Lung function impairment as a guide to exercise limitation in work-related lung disorders

Our plain-English summary of Lung function impairment as a guide to exercise limitation in work-related lung disorders, by J.E. Cotes, J. Zejda, B. King (The American Review of Respiratory Disease, 1988).

The study

• Authors: J.E. Cotes, J. Zejda, B. King
• Journal: The American Review of Respiratory Disease
• Published: 1988;137(5):1089-93
• Cited by: 57 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. 002590).

Abstract

The hypothesis that exercise limitation of respiratory origin can be predicted accurately from the lung function impairment has been tested using maximal oxygen uptake (VO2max) as the dependent variable in a multiple regression analysis. The subjects were 157 men who met objective criteria for exercise being limited by respiratory impairment. VO2max (mean value, 1.38 L min-1) was described by FEV1 and single-breath lung transfer factor (diffusing capacity) for carbon monoxide (TL') singly or in combination, but the accuracy was poor (at best, standard error of the estimate, 0.36 L min-1; r2, 29.1%). FEV1 could be replaced by FVC and FEV1/FVC. Description of VO2max was improved by also including in the equation the variables age, fat-free mass, and submaximal exercise ventilation (VE). Transfer factor did not then contribute significantly. VO2max as percent of predicted (mean value of 60%) was described by %FVC or %FEV1, but the accuracy was poor (SEE, 16.0%; r2, 14%). Prediction was improved somewhat by the alternative use of inspiratory vital capacity and FEV1/FVC. Transfer factor did not contribute additional information; however, inclusion of VE materially improved the accuracy (SEE, 12.9%; r2, 44%). Among a subgroup of 35 men whose lung disease was due to asbestos, %TL' or transfer factor measured using a multibreath estimate of residual volume (%TLCO) made a small contribution to the explained variance, e.g.: %VO2max = 0.44% FEV1 -0.78 VE + 0.16% TLCO + 52.3 SEE 7.27%. This equation also described the %VO2max of all subjects (SEE, 13%).(ABSTRACT TRUNCATED AT 250 WORDS)

In plain English

This study tested whether exercise limitation caused by lung impairment could be predicted accurately from standard lung function tests. The subjects were 157 men who met objective criteria for exercise being limited by respiratory impairment. All had been referred for confirmed or suspected work-related lung disorders, including coal workers' pneumoconiosis, silicosis and disease caused by asbestos. Lung function tests used singly or together described maximal oxygen uptake poorly, explaining at best 29.1% of its variation. Including ventilation (breathing) measured during submaximal exercise raised this to 59% for absolute oxygen uptake, in an equation that also included age and fat-free mass. It raised it to 44% for oxygen uptake as a percentage of the predicted value. In a subgroup of 35 men whose lung disease was due to asbestos, the physiologic measures together explained as much as 71% of the variation, but transfer factor (a test of how well the lungs take up gas) added only 3.1%. The authors concluded that exercise limitation could not be assessed accurately from FEV1, FVC and transfer factor, and that additional measures were needed.

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 lung function and exercise test results, using multiple regression to predict maximal oxygen uptake
• Who was studied: 157 men referred to the laboratory for confirmed or suspected work-related lung disorders, selected because their exercise was limited by respiratory impairment. The text does not state study dates.
• Exposure: Confirmed or suspected work-related lung disorders: coal workers' pneumoconiosis, silicosis, siderosis, extrinsic allergic alveolitis, asthma possibly of occupational origin, and disease caused by asbestos. No fiber types or doses are given.
• Main results:
  • In all 157 men, FEV1 and transfer factor, singly or combined, described maximal oxygen uptake with poor accuracy. At best the standard error of the estimate was 0.36 L per minute and the explained variance was 29.1%.
  • In all 157 men, an equation including FEV1, submaximal exercise ventilation, fat-free mass and age explained 59% of the variance in absolute maximal oxygen uptake, with a standard error of the estimate of 0.26 L per minute.
  • In all 157 men, maximal oxygen uptake as percent of predicted averaged 60%. Percent FVC or percent FEV1 described it with poor accuracy: standard error 16.0%, explained variance 14%.
  • In all 157 men, adding submaximal exercise ventilation reduced the standard error to 12.9% and raised the explained variance in percent-predicted maximal oxygen uptake to 44%. Transfer factor did not contribute additional information.
  • In the subgroup of 35 men with lung disease caused by asbestos, mean transfer factor was 60% of ATS reference values, compared with 70% in the other men in the defined group.
  • In the asbestos subgroup, the physiologic measures accounted for as much as 71% of the variance in percent-predicted maximal oxygen uptake.
  • In the asbestos subgroup, when percent FEV1 and submaximal exercise ventilation were already included, transfer factor accounted for only 3.1% of the variance.
• The authors' conclusion: The authors concluded that, in patients whose exercise capacity was limited by respiratory factors, the limitation could not be assessed accurately from FEV1, FVC and transfer factor. They found these measures were not independent and predicted poorly. They concluded that additional measures, such as ventilation at a standard oxygen uptake during submaximal exercise, were needed for acceptable accuracy.
• Limitations the authors state:
  • The subjects were claimants for pneumoconiosis benefit, and some were anxious. A few hyperventilated or exaggerated their symptoms. The authors reported that excluding the 15 men with signs of hyperventilation did not significantly change the result.
  • The reference equations for maximal oxygen uptake were based on cycle exercise, but the tests were done on a treadmill. The authors stated that any small error from this applied to all subjects.
  • The study did not consider social and occupational factors that contribute to handicap.

Topics

Medical terms in this study, explained in our Lexicon: FEV1, Diffusing Capacity (DLCO), FEV1/FVC Ratio.

Related studies

• Relation between lung function, exercise capacity, and exposure to asbestos cement — P. Wollmer, L. Eriksson, et al. (1987)
• Exercise alveolar-arterial oxygen pressure difference in interstitial lung disease — C. Risk, G.R. Epler, et al. (1984)
• Lung function and exercise performance in smoking and nonsmoking asbestos-exposed workers — D.Y. Sue, A. Oren, et al. (1985)
• Abnormal wasted ventilation fraction and normal pulmonary hemodynamics during exercise in patients with exertional dyspnea — Z. Mohsenifar, H.V. Brown, et al. (1982)
• Exercise performance and functional impairment in asbestos-exposed workers — J. Pearle (1981)
• The validity of static lung compliance in asbestos-induced diseases — J. Schneider, R. Arhelger, et al. (2012)

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