradually develop, and the onset of COPD is most common in long-term smokers aged 40 years and older. The European Respiratory Society carried out research into occupational exposures and their relation to COPD, their latest research in 2020 named ‘Occupational exposures and 20-year incidence of COPD: the European Community Respiratory Health Survey’  observed workers who had normal spirometry initially, and then a follow-up spirometry test was performed 20 years later. They tested 3343 workers and 89 of the workers had COPD 20 years later, the workers exposed to biological dust had a higher prevalence of COPD than those not, as with those exposed to gases, fumes, and pesticides. The researchers summarised the results strengthen the evidence for occupational exposures as an important risk factor for COPD³.

The usefulness of spirometry in the detection of COPD

Spirometry is accepted as the gold standard diagnostic test to assess airflow obstruction and classify disease severity based on specific cut-off points. Spirometry is a safe, practical, and reproducible maximum breathing test that can be used in Occupational Health to get a baseline test for the worker and to monitor workers who may work with hazardous chemicals and substances to see whether the PPE is efficient. The test is relatively quick to perform and well tolerated by most people. It is important to appreciate that the clinical value of spirometry is critically dependent on the correct operation and accuracy of the spirometer, performance of the correct maximal breathing manoeuvre, selection of the best test results to use, and correct interpretation.

Where is the latest guidance for good technique?

In 2019 the American Thoracic Society (ATS) and European Respiratory Society  (ERS) updated the previous 2005 standards for performing spirometry. The standards provide guidance on technical specifications in equipment and pre-test considerations on how to perform quality-assured spirometry. They have updated various elements of spirometry within the document, with the technique being one of the main updates. The importance of these guidelines is that they are evidence-based which increases accuracy. They stated that ‘improvements in instrumentation and computational capabilities, together with new research studies and enhanced quality assurance approaches, have led to the need to update the 2005 technical standards for spirometry to take full advantage of current technical capabilities’. Spirometry within Occupational Health is utilized in various ways mentioned earlier in this article. Therefore, the importance of obtaining good techniques is important so that those with COPD can be detected at any stage of their working life using spirometry. It is important to note that spirometry is just one piece of the puzzle in the diagnosis of COPD which requires additional tests and investigations.

What makes good spirometry technique?

 It is important to note good technique begins with the preparation of the patient, this involves a clear explanation and demonstration of the test.  Figure 1 shows the new criterion for acceptability and usability.

Figure 1

2019 American thoracic society and European respiratory society (ATS/ERS) technical acceptability criteria.

Figure 2

Normal and obstructive flow-volume loops.

Important considerations in COPD

Spirometry is commonly seen as a simple physiological test but it can be challenging to perform and interpret, particularly for those with COPD. The ATS and ERS have done research looking at factors that may contribute to COPD misdiagnosis.  Researchers looked at the evidence from different literature on errors in the diagnostic process to determine what factors may be causing misdiagnosis and they looked at 73 papers and investigated various factors that contribute to the misdiagnosis of COPD, spirometry technique error was identified as the third leading potential cause of COPD misdiagnosis. Technique factors included poor testing quality, technological errors, patient errors, and test administration and interpreting errors. Therefore, this highlights that improved spirometry quality may limit misdiagnosis⁶. Although in Occupational Health diagnosis is not routine early detection of any obstruction in the occupational setting may beneficial for the worker’s disease pathway.

An important criterion in spirometry is getting the person to completely empty their lungs to reach the plateau, however, people with COPD tend to have a reduced expiratory rate, so they tend to breathe out slower because of the airway narrowing. When spirometry is performed in someone with COPD distinctive pattern comes up showing a concaved loop that differs from a healthy person’s flow-volume loop. This is because the maximum flow achieved during forced expiration decreases progressively as lung volume falls and is most evident in the expiratory flow-volume curve where flow is plotted as a function of volume Figure 2. The more concaved the flow volume is the more severe the obstruction present.

When testing someone with COPD they are likely to get fatigued easily. A minimum of 30s should be left between repeat attempts to allow the patient to recover, be aware not to make the person repeat the test before they have recovered.

In patients with airflow obstruction exhalation, either forced or relaxed can be more than 10 s and never achieve a plateau. In the past, people with COPD would fail the test because they couldn’t meet the criteria due to the long exhalation time. The 2019 Spirometry guidelines have replaced the previously termed ‘End of Test (EOT)’ criteria with ‘End of forced expiration criteria (EOFE)’ also shown in figure 1. The EOFE criteria included exhalation ≥ 15 seconds. Research showed that any volume obtained past 15 seconds is unlikely to change clinical decisions and that multiple prolonged expirations are seldom justified and may cause light-headedness, syncope, undue fatigue, and unnecessary discomfort.

Obtaining good techniques in workers who may have COPD will be beneficial as having technically acceptable results will lead to a more accurate representation of the person’s obstruction and may lead to a better prognosis.

Charlene Mhangami, Senior Clinical Application specialist, Vitalograph

References

1. Johns DP, Walters JA, Walters EH. Diagnosis and early detection of COPD using spirometry. J Thorac Dis 2014;6(11):1557-1569. doi: 10.3978/j.issn.2072-1439.2014.08.18
2. Chronic obstructive pulmonary disease (COPD) statistics (no date) Chronic obstructive pulmonary disease (COPD) statistics | British Lung Foundation. Available at: https://statistics.blf.org.uk/copd (Accessed: January 30, 2023).
3. Lytras, T. et al. (2018) “Occupational exposures and 20-year incidence of COPD: The European Community Respiratory Health Survey,” Thorax, 73(11), pp. 1008–1015. Available at: https://doi.org/10.1136/thoraxjnl-2017-211158.
4. Minov, Jordan et al “Chronic obstructive pulmonary disease in workers from different sectors.” European Respiratory Journal 56.suppl 64 (2020)
5. Johns DP, Walters JA, Walters EH. Diagnosis and early detection of COPD using spirometry. J Thorac Dis. 2014 Nov;6(11):1557-69. doi: 10.3978/j.issn.2072-1439.2014.08.18. PMID: 25478197; PMCID: PMC4255165.

   Figure 1 .  Graham, B.L. et al. (2019) “Standardization of spirometry 2019 update. an official American Thoracic Society and European Respiratory Society Technical Statement,” American Journal of Respiratory and Critical Care Medicine, 200(8). Available at: https://doi.org/10.1164/rccm.201908-1590st.

6. Christopher Chalk, D.C. (2022) Errors in spirometry, primary care contribute to COPD misdiagnosis, Pulmonology Advisor. Available at: https://www.pulmonologyadvisor.com/home/topics/copd/errors-in-spirometry-primary-care-contribute-to-copd-misdiagnosis/ (Accessed: January 15, 2023).
7. https://www.hse.gov.uk/copd/employers.htm (Accessed: January 18, 2023).
   Figure2 . https://respiratorycram.com/flow-volume-loops/(Accessed: January 18, 2023).