Advances in spirometry testing for lung function analysis

ABSTRACT

Introduction: Spirometry, the most common lung function test, is used to evaluate individuals with respiratory complaints or known respiratory disease. However, its underutilization and the misinterpretation of its parameters are causes for concern.

Areas covered: This review describes new spirometry-derived metrics, new reference equations, recent recommendations for presentation of results, recent spirometry-based prevalence studies, and technological advances in spirometry equipment.

Expert opinion: The underutilization of spirometry can be overcome by increasing access to portable, hand-held, and user-friendly spirometers, together with strategies that increase awareness of the importance of spirometry. New metrics derived from spirometry, together with traditional spirometric criteria, can identify individuals with structural lung disease and respiratory morbidity. Some problems with the reference equations were solved by the Global Lung Function Initiative (GLI), which covers a wider age range and more ethnic groups and provides limits of normality using the z-score. Despite these advantages, the GLI equations lack data from large populations (especially those from Africa, South Asia, and Latin America) and greater representation of older people. Another disadvantage attributed to the GLI is the lack of predicted values for peak expiratory flow and other airflows, limiting the interpretation of the maximal expiratory flow-volume curve.

KEYWORDS:

• Spirometry
• pulmonary function
• reference equations
• asthma
• chronic obstructive pulmonary disease
• education
• new technologies

Article Highlights

• Increased use of spirometry may result in an increased proportion of patients diagnosed early from a functional point of view and, possibly, in better management of airway disease during follow-up.

• New metrics derived from maximal expiratory volume-time and maximal expiratory flow-volume curves are associated with structural lung disease, dyspnea, and respiratory quality of life in computed tomography and may be useful for individuals with borderline or mild lung disease according to traditional spirometric criteria.

• There has been much enthusiasm for adopting Global Lung Function Initiative (GLI) equations because they are applicable to a wider age range and more ethnic groups and eliminate problems related to shifting between equations during growth.

• A graph showing the differences between test results and predicted values in standard deviation units (z-score) may help with understanding abnormalities in lung function.

• In spirometry reports, attention should be given to the limited number of parameters and presenting the lower limit of normal next to the measured value can improve the interpretive precision of the test.

• The international data repository of the GLI allows the development and ongoing evaluation of reference values.

• In addition to overdiagnosis in the elderly, Global Initiative for Chronic Obstructive Lung Disease criteria may underestimate the diagnosis of chronic obstructive pulmonary disease (COPD) in younger patients.

• Spirometry is not sufficiently sensitive to detect structural changes in all patients at risk, and therefore, it should be complemented with imaging tests and other functional tests.

• Spirometry performed in the workplace should be part of a comprehensive respiratory health program.

• Spirometric parameters appear to be more important than fractional exhaled nitric oxide measurements for predicting the outcomes of asthma.

• In addition to spirometric parameters, the diagnosis of asthma-COPD overlap should consider environmental exposure, especially in low- and middle-income countries.

Declaration of interest

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewers Disclosure

Peer reviewers on this manuscript have no relevant financial relationships or otherwise to disclose.

Additional information

Funding

This research was supported by the National Council for Scientific and Technological Development (#304625/2016-7), Coordination for the Improvement of Higher Education Personnel (Finance Code 001), and Foundation Carlos Chagas Filho Research Support of the State of Rio de Janeiro (#E-26/202.679/2018).