acoem guidance statement...major spirometry developments since publication of acoem’s 2011...

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Copyright © 2020 American College of Occupational and Environmental Medicine. Unauthorized reproduction of this article is prohibited

Spirometry in Occupational Health—2020

Mary C. Townsend, DrPH

Spirometry in the occupational health setting

plays a critical role in the primary, secondary,

and tertiary prevention of workplace-related lung

disease. Recognizing the central role of spirom-

etry in workplace respiratory programs, the

American College of Occupational and Environ-

mental Medicine (ACOEM) developed three spi-

rometry position statements in the past two

decades, which summarized advances of partic-

ular relevance to occupational health practice.

However, since these statements were published,

there have been important developments in fed-

eral regulations and in official American Tho-

racic Society recommendations which affect

occupational spirometry testing. This 2020

ACOEM guidance statement incorporates these

spirometry testing changes into its recommenda-

tions to provide current information for all users

of spirometry test results, from those who per-

form or supervise testing to those who only

interpret or review results.

S pirometry, the most frequently per-formed pulmonary function test

(PFT), is the cornerstone of occupationalrespiratory evaluation programs. In theoccupational health setting, spirometryplays a critical role in the primary, second-ary, and tertiary prevention of workplace-related lung disease.1,2 The primary aim ofworkplace spirometry is to identify workerswho should have further evaluation forpossible disease. Consistency over timeof testing techniques, equipment, and inter-pretation approaches are essential in occu-pational testing since workers are oftenevaluated over decades of employment.Testing is required by some regulationsbased on employee work exposures and

testing may also be used to assess thepresence of impairment in symptomaticworkers. Used for both screening and clini-cal evaluations, spirometry tests are per-formed in a variety of venues ranging fromsmall clinical practices to large testingfacilities and multiple plant medical depart-ments within an industry.

Physicians and other health care pro-fessionals may conduct spirometry teststhemselves, supervise others conductingthe tests, or be involved only in interpretingtest results. Whatever their level of involve-ment in the actual testing, spirometry usersneed to be aware that spirometry differsfrom many other medical measurementssince it depends on multiple factors forits results to be valid. If subject effort isflawed, equipment is not accurate, or tech-nicians fail to elicit maximal cooperationand effort, results can be falsely elevated orreduced. If uncorrected, these problemsmay profoundly impact conclusions thatare drawn about a worker’s pulmonaryfunction with potentially adverse conse-quences for workers (Table 1).

Recognizing the central role of spi-rometry in workplace respiratory programs,the American College of Occupational andEnvironmental Medicine (ACOEM) devel-oped three spirometry position statementsin the past two decades, which summarizeadvances of particular relevance to occupa-tional health practice.1,3,4

However, since these statementswere published, there have been a numberof developments which affect occupationalspirometry testing. First, the AmericanThoracic Society (ATS) and the EuropeanRespiratory Society (ERS) issued an Offi-cial Technical Statement on Standardiza-tion of Spirometry 2019 Update,5 as well asa correction,6 and explanation of an errormade in the 2005 Spirometry Statement.7

Second, the US Occupational Safety andHealth Administration (OSHA) issued itsBest Practices Guidance on SpirometryTesting in Occupational Health Programs.8

Third, the ATS issued Official TechnicalStandards on Occupational SpirometryTesting2 and on Standardized PulmonaryFunction Reports.9 Fourth, OSHA promul-gated the Respirable Crystalline SilicaStandards for construction (29 CFR1926.1153) and for general industry (29CFR 1910.1053) and maritime (29 CFR1915.1053).10,11 Fifth, in 2014, the USMine Safety and Health Administrationadded spirometry to coal miner medicalsurveillance exams,12 and in 2016, theNational Institute for Occupational Safetyand Health (NIOSH) began approving clin-ics to test coal miners as part of the CoalWorker Health Surveillance Program(CWHSP).13,14 Effective July 15, 2019,OSHA updated the Cotton Dust Standard(29 CFR 1910.1043), the landmark regula-tion in which OSHA first specified how

From the American College of Occupational andEnvironmental Medicine, Elk Grove, Illinois.

This position paper was developed by ACOEMunder the auspices of the Council of ScientificAdvisors. It was reviewed by the Committee onPolicy, Procedures, and Public Positions, andapproved by the ACOEM Board of Directors.ACOEM requires all substantive contributors toits documents to disclose any potential compet-ing interests, which are carefully considered.ACOEM emphasizes that the judgmentsexpressed herein represent the best availableevidence at the time of publication and shallbe considered the position of ACOEM and notthe individual opinions of contributing authors.

The author declares no conflicts of interest.Address correspondence to: Marianne Dreger, MA,

ACOEM, 25 Northwest Point Blvd, Suite 700,Elk Grove Village, IL 60007 ([email protected]).

Copyright � 2020 American College of Occupa-tional and Environmental Medicine

DOI: 10.1097/JOM.0000000000001851

TABLE 1. Spirometry in Occupational Health—2020 Topics

1. Equipment Performance(a) Spirometer Specifications and Validation Testing Recommendations(b) Spirometer Accuracy Checks(c) Avoid Sensor Errors during Subject Tests

2. Conducting Tests(a) Technician Training(b) Conducting the Test(c) Testing Goal for a Valid Test(d) Reporting Results(e) Quality Assurance (QA) Reviews

3. Comparing Results with Reference Values(a) Reference Values(b) Race-Adjustment of Predicted Values and LLNs(c) Interpretation Algorithm

4. Longitudinal Interpretation(a) Spirometry Testing Quality and Test Variability(b) Frequency and Duration of Testing(c) Determination of Abnormally Reduced or Highly Variable FEV1

5. Further Evaluation of Spirometric Abnormalities6. Recordkeeping

FEV1, Forced Expiratory Volume in One Second; LLN, Lower Limit of Normal; A, Quality Assurance.

e208 JOEM � Volume 62, Number 5, May 2020

ACOEM GUIDANCE STATEMENT

mailto:[email protected]


occupational spirometry testing must beconducted.15 And finally, OSHA has issueda Letter of Interpretation regarding respon-sibility for maintaining medical recordsunder the Silica and Respiratory ProtectionStandards.16 Table 2 summarizes thesemajor developments since publication ofthe last ACOEM spirometry statementin 2011.

ACOEM has developed this 2020statement to incorporate these spirometrytesting changes into its recommendations.The goal of this statement is to provide

comprehensive current information for allusers of spirometry test results, from thosewho perform or supervise testing to thosewho only interpret or review results. Thedocument allows those with specific inter-ests to review those sections that are rele-vant to them. As shown in Table 1, sixmajor topics are covered in this statement:(1) Equipment Performance; (2) Conduct-ing Tests; (3) Comparing Results with Ref-erence Values; (4) Evaluating Results overTime; (5) Further Evaluation of SpirometricAbnormalities; and (6) Recordkeeping.

Major recommendations are summarizedat the end of the document in ACOEMRecommendations—2020. To assist read-ers in understanding the material, particu-larly in sections on Equipment Performanceand Conducting Tests, Fig. 1 presents aspirogram from a valid test, to comparewith the flawed test results shown inFigs. 2 and 3, as discussed below.

EQUIPMENT PERFORMANCEFour elements contribute to accurate

spirometer performance: (1) ATS/ERS5,7

TABLE 2. Major Spirometry Developments Since Publication of ACOEM’s 2011 Statement4

1. Effective July 15, 2019, OSHA updated the Cotton Dust Standard (29 CFR 1910.1043), the landmark regulation in which OSHA first specified howoccupational spirometry testing must be conducted.15

2. OSHA issued Best Practice Guidance for Occupational Spirometry Testing.8

3. NIOSH-approved spirometry courses for technicians are required by the Cotton Dust Standard,15 Respirable Crystalline Silica Standards,10,11 and theNIOSH Coal Worker Health Surveillance Program (CWHSP),13 and recommended by OSHA Guidance.8

4. NIOSH maintains a list of spirometers approved for use in the CWHSP.17

5. NIOSH released spirometry training videos.18

6. OSHA and NIOSH promulgate record-keeping requirements,10,13,15,16 and ATS and OSHA make record-keeping recommendations.2,8

7. ATS/ERS states that ‘‘There is no requirement for minimum FET’’ (length of exhalation).5 Subjects who are young, have small thoracic cavities, orhave restrictive impairment often have spirometry maneuvers with plateaus and repeatable results, but with exhalation times less than 6 s.5,6,8,9 Suchmaneuvers are now recognized as acceptable and can be used to meet requirements for a valid test.

8. ATS/ERS confirms that the occupational spirometry testing protocol which records only maximal expiration meets the requirements of the 2019Update of the ATS/ERS Spirometry Standards.19-21 This permits occupational settings to maintain essential consistency in their testing proceduresover time.

9. ATS/ERS confirms that for occupational spirometry testing in the United States, the use of the NHANES III22 spirometry reference values is in fullcompliance with the 2019 Update of the ATS/ERS Spirometry Standards.19-21 Since consistency over time is essential, NHANES III remains therequired or recommended reference value set for occupational testing in the United States.2,8,9,15

10. A 0.88 scaling factor, applied to NHANES III22 Caucasian reference values for FVC and FEV1, is recommended or required when testing Asian-American workers.2,8,15 However, the Caucasian FEV1/FVC reference values are not adjusted.

11. Spirometry abnormality is assessed using the 5th percentile LLN, but values close to the LLN should be interpreted with caution.9

12. Especially for workers with initial FEV1 above 100% of predicted, longitudinal evaluation of FEV1 can be used as a tool to determine whether moreevaluation for possible disease is indicated.2

13. ATS recommends further medical evaluation steps when screening abnormalities are found.2

ACOEM, American College of Occupational and Environmental Medicine; ATS, American Thoracic Society; CWHSP, Coal Worker Health Surveillance Program; ERS,European Respiratory Society; nnnnnnnnnn Occupational Safety and Health Administration; LLN, Lower Limit of Normal; NHANES III, National Health and Nutrition ExaminationStudy, Round III; NIOSH, National Institute for Occupational Safety and Health.

