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Communications to the Editor |

Inaccurate Spirometry Results? : Let’s Blame It on the Computer! FREE TO VIEW

Marshall B. Dunning, III, PhD, MS
Author and Funding Information

Affiliations: Medical College of Wisconsin, Milwaukee, WI,  M.C. Townsend Associates, Pittsburgh, PA Hankinson Consulting, Inc, Valdosta, GA Gundersen Lutheran Medical Center, Onalaska, WI

Correspondence to: Marshall B. Dunning, III, PhD, MS, Associate Professor of Medicine, MCW-Pulmonary/Critical Care Medicine, 9200 W Wisconsin Ave, Milwaukee, WI 53226; e-mail: mdunning@mcw.edu



Chest. 2005;127(1):409-411. doi:10.1378/chest.127.1.409
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Published online

To the Editor:

I read the article by Townsend et al (May 2004)1 with great interest as well as consternation. Although the authors would have the reader believe that the errors referred to are due to equipment error, based on the examples given, whether or not there is a hardware problem (eg, flow-sensor “zero error”) or a software problem (eg, the inability to delete inaccurate volume-time or flow-volume curves), the individual who is administering the spirometry test and/or the individual interpreting the results should be able to recognize that a problem exists. I submit that the individuals administering the spirometry tests were ill-trained; otherwise, these errors would not have escaped their scrutiny. I was especially disturbed by the data presented on respiratory screening programs for respirator clearance. Why was this not picked up? Again, I submit, human error. The authors point out that the results of the aforementioned tests were useless and “… could be harmful to the employee….” I would ask, if any of the aforementioned cases went to litigation, who would be the defendant, the “spirometer” or the technician and interpreter?

In an attempt to address the problem, the authors put forth seven recommendations. The first hinted at the obvious; however, it did not go far enough. They stated, “Spirometry users at all levels, from the technician to the interpreter of the results, should be aware of the potential for and the appearance of these errors in spirograms.” It is quite obvious based on this article, that neither the technician nor the interpreter was aware of these problems. What the authors failed to do was recommend some type of formal and/or supervised training. The American Thoracic Society recommends training not only for the technician,2but also for the medical director.3In the occupational area, the National Institute for Occupational Safety and Health mandates training for individuals who are administering spirometry tests on employees working in certain industries.4

In conclusion, I agree wholeheartedly with the authors that errors do exist and often go undetected. However, I take issue with their not identifying the real source of those errors. We are all too often quick to blame it on the computer and not the operator!

References

Townsend, MC, Hankinson, JL, Lindesmith, LA, et al (2004) Is my lung function really that good? Flow-type spirometer problems that elevate test results.Chest125,1902-1909. [CrossRef] [PubMed]
 
American Thoracic Society. Standardization of spirometry, 1994 update.Am J Respir Crit Care Med1995;152,1107-1136. [PubMed]
 
American Thoracic Society. ATS respiratory care committee position paper: director of pulmonary function laboratory. ATS News. 1978;;4 ,.:6
 
Occupational Safety and Health Administration. Occupational Safety and Health Administration pulmonary function standards for cotton dust. 29 Code of Federal Regulations; 1910.1043 Cotton Dust 1980; 808–832.
 
To the Editor:

We would like to thank Dr. Dunning for his thoughtful evaluation of our article (May 2004).1 We agree with him on the need for the formal training of spirometry technicians and interpreters, and on the need for those individuals to recognize spirometry errors like those we described. All of our authors have been involved in teaching spirometry courses that have been approved by the National Institute for Occupational Safety and Health, and, in writing this article, it was our goal to introduce a different class of errors (equipment errors that develop during subject testing) into the discussion of spirometry quality assurance and into spirometry training courses. To be effective, training should cover all types of errors that spirometry users may encounter and address how to correct the problems. If errors with currently available spirometers are not discussed in the medical literature, the appearance of the errors, their probable causes, and their solutions will remain anecdotal, and will not come to the attention of many spirometry users. We wrote the article because the zero errors and contaminated sensor errors differ from the types of errors that are usually discussed in training courses, and these have the following four important ramifications:

  1. To date, the focus of the pulmonary medicine community has been on errors in testing technique and leaks in volume spirometers, most of which lower the measured values. When these errors are corrected, there is no residual effect on the reported measurements, since inaccurate values are replaced by larger, more accurate values. Thus, the Occupational Safety and Health Administration/American Thoracic Society algorithm, which reports the largest FVC and FEV1 values, functions well. However, since the errors that we described elevate the test result values, they will be reported as the subject’s measured values, displacing any lower but accurate results if they are not recognized and deleted.

  2. It is widely assumed that checking or setting the calibration of a spirometer guarantees the accuracy of subsequent results that have been recorded on that spirometer. However, we reported errors that develop during the subject test, after the calibration has been verified or set. The existence of these errors means that the shapes of spirograms and the temporal patterns of test results should be monitored continually, and that passing a calibration check, while essential, does not guarantee the accuracy of later subject tests. The clinical settings that produced the screening data shown in Figure 5 in our article assumed that the measurements were accurate because the spirometer was calibrated successfully, and no errors were flagged during the tests (ie, the temporal patterns of the results were not scrutinized).

  3. There is a common tendency for technicians to rely on computer diagnostic messages during testing. If no message is given, it is assumed that the test is acceptable. Many spirometers now being marketed have either no visual display or a very small display, which is a much different design than that of the spirometers available in 1978 when the Occupational Safety and Health Administration Cotton Dust Standard was promulgated. None of the errors that we presented in our article were flagged by the spirometer on which they were recorded, except perhaps as showing excessive variability.

  4. Finally, lack of reproducible results is generally assumed to be caused by the failure of the patient to perform the maneuvers in a consistent fashion. However, the zero errors and contaminated sensor errors that we presented in our article are likely to cause excessive variability, and this fact needs to be presented as an alternative explanation for poor reproducibility in our training courses.

In conclusion, again, we concur with Dr. Dunning’s comments on the importance of formal spirometry training programs. However, we do not think that the problems we described are completely caused by poorly motivated or poorly trained technicians. We must also keep in mind that the problems would not exist if spirometers worked without errors. It is our hope that the visual presentation of errors that are not often discussed but that occur, in our experience, not infrequently will improve the comprehensive content of spirometry training courses, and will allow these problems to be detected and corrected before they are reported as pulmonary function results. We also hope that manufacturers will advise their clients of the possibility of the errors occurring and of measures that should be taken to detect, prevent, or correct these errors.

References
Townsend, MC, Hankinson, JL, Lindesmith, LA, et al Is my lung function really that good? Flow-type spirometer problems that elevate test results.Chest2004;125,1902-1909. [CrossRef] [PubMed]
 

Figures

Tables

References

Townsend, MC, Hankinson, JL, Lindesmith, LA, et al (2004) Is my lung function really that good? Flow-type spirometer problems that elevate test results.Chest125,1902-1909. [CrossRef] [PubMed]
 
American Thoracic Society. Standardization of spirometry, 1994 update.Am J Respir Crit Care Med1995;152,1107-1136. [PubMed]
 
American Thoracic Society. ATS respiratory care committee position paper: director of pulmonary function laboratory. ATS News. 1978;;4 ,.:6
 
Occupational Safety and Health Administration. Occupational Safety and Health Administration pulmonary function standards for cotton dust. 29 Code of Federal Regulations; 1910.1043 Cotton Dust 1980; 808–832.
 
Townsend, MC, Hankinson, JL, Lindesmith, LA, et al Is my lung function really that good? Flow-type spirometer problems that elevate test results.Chest2004;125,1902-1909. [CrossRef] [PubMed]
 
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