Regional lung function in asbestos workers: observations and speculations

Our plain-English summary of Regional lung function in asbestos workers: observations and speculations, by R.H. Secker-Walker, J.E. Ho (Respiration; International Review of Thoracic Diseases, 1982).

The study

• Authors: R.H. Secker-Walker, J.E. Ho
• Journal: Respiration; International Review of Thoracic Diseases
• Published: 1982;43(1):8-22
• Cited by: 9 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. 001803).

Abstract

The clinical findings, occupational exposure, smoking history, pulmonary function, chest radiograph and ventilation-perfusion studies have been examined in 12 men exposed to asbestos fibers in the course of their work. Minor abnormalities of regional ventilation, consistent with early small airway dysfunction, were found in the fibrotic zones of most of the nonsmokers or mild cigarette smokers. The whole-lung washout times, estimated by visual inspection of serial washout images, were strongly correlated with measurements of airflow obstruction, but not with pack-years of smoking. There was a close correspondence between radiographic extent of pulmonary fibrosis and the abnormalities in pulmonary blood flow in these regions. The severity of the abnormalities in regional pulmonary blood flow was significantly correlated with the years of asbestos exposure (r = + 0.73, p less than 0.01). It is suggested that the magnitude of the disturbance in pulmonary blood flow in the fibrotic zones could be used to estimate the proportion of pulmonary dysfunction due to asbestos exposure.

In plain English

The authors studied 12 men exposed to asbestos fiber at work. The men were usually evaluated in connection with workers' compensation claims. They were aged 48 to 65, with a mean of 25.9 years of asbestos exposure in jobs such as insulation, asbestos yarn, cement-asbestos pipe and roofing shingle work. Their smoking ranged from 0 to 90 pack-years. Each man had lung function tests, a chest X-ray, and scans of regional ventilation (using xenon-133 gas) and blood flow (using a technetium-99m tracer). Years of asbestos exposure correlated with blood-flow abnormalities in lung zones showing scarring (fibrosis) on X-ray (r = +0.73, p less than 0.01). Smoking was not significantly correlated with any lung function test or scan result. Slower gas clearance went along with greater airflow obstruction. In 5 of 6 nonsmokers or mild smokers, the fibrotic zones showed minor abnormalities of regional ventilation, consistent with small airway dysfunction. The authors suggested that blood-flow scores in fibrotic zones, as a share of the total score, might estimate the proportion of lung dysfunction due to asbestos. They added that they could not conceive of a way to validate such a method.

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 a small group of asbestos-exposed workers (case series) using lung function tests, chest radiographs and xenon-133 ventilation and technetium-99m perfusion scans
• Who was studied: 12 men exposed to asbestos at work, aged 48 to 65 (mean 57.8), usually evaluated in connection with workers' compensation claims; the examination site and study dates are not stated (the authors were at St. Louis University School of Medicine)
• Exposure: Occupational asbestos fiber exposure (fiber types not named) with a mean duration of 25.9 years. Jobs included insulator; carding, spinning and weaving asbestos yarn; cement-asbestos pipe worker; roofing shingles and siding worker; pipefitter and welder; and carpenter. Cigarette smoking ranged from 0 to 90 pack-years.
• Main results:
  • Lung function testing showed a restrictive pattern in 3 men, a mixed restrictive and obstructive pattern in 3, and an obstructive pattern in the remaining 6
  • Chest radiographs showed changes consistent with interstitial fibrosis in 11 men (minimal in 3), pleural thickening in 10 and diaphragmatic calcification in 6
  • Xenon-133 washout was normal in only 1 man. Washout was mildly prolonged but symmetrical in 4 men, and prolonged, asymmetrical and uneven in 7.
  • Years of asbestos exposure correlated with whole-lung perfusion scores (r = +0.77, p less than 0.01), forced vital capacity (r = -0.70, p less than 0.02) and FEV1 (r = -0.71, p less than 0.01). They did not correlate with the other lung function tests or with washout times.
  • Perfusion scores of the 26 lung zones with radiographic evidence of fibrosis correlated with years of asbestos exposure (r = +0.73, p less than 0.01)
  • Pack-years of smoking were not significantly correlated with the lung function tests or the ventilation-perfusion studies. The correlation with perfusion scores of the remaining 46 zones (r = +0.52) approached but did not reach statistical significance.
  • Whole-lung washout times correlated with measures of airflow obstruction: FEV1 (r = -0.70), FEV1/FVC (r = -0.73) and maximum midflow rate (r = -0.73). They also correlated with residual volume (r = +0.67).
  • Minor abnormalities of regional ventilation consistent with small airway dysfunction were seen in the fibrotic zones of 5 of the 6 nonsmokers or mild smokers
• The authors' conclusion: The authors suggested that the blood-flow disturbance in fibrotic zones, expressed as a proportion of the total blood-flow disturbance, could be used to estimate the proportion of lung dysfunction due to asbestos exposure. As an example, they gave an estimate of 62.5% for worker 4.
• Limitations the authors state:
  • Ventilation studies were assessed by visual inspection because no digital computer was available
  • Years of asbestos exposure are a relatively crude measure of real exposure
  • The upper, mid and lower zones on perfusion images may not correspond precisely to those on ventilation images or chest radiographs
  • The authors stated they could not conceive of a way to establish the validity of their proposed proportioning method
  • Two workers (No. 8 and No. 11) had 15 and 25 years of exposure but were likely to have had very little real exposure to asbestos fiber, judged by their job descriptions

Topics

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

Medical terms in this study, explained in our Lexicon: Occupational Exposure, Chest X-Ray, Obstructive Lung Disease, Pulmonary Fibrosis, Asbestos Exposure.

Related studies

• Lung function in relation to radiographic changes in asbestos workers — S. Zedda, G. Aresini, et al. (1973)
• Lung function and respiratory symptoms in subjects with asbestos-related disorders: a cross-sectional study — B. Hilt, J.T. Lien, et al. (1987)
• Lung cinescintigraphy in the dynamic assessment of ventilation and mucociliary clearance of asbestos cement workers — L. Di Lorenzo, M. Mele, et al. (1996)
• Regional lung function in asbestos workers — D. Seaton (1977)
• The protective effect of beta-carotene and retinol on ventilatory function in an asbestos-exposed cohort — P. Chuwers, S. Barnhart, et al. (1997)
• Radiographic changes and lung function in relation to activity of the glutathione transferases theta and mu among asbestos cement workers — K. Jakobsson, A. Rannug, et al. (1995)

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