FIGURE 1. Valid test. Flow-volume curve (left) emphasizes start of test, rising immediately to a sharp peak and smoothlydescending to zero flow. Volume-time curve (right) emphasizes end of test, initially rising rapidly, and then gradually flattening outand reaching 1 second of no visible volume change, at the FVC plateau. To permit effective subject coaching, ATS/ERSrecommends using spirometers that show both graphical displays real-time and of sufficient size to clearly reveal technicalerrors.5,7

JOEM � Volume 62, Number 5, May 2020 Spirometry in Occupational Health—2020

� 2020 American College of Occupational and Environmental Medicine e209


FIGURE 2. (A). Sensor contaminated or blocked by condensation, mucus, or fingers. DISCARD THIS CURVE. The last curve (#8)shows the impact of blockage or contamination of the sensor after the 7th maneuver was recorded. The FVC and FEV1 values arefalsely increased on curve #8, exceeding values from the earlier maneuvers (curves #1 and #7) by more than 0.40 L. Techniciansmust replace the sensor if it becomes contaminated during the test. Based on ‘‘Spirometry Testing in Occupational Health Programs:Best Practices for Healthcare Professionals.’’ OSHA 3637-2013.8 FIGURE 2. (B) Error: Inconsistent Zero-Flow Errors Causing Flows tobe Over-Recorded. DELETE THIS TEST. This spirometer’s zero-flow reference point was set at different incorrect levels before thefirst two maneuvers, causing the volume-time curves (bottom figure) to be splayed apart and extended tails to be drawn to theright on the flow-volume curves (top figure). FVC is increased more than FEV1, falsely reducing the FEV1/FVC and probably leadingto an erroneous ‘‘obstructive impairment’’ pattern. Block sensor when the spirometer is zeroed and hold sensor still during subjecttesting to avoid this problem. Based on ‘‘Spirometry Testing in Occupational Health Programs: Best Practices for HealthcareProfessionals.’’ OSHA 3637-2013.8

Townsend JOEM � Volume 62, Number 5, May 2020

e210 � 2020 American College of Occupational and Environmental Medicine


FIGURE 2. (C) Error: Zero-Flow Error Causing Flows to be Under-Recorded. DELETE THIS TEST. FVC is much more reduced thanFEV1, falsely increasing the FEV1/FVC and possibly masking true airways obstruction. Block the sensor when the spirometer iszeroed and hold sensor still during subject testing to avoid this problem. Based on ‘‘Spirometry Testing in Occupational HealthPrograms: Best Practices for Healthcare Professionals.’’ OSHA 3637-2013.8 FIGURE 2. (D) Error: Consistent Zero-Flow Error CausingFlows to be Over-Recorded (left). DELETE THIS TEST. This spirometer’s zero-flow reference point was set only once per test, beforea complete set of maneuvers. The test on the left shows a zero-flow error, while the test on the right shows valid results; both testswere recorded by the same subject. The zero-flow error on the left produced erroneous but consistent results for all maneuvers,elevating the FVC more than the FEV1 and falsely reducing the FEV1/FVC. This zero-flow error may erroneously indicate an‘‘obstructive impairment’’ pattern. Consistency of the flawed curves on the left may make this error difficult to detect, buttechnicians should watch out for extended tails that are drawn to the right on the flow-volume curves (top figure), and volume-time curves that climb at a constant rate without reaching a plateau, until the spirometer terminates data collection (bottomfigure). Block the sensor when the spirometer is zeroed and hold sensor still during subject testing to avoid this problem. Based on‘‘Spirometry Testing in Occupational Health Programs: Best Practices for Healthcare Professionals.’’ OSHA 3637-2013.8 OSHA;Occupational Safety and Health Administration.




and ISO23 recommend minimum perfor-mance-based standards for spirometers ofall types; (2) prototype spirometers andtheir software should undergo validationtesting, preferably by an independent test-ing laboratory, to demonstrate they meetthese specifications5,7; (3) spirometer usersshould perform daily accuracy checks (ie,‘‘calibration checks’’) of the spirometer sothat defective spirometers can be removedfrom service until they are repaired5,7; and(4) if sensor errors develop during subjecttesting, users need to recognize the errorsand delete the resulting invalid tests even ifnot labeled as errors by the spirometer’ssoftware.5,24

Though these elements of accuratespirometer performance have not changedsignificantly since 2011, increasing atten-tion has been paid to their implementation.The OSHA Guidance document endorsesthese elements as best practice for assuringaccurate equipment performance andpresents a list of recommended featuresfor newly purchased spirometers.8 Innonmandatory Appendix B, the OSHARespirable Crystalline Silica Standards rec-ommend following these elements in occu-pational spirometry testing.10 But eventhough general comments about desirablespirometer properties are available, untilnow there has been little information aboutspecific manufacturers and models of spi-rometers that might be appropriate for theoccupational health setting.

As NIOSH developed requirementsfor its clinics approved for spirometry testing

of coal miners, NIOSH evaluated documen-tation submitted by manufacturers for inclu-sion in its CWHSP. As discussed below,though the list of spirometers approved byNIOSH for their CWHSP is not exhaustiveand includes some program-specific require-ments, it does provide some possible con-crete guidance for spirometer selection byclinics for whom no specific recommenda-tions have been available previously. NIOSHrequires that spirometers used in its CWHSPmeet the criteria listed below, as presented inan online NIOSH table of spirometersapproved for CWHSP.17

ATS/ERS, ACOEM, and OSHA rec-ommend that facilities performing occupa-tional spirometry tests maintain a proceduremanual documenting the details of equip-ment type, spirometer configuration, manu-facturer’s guidelines, calibration log,service and repair records, personnel train-ing, and standard operating procedures.5,8

Such a manual will permit troubleshootingif problems with anomalous test resultsarise.

Spirometer Specifications andValidation TestingRecommendations

ACOEM4 and OSHA8,10,15 recom-mend or require selecting spirometers thatmeet the ATS/ERS recommendations foroccupational testing.7 In addition, NIOSHoperates the CWHSP to conduct mandatedsurveillance of working US coal miners’respiratory health. As part of CWHSP, spi-rometry is performed upon entry into the

coal mining workforce and periodicallythroughout the miner’s coal mining career.NIOSH approves facilities to test minersand has established requirements forthe spirometers used at these facilities.Spirometers used in NIOSH-approved clin-ics must17:

1. Comply with ATS performance stand-ards for accuracy and precision andreal-time display size.7

2. Meet NIOSH requirements for the con-tent of spirometry test reports.

3. Produce output data in standardizedelectronic spirometry data file formatwhich allows NIOSH to reconstructindividual spirometry curves for qualityreview of the coal miner spirometry test.

Though the third item is specific toNIOSH’s coal miner clinic requirements,meeting the first two criteria means that thespirometer meets ATS/ERS recommenda-tions, as recommended or required byACOEM4 and OSHA.8,10,15 Specifically,NIOSH criteria include17:

1. Obtaining written verification docu-menting spirometer validation testingby a third-party laboratory. The lettershould be obtained from the spirometermanufacturer and indicates that a spi-rometer model prototype measured atleast 21 of the 24 ATS waveforms withacceptable accuracy and precision.7 In2019, the ATS/ERS recommendedusing ISO standard waveforms23 toevaluate spirometers.5

FIGURE 3. (A) Error: Excessive Hesitation (solid curves). Discard this curve. Because the worker’s initial blast is delayed, the peak of theflow-volumecurve (top figure) isdisplaced to the right, andagradually climbing tail is seenat the start of thevolume-timecurve (bottomfigure). Coach the worker: ‘‘blast out as soon as you are ready.’’ Based on ‘‘Spirometry Testing in Occupational Health Programs: BestPractices for Healthcare Professionals.’’ OSHA 3637-2013.8




2. The spirometry system has a dedicatedcalibration check routine consistentwith the 2005 ATS/ERS recommenda-tions.2,5,7,8

3. Graphical displays meeting a minimumsize requirement provide real-time vol-ume-time and flow-volume curves dur-ing the test to enhance techniciancoaching.4,5,7,8

4. The spirometer software automaticallyperforms quality assurance checks onexpiratory maneuvers during each spi-rometry test.2,5,9 ‘‘However, techniciansshould be trained not to rely exclusivelyon these quality-control prompts, sincetechnical errors may occur that are notamong those recognized by the soft-ware.’’25

5. The spirometer can: (a) store values fromat least eight maneuvers within one testingsession; and (b) the spirometry softwarecan save and recall curves and results fromat least three acceptable maneuvers andpreferably from all curves.8,9

6. The spirometry data file retains resultsfor all parameters defined in the2005 ATS/ERS recommendations.7

FIGURE 3. (B) Error: Cough in 1st Second (solid curves). DISCARD THIS CURVE. Because cough in the first second repeatedlyinterrupts the airflow early in the expiration, the flow-volume curve (top figure) clearly shows steep changes (interruptions) in theflow rate, while the volume-time curve (bottom figure) shows only subtle steps in the first second. A drink of water may solve thisproblem. Based on ‘‘Spirometry Testing in Occupational Health Programs: Best Practices for Healthcare Professionals.’’OSHA3637-2013.8 FIGURE 3. (C) Error: No Blast (solid curves). This worker failed to blast out initially, so the expiratory speed was never rapid.The flow-volume curve (top figure) is very small and has no sharp peak, and the volume-time curve (bottom figure) shows aslanted start of expiration. Such a weak push reduces the FEV1 and FEV1/FVC, and may be caused by the worker trying to ‘‘save’’ airso that they can exhale for many seconds. This error causes false spirometer interpretations of ‘‘obstructive impairment.’’ Coach‘‘blast out hard and fast’’ to solve this problem. Based on ‘‘Spirometry Testing in Occupational Health Programs: Best Practices forHealthcare Professionals.’’ OSHA 3637-2013.8




FIGURE 3. (D) Error: Sub maximal Inspiration (solid curves). The solid volume-time curve (bottom figure) resulted from a worker failingto inhale maximally before the forced expiration. The solid curve is considerably lower than the dashed curve that was drawn when theworker inhaled maximally before the forced exhalation, and this very low curve is not ‘‘acceptable.’’ An incomplete inspiration can givethe appearance of reduced FEV1 and FVC, and maycause false spirometer interpretations of ‘‘restrictive impairment.’’ Coach the worker:‘‘fill your lungs.’’ Based on ‘‘Spirometry Testing in Occupational Health Programs: Best Practices for Healthcare Professionals.’’ OSHA 3637-2013.8 FIGURE 3. (E) Error: Early Termination (solid curves). When expiration stops before the volume-time curve flattens into a 1-second plateau, the FVC may not be fully recorded. The solid lines show expirations for a subject with airways obstruction whoterminated the exhalations early. Such incomplete recordings falsely increase the FEV1/FVC and may cause the spirometer interpretationto be ‘‘normal’’ even when airways obstruction is present. The dashed line shows the increase in FVC that wouldhave occurred with only5 more seconds of expiration for this subject. The resulting higher FVC and the lower, more accurate FEV1/FVC would trigger a correctinterpretation of ‘‘airways obstruction.’’(Note: though not shown here, subjects should try to exhale to a1-second plateau whenpossible. However, curves longer than 15 seconds should not be recorded.5) Coach ‘‘keep blowing until I tell you to stop.’’ Based on‘‘Spirometry Testing in Occupational Health Programs: Best Practices for Healthcare Professionals.’’ OSHA 3637-2013.8




FIGURE 3. (F) Acceptable Test for Young Worker with FVC Plateau. Because the subject recorded 1-second FVC plateaus and thecurves are repeatable, the maneuvers are acceptable.5,6,9 Spirometer error messages about ‘‘early termination’’ or ‘‘unacceptabletest’’ should be ignored. Based on ‘‘Spirometry Testing in Occupational Health Programs: Best Practices for Healthcare Professionals.‘‘OSHA 3637-2013.8 FIGURE 3. (G) Error: Extra Breath through the Nose at End of Test (solid curves). DISCARD THIS CURVE. At theend of the forced expiration, this worker inhaled additional air through the nose and quickly exhaled it into the spirometermouthpiece. The flow-volume curve (top figure) shows multiple maneuvers and the volume-time curve (bottom figure) showsadditional expirations in increasing steps at the end of the test. This error erroneously elevates the FVC, greatly reduces the FEV1/FVC, and causes a false spirometer interpretation of ‘‘airways obstruction.’’ Solution: have the worker wear nose clips. 27 Based on‘‘Spirometry Testing in Occupational Health Programs: Best Practices for Healthcare Professionals.’’ OSHA 3637-2013.8 OSHA;Occupational Safety and Health Administration.




7. For use in a NIOSH-approved CWHSPclinic, spirometers must provide elec-tronic transfer of spirometry data filesusing a NIOSH-approved procedure forthe format, content, and data structurespecified by the 2005 ATS/ERS recom-mendations.7

Items 1 to 5 have also been recom-mended or required by ACOEM4 and byOSHA8,15 and an image made to scale ofthe minimum recommended display size isavailable in Appendix A.4,8 An onlineNIOSH table of spirometers approved foruse in the CWHSP is available.17 Thoughthis list is not an exhaustive compilation ofspirometers that meet ATS recommenda-tions, it may provide a useful starting pointfor clinics that need to purchase spirometers.

