Evaluation of breathlessness in asbestos workers. Results of exercise testing

Our plain-English summary of Evaluation of breathlessness in asbestos workers. Results of exercise testing, by P. Agostoni, D.D. Smith, R.B. Schoene, et al (The American Review of Respiratory Disease, 1987).

The study

• Authors: P. Agostoni, D.D. Smith, R.B. Schoene, H.T. Robertson, J. Butler
• Journal: The American Review of Respiratory Disease
• Published: 1987;135(4):812-6
• 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. 000293).

Abstract

We studied 120 asbestos-exposed workers seeking compensation for asbestos-related ventilatory impairment who were referred to us for evaluation of their complaint of dyspnea. We reviewed history, chest radiographs, pulmonary function studies, and exercise tests. The workers were 59.9 +/- 9.5 (mean +/- SD) yr of age and their first asbestos exposure had been 34.4 +/- 10 yr prior to the study; 63% were smokers, 19% were ex-smokers, and 18% were nonsmokers. Chest radiographs were normal in 4%, showed only pleural disease in 35%, only parenchymal diseases in 5%, and pleuroparenchymal disease in 56%. Restrictive pulmonary function abnormalities were present in 25% of the workers, and obstructive abnormalities were present in 27%. Because the impairment of one of several organ systems (i.e., ventilatory, cardiac, pulmonary vascular, or peripheral circulatory) may limit exercise performance, we designed an exercise test score in an attempt to identify the system causing the limitation. No abnormal limitation was detectable in half (49.2%) of the subjects. Only 26% had a ventilatory limitation, which was much more frequent in smokers (32%) than in nonsmokers (9%) (p less than 0.05). Unexpectedly, rather more (37%) had a cardiac rather than a ventilatory limitation. We conclude that the complaint of dyspnea in these asbestos-exposed workers was usually not caused by a ventilatory dysfunction.

In plain English

The authors looked back at 120 men, mostly current or former shipyard workers, who were seeking compensation for breathlessness they attributed to asbestos and were referred to the authors for evaluation. The authors reviewed chest X-rays, breathing tests and exercise tests, and designed their own score to judge which body system, if any, limited each man's exercise. X-rays were normal in 4%, showed pleural disease only in 35%, and showed lung-tissue (parenchymal) changes, alone or with pleural disease, in the rest. Half (49.2%) had no abnormal exercise limitation. A ventilatory (breathing) limitation was found in 26% and a heart-related (cardiac) limitation in 37%. Ventilatory limitation was found in 32% of smokers, 22% of ex-smokers and 9% of nonsmokers; the smoker versus nonsmoker difference was statistically significant. The authors concluded that these workers' breathlessness was usually not caused by ventilatory dysfunction. They noted that the study was retrospective, that about 1 in 5 men did not give a maximal effort, and that the results cannot be applied to all asbestos-exposed workers.

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: Retrospective study of consecutive referred patients (case series) evaluated with chest radiographs, resting lung function tests and incremental exercise testing scored with a system the authors designed
• Who was studied: 120 asbestos-exposed workers who were seeking compensation for breathlessness and were referred over a 4-year period because of pending litigation. 126 were evaluated and 6 were excluded for drug effects or beta-blocker use. All were men and 116 were white. Mean age was 59.9 years (SD 9.5). 75 (62.5%) were smokers, 23 ex-smokers and 22 nonsmokers. The authors were at the Division of Respiratory Diseases, University of Washington, Seattle.
• Exposure: Occupational asbestos dust exposure, mostly in shipyard work. Fiber types are not stated. Length of exposure ranged from 0.5 to 45 years (mean 23.3). First exposure was on average 34.4 years before testing. Exposure history was documented in 117 subjects.
• Main results:
  • Chest radiographs of the 120 workers: normal in 4%, pleural disease only in 35%, parenchymal disease only in 5%, combined pleuroparenchymal disease in 56%
  • Resting lung function: restrictive abnormalities in 25% of workers, obstructive abnormalities in 27%
  • On exercise testing, 49.2% of the 120 subjects had no abnormal limitation
  • 26% of all subjects had a ventilatory limitation: 32% of smokers and 9% of nonsmokers, a difference with p less than 0.05
  • Among ex-smokers, 22% had a ventilatory limitation
  • 37% had a cardiac limitation, more than had a ventilatory limitation
  • 17 subjects (14%) had a combined cardiac and ventilatory limitation
  • Both nonsmokers with ventilatory limitation also had obstructive abnormalities. The authors considered asthma likely.
  • Of the 26% with ventilatory limitation, 9% were identified by extrapolation rather than direct measurement
• The authors' conclusion: The authors concluded that breathlessness in these asbestos-exposed workers was usually not caused by ventilatory dysfunction. They also found that objectively documented ventilatory limitation from restrictive abnormalities was relatively uncommon in this group.
• Limitations the authors state:
  • The study was retrospective
  • The authors described their scoring system as arbitrary and incomplete. They said identifying the limiting system is arbitrary and the score must be applied and interpreted cautiously.
  • About 1 in 5 subjects did not make a maximal effort
  • The linear extrapolation used to estimate maximal ventilation could give values that are too low. The authors said this tends to underestimate how often ventilatory limitation occurs.
  • Some subjects classed as cardiac-limited on the basis of oxygen pulse during submaximal effort may have been wrongly classified
  • The results cannot be generalized to all workers with past asbestos exposure, because all subjects were compensation claimants complaining of breathlessness
  • The degree of breathlessness was not measured

Topics

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

Medical terms in this study, explained in our Lexicon: Dyspnea, Chest X-Ray, Asbestos Exposure.

Related studies

• Role of exercise testing in assessing functional respiratory impairment due to asbestos exposure — J. Howard, Z. Mohsenifar, et al. (1982)
• Exercise performance and functional impairment in asbestos-exposed workers — J. Pearle (1981)
• Factors influencing exercise performance in thoracic cancer — R. England, M. Maddocks, et al. (2012)
• Mechanisms affecting exercise performance in subjects with asbestos-related pleural fibrosis — C. Picado, D. Laporta, et al. (1987)
• Individual experiences and impacts of a physiotherapist-led, non-pharmacological breathlessness programme for patients with intrathoracic malignancy: a qualitative study — H. Wood, S. Connors, et al. (2013)
• Abnormal wasted ventilation fraction and normal pulmonary hemodynamics during exercise in patients with exertional dyspnea — Z. Mohsenifar, H.V. Brown, et al. (1982)

Browse more research in The American Review of Respiratory Disease, or return to medical research.