Role of exercise testing in assessing functional respiratory impairment due to asbestos exposure

Our plain-English summary of Role of exercise testing in assessing functional respiratory impairment due to asbestos exposure, by J. Howard, Z. Mohsenifar, H.V. Brown, et al (Journal of Occupational Medicine., 1982).

The study

• Authors: J. Howard, Z. Mohsenifar, H.V. Brown, S.K. Koerner
• Journal: Journal of Occupational Medicine.
• Published: 1982;24(9):685-9
• Cited by: 23 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. 000679).

Abstract

To evaluate the complaint of exertional dyspnea in asbestos-exposed shipyard workers, pulmonary function tests were performed at rest and during exercise on 90 subjects with pleural plaques. We divided the subjects into four groups based on resting pulmonary function studies. Group I subjects (eight) had a restrictive defect; group II subjects (30) had an obstructive defect; group III subjects (six) had an isolated reduction in diffusing capacity; and group IV subjects (46) had a normal study. Subjects with a restrictive defect demonstrated minor physiologic abnormalities during exercise. Subjects with an obstructive defect demonstrated abnormalities consistent with their obstructive defect. Subjects in groups III and IV demonstrated an abnormally elevated wasted ventilation fraction, which may be an early indicator of interstitial disease due to asbestos exposure. We believe exercise testing was a useful tool in excluding the presence of significant functional exercise limitation due to asbestos exposure in the majority of subjects and also in disclosing some physiologic abnormalities in some of the subjects in our study.

In plain English

This study examined 90 male workers from the Long Beach Naval Shipyard in southern California. The Department of Labor had sent them to Cedars-Sinai Medical Center to assess breathing impairment related to asbestos exposure. All reported shortness of breath on exertion, and all had pleural thickening on chest X-ray. The article does not name asbestos fiber types. On breathing tests at rest, 46 men had normal results, 30 had an obstructive defect, 8 had a restrictive defect and 6 had only a reduced diffusing capacity. Each man then did an exercise test on a stationary cycle. Mean oxygen uptake at maximal exercise was 68% to 80% of predicted across the four groups. Only one man showed a breathing limit to exercise. Statistical analysis found no significant differences between the groups in any exercise measurement. An elevated wasted ventilation fraction was found in 4, 19, 4 and 13 men in the four groups. Two men met published criteria for asbestosis (2.2%). The authors concluded that exercise testing helped rule out significant exercise limitation due to asbestos exposure in most subjects. They said it also revealed abnormalities that might explain the men's breathlessness.

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: Clinical study of resting and exercise lung function testing in referred shipyard workers, with comparison between four groups defined by resting test results
• Who was studied: 90 male workers from the Long Beach Naval Shipyard, examined at Cedars-Sinai Medical Center, Los Angeles, over a 12-month period. All had exertional shortness of breath and asbestos-related abnormalities on chest X-ray. They were selected from 113 workers referred by the Department of Labor: 10 were excluded for no exertional dyspnea and 13 for no asbestos-related X-ray abnormalities. Mean age was 56 ± 18 years.
• Exposure: Occupational asbestos exposure at a naval shipyard, with no fiber type named. Mean exposure was 18 ± 8 years. By type of contact, 70 men had primary exposure (worked directly with asbestos materials) and 20 had secondary exposure (worked in the same area). By intensity, 65 had heavy, 17 moderate and 8 light exposure.
• Main results:
  • On resting tests, 51% (group IV, 46 men) were normal, 33% (group II, 30 men) had an obstructive defect, 7% (group III, 6 men) had an isolated reduction in diffusing capacity, and 9% (group I, 8 men) had a restrictive defect.
  • All 90 subjects had pleural thickening on chest X-ray: 18 grade 1, 34 grade 2 and 38 grade 3. The authors found no relationship between the degree of pleural thickening and resting lung function.
  • 79 subjects stopped exercise because of shortness of breath or fatigue. Only one subject (group II) showed a ventilatory limitation to exercise.
  • Mean oxygen uptake at maximal exercise, as a share of predicted maximum, was 71% in group I, 75% in group II, 68% in group III and 80% in group IV.
  • Statistical analysis found no significant differences between the four groups in any exercise measurement.
  • An elevated wasted ventilation fraction (VD/VT) was found in 4 subjects in group I, 19 in group II, 4 in group III and 13 in group IV.
  • Among subjects with elevated VD/VT, increased interstitial markings on chest X-ray were seen in 3 of 19 in group II, 2 of 4 in group III and 8 of 13 in group IV. The authors described this as suggesting subclinical interstitial lung disease.
  • Two subjects, both in group I, met the Murphy criteria for asbestosis, an overall rate of 2.2%.
• The authors' conclusion: The authors concluded that exercise testing was useful for excluding significant functional exercise limitation due to asbestos exposure in most subjects. They also said it helped reveal physiologic abnormalities that might account for the subjects' shortness of breath.
• Limitations the authors state:
  • The authors note that reports conflict about what an abnormal wasted ventilation fraction means in people with normal resting lung function (such as group IV).

Topics

The National Library of Medicine indexes this study under subjects our site covers: Asbestosis.

Medical terms in this study, explained in our Lexicon: Asbestos Exposure, Dyspnea, Pulmonary Function Test (PFT), Pleural Plaques, Diffusing Capacity (DLCO), Interstitial.

Related studies

• Spiroergometric parameters at maximal exercise testing assessed functional respiratory impairment in asbestos-induced fibrosis — J. Schneider, R. Arhelger, et al. (2014)
• Exercise performance and functional impairment in asbestos-exposed workers — J. Pearle (1981)
• Diagnostic value of exercise testing in asbestosis — J. Zejda (1989)
• Exercise impairment in asbestos-induced pleural fibrosis. Is it really just interstitial fibrosis? — E.T. Mannix, W.J. Martin (1994)
• Evaluation of breathlessness in asbestos workers. Results of exercise testing — P. Agostoni, D.D. Smith, et al. (1987)
• Functional exercise capacity and health-related quality of life in people with asbestos related pleural disease: an observational study — M.T. Dale, Z.J. McKeough, et al. (2013)

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