Office Spirometry for Lung Health Assessment in Adults: A Consensus Statement From the National Lung Health Education Program

Gary T. Ferguson, MD, FCCP; Paul L. Enright, MD; A. Sonia Buist, MD; and Millicent W. Higgins, MD, Honorary FCCP, *From the University of Arizona (Dr. Enright), Tucson, AZ; Botsford Pulmonary Associates (Dr. Ferguson), FramingtonHills, MI; Oregon Health Sciences University (Dr. Buist), Portland,OR; and the University of Michigan (Dr. Higgins), AnnArbor, MI.

Disclosures

CHEST. 2000;117(4) 

In This Article

Technical Requirements for Office Spirometers

A new category of spirometers, office spirometers, should be available for use in the primary-care setting. Each new model must successfully pass a validation study (see Appendix 1).

Rationale: Traditionally, spirometry has been used as a diagnostic test, with the usefulness and accuracy of spirometry measurements depending on both the equipment and proper test performance. Although simple to learn, spirometry is an effort-dependent test that requires a cooperative patient and a trained person capable of administering the test. Specific recommendations have been developed by the ATS and other professional organizations to ensure accurate and reproducible measurements when using diagnostic spirometers.[13,106,107,108,109] In many cases, a diagnostic spirometer that meets ATS standards will be the preferred choice for a hospital, outpatient clinic, or doctor's office since it permits diagnostic and follow-up testing (tracking) of lung function. Currently available diagnostic spirometers also may be used in the primary-care setting to evaluate smokers for COPD. However, some characteristics of diagnostic spirometers create a barrier to their widespread use for this purpose. Advantages of the newly proposed category of office spirometers for this purpose include lower instrument cost, smaller size, less effort to perform the test, improved ease of calibration checks, and an improved quality-assurance program. Office spirometers should not be utilized for diagnostic testing, surveillance for occupational lung disease, disability evaluations, or research purposes.

Current ATS recommendations for diagnostic spirometry 1 must be followed for office spirometry, except for the following seven factors.

1
, FEV 6 , and the FEV 1 /FEV 6
Ratio

The reported FEV1 and FEV6 values should be rounded to the nearest 0.1 L and the percent predicted as an integer (for instance, 72%); and the FEV1 /FEV6 ratio should be calculated as a fraction with only two decimal places (for instance, 0.65). An indication should be made next to the reported value (an asterisk for instance) when the patient's values fall below the LLN range for the variable. The false-positive rate increases when additional variables (for instance, the midexpiratory phase of forced expiratory flow) are used to define abnormality.[110]

Rationale: Spirometry is a simple test that measures the volume of air expelled from fully inflated lungs as a function time.[111] Following inspiration to a maximal lung volume, the patient is instructed to exhale as fast and hard as possible. Many lung function indexes may be derived from spirometry; however, the most valuable indexes are the total volume of exhaled air and the FEV1 . [1]

Rationale: The measurement of FVC should be replaced by that of FEV6 so that each maneuver need last for only 6 s. The advantages of using FEV6 for office spirometry are the following: (1) it is easier for the patient and the technician when maneuvers last only 6 s; (2) technical problems with flow sensors related to accurately measuring very low flows over several seconds of time (resolution and zero drift) are minimized; (3) the FEV6 is more reproducible than the FVC in patients with airways obstruction; (4) using the FEV6 reduces the overall time to perform a test; and (5) shorter maneuvers reduce the risk of syncope. The FEV6 has long been proposed as a surrogate measurement for FVC 112 ; however, reference values for FEV6 and the FEV1 /FEV6 ratio have only recently become available.[27] The validity of using FEV6 as a surrogate for FVC is now being established. For example, unpublished data from the LHS suggest that the FEV1 /FEV6 ratio is as good as the FEV1 /FVC ratio in predicting the decline in FEV1 over the subsequent 5 years in adult smokers. Some healthy children and some young adults empty their lungs before 6 s has elapsed; in those cases, their FVC and FEV6 values should be considered equivalent if their end-of-test volume is not too high (suggesting that their FEV6 has been underestimated).

1
/FEV 6
Ratio and the FEV 1
Percent Predicted Are Both Below Their LLNs

The FEV1 percent predicted may optionally be used to categorize the severity of the abnormality (Table 3). Report FEV1 as a percent of predicted to patients. This is "the number" the patient should remember.

