An Emerging Tool for Evaluating Lung Function in an Expanding Service Base
A high-quality spirometric study is an essential foundation to the diagnosis and treatment of COPD.
Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity and mortality and has emerged as the third leading cause of death in the United States.1 COPD is comprised of a group of debilitating respiratory conditions (emphysema, chronic bronchitis, asthma, and bronchiectasis) characterized by difficulty breathing and/or shortness of breath, airflow limitation, cough, and recurrent exacerbations. COPD is typically associated with a history of cigarette smoke exposure, either primary or secondary hand smoke. Because of the disease presentation and ongoing variable progression, the disease encompasses considerable heterogeneity, which has been considered in many of the new guidelines for detection and treatment.
Recent data indicate that 6.3% of US adults have been told that they have COPD and that the disease prevalence increases with advancing age.2 Of those reporting having COPD, 71.4% received their diagnosis as determined by spirometry and the number of those reporting the use of spirometry increased with age.2 Further, after adjusting for age, an estimated 50.8% reported using at least one daily medication to manage their COPD-related symptoms with 18.6% reporting using an emergency department or hospital admission within the preceding 12 months for a COPD exacerbation.2 Some suggest that these figures underestimate the true prevalence of the COPD epidemic and that more should be done to identify and treat those at risk. Certainly, smoking cessation is a high priority and there is no need to perform diagnostic testing before smoking cessation is implemented. However, because pulmonary function varies considerably from individual to individual, it is also recommended that a good spirometric baseline study be conducted and retained for future comparison in those who smoke.
Spirometry is required to establish the diagnosis of COPD and should be part of a multidimensional assessment to establish treatment parameters that extend beyond physiologic assessment of pulmonary function. In 2010, the National Institute for Health and Clinical Excellence (NICE) in the United Kingdom upgraded their guidelines in order to specifically address the multidimensional and often variable aspects of the disease.3
Using spirometry to establish the diagnosis, the multidimensional algorithm then focused on symptom severity and exacerbations to guide the treatment plan. In 2011, the Global Initiative for Chronic Obstructive Lung Disease (GOLD) updated their strategy maintaining spirometry, particularly the forced expiratory volume in 1 second (FEV1), as the physiologic index for evaluating dysfunction; they also included exacerbation history and symptom scores as assessed by either the modified Medical Research Council (mMRC) or the COPD Assessment Test (CAT) score4 (Table 1). Thus, a quality spirometric study is essential and provides the foundation upon which all other treatment options are based. More specifically, the presence of a real physiologic post-bronchodilator FEV1/FVC < .70 confirms the presence of airflow limitation—COPD.4
Spirometry is a physiologic test for measuring how efficiently an individual inhales or exhales volumes of air as a function of time. Yet, a quality spirometric measurement is difficult to obtain, and, for those not well versed in spirometric testing, it is plagued with technical and effort dependent errors that can lead to erroneous measurements and treatment.
The American Thoracic Society (ATS)/European Respiratory Society (ERS) have published and updated their standards for spirometric testing to improve validity and reliability.5-7 Spirometers are in a state of continual diagnostic and quality improvement as algorithms are incorporated into the software to assess spirometric indices, evaluate critical parameters for validity and reliability, and determine means to assist in evaluating subject effort. Yet, two major forces still impact heavily on the overall outcomes of testing: technician skill and determination of patient effort.
For quality spirometry, the instrument used must meet published standards, be in good working order, and be routinely calibrated against known standards. Second, while each microprocessor-based spirometer typically comes preloaded with various prediction equations for establishing normality comparisons, each lab should select the appropriate comparison data based on their study populations. Otherwise, subjects may be wrongly flagged as being either inside or outside of normal limits.
In 2005, the ATS/ERS advocated the race and ethnicity specific National Health and Nutrition Examination Survey III equations be used for North America.8 Further, they recommended that each lab should weigh and measure the height of each individual tested to ensure consistency of reporting using an accurate and calibrated instrument.
Each technician performing spirometry should be well educated with respect to patient testing, instrumentation knowledge, safety issues, and potential technical errors that can lead to erroneous data and subsequent misinterpretation. Technicians should record a minimum of three acceptable spirometric maneuvers with consistent (repeatable) results for both the FVC and the FEV1 and make note of any difficulty experienced during testing on the report. Repeatability is judged by taking the largest and second largest values for both the FVC and FEV1 and the difference should be 150 mL (.15 L) or less.
