Pleural determinants of restrictive lung function and respiratory symptoms in an asbestos-exposed population

Our plain-English summary of Pleural determinants of restrictive lung function and respiratory symptoms in an asbestos-exposed population, by A. Broderick, L.J. Fuortes, J.A. Merchant, et al (Chest, 1992).

The study

• Authors: A. Broderick, L.J. Fuortes, J.A. Merchant, J.R. Galvin, D.A. Schwartz
• Journal: Chest
• Published: 1992;101(3):684-91
• Cited by: 32 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. 004123).

Abstract

To further define the relationship between asbestos-induced pleural fibrosis and restrictive lung function, we investigated the pleural determinants of respiratory symptoms and restrictive physiology in 1,211 sheet metal workers. We evaluated the relationship between specific components of pleural fibrosis (costophrenic angle involvement, diaphragmatic plaques, width and length of pleural fibrosis, pleural calcification, and the type of fibrosis-circumscribed plaque or diffuse pleural thickening) and both forced vital capacity and respiratory symptoms. We found that costophrenic angle involvement, the width and length of pleural fibrosis, and the presence of either circumscribed plaque or diffuse pleural thickening were each significantly associated with a lower FVC. No consistent relationship was observed between FVC and either diaphragmatic plaques or pleural calcification. However, since the pleural abnormalities were highly collinear, none of these abnormalities alone or in combination predicted the reduction in FVC significantly better than a model that included circumscribed plaques and diffuse pleural thickening. We also investigated the relationship of each component of pleural fibrosis with cough, dyspnea, and chest pain. After controlling for appropriate confounders, a trend toward significance was observed between increased width and length of fibrosis and dyspnea with exertion. Otherwise, these pleural abnormalities were not consistently related to any of the three respiratory symptoms. Our results indicate that although pleural plaques and diffuse pleural thickening and their components are independently associated with a lower FVC, these components of pleural fibrosis do not substantially improve the previously defined relationship between FVC and both circumscribed plaques and diffuse pleural thickening. In addition, a trend toward significance was observed between the width and length of the pleural abnormality and dyspnea while hurrying.

In plain English

This study examined whether specific features of pleural fibrosis (scarring of the lining around the lungs) seen on chest X-rays were linked to lower lung volume and to breathing symptoms. The authors analyzed 1,211 sheet metal workers in the midwest United States who had at least 25 years in the trade and took part in a 1986 union medical evaluation. Pleural abnormalities appeared in 334 (27.6 percent): 260 had circumscribed plaques and 74 had diffuse pleural thickening. After adjusting for age, height, smoking, years in the trade and X-ray lung scarring, lower forced vital capacity (FVC, how much air can be blown out) was associated with plaques, diffuse thickening, costophrenic angle involvement, and the width and length of fibrosis. After adjustment, no statistically significant association was found between FVC and diaphragmatic plaques or pleural calcification. No feature predicted FVC significantly better than plaque and diffuse thickening together. After adjustment, the features were not consistently related to cough, chest pain at rest, or walking slower than peers. The authors reported a trend toward significance between wider and longer fibrosis and breathlessness when hurrying. They could not tell whether workers knew their diagnoses.

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: Cross-sectional analysis of data from a union medical screening program. The data were questionnaires, spirometry, and chest X-rays read with the ILO 1980 classification.
• Who was studied: 1,211 sheet metal workers (men, almost all white) from 12 union locals in the midwest United States, evaluated in 1986. Of 2,643 members offered the evaluation, 1,223 (46.3 percent) took part. Twelve were excluded because they had no chest X-ray.
• Exposure: Sheet metal work near asbestos-containing materials, including use of asbestos materials to insulate ventilation ducts. Fiber types were not named. Workers averaged 34 years in the trade, and the average time since first asbestos exposure was 35.7 years. Earlier reports, not this study, gave workplace concentrations of 0.1 to 8.9 fibers/ml.
• Main results:
  • Among the 1,211 workers, 334 (27.6 percent) had pleural abnormalities: 260 (21.5 percent) with circumscribed plaques and 74 (6.1 percent) with diffuse pleural thickening.
  • In unadjusted (univariate) analysis, FVC was significantly related to all of the pleural abnormalities examined.
  • After adjustment for confounders, lower FVC was significantly related to circumscribed plaque (p = 0.006), diffuse pleural thickening (p = 0.0003), costophrenic angle involvement (p = 0.004), width of pleural disease (p = 0.037) and length of pleural disease. The p-value for length is damaged in the scan.
  • After adjustment, no statistically significant relationship was found between FVC and diaphragmatic plaque (p = 0.54) or calcification (p = 0.67).
  • In the regression model, unilateral costophrenic angle involvement corresponded to a 180 ml lower FVC and bilateral involvement to a 360 ml lower FVC.
  • In the regression model, pleural fibrosis less than 5 mm wide corresponded to a 140 ml lower FVC, and fibrosis at least 5 mm wide to a 280 ml lower FVC.
  • No individual pleural feature significantly improved on a model that already included circumscribed plaques and diffuse pleural thickening. That model had an r2 of 0.47.
  • In unadjusted analyses, no pleural abnormality was significantly related to cough.
  • After controlling for confounders, the apparent relationships between pleural abnormalities and both walking slower than peers because of breathlessness and chest pain at rest were virtually eliminated.
  • After adjustment, there was a trend toward significance between greater width and length of pleural abnormality and breathlessness while hurrying.
  • In the adjusted analysis of breathlessness while hurrying, pleural disease at least 5 mm wide had an odds ratio of 1.74 (95 percent confidence interval 0.96 to 3.17).
• The authors' conclusion: The authors concluded that reduced lung function appears related to the type of pleural fibrosis (circumscribed plaques and diffuse pleural thickening), its width and length, and costophrenic involvement. They concluded that only the length and width of the abnormality appear related to breathlessness.
• Limitations the authors state:
  • Nothing was known about the workers who did not take part.
  • The authors did not know why workers participated or whether they knew their diagnoses, which could affect symptom reporting.
  • Random misclassification of symptoms may have obscured a relationship between pleural fibrosis and symptoms.

Topics

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

Medical terms in this study, explained in our Lexicon: Restrictive Lung Disease, Fibrosis, Costophrenic angle, Pleural Calcification, Diffuse Pleural Thickening, Dyspnea, Pleural Plaques.

Related studies

• Pleural determinants of restrictive lung function and respiratory symptoms in an asbestos-exposed population — P.H. Wright (1993)
• Determinants of restrictive lung function in asbestos-induced pleural fibrosis — D.A. Schwartz, J.R. Galvin, et al. (1990)
• Determinants of restrictive lung function in asbestos-induced pleural fibrosis — C.J. Bergin (1991)
• Asbestos-induced pleural fibrosis and impaired lung function — D.A. Schwartz, L.J. Fuortes, et al. (1990)
• Findings from high resolution computed tomography of the lung and pleura of symptom free workers exposed to amosite who had normal chest radiographs and pulmonary function tests — S. Neri, A. Antonelli, et al. (1994)
• Determinants of respiratory symptoms in insulation workers exposed to asbestos and synthetic mineral fibres — P. Ernst, S. Shapiro, et al. (1987)

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