Rationale: The ATS recommends that the FEV1 / FVC ratio be used to diagnose airways obstruc 13,106 The FEV1 /FEV6 ratio is a good surrogate for the FEV1 /FVC ratio (see above). The LLN is now well defined for all ages of African Americans, Hispanic Americans, and whites, with a mean of about 73%, ranging from 70 to 76% depending on age, gender, and race.[27]

This recommendation for using the FEV1 /FEV6 ratio with office spirometers should not discourage clinicians from continuing to use an older diagnostic-quality spirometer that reports the FEV1 /FVC ratio and its LLN, but not the FEV1 /FEV6 ratio. How the FVC is defined as the maximum amount of air that the patient can exhale, and most adult patients can exhale more air after 6 s. Therefore, when using traditional reference equations and an interpretation of airways obstruction based on the FEV1 /FVC ratio, airway obstruction may be missed (a false-negative result) if the patient is not coached to exhale completely (usually ≥ 10 s).

In patients with COPD, the FEV1 percent predicted is directly proportional their quality of life and ability to perform exercise.[113] Clinicians and patients understand the semiquantitative terms mild, moderate, and severe better than percent predicted when discussing the relative severity of diseases. A stronger admonition and the patient's adherence to the recommended intervention may be more likely when the abnormality is reported as moderate or severe.

Also, when the abnormality is moderate or severe, the likelihood that the test result is falsely positive is much lower than when the abnormality is mild. The severity category cut-points suggested in Table 3 (40% and 60%) correspond roughly to z scores of 2 and 3 in the distribution of the percent predicted for FEV1 in patients with COPD and are in widespread clinical use.[106]

Rationale: Many performance standards essential to reliable spirometry measurements 1 already have been automated and included within spirometry devices to reduce the likelihood of poor-quality test results.[40,112,114] Additional built-in performance checks are necessary for office spirometers that do not display or print spirograms or flow-volume curves, which the technician or physician can review for acceptability and reproducibility of the maneuvers. Table 4 lists quality control (QC) criteria that must be monitored electronically along with recommended messages to be displayed when these maneuver quality errors are detected. These thresholds were designed so that > 90% of adult patients (even the elderly) can pass all the QC checks within five maneuvers if coached by a technician who has good training, motivation, and experience. Devices should present the numeric spirometry results and interpretations only if all maneuver QC criteria are met. While we believe that these electronic quality checks will reasonably ensure good-quality tests, studies are necessary to validate their performance in primary-care settings.

Rationale: Standards for diagnostic spirometry require that graphs of the maneuvers be produced so that technicians who perform the tests, physicians who interpret the results, and those who later review the test reports may recognize problems with maneuver quality.[13] The graphs also assist physicians in the recognition of the characteristic patterns of different types of abnormalities, such as generalized airways obstruction, restriction of lung volumes, and the rare upper airways obstruction.[111,115] However, a graphic display or a printer usually increases the size, cost, and complexity of spirometers, reducing their widespread acceptability in the primary-care setting. It is also likely that many technicians and physicians will not learn to recognize the patterns of unacceptable spirometry maneuvers and that many physicians will not recognize the patterns of abnormality. We believe that automated-maneuver QC checks and messages are generally more reliable now for quality-assurance purposes than are programs to teach pattern recognition of spirometry graphs, although no published studies demonstrate this.

These educational materials should include procedure manuals, audiovisual instructional aids (such as a videotape or multimedia CD ROM), and patient handouts that describe the potential risks and benefits of NLHEP spirometry, interpretation of the results, and limitations of the test.

Rationale: It is unlikely that many primary-care physicians will spend the time and money necessary to send their technician or nurse to a 2-day spirometry training course.[116] Emphasis in training materials must be placed on effective interactions between the technician and the patient when performing spirometry tests (Table 5). In order to minimize the number of breathing maneuvers needed to obtain a good-quality test session, technicians always must demonstrate the correct maneuver themselves before instructing patients to perform them. The technician must then enthusiastically coach and watch the patient throughout the three phases of each maneuver: (1) maximal inhalation, (2) blast out quickly, and (3) continue exhalation for 6 s. Most maneuver errors are easily recognized by watching the patient. When the technician or the automated spirometer maneuver QC checks detect poor-quality maneuvers, the technician must tell the patient what went wrong and again demonstrate how to perform the maneuver correctly. After eight maneuvers are performed and the test session is of poor quality, the test should be rescheduled for a later date.

