Biphasic lung diffusing capacity: detection of early asbestos induced changes in lung function

Our plain-English summary of Biphasic lung diffusing capacity: detection of early asbestos induced changes in lung function, by Z. Dujić, J. Tocilj, S. Boschi, et al (British Journal of Industrial Medicine, 1992).

The study

• Authors: Z. Dujić, J. Tocilj, S. Boschi, M. Sarić, D. Eterović
• Journal: British Journal of Industrial Medicine
• Published: 1992;49(4):260-7
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 004126).

Abstract

Asbestos related changes in the single breath carbon monoxide diffusing capacity (DLCO) were longitudinally analysed in 14 subjects exposed predominantly to chrysotile asbestos in an asbestos cement factory. These subjects were examined annually over the past nine years; their lung function was initially characterised with increased DLCO as the sole functional abnormality and they had normal chest radiographs. The radiological examination included a chest x ray film and, in the past two years, high resolution computed tomography (HRCT). A biphasic DLCO change was found: an initial increase followed by a relative decrease. The increase in DLCO was mainly caused by an increase in the membrane component (Dm). Indomethacin treatment applied after the sixth annual follow up significantly reduced DLCO and Dm. The decrease in DLCO correlated well with the parenchymal abnormalities found on HRCT, whereas the chest x ray film profusion score for small opacities (ILO classification) was unchanged. In conclusion, the data suggested that, as well as the absolute values of pulmonary function tests, the measurement of progression of functional parameters is essential in the assessment of pleural and parenchymal disease of the lung related to exposure to asbestos. High resolution computed tomography is suggested as the radiological method of choice in subjects with an isolated decrease in DLCO. Exposure to asbestos can be associated not only with a reduction in DLCO, but also with a temporary increase in DLCO caused by a subclinical inflammatory reaction.

In plain English

This nine-year follow-up study tracked 14 asbestos cement workers, exposed predominantly to chrysotile asbestos, out of 215 in a survey begun in 1979. They were selected because their carbon monoxide diffusing capacity (DLCO, a measure of gas transfer from lungs to blood) exceeded 120% of predicted at the sixth check. At the start all 14 had normal lung function, including DLCO, and normal chest x-rays. The rise came mainly from DLCO's membrane component (Dm). A seven-day course of indomethacin, an anti-inflammatory drug, significantly reduced DLCO and Dm. By year nine DLCO was again in the normal range but still higher than at the first examination. No chest x-ray reached an ILO small-opacity score of 1/0; high resolution CT (HRCT) rated nine workers intermediate, four low and one high probability for asbestosis. The authors concluded that DLCO may change in two phases, an early rise probably from subclinical inflammation followed by a relative fall. They suggested HRCT as the radiological method of choice in workers with an isolated decrease in DLCO, calling their HRCT-versus-x-ray comparison tentative given the small sample.

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: Longitudinal follow-up study with annual examinations over nine years, including a seven-day indomethacin treatment after the sixth follow-up
• Who was studied: 14 asbestos cement workers, selected from 215 exposed workers (7%) in a continuous survey started in 1979, because their DLCO was above 120% of predicted at the end of the sixth follow-up. All had normal lung function and chest radiographs and no symptoms at the start. At the end of follow-up their average age was 42 (SD 8) years. There were 11 non-smokers and three smokers. The authors were based in Split and Zagreb, Croatia.
• Exposure: Manufacture of asbestos cement products, where chrysotile asbestos was predominantly used. Exposure duration at the start ranged from 2 to 23 years, and the mean exposure at the end of follow-up was 21 (SD 6) years.
• Main results:
  • At the start of the study, all 14 subjects had normal lung function and normal chest radiographs (mean DLCO 92% of predicted, SD 5).
  • At the sixth follow-up, DLCO, DLCO/VA, Dm and Vc were increased compared with the first follow-up (DLCO p less than 0.0001; mean DLCO 144% of predicted, SD 10). Chest radiographs were still normal.
  • The initial DLCO increase was mainly due to an increase in the membrane component (Dm), not the pulmonary capillary blood volume (Vc).
  • After indomethacin 125 mg per day for seven days, given after the sixth follow-up, mean DLCO and Dm were significantly reduced compared with pretreatment values (p less than 0.01). Vc was unaffected. After treatment, DLCO and Dm were still above predicted values.
  • At the end of nine years, all 14 subjects had DLCO, DLCO/VA, Dm and Vc within the normal range (within 20% of predicted), and two subjects had FVC below 80%. DLCO (p less than 0.05) and DLCO/VA were still increased compared with the first follow-up (mean DLCO 102% of predicted, SD 12).
  • Pleural thickening was found in four subjects on chest x-ray (three focal, one diffuse) and in six subjects on HRCT, including those four.
  • At the end of follow-up, all 14 subjects had an ILO profusion score for small opacities below 1/0.
  • HRCT rated nine subjects as intermediate, four as low and one as high probability for developing asbestosis.
  • At the end of follow-up, DLCO (% predicted) was correlated with the HRCT score (r = 0.650, p = 0.012). The ILO chest x-ray profusion score was not significantly correlated with DLCO (r = 0.112).
• The authors' conclusion: The authors concluded that exposure to asbestos can lead to a biphasic change in DLCO, an initial increase followed by a relative decrease. They concluded that DLCO might be an early and sensitive indicator of future interstitial asbestosis, and that the initial increase was probably due to a subclinical inflammatory response, with prostaglandins as one possible mediator. They suggested HRCT as the radiological method of choice in subjects with an isolated decrease in DLCO, that is, for early detection of asbestosis indicated by a reduction in DLCO.
• Limitations the authors state:
  • The authors stated that the small sample size (14 subjects) makes their conclusion that HRCT is more sensitive than chest radiography tentative.
  • All six subjects with pleural thickening on HRCT also had parenchymal abnormalities, so the authors could not separately study the effect of isolated pleural thickening on lung function.

Topics

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

Medical terms in this study, explained in our Lexicon: Biphasic Mesothelioma, Diffusing Capacity (DLCO), Chrysotile, Asbestos-Cement, Chest X-Ray, High-Resolution CT (HRCT), ILO Classification, Pulmonary Function Test (PFT).

Related studies

• Diffusing capacity and forced vital capacity in 5,003 asbestos-exposed workers: relationships to interstitial fibrosis (ILO profusion score) and pleural thickening — A. Miller, R. Warshaw, et al. (2013)
• Pulmonary elastic recoil and diffusing capacity in subjects with intermediate concentrations of alpha-1 antitrypsin — A.W. Musk, P.W. Robertson (1976)
• Single breath diffusing capacity in the industrial setting — B. Make, A. Miller, et al. (1982)
• Association between neutrophil concentration in bronchoalveolar lavage fluid and recent losses in diffusing capacity in men formerly exposed to asbestos — M.R. Cullen, W.W. Merrill (1992)
• Lung diffusing capacity relates better to short-term progression on HRCT abnormalities than spirometry in mild asbestosis — C.R. Nogueira, L.M. Nápolis, et al. (2011)
• Relationship of mortality, occupation, and pulmonary diffusing capacity to pleural thickening in the First National Health and Nutrition Examination Survey — D.P. Loomis, G.W. Collman, et al. (1989)

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