Cardiorespiratory responses to incremental exercise in patients with asbestos-related pleural thickening and normal or slightly abnormal lung function

Our plain-English summary of Cardiorespiratory responses to incremental exercise in patients with asbestos-related pleural thickening and normal or slightly abnormal lung function, by A. Miller, A. Bhuptani, M.F. Sloane, et al (Chest, 1993).

The study

• Authors: A. Miller, A. Bhuptani, M.F. Sloane, L.K. Brown, A.S. Teirstein
• Journal: Chest
• Published: 1993;103(4):1045-50
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

An increasing number of patients with asbestos exposure are being identified with pleural thickening (PT) alone, with little or no impairment in standard tests of lung function despite their frequent complaint of dyspnea. We have employed incremental cardiorespiratory exercise testing to evaluate the types and mechanisms of impairment in 23 such patients. All had normal lung fields on radiographic examinations and normal (group 1, n = 12) or minimally reduced (group 2A slight restriction, n = 5, group 2B, slight obstruction, n = 6), lung function. Excessive ventilation was common in all groups, but especially in group 2B. Abnormal dead space ventilation (VD/VT) was more frequent in groups 2A (4/5) and 2B (4/6) than in group 1 (3/12). It was associated with O2 desaturation in three patients in groups 2A and B. Cardiovascular abnormalities were rare (1/23). Excessive ventilation and dead space provide a basis for the symptom of dyspnea in these patients.

In plain English

This study tested how 23 people with asbestos-related pleural thickening responded to a gradually increasing exercise test. All were referred to Mount Sinai Medical Center in New York. Twenty-one were men exposed at work as insulators or in shipyards, and two were wives of such workers. Ten had diffuse and 13 had circumscribed pleural thickening, and all had normal lung fields on X-ray. Twelve had normal standard lung tests (group 1), five had slight restriction (group 2A) and six had slight obstruction (group 2B). Excessive breathing during exercise was found in 6 of 12, 3 of 5 and 6 of 6 patients in these groups. Abnormal dead space ventilation during exercise was found in 3 of 12 in group 1 and 8 of 11 in group 2. Three group 2 patients had a fall in blood oxygen. Heart-related abnormalities were rare (1 of 23), but people with known heart disease were excluded. The authors concluded these findings give insight into breathlessness in such patients. They noted smoking might explain some findings: 18 were former smokers.

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: Clinical study (case series) of incremental cardiorespiratory exercise testing in referred patients, divided into groups by resting lung function
• Who was studied: 23 patients referred to Mount Sinai Medical Center, New York, for evaluation of asbestos-related disease. 21 were male and 2 were wives of asbestos workers. Mean age was 61 years (range 37 to 74). 5 were lifetime nonsmokers and 18 were former smokers. All had pleural thickening (10 diffuse, 13 circumscribed) and normal lung fields on X-ray. Group 1 (n = 12) had normal lung function, group 2A (n = 5) slight restriction and group 2B (n = 6) slight obstruction. Study dates were not given.
• Exposure: Occupational asbestos exposure as insulators or in shipyards, beginning 18 or more years earlier, lasting from less than 1 year to more than 30 years. Two wives had household exposure. Fiber types were not stated.
• Main results:
  • At least one abnormal test of ventilation (excessive breathing) on exercise was found in 6 of 12 patients with normal lung function, 3 of 5 with slight restriction and 6 of 6 with slight obstruction (15 of 23 overall).
  • Abnormal dead space ventilation on exercise was found in 3 of 12 patients in group 1 and 8 of 11 in group 2 (4 of 5 with slight restriction, 4 of 6 with slight obstruction).
  • Oxygen desaturation on exercise was seen in three patients in group 2, all of whom had a decreased diffusing capacity. It was not seen in group 1.
  • Cardiovascular abnormalities were found in 1 of 23 patients. Patients with clinically apparent heart disease had been excluded.
  • Abnormal dead space ventilation was found in 10 of the 16 patients (63 percent) who complained of breathlessness, compared with 2 of the 7 (29 percent) who did not.
  • Mean FVC was lower in patients with diffuse pleural thickening (77.2 percent of predicted) than in those with circumscribed pleural thickening (88.2 percent of predicted).
• The authors' conclusion: The authors concluded that excessive ventilation and elevated dead space ventilation during exercise in asbestos-exposed patients with pleural disease alone provide insight into their symptom of breathlessness. They considered abnormal gas exchange better attributed to involvement of the lung tissue itself.
• Limitations the authors state:
  • Whether some of the findings are due to smoking is an open question; 18 of the 23 were former smokers.
  • The authors could not recruit enough asbestos-exposed lifetime nonsmokers who met the other study criteria.
  • The study was not a measure of how common heart disease is in these patients, because those with clinically apparent heart disease were excluded.
  • Exercise testing can detect and measure impairment but cannot diagnose the underlying respiratory disorder.
  • Because patients were selected for normal or only slightly impaired lung function, they cannot be compared with large population studies.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Pleural plaques and thickening.

Medical terms in this study, explained in our Lexicon: Pleural Thickening, Asbestos Exposure, Dyspnea.

Related studies

• Exercise impairment in asbestos-induced pleural fibrosis. Is it really just interstitial fibrosis? — E.T. Mannix, W.J. Martin (1994)
• Asbestos-related lesions of the pleura: parietal plaques compared to diffuse thickening studied with chest roentgenography, computed tomography, lung function, and gas exchange — G. Hillerdal, P. Malmberg, et al. (1990)
• Pulmonary function in asbestosis and asbestos-related pleural disease — A. Miller (1993)
• Abnormal wasted ventilation fraction and normal pulmonary hemodynamics during exercise in patients with exertional dyspnea — Z. Mohsenifar, H.V. Brown, et al. (1982)
• Abnormal lung function associated with asbestos disease of the pleura, the lung, and both: a comparative analysis — K.H. Kilburn, R.H. Warshaw (1991)
• Abnormal pulmonary function associated with diaphragmatic pleural plaques due to exposure to asbestos — K.H. Kilburn, R.H. Warshaw (1990)

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