ACOEM recommends that spiro-meters used for all occupational spirometrytests meet NIOSH criteria 1 to 5 above.Meeting these criteria will ensure thatoccupational spirometers comply withthe ATS/ERS recommendations.5,7,8 ForNIOSH-approved clinics that test coal min-ers, criteria 1 to 5 are currently in place andcriteria 6 to 7 will soon be fully in place.17

Spirometer Accuracy ChecksATS/ERS,2,5,7 ACOEM,4 OSHA,8,15

and NIOSH13 all recommend or requiredaily checking of spirometer accuracy whenthe spirometer is in use, more frequentlywhen the ambient conditions change, andat least every 4 hours when many tests areperformed throughout the day.8 Such fre-quent ‘‘calibration checks’’ ensure that spi-rometers are accurate when in use,preventing interpretation of erroneous testresults caused by inaccurate equipment.Details of the checks given by ATS/ERS,5

ACOEM,4 and OSHA8,15 are summarized inTable 3. Further details were given by ATS/ERS in Tables 3 and 4 of the 2019 Spirome-try Standardization document.5

For many models of spirometers, thecalibration is checked but cannot beadjusted by the user. If these spirometers

become inaccurate and repeatedly fail theircalibration checks, and there are no obviousmechanical causes for the inaccuracy, theymust be recalibrated by the manufacturer.But some spirometers require recalibrationon a regular basis. In this case, the techni-cian must carefully follow the manufac-turer’s instructions since the spirometer’scalibration factor will be reset by this pro-cedure. Once the spirometer is recalibrated,technicians should then perform the cali-bration checks listed in Table 3. Techniciansshould use spirometer software programsdesigned for calibration checks wheneverpossible.8

ACOEM, ATS, ATS/ERS, and OSHArecommend saving these calibration checkrecords indefinitely.2,4,5,8 ‘‘Availability ofsuch records permits later troubleshootingof problematic spirometry test results, whichis particularly important when conductingperiodic spirometry testing.’’2 ATS also rec-ommends performing calibration checkswhen spirometry software is updated and‘‘supplement[ing] calibration checks byusing standard subjects as biological con-trols.’’2,5

ACOEM, ATS, and OSHA recom-mend or require checking spirometer

accuracy, ie, performing ‘‘calibrationchecks,’’ daily when spirometers are inuse. They also recommend saving calibra-tion records indefinitely and keeping a logof technical problems found and solved, aswell as all changes in protocol, computersoftware, or equipment. As noted earlier,the purchase of spirometers with dedicatedcalibration check routines for use in theoccupational setting is recommended. Andsupplementing calibration checks by usingstandard subjects as biological controls isvaluable.2,5

Avoid Sensor Errors duringSubject Tests

Even though a spirometer passes itscheck of calibration accuracy, subject testresults can be invalidated by equipmenterrors occurring during subject tests.5,24

Two errors that can occur during subjecttesting using some flow-type spirometersare contamination or blockage of a spirom-eter sensor, and incorrect setting of thezero-flow reference point.

First, if a subject’s fingers, secre-tions, or water vapor block or contaminatea flow-type spirometer’s sensor, increasingits resistance, the test results will be falselyincreased and become invalid. The impactof this problem is seen by comparing a validtest (Fig. 1) with a test having sensor con-tamination (Fig. 2A). Even though suchcontaminated sensor problems are not iden-tified as errors by the spirometer, the tech-nician needs to identify the error when itoccurs and discard the erroneous curveimmediately so that the results are notreported as the largest results from thetest session.

Second, most flow-type spirometersset a zero-flow reference point before eachmaneuver, or before each set of maneuvers.All flows during a subject’s subsequentexpiration(s) are measured relative to thisreference point. The ‘‘zero’’ flow referencebaseline can be incorrect if: (1) a gravity-

TABLE 4. Spirometry Test Acceptability Requirements for Adults�

1. Maximal inhalation2. A good start of exhalation with extrapolated volume <5% of FVC or 0.10 L, whichever is

greater, that is, no excessive hesitation5

3. Free from artifacts4. No cough during first second of exhalation (for FEV1)5. No glottis closure or abrupt termination (for FVC)6. No early termination or cutoff (for FVC). Timed expiratory volumes can be reported in

maneuvers with early termination, but FVC should be reported only with qualification.7. Maximal effort provided throughout the maneuver: inhalation, blast, complete exhalation8. No obstructed mouthpiece9. No extra breaths taken through the nose10. No zero-flow errors

�FVC and FEV1 are each considered separately for acceptability. FEV1 acceptability does not consider anythingafter the first second, whereas FVC does.

Adapted from Ref. [9].

TABLE 3. Daily Calibration Checks4,5,8

Flow Spirometers:1. Inject 3 L of air at three different speeds (taking approximately 0.5 s, 3 s, and 6 s).2. Verify that the recorded value is between 2.91 and 3.09 L at all three speeds (ie, �3% of 3.00

L).5

Volume Spirometers�:1. Check that there are no leaks causing an air loss > 0.030 L/min (30 mL/min.).2. Inject 3 L of air and verify that the recorded value is between 2.91 and 3.09 L (ie, �3.0% of

3.00 L).5

�Quarterly checks of linearity are also needed for volume spirometers—see reference8 for details.Do not conduct spirometry tests if the spirometer fails any calibration checks, until the cause of

failure is identified and corrected.Adapted from ‘‘Spirometry Testing in Occupational Health Programs: Best Practices for Healthcare

Professionals.’’ OSHA 3637-2013.8

OSHA; Occupational Safety and Health Administration.




sensitive pressure-transducer movesduring the subject test; (2) pressure tubingis disconnected or loose; (3) a sensor isdegrading; (4) electronics are unstable; or(5) very slow airflow passes throughthe sensor in either direction while ‘‘zero-ing’’ is in progress. Such airflow mightbe caused by slight sensor motion, back-ground fans, or forced air ventilation.Blocking the sensor and holding it still nextto the subject’s face often prevents theseerrors.5,24

Unless a zero-flow error is large,most spirometers do not alert the user tothis problem. Zero-flow errors can be rec-ognized by the apparently constant flowrate that appears near the end of themaneuver in both the flow-volume andvolume-time curves, as can be seen inFig. 2B to D. Even though such zero-flowproblems may not be identified as errorsby available spirometers, the erroneouscurves should be discarded immediately(not saved), so that their results are notreported as the results from the test ses-sion.

Since neither of these types of errorsare typically detected by spirometer soft-ware, health professionals need to recog-nize the effects of contaminated sensors andzero-flow errors on test results and curveshapes. Both errors can produce very incon-sistent results (failing to meet repeatabilitycriteria, as discussed below), sometimesalong with large percent of predicted val-ues, exceeding 130% to 140%. Tests withzero-flow errors often are falsely inter-preted by the spirometer as indicatingobstructive impairment.

ACOEM and OSHA recommend thatusers of flow-type spirometers becomefamiliar with the flawed patterns shownin Fig. 2, and institute protocols of preven-tive actions as well as corrective actions ifthose patterns are observed. Such protocolsmight include occluding sensors5 duringpremaneuver sensor ‘‘zeroing,’’ frequentchecks for sensor moisture and mucusdeposits, maintaining sensors in an uprightposition to minimize accumulation of con-densation, and keeping subjects’ fingers farfrom the sensor outlet.

CONDUCTING TESTS

Technician TrainingIn 1978 and again in 2019, the

OSHA Cotton Dust Standard stated thatthe goal of spirometry training courses isto provide technicians with ‘‘the basicknowledge required to produce meaningfultest results.’’15 In the regulation’s preamble,OSHA noted that:

The most important quality of a pulmo-nary function technician is the motiva-tion to do the very best test on every

employee. The technician must also beable to judge the degree of effort andcooperation of the subject. The testresults obtained by a technician wholacks these skills are not only useless,but also convey false information whichcould be harmful to the employee.

NIOSH was designated as theagency responsible for reviewing andapproving occupational spirometry trainingcourses, based on topics addressed byAppendix D of OSHA’s Cotton Dust Stan-dard (29 CFR 1910.1043). NIOSH appro-ves both initial Spirometry courses andSpirometry Refresher courses, which mustbe taken every 5 years (in addition toallowing for a 7 month additional graceperiod) to maintain the certificate of com-pletion from a NIOSH-approved course.NIOSH conducts on-site course auditsand periodic reviews of course approvalstatus to monitor the quality of its approvedcourses. The NIOSH web page lists aschedule of NIOSH-approved courses,26

and NIOSH spirometry training videosare available.18 ATS/ERS has endorsedNIOSH-approved courses as prototypesfor technician training,2,25 and morerecently stated that ‘‘Technicians shouldundergo initial practical training andrefresher courses to maintain their skills.’’2

Most recently, ATS/ERS stated that ‘‘Oper-ator training and attainment and mainte-nance of competency must be integratedin any spirometry testing service.’’5

Since 2016, both OSHA’s RespirableCrystalline Silica Standards for Construc-tion, General Industry, and Maritime andNIOSH’s CWHSP have required that spi-rometry tests conducted under these regu-lations must be conducted by individualswho have a current certificate from aNIOSH-approved course.10,11,13 Such train-ing is also required by OSHA’s Cotton DustStandard.15 The Cotton Dust Standardrequires persons other than licensed physi-cians to complete the NIOSH approvedcourse, while the Silica Standard requiresall technicians to complete the NIOSHapproved course. An OSHA Letter of Inter-pretation has recently stated that under thesilica standard, OSHA views all medicalpersonnel (eg, physicians, physicians’assistants, nurses) who administer spirom-etry testing as technicians.11

In 2013, OSHA’s Guidance also rec-ommended that:

All technicians and other persons con-ducting occupational spirometry testsobtain certification by completing aNIOSH-approved course; and that‘‘Supervisors and/or interpreters oftest results also complete a NIOSH-approved spirometry course or equiva-lent training that emphasizes recognition

and troubleshooting of technical errorsand the interpretation of spirometryresults.’’8

OSHA requires that individuals con-ducting spirometry tests required by theRespirable Crystalline Silica or CottonDust Standards maintain a current certifi-cate from a NIOSH-approved course.10,11,15

NIOSH requires completion of such acourse when technicians test coal minersin NIOSH’s CWHSP.13 ACOEM4 andOSHA8 recommend that all techniciansconducting occupational spirometry testsshould complete NIOSH-approved courses.And ATS/ERS2,25 recommend that coursessimilar to Initial and Refresher NIOSH-approved courses should be taken todevelop and maintain technician skills.

Conducting the Test‘‘Perhaps the most important com-

ponent in successful pulmonary functiontesting is a well-motivated, enthusiastictechnician.’’25 ATS/ERS,5,7 ACOEM,4

and OSHA8 emphasize that techniciansexplain, demonstrate, and coach subjectsthroughout their maneuvers, even whenworkers have performed the test previously.Consistent with decades-long occupationalspirometry testing protocol, techniciansneed to encourage maximal inhalations,hard initial blasts, and complete exhala-tions. In 2019, the ATS/ERS presentedseparate protocols for testing that measuresthe forced expiration only, as has been donein occupational testing since 1978, and fortesting that measures forced expiration fol-lowed by a maximal inspiration.5 ATS/ERShas confirmed that the former protocol,used in occupational testing and requiredby OSHA15 and NIOSH,13 meets therequirements of the 2019 Update of theATS/ERS Spirometry Statement.19–21

Occupational spirometry tests tradi-tionally have been conducted with workersin the standing posture, permitting maximalinspirations and blasts on expiration, andyielding maximal FEV1s and FVCs.1,4,8

ATS/ERS has noted that subjects with‘‘excessive weight at the mid-section’’achieve larger inspirations when stand-ing,25 and ATS also ‘‘recognize[ed] thatstanding may yield slightly increased val-ues.’’2 A chair without wheels is to beplaced behind the subject, and the techni-cian must be ready to assist the subject intothe chair if the subject begins to feel faint. Ifthere is a history of fainting or if the subjectis deemed to be at risk from fainting orfalling, the test should be conducted in thesitting position. In all cases, the test postureshould be documented and kept consistentover time whenever possible. Changes intest posture need to be taken into accountwhen interpreting results over time.2




The subject’s head is to be slightlyelevated and he/she needs to stand or situpright. The tongue cannot block themouthpiece, and lips are to be tightly sealedaround it. ATS/ERS recommends that noseclips be used for all spirometry tests,5,7

which prevents extra breaths through thenose, a technical error that invalidatesresults,27 but is not detected by most spi-rometry software—see Fig. 3G.

