Maximal expiratory flow volume curves in workers exposed to asbestos

Our plain-English summary of Maximal expiratory flow volume curves in workers exposed to asbestos, by R. Rodriguez-Roisin, J.E. Merchant, G.M. Cochrane, et al (Respiration; International Review of Thoracic Diseases, 1980).

The study

• Authors: R. Rodriguez-Roisin, J.E. Merchant, G.M. Cochrane, B.P. Hickey, M. Turner-Warwick, T.J. Clark
• Journal: Respiration; International Review of Thoracic Diseases
• Published: 1980;39(3):158-65
• Cited by: 40 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. 000852).

Abstract

We have studied 40 workers with varying industrial exposure to asbestos, using routine spirometry and maximal expiratory flow volume curves (MEFVC). Abnormalities of MEFVC were common and seen in those with normal spirometry and total lung capacity. The high incidence of abnormal MEFVC suggests that air flow dysfunction in small airways may follow prolonged asbestos exposure. Our findings support, therefore, the idea that asbestos exposure may cause an obstruction to airflow arising particularly in small airways, and that one of the common functional abnormalities attributable to asbestos exposure is airways obstruction.

In plain English

This study tested the lungs of 40 workers (39 men, 1 woman, aged 37 to 73) exposed to asbestos for 1 to 50 years. They were referred to the Brompton Hospital Pneumoconiosis Medical Panel, London, for respiratory symptoms, signs and/or X-ray abnormalities. Fiber types were not stated, and because no satisfactory dust measurements were available, the authors counted exposure as years since first exposure. Standard tests classed 15 workers as normal, 6 obstructive, 12 restrictive and 7 mixed. A more detailed test, the maximal expiratory flow volume curve, showed reduced late flow in 34 of 40 workers (85%). In 15 workers, significant airflow dysfunction appeared only on this test. Reduced flow rates showed no significant correlation with epidemiological, clinical or radiological criteria, but smoking history was weakly related to reduced flow at 75%. Among 7 workers grouped as non-smokers or ex-smokers (one had smoked 26 pack-years), mean flows at 50% and 75% were 63% and 42% of predicted. The authors wrote that airway dysfunction did not appear correlated with asbestos exposure and was not completely explained by smoking. They concluded that it can be considered a functional sign of asbestos exposure.

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: Lung function study of a series of asbestos-exposed workers, comparing routine spirometry and lung volumes with maximal expiratory flow volume curves (MEFVC). Results were compared against predicted normal values. There was no separate unexposed group.
• Who was studied: 40 workers (39 male, 1 female; aged 37 to 73, mean 57.5) referred to the Pneumoconiosis Medical Panel of the Brompton Hospital, London, because of respiratory symptoms, signs and/or pleuropulmonary radiological abnormalities. 23 were smokers and 9 were ex-smokers. Dates of testing are not stated.
• Exposure: Varying occupational exposure to asbestos dust lasting 1 to 50 years (mean 21.8). Fiber types and jobs are not specified. No satisfactory dust concentration measurements were available, so exposure was measured as the number of years since first exposure.
• Main results:
  • On routine lung function tests, 15 workers had a normal pattern, 6 an obstructive pattern, 12 a restrictive pattern and 7 a mixed pattern.
  • Reduced flow at 75% of vital capacity (adjusted for lung size) was found in 34 of 40 workers (85%), including all 15 in the routinely normal group. Reduced flow at 50% was found in 27 of 40 (67%), and reduced mid-expiratory flow in 29 of 40 (72%).
  • The authors set aside the 13 workers with obstruction on routine spirometry and 6 classed as restrictive. That left 15 workers who appeared to have significant airflow dysfunction only on the flow volume curves.
  • Reduced flow rates showed no significant correlation with epidemiological, clinical or radiological criteria. Smoking history was weakly related specifically to reduced flow at 75%.
  • Table II covers 7 workers labelled non-smokers or ex-smokers (one had smoked 26 pack-years and quit 13 years earlier). In these 7, mean flow at 50% was 63% of predicted and mean flow at 75% was 42% of predicted. The authors described these values as suggestive of dysfunction in peripheral airways.
  • In these 7 workers, mean vital capacity was 85% of predicted. The authors judged the flow reduction unlikely to be due to a significant restrictive defect, at least in 4 of them.
  • The authors wrote that the presence and degree of airways dysfunction did not appear to be correlated with asbestos exposure and could not be completely accounted for by smoking.
  • After inhalation of isoprenaline (an airway-opening drug), no worker's flow volume curve improved by more than 10%.
• The authors' conclusion: The authors concluded that their findings support the idea that airways dysfunction can be considered a functional sign of exposure to asbestos fibres. They suggested that if it reflects early involvement, flow volume curves might help detect asbestos lung damage early.
• Limitations the authors state:
  • No satisfactory dust concentration measurements were available, so exposure was based only on years since first exposure.
  • Clinical and radiological data were collected but not reported.
  • It is unknown whether small airways dysfunction is an early or a late stage of asbestosis.

Topics

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

Medical terms in this study, explained in our Lexicon: Spirometry, Total Lung Capacity (TLC), Asbestos Exposure.

Related studies

• Vital capacity and one-second forced expiratory volume in Australian male asbestos cement workers — L.N. Balaam, S.F. McCullagh (1975)
• Early detection of interstitial lung disease in asbestos exposed non-smoking workers by mid-expiratory flow rate and high resolution computed tomography — Z. Dujić, J. Tocilj, et al. (1991)
• Airway obstruction in asbestos-exposed shipyard workers: with and without irregular opacities — K.H. Kilburn, R.H. Warshaw (1990)
• High prevalence of reversible airway obstruction in asbestos-exposed workers — S. Delpierre, M.J. Delvolgo-Gori, et al. (2002)
• Airway disease in non-smoking asbestos workers — K.H. Kilburn, R.H. Warshaw, et al. (1985)
• Expiratory and inspiratory forced vital capacity and one-second forced volume in asymptomatic never-smokers in Norway — A. Gulsvik, T. Tosteson, et al. (2001)

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