Mechanisms affecting exercise performance in subjects with asbestos-related pleural fibrosis

Our plain-English summary of Mechanisms affecting exercise performance in subjects with asbestos-related pleural fibrosis, by C. Picado, D. Laporta, A. Grassino, et al (Lung, 1987).

The study

• Authors: C. Picado, D. Laporta, A. Grassino, M. Cosio, M. Thibodeau, M.R. Becklake
• Journal: Lung
• Published: 1987;165(1):45-57
• Cited by: 19 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. 000343).

In plain English

This study examined six asbestos-exposed people (five men and one woman, aged 39 to 62) who had fibrosis of the pleura, the lining around the lungs, and whose effort was limited by shortness of breath. They were selected from patients referred for investigation: two insulators, three asbestos miners and one person with environmental exposure. Lung-tissue disease was judged absent or minimal from X-rays, lung function tests and CT scans; gallium scans in the two subjects with the most extensive pleural disease were negative. Each did a progressive cycling test, and three had diaphragm fatigue tests. All six showed limited maximum exercise capacity, and only one reached more than 80% of predicted maximum oxygen uptake. Five breathed faster and shallower than expected. All stopped because of breathlessness. Heart rate responses were normal, and the diaphragm showed no signs of fatigue in the three tested. The authors concluded that the study suggests pleural fibrosis can cause severe shortness of breath on exertion through changes in breathing pattern. They noted that minor hidden lung fibrosis, and psychogenic factors, could not be completely excluded.

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 physiological study of a small selected group of patients (six subjects), using exercise testing and diaphragm measurements
• Who was studied: 6 subjects with asbestos-related pleural fibrosis and effort-limiting shortness of breath, selected from a series of asbestos-exposed patients referred for investigation. There were 5 men and 1 woman, aged 39 to 62. Their parenchymal abnormality was not read as greater than 0/1 on the ILO/UC classification. All except subject 1 were smokers.
• Exposure: Occupational exposure in 5 subjects: 2 insulators (13 and 24 years) and 3 asbestos miners (30, 38 and 39 years). One woman had environmental exposure (32 years). Fiber types were not named.
• Main results:
  • Parenchymal (lung tissue) disease was judged absent or minimal using radiographs, routine lung function tests and CT. In the 2 subjects with the most extensive pleural disease (2 and 6), gallium scans were negative and DLco was over 80% predicted.
  • All subjects showed limitation of maximum exercise capacity. Only 1 subject (subject 5, one of the two with the least extensive pleural thickening) reached more than 80% of predicted maximum oxygen consumption.
  • 5 of the 6 subjects showed increased minute ventilation, breathing frequency and inspiratory flow rates, decreased tidal volume, and elevated dead space to tidal volume ratios during submaximal exercise.
  • On average, the subjects' maximum tidal volume to vital capacity ratio was 0.44 (predicted for normal subjects 0.6 to 0.7), and tidal volume reached only 64% of predicted.
  • At an average tidal volume of 1.40 L, the dead space to tidal volume ratio averaged 0.28 in the subjects, compared with a maximum of approximately 0.24 described for normal subjects.
  • Forced vital capacity was reduced on average, and was as low as 52% of predicted.
  • In the 3 subjects tested (2, 4, 6), the diaphragm tension-time index stayed below 0.15, the level associated with diaphragmatic fatigue, throughout exercise. The diaphragm EMG showed no changes suggesting fatigue.
  • In the 3 subjects tested, gastric pressure swings were negative during inspiration. The authors contrasted this with normal subjects, in whom these swings were positive.
  • All subjects said they stopped exercise because of shortness of breath. Heart rate response was normal in all, and cardiac output increased normally in the 4 subjects in whom it was measured.
• The authors' conclusion: The authors concluded that the study suggests pleural fibrosis can cause severe shortness of breath on exertion due to alterations in the breathing pattern. They proposed that this pattern could be accounted for by increased chest wall impedance from reduced compliance of the parietal pleura.
• Limitations the authors state:
  • Minor subclinical degrees of parenchymal (lung tissue) fibrosis could not be definitely excluded, even with negative radiologic findings.
  • Chest wall compliance was not measured; it was assumed to be reduced.
  • Fatigue of the intercostal accessory muscles was not evaluated.
  • Psychogenic factors could not be completely excluded, particularly in evoking the complaint of dyspnea.
  • The physiological assessments could not precisely identify the mechanism of dyspnea.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Fibrosis.

Related studies

• Factors influencing exercise performance in thoracic cancer — R. England, M. Maddocks, et al. (2012)
• Exercise performance and functional impairment in asbestos-exposed workers — J. Pearle (1981)
• Exercise training for asbestos-related and other dust-related respiratory diseases: a randomised controlled trial — M.T. Dale, Z.J. McKeough, et al. (2014)
• Cardiorespiratory responses to incremental exercise in patients with asbestos-related pleural thickening and normal or slightly abnormal lung function — A. Miller, A. Bhuptani, et al. (1993)
• Evaluation of breathlessness in asbestos workers. Results of exercise testing — P. Agostoni, D.D. Smith, et al. (1987)
• Lung function and exercise performance in smoking and nonsmoking asbestos-exposed workers — D.Y. Sue, A. Oren, et al. (1985)

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