ACOEM, ATS/ERS, and OSHA rec-ommend that technicians explain, demon-strate, and actively coach workers toperform maximal inspirations, hard andfast expiratory blasts, and complete expi-rations. Occupational testing should beconducted standing, unless workers haveexperienced problems with fainting in thepast, or are deemed to be at risk fromfainting or falling. Testing posture shouldbe recorded on the spirometry record andthe same posture should be used for serialtests over time. Disposable nose clips arerecommended.

Testing Goal for a Valid TestATS/ERS5,7,9 continues to define a

valid spirometry test as having two compo-nents: (1) at least three ‘‘acceptable’’curves that are free of technical flaws;and (2) ‘‘repeatable’’ results for the FVCand FEV1 among the acceptable curves, asdefined below. Most healthy workers canachieve this testing goal, and up to eightmaneuvers ‘‘is generally a practical upperlimit for most adults.’’5,7

Acceptable CurvesThe components of ‘‘acceptable’’

occupational spirometry maneuvers— max-imal inhalations, hard initial blasts, and com-plete exhalations—have not beenchanged.4,7,9,19–21 However, since somesubjects experience difficulty in fully record-ing their FVCs, ATS/ERS5,7 recognized thatcurves that do not completely record theexhalation may be ‘‘usable’’ for FEV1 mea-surement if they are free of hesitation andcough in the first second (Fig. 3A and B).

ATS/ERS has recently stated that‘‘there is no [longer a] requirement for aminimum Forced Expiratory Time(FET),’’5 though other End of Forced Expi-ration (EOFE) criteria are still applied to‘‘ensure the best estimate of FVC.’’6 Thegoal for an acceptable EOFE is still: (1) toreach a one-second FVC plateau,4,5,6,8,9 or(2) to exhale for 15 seconds, or (3) ‘‘if thepatient cannot expire long enough to reacha plateau (eg, children with high elasticrecoil or patients with restrictive lung dis-ease). . .to repeatedly achieve the sameFVC.’’5 Length of exhalation should belimited to 15 seconds since longer exhala-tions will not affect clinical decisions madeabout the subject.5,7,8 Though many

spirometers will continue to flag curvesas incomplete and unacceptable if theyare recorded for <6 seconds (until testingsoftware is updated), users should nowignore those messages and determinewhether one of the 3 EOFE criteria abovehas been met. Fig. 3E shows the impact ofearly termination for a worker with airwaysobstruction: the FVC is under-recorded, theFEV1/FVC ratio is falsely elevated, andtrue airways obstruction may be missed.

Since working populations are oftenyounger and healthier than clinic patients,the decision by the ATS/ERS to no longerrequire a minimum FET for an acceptablecurve permits many workers to be labeledcorrectly as having achieved valid tests.The time taken to achieve a plateau gener-ally increases with age, decreases withbody size, and decreases in the presenceof restrictive lung disease, so that youngworkers, adults with small body frames (eg,Asian females), and patients with restrictivelung disease may reach plateaus quickly,before 6 seconds has elapsed. Their results[can] be considered acceptable in suchcases and an appropriate comment by thereviewer should be made.’’6,9 Until spirom-eter software is updated, if a curve thatplateaued in less than 6 seconds is labeledas unacceptable, technicians should marksuch curves as ‘‘acceptable’’ so that theresults will be included in the final testresults. Similar to the worker shown inFig. 3F, 54% of 4568 healthy nonsmokingsubjects aged 19 or older in the NHANESIII study group reached their FVC plateaubefore 6 seconds elapsed.9,28 Examples of avalid test with an exhalation less than 6 sec-onds in length, and of unacceptable curvescaused by flawed testing technique areshown in Fig. 3A to G. Acceptability crite-ria are summarized in Table 4.

Repeatable FVC and FEV1

Since 2005, ATS/ERS5,7,9 hasdefined the level of consistency to beachieved among test results as a differenceof up to 0.15 L (150 mL) between thelargest and second largest values of theFVC and the FEV1. In general, up to eighttotal maneuvers can be attempted, empha-sizing maximal inhalation, if repeatabilityamong acceptable curves exceeds 0.15 L.

As ATS recently stated:‘The most common reason for low FVC,FEV1, and PEF values is an incompleteinhalation. Achievement of maximalinhalation is best assessed by measuresof repeatability and also by the consis-tency of the shape of the flow-volume orvolume-time curve.9 (See Fig. 3D).

To emphasize the importance of acomplete inhalation in a valid spirometrytest, technicians should exaggerate the

maximal inhalation as they demonstrateperformance of the test. Failure to achieverepeatability does not rule out interpretationof results, since it may also occasionally becaused by underlying respiratory disease.9

Lack of repeatability needs to be docu-mented and taken into account during theinterpretation process.

ACOEM recommends that occupa-tional spirometry tests strive to meet ATS/ERS criteria for a valid test, that is, record-ing three or more acceptable curves, withFVC and FEV1 repeatability of less than orequal to 0.15 L (150 mL.) The recent deci-sion by the ATS/ERS to no longer require aminimum FET5 means that healthy workerswho reach their FVC plateau in a short timewill now be labeled as having valid testswhen the FVCs are consistent amongcurves. Failure to achieve FVC repeatabil-ity is often caused by inhalations that arenot maximal.

Reporting Results

Values to be ReportedThe largest FVC and the largest

FEV1 from all acceptable curves arereported as the test results even if theyare taken from different curves. TheFEV1/FVC is calculated using these twovalues.4,5,7,8,15 To permit thorough reviewof a spirometry test, results from all accept-able curves, or at least the three best curves,should be shown on the spirometry report.As discussed below, ATS continues tostrongly discourage evaluating the forcedexpiratory flow (FEF) rates, recently sayingthat ‘‘forced expiratory flow at 75% of FVC(FEF75%) and FEF25% to 75% have not dem-onstrated added value for identifyingobstruction . . . and therefore are not rec-ommended for routine use.’’6,9 But ifreported, all FEF, except for the Peak Expi-ratory Flow (PEF), are to be drawn fromone acceptable curve with the highest sumof (FEV1 þ FVC). The highest PEFrecorded from among all acceptable curvesis to be reported.4,6,8

Test Report FormatATS recently issued an Official

Technical Standard on ‘‘Recommendationsfor a Standardized Pulmonary FunctionReport.’’9 Key points from that standardrelevant to occupational spirometry reportsinclude:

1. Keep the reports simple: Include subjectidentification number, sex, date of birth,height, weight, ethnicity, date of test,normal reference source, Lower Limitof Normal (LLN), flow-volume andvolume-time graphs showing technicalquality, percentage of Predicted values,9

and test posture.2 Scales of the graphs




have been previously defined,4,7,8 andcan be adjusted as needed ‘‘to maximizethe image within the available space forthe report.’’9 Z-scores of the results (thenumber of standardized residuals belowthe predicted value) are optional.9

Exclude parameters with no clinicalvalue, limiting parameters to FVC,FEV1, FEV1/FVC, [PEF,] and FET fortechnical quality assessment. ‘‘Limitingthe number of parameters reported andshowing the LLN next to the measuredvalue should improve interpretive accu-racy, particularly for those less experi-enced.’’9

There should be a ‘‘place for techniciancomments on the test session, any qual-ity issues, date of last calibration orcalibration check,8 and other relevantinformation that may aid in interpreta-tion.’’9

2. Specify whether the reference valuesare adjusted for race (and what adjust-ment factor is used).2,9

3. ‘‘Standardized electronic formats forthe saving of all PFT data, includingeach individual maneuver, are . . . rec-ommended. This will allow reviewersthe flexibility to see additional detail orto reanalyze previous PFTs or applynew reference values as they becomeavailable.’’9

Many of these recommendationshave also been made by ACOEM4 and byOSHA.8

ACOEM, ATS, and OSHA recom-mend or require that occupational spirom-etry test reports include values and curvesfrom all acceptable curves (or at least thethree best curves) and that the largest FVCand largest FEV1 be interpreted, even ifthey come from different curves. Defaultspirometer configurations often need tobe adjusted to meet these recommenda-tions. Technicians should also check to besure that ambient conditions are correctlyrecorded.

Quality Assurance (QA) ReviewsIn addition to technician training,

ATS recently emphasized the importanceof periodic technical review of spirogramsto provide on-going feedback on the qualityof each technician’s testing.2,9,25 Samplesof randomly selected tests, all invalid tests,and tests with abnormally low or improba-bly high results (FEV1 or FVC >130% ofpredicted) can be reviewed. Around 80% ormore of an occupational health program’sspirometry tests should be technicallyacceptable.8,29 Figures illustrating someof the technical errors that can affect spi-rometry test results are presented in Figs. 2and 3 in this statement, in the 1994 ATSSpirometry Update,30 the 2019 ATS/ERSSpirometry Statement Online Supplement,5

and the OSHA Best Practices Guidancedocument.8

In 2017, ATS stated that ‘‘qualityreview of PFTs needs to move beyond‘did, or did not, meet ATS standards,’ buta grading system is most helpful if thegrades have a common meaning; thereforeadoption of a uniform system is desirable.’’A standard scheme for grading spirometrytests on a scale of A-F was recom-mended,5,9 with the grades incorporatingboth acceptability and repeatability. ‘‘Agrading system allows the user to evaluatethe likelihood that spirometry results arerepresentative of true values in the face oftest performance that is not ideal.’’9 But asnoted above, ‘‘technicians should be trainednot to rely exclusively on spirometer qual-ity-control prompts, since technical errorsmay occur that are not among those recog-nized by the software,’’25 and incorporatedinto the letter grade (Table 5).

‘‘While strict application of the grad-ing criteria can be done by computer soft-ware, the reviewer’s role is to applyjudgment by reviewing the individualcurves, which may change the scoringand allow interpretation.’’9 The grades aresummarized in Table 6.9 ‘‘In general, testswith grades of A, B, or C are usable; testswith grade D are suspect; tests with grade Emight be used by the interpreter only toshow values ‘within the normal range’ or at‘at least as high as,’ without demonstrated

repeatability; and tests with grade F shouldnot be used.’’9

ACOEM, ATS, and OSHA recom-mend that technicians ‘‘receive on-goingfeedback about the quality of the tests theyperform, and how to correct problems intest performance.’’2 The frequency of suchreviews should be at least quarterly, andmore often if technicians are inexperiencedor if poor technical quality is observed. It isrecommended that reviews be conducted bythose experienced in recognizing and cor-recting flawed spirometry tests results.29

When used with caution, test quality gradesmay be helpful in evaluating spirometry testresults.