Rationale: One-liter calibration syringes may be as effective as 3-L syringes, and they are smaller and less expensive. It is also possible that precisely manufactured plastic (Mylar; 3M Corp; St. Paul, MN) bags could be used to check volume accuracy on a daily basis. However, until alternative calibration methods are proven to check spirometer calibration effectively, the use of calibrated 3-L syringes on a regular basis is necessary. If a calibration syringe is not available in a primary-care setting, calibration checks using a standard 3.00-L calibration syringe may be performed at regular intervals by a local diagnostic PF laboratory at minimal cost. A proper interval cannot be arbitrarily set for all spirometers. Manufacturers should validate the acceptable calibration interval specified for their office spirometers that ensures that they remain accurate when used as directed in the primary-care setting. Third-party testing of the between-sensor (within-batch) accuracy of single-use flow sensors should be established.

Periodic testing of a biological control also should be used to check the long-term performance of office spirometers. The individuals chosen as biological control subjects must be > 25 years old and must not have an obstructive lung disease. Their FEV1 and FEV6 first must be measured on 10 days, and the average values and ranges must be calculated. The range of measurements for FEV1 and FEV6 (largest minus smallest) should not exceed 10% of the average value, otherwise a different biological control subject should be chosen. If disposable flow sensors are used, the biological control subject may reuse a single-flow sensor, and it should be stored with the subject's name on it. The biological control subject then should be tested on each day that patients are tested. If the control subject's measured FEV1 or FEV6 is > 10% from the average value, the test should be repeated. If the FEV1 remains "out of bounds," even after replacing or cleaning the sensor, the device should not be used on patients until repaired.

1
and FEV 6
Must Be Corrected to BTPS Conditions

The device should sense the temperature automatically if necessary for accurate body temperature, ambient temperature, and saturation with water vapor (BTPS) corrections. The technician should not be asked to enter the temperature.

Rationale: The measurement of ambient or spirometer temperature and barometric pressure may not be needed for some spirometers in which the design allows the use of a fixed BTPS correction factor.[117] Errors in measuring FEV1 and FEV6 must remain , 3% (according to BTPS testing methods recommended by the ATS). Manufacturers must specify the range of ambient temperatures and altitudes in which the results remain accurate.

Staff performing spirometry tests must be instructed to wash their hands before and after assisting each patient with the test. If patients are only exhaling through the devices, proper use of disposable mouthpieces is all that is needed to minimize the risk of the transmission of infections. In particular, disposable in-line filters are not mandated.[13,116] All devices should be inspected and kept clean to meet good hygiene standards. Devices with completely disposable flow sensors or with mouthpieces that have one-way valves should be used if testing is to be performed in patients likely to inhale through the mouthpiece. Manufacturers should give explicit instructions about cleaning techniques and frequency of cleaning.

Rationale: Charges should be kept as low as possible but should at least cover the real costs of the test. It seems imprudent to charge patients or third-party insurers for diagnostic-quality spirometry tests when office spirometry tests are performed, since office spirometry tests will require less expensive instruments, less technician time, and less training to interpret.

There is insufficient published evidence related to many of the technical and procedural issues associated with the above recommendations for office spirometry. More detailed information is needed about the following issues: levels of training required to obtain results of acceptable quality; levels of inaccuracy and imprecision; reliability; durability; and the necessary frequency and type of calibration checks (see Appendix 1). Outcomes to be assessed include sensitivity of detection, frequency of false-positive test results, and the overall impact on patient care, quality of life, and cost-benefit analyses. These issues should be examined both for pulmonary diseases and as a part of total health care. Additional areas requiring research include the role of office spirometry in lower risk individuals (ie, nonsmokers, former smokers, and those without respiratory symptoms) and the prospective utility of office spirometry in the intervention and management of global disease processes. Research in these areas is strongly encouraged in order to validate and improve the above recommendations.

Abbreviations: ACCP = American College of Chest Physicians; ATS = American Thoracic Society; BTPS = body temperature, ambient temperature, and saturation with water vapor; FET = forced expiratory time; FEV6 = forced expiratory volume in 6 s; HRCT = high-resolution CT; LHS = Lung Health Study; LLN = lower limit of normal; NHANES = National Health and Nutrition Examination Survey; NHLBI = National Heart Lung and Blood Institute; NLHEP = National Lung Health Education Program; PCP = primary-care provider; PEF = peak expiratory flow; PEFT = peak expiratory flow time; PF = pulmonary function; QC = quality control

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