Chest
Volume 93, Issue 2, February 1988, Pages 299-302
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Clinical Investigations
Total Lung Capacity: An Insensitive Measure of Impairment in Patients with Asbestosis and Chronic Obstructive Pulmonary Disease?

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The total lung capacity (TLC) is frequently used as a measure of respiratory impairment in patients with asbestosis. Because asbestosis and chronic obstructive pulmonary disease (COPD) exert opposite effects on the TLC, it may be an insensitive measure of impairment in patients with both abnormalities. To assess this, we compared asbestos-exposed patients with functional evidence of COPD and radiographic evidence of interstitial fibrosis (group 1) to those with interstitial fibrosis alone (group 2). Despite the two groups being comparable in degree of radiographic “fibrosis,” no case of restrictive impairment (reduced TLC) was identified among those with both interstitial fibrosis and COPD (group 1) compared to 33 percent of those with interstitial fibrosis alone (group 2). In addition, those patients with both interstitial fibrosis and COPD, compared to those with interstitial fibrosis alone, were found to have greater impairment as measured by alveolar-arterial oxygen difference and diffusing capacity. We conclude that the TLC is an insensitive measure of impairment due to asbestosis in patients with the common setting of coexistent asbestosis and COPD.

Section snippets

Population

The eligible population was comprised of all patients seen in the Occupational Medicine Programs diagnostic clinic in whom a retrospective chart review identified a history of exposure to asbestos and the presence of interstitial fibrosis (International Labor Organizations [ILO] profusion greater than or equal to 1/0, referred to as ILO≥1/0), and for whom TLC, D, and arterial blood gas levels had been obtained.7 The eligible population consisted of 141 subjects; among these, 64 had radiographic

RESULTS

There were no significant differences between groups 1 and 2 in age, race, or height (Table 1). Additionally, there were no significant differences between groups 1 and 2 in pack-years of smoking or mean number of years from first exposure to asbestos (Table 2). Group 1 had fewer individuals at higher grades of profusion compared to group 2 (53 percent [9/17] of group 1 and 63 percent [15/24] of group 2 had ILO profusion grades of ≥1/1), but neither this nor the prevalence of pleural

DISCUSSION

Asbestosis continues to be a pneumoconiosis of high prevalence among workers of many trades, including construction and shipbuilding.1 Given the long latency of 20 or more years between the first exposure and the development of interstitial fibrosis, and the continued heavy exposure of many workers to asbestos fibers into the 1970s, the prevalence of asbestos-related pulmonary disease will continue to remain high through the end of this century.12 Because asbestos exposure has been associated

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  • Cited by (0)

    Manuscript received March 30; revision accepted July 13.

    American College of Physicians Teaching and Research Scholar

    Henry J. Kaiser Family Foundation Faculty Scholar in General Internal Medicine

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