COMPARING RESULTS WITHREFERENCE VALUES

After establishing the technicalvalidity of a test, spirometry results areevaluated at the time of the test, comparingthe worker’s results with the normal rangeexpected for his/her current demographiccharacteristics. The likely presence orabsence of impairment is based on thisevaluation and details are presented below.In addition, a worker’s results are oftenevaluated longitudinally, comparing theircurrent results with their previous testresults. This assessment serves as a helpfuladjunct to traditional cross-sectional evalu-ation since increased change over time mayindicate that further medical assessment is

TABLE 6. Test Quality Categories for FVC or FEV1 in Adults

Grade No. of Acceptable Curves Repeatability

A �3 �0.150 LB �2 �0.150 LC �2 �0.200 LD �2 �0.250 LE 1 N/AF 0 N/A

Adapted from Official American Thoracic Society Technical Statement: Recommendations for a StandardizedPulmonary Function Report. AJRCCM. 2017;196:1463–1472.9

TABLE 5. Importance of a Valid Test: Summary

� Some spirometry errors falsely elevate FVC and/or FEV1: excessive hesitations (Fig. 3A), extrainhalations through the nose (Fig. 3G), contaminated sensors (Fig. 2A), and over-recorded flowscaused by zero-flow errors (Fig. 2B and C). It is especially important to reject these curvesbecause spirometers use the largest test results to interpret the test.

� Other errors, such as submaximal inhalations (Fig. 3D) and weak expiratory pushes (Fig. 3C)often falsely reduce FVC and/or FEV1. Spirometers usually discard such falsely low valueswhen good coaching leads to higher, more accurate results on subsequent maneuvers.

� However, even if it leads to reduced FEV1, coughs in the first second of exhalation (Fig. 3B)make the maneuver unusable.6

� Interpretation of falsely elevated or reduced results may indicate incorrectly that impairmentexists when a worker is normal, or that a worker is normal when impairment in fact exists.

Based on ‘‘Spirometry Testing in Occupational Health Programs: Best Practices for Healthcare Professionals.’’OSHA 3637-2013.8

OSHA; Occupational Safety and Health Administration.




appropriate for a worker even though he/sheis not impaired based on traditional evalua-tion. Updated recommendations for longi-tudinal interpretation are summarized in theLongitudinal Interpretation section.

Three critical aspects of traditionalpulmonary function evaluation influencecross-sectional interpretation: (a) thesource of the reference values used; (b)how the reference values are adjusted whena worker’s race/ethnicity differs from thereference study subjects; and (c) selectionof the interpretation algorithm used to cat-egorize pulmonary function as normal orabnormal, that is, the choice of lung func-tion parameters to be evaluated and thesequence in which they are examined.

Reference ValuesAs stated by the ATS 1991, ‘‘A refer-

ence population should, ideally, be represen-tative of the general population from whichthe clientele of the laboratory comes.’’31

Reference values define the average andthe lower boundary of the normal rangefor individuals similar to the tested workerfor factors related to the size and shape of thethoracic cavity, that is, age, height, race, andsex. Obtaining accurate information on thesecharacteristics for the worker is critical toaccurately interpreting spirometry results,and inaccurate information can lead to incor-rect assessment of a worker’s pulmonaryfunction. Referencevalues are obtained fromresearch studies of asymptomatic neversmokers of varying ages, heights, and sex,and optimally, varying ethnic/racial back-grounds. Subject ethnic/racial group shouldbe based on self-report and standing heightin stocking feet should be measured period-ically and not simply reported by the sub-ject.5 The worker’s sex should be sexassigned at birth,5,32,33 though this mightmisclassify some transgender workers whobegan gender-affirming hormone therapybefore the onset of puberty. (Defining bestpractices to elicit an accurate sex designationfrom transgender workers warrants furtherresearch.) The relationships of pulmonaryfunction parameters with these four demo-graphic variables are summarized in regres-sion equations, which produce average‘‘predicted’’ values and 5th percentileLLN. (Note that LLN is equivalent to a Z-score of�1.645). Since predicted values andLLNs describe the average and the bottom ofthe normal range based on a single researchstudy, both indices need to be drawn from asingle source of reference values.31,34

Many reference values studies havebeen conducted in a single geographicallocation,35,36 but ATS/ERS,2,9,19–21,34

ACOEM,4 OSHA,8,15 and the AMA Guides6th edition,37 support using reference val-ues from the National Health and NutritionExamination Study, Round III (NHANES

III)22 for occupational testing in the US.NHANES III tested large random samplesof nonsmoking asymptomatic US Cauca-sians, African Americans, and MexicanAmericans. Equipment and testing protocolswere held constant and quality control wasstrictly maintained, so that observed differ-ences between groups reflect biological dif-ferences and not simply varying equipmentor testing techniques. Race-specificNHANES III reference equations are avail-able for Caucasians, African-Americans,and Mexican-Americans (Hispanics).

However, uncertainty about whetherthe NHANES III values were a good fit forcountries outside of the United States pre-vented the ATS/ERS from recommendingNHANES III for use in Europe and othercountries. To meet the need for referencevalues for Europe and other parts of theworld, and for subjects younger and olderthan the NHANES population, the GlobalLung Function Initiative (GLI) combineddata from 70 research studies in 26 countries(mostly outside of North America) and pub-lished the GLI-12 equations.38 Though ATS/ERS recently recommended use of the GLIequations in Europe, Australia, New Zea-land, and North America,5,9 particularly inclinical research studies to permit compar-isons with international studies, they statedthat the NHANES III values ‘‘remain appro-priate where maintaining continuity isimportant,’’9 as it is the occupational set-ting.2 Also in November, 2019, the ATS/ERSstated that ‘‘for occupational spirometry test-ing in the United States, the use of theNHANES III spirometry reference valuesis in full compliance with the 2019 Updateof the ATS/ERS Spirometry Standards.’’19–

21 Effective July 15, 2019, OSHA mandateduse of the NHANES III reference valueswhen workers are tested under the updatedcotton dust standard.15 And since ‘‘a refer-ence population should, ideally, be represen-tative of the general population from whichthe [subjects come],’’31 workers who aretested in the United States are best comparedwith values obtained from the highly stan-dardized NHANES III research study con-ducted in the United States.

OSHA mandates use of the NHANESIII (Hankinson 1999) reference values foroccupational spirometry testing required bythe updated Cotton Dust Standard15 andrecommends NHANES III normal valuesfor use8 in occupational testing under otherregulations, unless a regulation mandatesanother specific set of reference values.ACOEM, ATS/ERS, and the AMA Guides6th edition endorse use of the NHANES IIIreference values in occupational testing inthe United States.22 Most spirometers cal-culate NHANES III reference values, andtables of NHANES III predicted values andLLNs are in Appendix A of the OSHA

Guidance document.8 If not calculated byolder spirometers, NHANES reference val-ues can be calculated using a ReferenceValue Calculator.39 Since reference valuescan vary significantly and affect the percentof predicted values, the selected referencevalues should always be identified on thespirometry printout, as noted earlier.

Race-Adjustment of PredictedValues and LLNs

If a worker’s self-reported race/ethnic-ity is the same as the referencevalue group, noadjustment of the reference values is required.Since NHANES III reference values weregenerated specifically for Caucasians, Afri-can-Americans, and Mexican Americans(used for Hispanics), the predicted valuesand LLNs are not adjusted when workersof these race/ethnicity groups are tested.However, when Asian-American workers(ie, Chinese, Japanese, Indian, or Pakistani)are tested, race-specific NHANES referencevalues are not available. To determine appro-priate Asian-American referencevalues, Cau-casian values for FVC and FEV1 should bemultiplied by a scaling factor to account forthe larger average thoracic cavities observedin Caucasians compared with Asian-Ameri-cans of the same age, height, and sex. Thescaling factor required by OSHA in 2019 andrecommended by ATS/ERS in 2014, 0.88,was based on recent evidence indicating thatit minimizes false positives when usedto calculate Asian-American reference val-ues.2,8,15,40

ACOEM and ATS/ERS recommendthat race-specific NHANES III referencevalues be used whenever possible, basingthe worker’s race/ethnicity on self-report. Toevaluate Asian-American workers, ACOEMrecommends applying a scaling factor of0.88 to Caucasian predicted values andLLNs for FVC and FEV1. Forcotton-exposedworkers, OSHA requires that the 0.88 scal-ing factor be used for Asian-American work-ers. Note that FEV1/FVC predicted valuesand LLNs are not adjusted.

Interpretation AlgorithmFor almost three decades, ATS has

recommended applying a stepwise algo-rithm to three pulmonary function parame-ters to interpret spirometry results.2,9,31,34

ACOEM endorsed this approach in its pre-vious statements1,4 and OSHA adopted it intheir Guidance document.8 Since consensusexists on how to distinguish normal fromabnormal results, and which measurementsidentify obstructive or possible restrictiveimpairment, these determinations are pre-sented in Fig. 4. Since recommendationsfor grading severity of impairment are quitedisparate,34,41 this statement’s interpretationalgorithm (Fig. 4) does not grade severityof impairment.




FIGURE 4. Spirometry interpretation algorithm. Based on ‘‘Spirometry Testing in Occupational Health Programs: Best Practicesfor Healthcare Professionals.’’ OSHA 3637-013.8 LLN, lower limit of normal; OSHA; Occupational Safety and Health Administra-tion.




LLN Defines AbnormalitySince 1991, ATS has officially

endorsed using the 5th percentile, the pointbelow which only 5% of nonexposed asymp-tomatic subjects are expected to fall, as theLLN range.2,9,31,34 (As previously noted, theLLN corresponds to a Z-score of �1.645.)

Determining what constitutes an abnor-mal versus a normal spirometry result isparticularly important when spirometryis performed related to the workplace. Inaddition to prompting further evaluationof a worker and workplace exposures,an ‘abnormal’ spirometry result can alsoimpact a worker’s job (eg, determiningjob placement). The ATS/ERS andACOEM recommend using the fifthpercentile lower limit of normal(LLN) to differentiate normality fromabnormality, rather than a fixed value,such as 80% of predicted for the FEV1

and FVC, or 0.70 for the observed ratioof FEV1/FVC.’2

Because the Global Initiative forChronic Obstructive Lung Disease criteriahave been used in the primary care settingto screen smokers and symptomaticpatients for chronic obstructive pulmonarydisease,42 clinics may erroneously adoptthe fixed cut-point of a measured ratio ofless than 0.70 to indicate the presence ofairways obstruction for all individuals.Since the measured ratio declines by about10% across the decades from 20 to 70, afixed cut-point is only accurate in the mid-dle of that age range and not in younger orolder individuals. As an example, for Cau-casian males, the NHANES III LLN for theFEV1/FVC ratio equals 0.70 at about age40. But at age 20, the ratio LLN is 0.74 andat age 70, it is 0.64. This means that youngpeople who should be exhaling 74% ormore of their volume in the first secondwill not be labeled with ‘‘airways obstruc-tion’’ until their ratio is less than 0.70 if theGOLD criterion for obstruction is used. Inoccupational settings, where the goal is toidentify impairment at an early stage, theseare unacceptable false negatives. The oldersubject has the opposite problem: manyolder people who are not obstructed willexhale less than 0.70 of their volume in thefirst second. These false positives mayresult in unnecessary job restrictionsor treatment.