It should be noted that using this criterion alone may not yield a maximal maneuver. Maximal patient effort is essential as judged from the shape, size, and consistency of the flow/volume curves. Thus, technician judgment and critical thinking skills are crucial for assuring quality and accurate spirometry.
Some of the commonly experienced errors that impact spirometric testing are: submaximal inhalation, excessive extrapolation of volume, delayed onset of a maximal effort, submaximal push out, cough during the maneuver, early termination of the maneuver, variable effort, glottis closure or breath holding, coughing during the test, a partially obstructed mouthpiece, air leak, extra breaths during the maneuver, and positive or negative zero flow to mention a few.
Many common obstacles to attaining a quality spirometric recording are related in some way to technique and the ability of the tester to coach the patient in achieving a quality and maximal effort. First and foremost, each patient should be correctly seated and instructed regarding posture for testing. Next, the technician should go over what the patient is expected to do, demonstrate the maneuver, and allow some practice blows. Then, after allowing the patient a short rest, proceed with the test. This will go a long way toward achieving quality spirometric data.
Once spirometric data are obtained, the next step is interpretation. Sometimes the internal software provides faulty interpretation by not recognizing poor patient effort. In some instances, patients are misclassified by these built-in algorithms. Thus, the clinician must have a good understanding of spirometric testing, pulmonary function, and which normative data set is appropriate, as well as discerning quality patient effort from the report.
Additional pitfalls include using a low FEF 25%-75% as indicative of small airway disease, a concept without sufficient evidence; and applying the 2001 Global Initiative for Chronic Obstructive Lung Disease (GOLD) FEV1/FVC < .70 for defining airway obstruction, which may lead to false-negative interpretation for children and young adults and a false-positive reading for individuals greater than 60 years of age.9
Spirometry is an invaluable tool for the assessment of lung function and is used in many different settings. Spirometry results will be of value only if testing is performed in an accurate, consistent, and effort dependent manner. Repeated expiratory maneuvers (minimum of three) should be recorded, and these should meet repeatability guidelines (5% or 100 mL, whichever is greater).4 To help ensure that quality data are obtained, a great deal of attention to detail, equipment calibration, and the use of a technician who is knowledgeable regarding pulmonary function and the equipment used is essential. Also, the technician must be able to communicate with patients in such a way that maximal efforts are elicited. Ongoing technician training and recertification will help to ensure that test results are clinically useful as they reflect actual state of lung function. For the reader, additional training and insights can be found at the below sites. RT
- GOLD: A spirometry guide for general practitioners and a teaching slide set is available
- American Thoracic Society
- British Thoracic Society
Rick Carter, PhD, MBA, is professor, exercise sciences, Lamar University, Beaumont, Tex; Brian L. Tiep, MD, FAACVPR, is medical director, Respiratory Disease Management Institute, Monrovia, Calif, and director of pulmonary rehabilitation, City of Hope, Duarte, Calif; and Yunsuk Koh, PhD, is assistant professor, exercise sciences, Lamar University. For further information, contact [email protected].
Kockanek KD, Xu J, Murphy SL, et al. Deaths: Final data for 2009. 2011.
Centers for Disease Prevention and Control. Chronic obstructive pulmonary disease among adults—United States 2011. Morb Mort Wkly Rep. 2012;61(46):938-943.
National Institute for Health and Clinical Excellence (NICE). 2010.
Gold Science Committee. Global Initiative for Chronic Obstructive Lung Disease: A Guide for Health Care Professionals. 2011:1-30.
Standardization of spirometry-1979 update. Am Rev Respir Dis. 1979;119:831-838.
Standardization of Spirometry 1994 Update. Am J Respir Crit Care Med. 1995;152:1107-1136.
Miller MR, Hankinson J, Brusasco V, et al. Standardisation of spirometry. Eur Respir J. 2005;26(2):319-338.
Hankinson JL, Odencrantz JR, Fedan KB. Spirometric reference values from a sample of the general U.S. population. Am J Respir Crit Care Med. 1999;159:179-187.
Hardie JA, Buist AS, Volimer WM, et al. Risk of over-diagnosis of COPD in asymptomatic elderly never-smokers. Eur Respir J. 2002;20:1117-1122.