The role of exercise testing in impairment evaluation

Our plain-English summary of The role of exercise testing in impairment evaluation, by A. Oren, D.Y. Sue, J.E. Hansen, et al (The American Review of Respiratory Disease, 1987).

The study

• Authors: A. Oren, D.Y. Sue, J.E. Hansen, D.J. Torrance, K. Wasserman
• Journal: The American Review of Respiratory Disease
• Published: 1987;135(1):230-5
• Cited by: 29 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 000340).

Abstract

To examine the usefulness of exercise testing in impairment evaluation, we reviewed the evaluation of 348 asbestos-exposed shipyard workers. We compared work capacity predicted from history, physical examination, chest roentgenogram, resting electrocardiogram, and resting pulmonary function tests with measured work capacity during an incremental cycle exercise test. The predicted work capacity was often incorrect when compared with measured maximal oxygen uptake (VO2). One third (22 of 66) of those predicted to have reduced work capacity had normal measured work capacity, and 46 of 148 workers (31%) predicted to have normal work capacity were found to have low maximal VO2 during exercise. Of 134 men for whom predicted work capacity was uncertain, maximal VO2 during exercise was low in 49 (37%), normal in 81 (60%), and remained indeterminate in 4 (3%). Thus, of the 138 workers who had low measured VO2, 43 were correctly predicted to have normal work capacity, 46 were incorrectly predicted, and the prediction was uncertain in 49. Only a few were limited by respiratory disease, and cardiovascular disorders limited 69% of those with a low maximal VO2 during exercise. Accordingly, resting VC, FEV1, and DLCO had a poor correlation with exercise performance. Finally, we found that resting DLCO was a poor predictor of abnormal exercise AaPO2, dead-space/tidal volume ratio, or arterial end-tidal PCO2 difference. We conclude that exercise testing is needed for accurate work capacity assessment in impairment evaluation. Exercise testing also facilitates the identification of the major limiting system in those with low work capacity.

In plain English

The authors, at Harbor-UCLA Medical Center in California, reviewed the impairment evaluations of 348 current or retired shipyard workers exposed to asbestos. These were the workers, out of 490 examined over 3 years, who were referred for an exercise test. Physicians first judged each worker's work capacity from history, physical examination, chest X-ray, resting electrocardiogram and resting lung tests. They then compared that judgment with maximal oxygen uptake measured on an exercise bicycle. Of 66 workers predicted to have reduced capacity, 22 (33%) tested normal. Of 148 predicted to be normal, 46 (31%) tested low. Among the 138 workers with low measured capacity, the authors judged heart and circulation disorders to be the main limit in 95 (69%), obstructive lung disease in 20 and restrictive lung disease in 5. Resting lung function correlated poorly with exercise performance. The authors concluded that exercise testing adds significantly to impairment evaluation. They suggested that the large number of heart-related limits may reflect the workers' age.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Review of clinical impairment evaluations comparing physicians' work-capacity predictions made without exercise testing (initial assessment) against capacity measured in an incremental cycle exercise test (final assessment)
• Who was studied: 348 current or retired shipyard workers who claimed or were suspected to have exercise limitation and were referred for exercise testing, out of 490 examined over a 3-year period. Workers judged severely impaired at rest were not referred and are not included. The authors were at Harbor-UCLA Medical Center, Torrance, California; study dates are not given.
• Exposure: Asbestos exposure in shipyard work, estimated from each worker's history (fiber type not stated): 334 reported substantial and prolonged exposure and 14 only minimal exposure. 274 were smokers averaging 37 pack-years and 74 had never smoked.
• Main results:
  • Before exercise testing, work capacity was predicted normal in 148, reduced in 66 and indeterminate in 134 workers. On exercise testing, 138 had low work capacity, 205 normal, and 5 remained uncertain because of insufficient effort.
  • Of the 66 workers predicted to have reduced work capacity, 22 (33%) had normal measured exercise capacity.
  • Of the 148 workers predicted to have normal work capacity, 46 (31%) had low maximal oxygen uptake during exercise.
  • Of the 134 workers whose capacity was initially indeterminate, measured capacity was reduced in 49 and normal in 81.
  • Of the 138 workers with low measured capacity, 43 had been correctly predicted to have reduced capacity, 46 had been predicted normal, and in 49 the prediction was uncertain.
  • Among the 138 with reduced capacity, 32 (23%) were severely reduced (maximal oxygen uptake below 60% predicted), 95 (69%) moderately reduced (60 to 80%) and 11 (8%) mildly reduced (81 to 83%).
  • Cardiovascular disorders limited exercise in 95 of the 138 workers with low work capacity (69%). This included 36 of the 46 (78%) whose low capacity had not been anticipated and 37 of the 49 (76%) in the indeterminate group.
  • Lung disease was the cause of reduced work capacity in a relatively small number: 20 of the 138 had obstructive lung disease and 5 were judged limited by restrictive lung disease.
  • Among the 43 correctly predicted to have low capacity, the limiting system was also correctly predicted in 32 (74%).
  • Reduced resting lung function (VC, FEV1, DLCO) was associated with low work capacity, but overall correlation between resting pulmonary function and work capacity was poor.
  • At a cutoff of 70% of predicted, resting DLCO was quite specific but insensitive for predicting abnormal gas exchange during exercise, and no single cutoff gave high sensitivity and specificity at the same time. A low DLCO reliably predicted abnormal exercise values, but a normal DLCO did not rule them out.
• The authors' conclusion: The authors concluded that measuring work capacity by exercise testing adds significantly to impairment evaluation compared with predicting it from resting data, and that it helps identify the major condition limiting exercise.
• Limitations the authors state:
  • The authors suggested that the large number of workers limited by cardiovascular disease may reflect the age of the group.
  • The authors noted that maximal oxygen uptake depends on the worker's effort as well as health, so other criteria may be needed to detect cardiovascular abnormalities.

Topics

Medical terms in this study, explained in our Lexicon: Pulmonary Function Test (PFT), FEV1, Diffusing Capacity (DLCO).

Related studies

• Role of exercise testing in assessing functional respiratory impairment due to asbestos exposure — J. Howard, Z. Mohsenifar, et al. (1982)
• Spiroergometric parameters at maximal exercise testing assessed functional respiratory impairment in asbestos-induced fibrosis — J. Schneider, R. Arhelger, et al. (2014)
• Evaluation of breathlessness in asbestos workers. Results of exercise testing — P. Agostoni, D.D. Smith, et al. (1987)
• Exercise impairment in asbestos-induced pleural fibrosis. Is it really just interstitial fibrosis? — E.T. Mannix, W.J. Martin (1994)
• Diagnostic value of exercise testing in asbestosis — J. Zejda (1989)
• Exercise performance and functional impairment in asbestos-exposed workers — J. Pearle (1981)

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