As ATS has stated: ‘‘The fixed val-ues commonly used. . . are estimates basedon middle-aged adults, and therefore erro-neous clinical decisions based on thesefixed cutoffs are more likely to occur’’2,9

in young workers and in those with smalllung volumes, ie, older, shorter, and/orfemale adults. And ‘‘because the FEV1/FVC ratio declines with age, using a fixedvalue, such as 0.70, to determine an

obstructive defect will result in false nega-tive results for younger workers, and false-positive results in older workers.’’2 Usingthe 5th percentile LLN to define abnormal-ity for the major spirometry measurementsavoids such problems.43,44

‘‘Spirometry values that are belowthe fifth percentile LLN are consideredabnormal, and may reflect a pulmonaryproblem. However, by definition, 5% of ahealthy population will also fall below thefifth percentile LLN’’2 and so false posi-tives are possible. According to ATS,‘‘interpreters should be aware of uncer-tainty when interpreting values near anydichotomous boundary . . . and so cautionis indicated when interpreting values closeto the LLN.’’9 ATS gives a practical exam-ple of how clinical circumstances affect adiagnosis of impairment:

For example, consider the meaning of aspirometric study that shows FEV1 val-ues and other expiratory flow rates to bejust above the lower limit of normal. Ifthe patient were a healthy male whosought medical assistance because hewas disqualified for life insurance onthe basis of his spirometry, it would beappropriate to interpret his spirometryas within normal limits. If, in contrast,the same data were obtained from asmoker with complaints of intermittentcoughing and occasional wheezing, itwould be appropriate to suggest that thestudy is consistent with mild obstructivedysfunction, although it could also rep-resent a variant of normal. In both ofthese instances, computer printouts, orrobotic physician interpretation thatsimplistically declare the results to be‘normal’ or ‘abnormal’ on the basis ofwhether the observed values fall to oneside or the other of a single number,could give information that does notperform a useful service to the patient[-emphasis added].31

Applying the InterpretationAlgorithm

Spirometry interpretations shouldspecify whether the worker’s lung functionis in the normal range, or shows an obstruc-tive, restrictive, or mixed impairment pat-tern. Merely stating which values arenormal or low, without concluding ifthere is an impairment pattern, is nothelpful.34

‘‘OSHA recommends following thealgorithm pictured in Fig. 4 to interpret lungfunction. This general approach has previ-ously been recommended by ACOEM,4

ATS/ERS,34 and NIOSH.45 Figure 4 liststhree steps to be followed in interpretingspirometry test results: first, evaluate thevalidity of the test results, second, assess

whether expiratory airflow is slowed(obstructive impairment), and finally, con-sider whether expired lung volumes mightbe reduced (restrictive impairment). It isimportant to follow the steps in the orderspecified to minimize false positive find-ings when interpreting spirometry testresults. All three steps should be evaluatedfor every set of test results.

The algorithm shown in Fig. 4 isused to classify the worker as having:

� Obstructive impairment (airwaysobstruction);

� Possible restrictive impairment;� Possible mixed impairment (both

obstructive and possible restrictiveimpairments); or

� Normal spirometry results (no obstruc-tive or restrictive impairment).

Each of these classifications isdescribed below, following the sequencein Fig. 4.’’8

Is Test Valid?As shown in Fig. 4, the first step in

interpreting spirometry test results is todetermine whether a valid test has beenperformed or if more maneuvers may beneeded. ATS/ERS has cautioned that‘‘omitting the quality review and relyingonly on numerical results for clinical deci-sion making is a common mistake, which ismore easily made by those who are depen-dent upon computer interpretations.’’34

Obstructive ImpairmentOnce test validity is established,

FEV1/FVC is the first measurement to beevaluated, to ‘‘distinguish obstructive fromnonobstructive patterns.’’31 When theFEV1/FVC and FEV1 are both less thanLLN, airways obstruction is present. How-ever, when FEV1/FVC is less than LLN, butFEV1 is greater than LLN, borderlineobstruction or ‘‘possible physiologic vari-ant’’ may exist.31,34

ATS/ERS cautions that FEV1/FVCless than LLN combined with FEV1 greaterthan equal to 100% of predicted is ‘‘some-times seen in healthy subjects, includingathletes’’ and ‘‘is probably due to ‘dysanap-tic’ or unequal growth of the airways andlung parenchyma.’’34 This pattern is labeledas a ‘‘possible physiologic variant,’’31,34 andis not unusual among physically fit non-smoking emergency responders, firefighters,and police. However, if these healthy work-ers are exposed to known hazardous sub-stances, the possibility of obstructiveimpairment needs to be considered when areduced FEV1/FVC is observed.

Restrictive ImpairmentFVC, the forced expiratory measure-

ment of vital capacity, is next evaluated to




determine whether restrictive impairmentmay exist. If FVC less than LLN, restrictiveimpairment is possible, and true restrictionwill need to be confirmed using additionalpulmonary function tests, such as lungvolume measurements.

However, in the presence of airwaysobstruction (FEV1/FVC <LLN), FVC lessthan LLN indicates a possible mixedimpairment pattern (not labeled in the flow-chart), whose restrictive component mayneed to be confirmed by additional pulmo-nary function tests.

Static lung volume measurements arenecessary to distinguish restrictive frommixed-restrictive and obstructive abnor-malities. When only spirometry is avail-able, it is not possible to determinewhether restriction is present, becausethe FVC may be reduced by restrictiondue to a reduced Total Lung Capacity(TLC) or by elevation of the residualvolume due to air trapping.6,34

Normal Spirometry ResultsIf FEV1/FVC �LLN, there is no

obstructive impairment and if FVC greaterthan equal to LLN, there is no restrictiveimpairment: the worker has normal spirom-etry results. Since the LLN is defined sothat 5% of healthy individuals will fallbelow it, spirometry results from a workerwithout any apparent health problems areoccasionally found to be slightly below theLLN. As noted above, such values, justabove or just below the LLN should beinterpreted with caution. The worker shouldbe retested at a later date to confirm theresults and, if still abnormal, the completeclinical presentation should be evaluated.Additional tests of pulmonary functionshould be done if clinically indicated.

Forced Expiratory Flow Rates(FEF)

As presented above, because of thewide variability of the FEF25% to 75% and theinstantaneous flow rates, both within andbetween healthy subjects, ATS/ERS con-tinues to discourage their use for diagnos-ing small airway disease in individualpatients,6,9,31,34 or for assessing respiratoryimpairment. Interpretation of FEF25% to 75%

and other flow rates is not generally rec-ommended if the FEV1 and the FEV1/FVCare within the normal range.46,47 If flowrates are interpreted at all, ‘‘the wide vari-ability of these tests in healthy subjectsmust be taken into account in their inter-pretation.’’34 ‘‘The practice of using 80% ofpredicted as the lower limit of normal forFEF25% to 75% or the instantaneous flowswill cause important errors since, for theseflows, the lower limits of normal are closerto 50% of predicted’’31,34

ACOEM and OSHA recommend thatoccupational medicine practitioners followthe algorithm pictured in Fig. 4 to separatenormal from abnormal test results. Thisgeneral approach has also been recom-mended by ATS/ERS34 and NIOSH.45 Pres-ence of airways obstruction is indicated byFEV1/FVC below the worker’s LLN, andpossible restrictive impairment is indicatedby FVC less than LLN. Practitioners needto remember that an FEV1/FVC that isbarely abnormal, in the presence of FEV1

�100% of predicted, may indicate ‘‘possi-ble physiologic variant’’ pattern in healthynonsmoking workers, such as emergencyresponders. However, if such healthy work-ers are exposed to known respiratory haz-ards, the possibility of airways obstructionshould also be considered when an abnor-mal FEV1/FVC is observed. Interpretationof results that are near the LLN should beperformed with caution.

LONGITUDINALINTERPRETATION

Since ‘‘workers can undergo peri-odic, often annual, spirometry tests inmandated or recommended medical sur-veillance programs, it is important to eval-uate such measurements not only relative tonormal ranges [based on predicted valuesand LLNs], but also relative to the workers’baselines, particularly when lung functionvalues are within the normal range. Manyworkers have FVC and FEV1 that exceedtheir predicted values. Such individualsmust lose a significant portion of their lungfunction before their spirometry results fallbelow the LLN, and they are identified asabnormal. Longitudinal evaluations of peri-odic spirometry testing may detect exces-sive lung function loss due to an exposureor underlying condition earlier than using asingle spirometry test’’2 for these individu-als. However, while an FEV1/FVC or FVCless than LLN is widely recognized asindicating obstructive or possible restrictivelung impairment, interpreting a greater thanexpected loss in FEV1 is less well standard-ized and should not be used to label workersas impaired, but rather as a guide to desig-nate workers who may need more medicalfollow-up.

‘‘How to evaluate loss of lung func-tion over years [had] not been directlyaddressed by the ATS or ERS,’’2,34 so anATS committee ‘‘performed an evidence-based systematic literature review to iden-tify evidence relevant to the question ofhow to evaluate excessive decline in lungfunction.’’2 Results from that review aresummarized here. ‘‘Assessment of declinein lung function is affected by several fac-tors [which are considered below], includ-ing: spirometry technical quality and testvariability; testing frequency and duration

of follow up; and definition of excessivedecline. The primary measurement used toassess longitudinal change should be theFEV1, as it is less affected by technicalfactors than the FVC.’’2,4,34

Spirometry Testing Quality andTest Variability

Some diseases cause increased vari-ability in spirometric measurements overtime.2,31,48–52 However, increased variabil-ity of measurements can also be due totechnical flaws in testing technique orequipment. ‘‘Comprehensive spirometryprograms should be established so thatvalid measurements are recorded over time.Even with good programs [emphasisadded], spirometer inaccuracy and impre-cision and survey biases (unexplained tech-nical changes) may limit the size of thedetectable change or contribute extraneousvariability to longitudinal measurements.2

Changes in weight over time should berecorded, since weight gain can contributeto decline in lung function.2,3,9 Maintainingcalibration check records and tracking spi-rometry results for groups of workers overtime (eg, mean FEV1, within-person varia-tion, proportions of high or low values) canhelp identify ongoing health hazards andalso anomalous results possibly resultingfrom technical issues.’’2,3,8

Frequency and Duration ofTesting

‘‘As length of follow up increases,real decline in pulmonary function becomeseasier to distinguish from background mea-surement variability. The precision of theestimated rate of FEV1 decline improveswith increasing frequency of measurementand duration of follow-up.2,53 Becausechronic occupational respiratory diseases(such as chronic obstructive pulmonarydisease and pneumoconioses) typicallydevelop over many years, spirometry per-formed less frequently than annually (eg,every 2 to 3 y) should be sufficient tomonitor for the development of such dis-eases.2 However, for diseases that candevelop more rapidly (such as flavoring-related lung disease or occupationalasthma), more frequent follow up at inter-vals of 6 months to 1 year may be appro-priate.’’2

Determination of AbnormallyReduced or Highly Variable FEV1

‘‘Great care is required in determin-ing what constitutes an ‘excessive’ FEV1

decline [or unusually variable measure-ments] when evaluating periodic testingin worker populations. It is important toavoid the consequences of either false-pos-itive or negative findings. The purpose ofsuch periodic testing is to detect




progressive lung disease at an earlier stage,which might otherwise be missed, espe-cially when lung function values are aboveLLN.’’2

Due to ‘‘the relatively large technicalvariability often encountered in spirometrytesting,’’ longitudinal evaluation ‘‘methodsare most effective for evaluating declines inFEV1 over relatively long time periods (�5y).’’2 ‘‘Excessive shorter-term (<5 y) lon-gitudinal FEV1 declines have been shownto presage long-term losses, but can bedifficult to interpret in any individualworker. . . . Despite this variability, to pro-tect lung health among workers with dis-eases that develop rapidly, clinicians mayneed to identify individuals who may haveexperienced declines in FEV1 over shortertime periods (months to a few years).’’2

But ATS cautions that ‘‘the greatesterrors occur when one attempts to interpretserial changes in subjects without diseasebecause test variability will usually farexceed the true annual decline, and reliablerates of change for an individual subjectcannot be calculated without prolongedfollow-up. Thus, ‘‘yearly changes [inFVC or FEV1] of 15% or more were gen-erally thought by the [ATS] Workshop to beclinically important.’’31,54

In 2014, ATS concluded that ‘‘Themost practical thresholds for clinicians touse in comparing longitudinal FEV1 meas-urements are based on a 15% loss frombaseline, taking into account expected age-related loss. . . . A threshold of 15% declinein FEV1 from baseline to follow up forlonger periods of time, beyond the expectedloss due to aging during the follow-upperiod, has been recommended by NIOSHto monitor coal miners55 and byACOEM.’’3,4 As also noted by the Califor-nia Department of Health,29 and OSHA,8

this cut-off is chosen to avoid the falsepositives that may occur when pulmonaryfunction is measured in many nonstandar-dized, real-world clinic situations. Thisapproach will identify FEV1s that are lowerthan expected due to aging, whether due tosteeper declines in function or unusuallyvariable measurements over time. And asnoted above, this method was designed tomonitor FEV1 from baseline on, regardlessof the length of follow-up.2,55

The easiest way to calculate theallowed FEV1 decline of 15% beyond thatexpected due to aging is to apply the ‘‘Per-cent Predicted Method’’2 (previouslyknown as ‘‘Method 1 for Baselines greaterthan 100% Predicted’’3):

Baseline (initial) FEV1% of predictedminus current FEV1% of predicted;Interpretation: If �15%, then observeddecline in FEV1 may be excessive, orvariability of measurements may beincreased.2

For example, if a worker’s initialFEV1 was 120% predicted, his declinemight be considered excessive or his resultsextremely variable if he falls to 105% pre-dicted (a decrease of 15% of predicted),even though he is still above average andremains well above the LLN. First his testswould be reviewed for technical quality andthe follow-up test possibly repeated. If theconclusion remained the same, a medicalevaluation would be considered asdescribed in section 5 below.

Though a ‘‘volume method’’2 wasoriginally described as ‘‘Method 2 forBaselines less than equal to 100% Pre-dicted,’’3 it is more cumbersome than thepercent predicted method and the twoapproaches ‘‘provide very similar thresh-olds for excessive decline in FEV1.’’2 Sim-ilarly, regression of FEV1 on time1,3

requires greater than or equal to 5 yearsof follow-up, is not appropriate if FEV1

decline is not linear, and a fixed mL/ythreshold will flag workers with low base-line FEV1s sooner than workers with higherFEV1s.2 Therefore, in clinical settings,ACOEM recommends adopting the simpler‘‘Percent of Predicted’’ method instead ofthe ‘‘volume’’ or regression methods.

The ‘‘Percent Predicted’’ approachand more complicated computerizedapproaches ‘‘are quantitatively similar’’when within-person testing variability isabout 6%, as is probably common inreal-world testing scenarios.31,54 And ‘‘spi-rometry programs with more variabilityshould evaluate if it is due to technicalissues or increased prevalence of disease,and should use the 15% approach above toevaluate individual results.’’2 So for mostoccupational testing, use of the ‘‘PercentPredicted Method’’ is recommended2 and itis appropriate for any length of follow-up.55

However, ‘‘for diseases that developrapidly, declines in FEV1 of less than 15%over shorter time periods may be clinicallyimportant,’’2 if they identify workers whoshould have further evaluation for possibledisease. If spirometry programs maintaintighter QA programs and their measure-ments have less within-person technicalvariability, declines of 10% to 15% mayindicate a problem. One computerizedapproach, Spirola, accounts for variabilityamong measurements as it determines athreshold for abnormal decline or measure-ment variability.56 For follow-ups less thanor equal to 5 to 8 years, the computerizedlower limit of longitudinal decline (LLD)method,56 may flag smaller declines as‘‘abnormal’’ when within-person variabil-ity is minimal. This may be particularlyimportant when ‘‘diseases that can developmore rapidly (such as flavoring-relatedlung disease or occupational asthma),’’are of concern, and ‘‘more frequent follow

up at intervals of 6 months to 1 year may beappropriate.’’2

But as ATS cautions, ‘‘these smallshort-term longitudinal changes (�5 years)may be difficult to interpret because of therelatively large inherent FEV1 technical var-iability in spirometry testing.’’2 It is essentialthat the assumptions that underlie applica-tion of a computerized program are under-stood. For example, Spirola requiresspecification of a within-subject variabilityof measurements and a reference rate of lossof function. Spirola’s recently used defaultsetting of 4% variability and 40 mL/y are notuniversally appropriate, and the assumedwithin-person variability, in particular, dra-matically impacts the number of subjectsflagged as having an abnormal FEV1 declineor abnormally variable measurements.57

It is important to note that NIOSHnow recommends setting Spirola’s defaultsto match ‘‘the ACOEM-recommended lon-gitudinal limit based on a decline of 15%from baseline in excess of that expected dueto aging. [This] can be specified by select-ing a 6% pairwise-within person variationand 30 mL/y referential rate of decline inthe Options tab. Those defaults will be usedin the next release of SPIROLA.’’58

Though the Percent Predicted methodcan be used to monitor ‘‘decline in FEV1

from baseline to follow up for longer periodsof time’’2 the computerized LLD method isnot recommended for follow-up greater than5 to 8 years. For these longer follow-ups, thecomputerized LLD method should bereplaced by the Percent of Predicted method.

And finally, it must be borne in mindthat an ‘‘abnormal’’ decline must be ‘‘con-sidered together with other information (eg,spirometry quality, respiratory symptoms,exposure to respiratory hazards such astobacco smoking or occupational expo-sures, radiological findings). Before mak-ing a final decision, the quality of thebaseline and final spirometry tests shouldbe evaluated, and if needed, spirometryshould be repeated.’’59 The ATS caveatabout avoiding errors ‘‘when one attemptsto interpret serial changes in subjects with-out disease’’31 must always be considered.

ACOEM recommends that the inter-pretation of pulmonary function change overtime start with an evaluation of technicalquality of the tests and an adequate length offollow-up. When high quality spirometrytesting is in place, ACOEM recommendsfurther medical evaluation for workerswhose FEV1 falls more than 15% below thatwhich is expected due to aging. The PercentPredicted method is the easiest way to assessFEV1 longitudinally for usual occupationalhealth clinic measurements and can be usedfor all lengths of follow-up.

Smaller declines of 10% to 15%,after allowing for the expected loss due




to aging, may be important in diseases thatprogress rapidly and have tests performedmore frequently than annually.60 Thesesmaller declines must first be confirmed,and then, if the technical quality of thepulmonary function measurement is ade-quate, acted upon. In such cases, a com-puterized approach may detect small butimportant early changes in function if thespirometry testing is of very high technicalquality.

FURTHER EVALUATION OFSPIROMETRIC

ABNORMALITIESAlthough ACOEM has stated that

‘‘excessive declines’’ in FEV1 should trig-ger further medical surveillance once thedeclines were confirmed, the details ofmedical follow-up were not specified.4

But in 2014, ATS described an ‘‘ActionPlan for Spirometry in the Work Setting.’’2

Steps in evaluating workplace spirometryresults and further medical evaluation planswere given in detail. Those details arepresented in this section.

‘‘Workers with values below theLLN and/or an excessive decline in FEV1

should be further evaluated for potentialcauses and preventable risk factors. Factorssuch as work exposures, respiratory symp-toms, and medical information (eg, diagno-ses, medications) should always also beconsidered, as spirometry values or ratesof decline can remain ‘‘normal’’ when otherfactors may indicate that further evaluationis needed.’’2

‘‘The specific steps to be taken willdepend on several considerations, includingthe exposures of concern, the magnitude of

the lung function abnormality and/or declineover time, and the clinical context.’’2

Detailed suggestions from ATS are shownin Table 7.2 Moreover ‘‘in addition to man-agement of the individual worker, the analy-sis of aggregate worker data (from the sameworkplace, company, job, or industry), bothcross-sectional and longitudinal, can offersignificant benefit.’’2

RECORDKEEPING‘‘Adequate recordkeeping is a criti-

cal component of a good spirometry pro-gram. To improve the quality of spirometrytesting programs, OSHA makes recommen-dations below on three recordkeeping com-ponents: (1) spirometry test reports; (2)equipment maintenance records; and (3)personnel training and evaluationrecords.’’8 ATS and ACOEM recommendthat ‘‘to protect worker confidentiality, pro-viders must not disclose individual work-ers’ personal health information toemployers without employee consent.’’2,61

1. Spirometry Test Reports: MostOSHA standards require employers toensure that medical records for eachworker, including the spirometry testresults, are maintained for at least 30 yearsfollowing the end of employment (see 29CFR 1910.1020).8 Details of the recom-mended spirometry report format are givenelsewhere.8 Record storage methods shouldbe updated as technology changes to assurefuture record access.

Under the OSHA silica rule, employ-ers must: (1) retain medical records whichare in their possession (eg, the Physician orLicensed Health Care Practitioner’s(PLHCP) written medical opinion aboutany limitations on respirator use); and (2)

ensure that medical records in the PLHCP’spossession (eg, written medical report) areretained. To meet the second obligation,employers can include the retentionrequirement in a written agreement withthe PLHCP, or the employer can otherwisespecifically communicate OSHA’s record-retention requirements to the PLHCP.10 Arecent Letter of Interpretation on this topicdescribes the limited amount of informationthat may be given to the employer underboth the Silica and Respiratory ProtectionStandards, stating that these standards ‘‘donot authorize the transfer of spirometry testor other medical records to employers.’’16

These issues and others are addressed inOSHA’s Occupational Exposure to Respi-rable Crystalline Silica 29 CFR §1910.1053and §1926.1153: Frequently Asked Ques-tions for General Industry and for Construc-tion.62,63

2. Equipment Maintenance Records:‘‘Since equipment maintenance records sup-port the accuracy of the spirometry testresults in the medical record, OSHA recom-mends saving the equipment calibrationcheck log and information about the spirom-eter. Availability of such records permitslater troubleshooting of problematic spirom-etry test results, which is particularly impor-tant when conducting periodic spirometrytesting.’’ Details of the recommended equip-ment maintenance records to be retained aregiven elsewhere.8 Record storage methodsshould be updated as technology changes toassure future record access.

3. Personnel Training and Evalua-tion Records: OSHA recommends that per-sonnel qualifications be documented andavailable for review. Records shouldinclude: technician continuing medicaleducation, certificates from completedNIOSH-approved spirometry trainingcourses, and results of evaluation and feed-back to technicians.

ACOEM Recommendations—2020

1. Equipment Performance� ACOEM recommends that facilities

performing occupational spirometrytests maintain a procedure manualdocumenting equipment type, spi-rometer configuration, manufac-turer’s guidelines, calibration checklog, service and repair records, per-sonnel training, and standard operat-ing procedures. Such a manual willpermit troubleshooting if problemsarise with test results.

a. Spirometer Specifications1. ACOEM recommends that spiro-meters of all types meet or exceed rec-ommendations made by ATS/ERS 2005and by ISO 26782:

TABLE 7. Workers Referred for Further Evaluation�

1. Assess technical quality of spirometry and repeat testing if indicated based on spirometry quality,and other relevant information below

2. Obtain comprehensive medical and occupational history and physical exam including:(a) Work and exposure history(b) Smoking history(c) Respiratory symptoms, timing in relationship to work(d) Physical exam, including lung exam and chest wall deformities(e) SDSs, results of workplace measurements, if available

3. Review preemployment, follow-up questionnaires and spirometry, if available4. Possible additional diagnostic testing:

(a) If airflow obstruction, spirometry with bronchodilator response(b) If restrictive pattern, full pulmonary function tests (lung volumes, diffusing capacity)(c) Chest imaging (chest x-ray, CT scan)(d) If asthma, consider peak flow recordings at and away from work(e) If interstitial lung disease, consider high resolution chest CT scan(f) If nonreversible airflow obstruction, consider occupational etiologies, even in smokers (eg,occupational COPD, bronchiolitis obliterans)

5. If a possible work-related problem is identified, consider other at-risk workers

SDS, Safety Data Sheet.�Reprinted with permission of the American Thoracic Society. Copyright � 2019 American Thoracic Society.

Redlich C, Tarlo S, Hankinson J, Townsend MC, et al. Official American Thoracic Society Technical Standards:Spirometry in the Occupational Setting. AJRCCM; 189(8):984–994, 2014. The American Journal of Respiratory andCritical Care Medicine is an official journal of the American Thoracic Society.2




� Performance-based criteria for spi-rometer operation, including, forexample, accuracy, precision, linear-ity, frequency response, expiratoryflow impedance, and other factors;

� Minimum sizes and aspect ratios forreal-time displays of flow-volumeand volume-time curves (AppendixA); and

� Standard electronic spirometer out-put of results and curves.

2. It is also recommended that spiro-meters which will be used in the occu-pational setting:� Store all information from up to eight

maneuvers in a subject test session;� Permit later editing and deletion of

earlier flawed test results;� Be capable of including flow-volume

and volume-time curves and testresults from at least the 3 bestmaneuvers, and preferably from allsaved efforts, in the spirometry testreport;

� Provide computer-derived technicalquality indicators;

� Provide a dedicated routine for veri-fying spirometer calibration; and

� Save indefinitely a comprehensiveelectronic record of all calibrationand calibration verification results.

b. Validation Testing of SpirometersIf spirometers are purchased for use inthe occupational health setting,ACOEM recommends that:� The manufacturer provides written

verification that the spirometer suc-cessfully passed its validation test-ing, preferably conducted by anindependent testing laboratory, andthat the tested spirometer and soft-ware version correspond with themodel and software version beingpurchased; and

� The spirometer meets the ATS/ERSrecommended minimum real-timedisplay for flow-volume and vol-ume-time curves and ISO minimumaspect ratios for these displays, aswell as providing a standard spirom-eter electronic output (Appendix A).

c. Spirometer Accuracy ChecksACOEM recommends that:� Spirometer accuracy be checked

daily when in use, following thesteps summarized in Table 3;

� Tracings and records from thesechecks be saved indefinitely;

� A log is kept of technical problemsfound and solved, as well as allchanges in protocol, computer soft-ware, or equipment; and

� Spirometers purchased for use in theoccupational setting have dedicatedcalibration check routines (as notedabove.)

d. Avoiding Sensor Errors during Sub-ject Tests� Users of flow-type spirometers need

to recognize the flawed curves andtest results that may be caused bysensor contamination or zero-flowerrors (Fig. 2), and

� Protocols need to be established andused to prevent these errors fromoccurring and to correct the errorsif they do occur. See text forspecific suggestions.

2. Conducting Testsa. Technician Training� All technicians conducting occupa-

tional spirometry tests should suc-cessfully complete a NIOSH-approved spirometry course initially,and a NIOSH-approved refreshercourse every 5 years. Such trainingis mandatory if cotton dust- or respi-rable crystalline silica-exposedworkers are tested. NIOSH-approvedcourses are also mandatory for thosetesting coal miners in the NIOSHCWHSP program.

b. Conducting the Test� Consistent with decades-long occu-

pational spirometry testing protocol,technicians need to explain, demon-strate, and actively coach workers toperform maximal inspirations, hardand fast expiratory blasts, and com-plete expirations. ATS/ERS has con-firmed that this protocol meets therequirements of the 2019 SpirometryUpdate.19–21

� Testing should be conducted stand-ing, positioning a sturdy chair with-out wheels behind the subject, unlessthe subject has previously sat for thetest or experienced a problem withfainting or is deemed to be at risk offainting or falling.

� Record test posture on the spirometryrecord and use the same posture forall serial tests over time.

� Disposable nose clips are recom-mended.

c. Testing Goal for a Valid Test� To achieve a valid test, occupational

spirometry should attempt to recordor more three acceptable curves, withFVC and FEV1 repeatability of 0.15L (150 mL) or less. See text for def-initions of terms.

� Failure to achieve repeatability isoften caused by submaximal inhala-tions, though very poor repeatability(eg, >0.50 L) may indicate sensorcontamination or zero-flow errors.

� Workers who are young, have smallbody frames, or restrictive lung dis-ease often reach their FVC plateausvery quickly. Such tests, if repeatable,

are valid, even if the spirometer flagsthe effort as unacceptable or invalid.There is no longer a minimumlength of exhalation required for anacceptable test,5 though it is unlikelythat spirometer software will beupdated immediately to reflect thischange.

� ATS test acceptability requirementsare presented in Table 4. Importanceof a valid test is summarized inTable 5.

d. Reporting Results� Spirometry test reports need to pres-

ent values and curves from all (or atleast the best three) acceptablemaneuvers to permit technical qual-ity to be fully evaluated, and

� The largest FVC and largest FEV1

are interpreted, even if they comefrom different ‘‘acceptable’’ curves.

� Default spirometer configurationsoften need to be adjusted to meetthese recommendations.

e. QA Reviews� ACOEM recommends that facilities

performing occupational spirometrytests need to establish on-going pro-grams providing QA reviewsof spirograms.

� Reviews need to be conducted atleast quarterly, and more often iftechnicians are inexperienced or ifpoor technical quality is observed.

� The goal of such reviews is to assurethat 80% or more of an occupationalhealth program’s spirometry tests aretechnically acceptable.

� It is recommended that QA reviewersbe experienced in recognizing andcorrecting flawed spirometry testresults.

� Table 6 presents ATS test qualitycategories for FVC and FEV1.

3. Comparing Results With ReferenceValuesa. Reference Values� ACOEM recommends that the

NHANES III (Hankinson) referencevalues22 be used for occupationalspirometry in the United Statesunless a regulation mandates anotherspecific set of reference values.OSHA mandates use of NHANESIII in the recently updated CottonDust Standard.15 NHANES III val-ues are recommended for the UnitedStates when continuity over time isimportant, as it is in occupationalhealth, and ATS/ERS has confirmedthat use of NHANES III referencevalues is in full compliance with the2019 ATS/ERS Spirometry Stan-dardization Statement.19–21

� It is essential to obtain accurateworker information on factors that




are related to the size and shape oftheir thoracic cavity, that is, age,height, sex, and race. Details of gath-ering this information are presented inthe section Comparing Results WithReference Values; Reference Values,and new recommendations are madefor testing transgender workers.5

b. Race-Adjustment of Predicted Val-ues and LLNs� Use NHANES III race-specific ref-

erence values, basing a worker’srace/ethnicity on self-report.

� As recommended by ACOEM andrequired by OSHA’s Cotton DustStandard,15 a scaling factor of 0.88should be applied to Caucasian pre-dicted values and LLNs for FVC andFEV1 to obtain appropriate referencevalues for Asian-American workers.

� The predicted FEV1/FVC and itsLLN are not race-adjusted.

c. Interpretation Algorithm� Spirometry results should always be

interpreted in light of the full clinicalpicture of the worker.

� Figure 4 presents a three-step inter-pretation algorithm to use when dis-tinguishing normal from impairedworkers.

� To separate normal from abnormaltest results, first examine the FEV1/FVC to determine whether obstruc-tive impairment is present, and thenevaluate the FVC to determine ifrestrictive impairment may exist.The FEV1 is examined if the FEV1/FVC indicates possible obstructiveimpairment, as shown in Fig. 4.

� All three indices of pulmonary func-tion are considered abnormal if theyfall below their 5th percentile LLN.Fixed cutoff points for abnormalitysuch as 80% of the predicted value oran observed FEV1/FVC ratio lessthan 0.70 should not be used in theoccupational health setting sincethey are known to cause known falsepositives and false negatives.

� An FEV1/FVC that is barely abnor-mal, in the presence of FEV1 greaterthan100% of predicted, may indicatea ‘‘possible physiologic variant’’ inhealthy individuals. However, if suchhealthy workers are exposed to knownrespiratory hazards, clinical judgmentis needed to evaluate the possibility ofearly airways obstruction.

� Values that are either just above orjust below the LLN should be inter-preted with caution.

4. Evaluating Results Over Time� Spirometry results should always be

interpreted in light of the full clinicalpicture of the worker.

� Evaluate technical quality of the spi-rometry tests and the adequacy of thefollow-up period before interpretingchange in pulmonary function overtime.

� ACOEM recommends that FEV1

losses of greater than equal to 15%since baseline, after allowing forthe expected loss due to aging,trigger further medical evaluationwhen spirometry is of high technicalquality. The simplest method touse is the Percent of Predictedmethod, comparing the baselineFEV1% Predicted with the follow-up FEV1% predicted, as described inSection 4c.

� The Percent of Predicted method andcomputerized methods give virtuallyidentical results when the length offollow-up is less than or equal to 5 to8 years. For longer follow-ups withmany measurements, ACOEM rec-ommends use of the Percent ofPredicted Method.

� ACOEM recommends that a con-firmed FEV1 decline of 10% to15% since baseline, after allowingfor the expected loss due to aging,would trigger further medical evalu-ation in rapidly developing diseaseswith very frequent measurements.For short-term follow-ups when hightechnical quality of testing is main-tained, a computerized algorithmmay be recommended.

� Assumptions that underlie applica-tion of a computerized program mustbe understood and evaluated forappropriateness. NIOSH now recom-mends setting Spirola defaults to beconsistent with ATS recommenda-tions: 6% within-person measure-ment variability and 30 mL/yexpected loss of FEV1 over time.58

5. Further Evaluation of SpirometricAbnormalities2

� Assess technical quality of spirome-try and repeat testing if indicatedbased on spirometry quality, andother relevant information below.

� Obtain comprehensive medical andoccupational history and physicalexam including: (a) work, exposure,and smoking histories; (b) respiratorysymptoms, timing in relationship towork; (c) physical exam, includinglung exam and chest wall deformities;and (d) SDSs, results of workplacemeasurements, if available.

� Review preemployment, follow-upquestionnaires and spirometry, ifavailable.

� Possible additional diagnostic testing:� If airflow obstruction, spirometry

with bronchodilator response

� If restrictive pattern, full pulmo-nary function tests (lung volumes,diffusing capacity)

� Chest imaging (chest x-ray, CTscan)

� If asthma, consider peak flowrecordings at and away from work

� If interstitial lung disease, considerhigh resolution chest CT scan

� If nonreversible airflow obstruc-tion, consider occupational etiol-ogies, even in smokers (eg,occupational chronic obstructivepulmonary disease, bronchiolitisobliterans).

� If a possible work-related problem isidentified, consider other at-risk workers.

6. Recordkeeping� Spirometry Test Reports: Under most

OSHA regulations, medical records,including spirometry test results,must be maintained for at least30 years following the end ofemployment (see 29 CFR1910.1020).8 A recent Letter ofInterpretation on this topic describesthe limited amount of informationthat may be given to the employerunder both the Silica and RespiratoryProtection Standards, stating thatthese standards ‘‘do not authorizethe transfer of spirometry test orother medical records to employ-ers.’’16

� Equipment Maintenance Records:Since spirometer maintenancerecords support the accuracy of thespirometry test results, OSHA rec-ommends saving the equipment cali-bration check log and informationabout the spirometer to support theaccuracy of the medical record.

� Personnel Training and EvaluationRecords: Records of techniciancontinuing medical education, certif-icates from completed NIOSH-approved spirometry trainingcourses, and results of evaluationand feedback to technicians shouldbe documented and availablefor review.

ACKNOWLEDGMENTSACOEM would like to acknowledge

the invaluable input from several reviewers:Drs Susan Tarlo, John Hankinson, and BillEschenbacher, and Kathleen Rogers, RRT,CPFT. Others too numerous to list alsoprovided valuable input.

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Appendix A



acoem guidance statement...major spirometry developments since publication of acoem’s 2011...

Documents