Lung sounds in asbestos induced pulmonary disorders

Our plain-English summary of Lung sounds in asbestos induced pulmonary disorders, by P. Piirilä, H. Lehtola, A. Zitting, et al (The European Respiratory Journal, 2000).

The study

• Authors: P. Piirilä, H. Lehtola, A. Zitting, L. Kivisaari, H. Koskinen, R. Luukkonen, S.P. Salo, T. Vehmas, H. Nordman, A.R. Sovijärvi
• Journal: The European Respiratory Journal
• Published: 2000;16(5):901-8
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The aim of the study was to compare the lung sounds in patients with asbestos related pulmonary disorders with findings in high-resolution computed tomography (HRCT), and with lung function variables, in order to find out associations of acoustic changes with radiological fibrosis, emphysema or with pulmonary gas transfer functions. Sixty-four patients with asbestos-related pleural disease, with or without pulmonary disease, were studied. Lung sound recording and analysis was carried out with a computerized lung sound analyser, and HRCT of the chest, as well as forced spirometry and diffusing capacity measurement were performed. The fibrosis score correlated positively with the quartile frequencies of the power spectrum of lung sounds in inspiration (f50) and expiration (f50) and crackle count in inspiration, as well as negatively with diffusing capacity. When the patients with crackling sounds and significant fibrosis were excluded (n=18), emphysema correlated negatively with expiratory quartile frequencies of the power spectrum, with f25 and f50. Furthermore, diffusing capacity correlated with inspiratory f25 and forced expiratory volume in one second with inspiratory f50 when crackles and fibrosis were excluded. Changes in lung sounds were significantly associated with radiologically verified abnormalities and gas transfer of pulmonary tissue. High sound frequencies were associated with fibrotic changes of the lung while low sound frequencies with pulmonary emphysema. Acoustic analysis gives complementary clinical information for evaluation of asbestos-related pulmonary disorders.

In plain English

This Finnish study compared computer-analysed lung sounds with high-resolution CT (HRCT) scans and lung function tests in 64 consecutive men. They came from a screening study of about 600 asbestos-exposed people with pleural plaques. Fifty-five were current or former smokers. The article did not name the asbestos fiber types. Sound analysis found crackles in 43 patients, while clinicians had noted crackles in 28. Higher HRCT fibrosis scores correlated with more inspiratory crackles and with higher sound frequencies. Among 15 patients with no crackles and no emphysema, the correlations between fibrosis and sound frequencies were not significant. In 29 men with little or no fibrosis and no emphysema, the extent and thickness of pleural thickenings correlated with inspiratory crackles. After crackles and significant fibrosis were excluded, emphysema correlated with lower expiratory sound frequencies. More inspiratory crackles went with lower diffusing capacity, a measure of how well the lungs pass gas into the blood. No association was found between asbestos exposure and the sound measures. The authors concluded that sound analysis gives complementary information and helps tell fibrosis from emphysema. They said its use for screening needs further study that includes healthy controls.

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 clinical study correlating computerized lung sound analysis with HRCT findings and lung function tests
• Who was studied: The first 64 consecutive male subjects of a screening study of about 600 asbestos-exposed individuals with pleural plaques in southern Finland, examined at the Finnish Institute of Occupational Health; 55 were current or ex-smokers
• Exposure: Asbestos exposure (fiber types, products and jobs not specified); duration of exposure was recorded, but the printed mean is garbled by the scan
• Main results:
  • Computerized sound analysis found crackles in 43 patients. Clinicians had indicated crackles in 28 patients, which the authors reported as significantly fewer (p less than 0.001).
  • Among all 64 patients, crackle count correlated with the semiquantitative HRCT fibrosis score. Table 3 gives a correlation of 0.625 (p 0.0001) for crackles during inspiration.
  • The HRCT fibrosis score correlated positively with sound quartile frequencies in inspiration and expiration in all patients. Table 4 gives correlations of 0.366 (p 0.0029) for inspiratory f50 and 0.406 (p 0.0009) for expiratory f50.
  • In the 15 patients with no crackles and an emphysema score of 0, the correlations between fibrosis score and quartile frequencies were not significant.
  • When the fibrosis score was below 1, the extent and average thickness of pleural thickenings correlated with inspiratory crackle count and with when crackling started and ended. Table 3 gives 0.560 (p 0.0016) for extent and 0.541 (p 0.0024) for thickness, both against inspiratory crackle count. Adherence scores did not correlate with sound parameters.
  • In Table 3, the pleural extent and thickness correlations were calculated in 29 patients who had both an emphysema score of 0 and a fibrosis score below 1.
  • With significant fibrosis and crackles excluded (n=18), the emphysema score correlated negatively with expiratory f25 (-0.478, p 0.045) and expiratory f50 (-0.482, p 0.043).
  • Emphysema correlated positively with the duration of crackling during expiration (0.276, p 0.027, all 64 patients in table 3). Otherwise, emphysema did not correlate with the crackle parameters.
  • In the whole patient group, inspiratory crackle count correlated negatively with diffusing capacity for carbon monoxide (rS = -0.334, p = 0.0075; n=63 in the figure).
  • No association was found between asbestos exposure and the lung sound parameters.
• The authors' conclusion: The authors concluded that lung sound analysis gives complementary information for evaluating asbestos-related pulmonary disorders and for telling apart fibrosis and emphysema components.
• Limitations the authors state:
  • There were no healthy controls. Whether lung sound analysis is useful for screening needs further study with healthy controls to assess sensitivity and specificity.
  • Earlier studies found a relationship between crackle count and asbestos exposure. This study could not repeat it, possibly because the patient group was smaller.
  • Breathing flow was standardized by visual monitoring and teaching, which does not completely exclude subjective variation.

Topics

Medical terms in this study, explained in our Lexicon: High-Resolution CT (HRCT), Fibrosis, Emphysema, Asbestos-Related Pleural Disease, Spirometry, Diffusing Capacity (DLCO).

Related studies

• The validity of static lung compliance in asbestos-induced diseases — J. Schneider, R. Arhelger, et al. (2012)
• Thin-section CT abnormalities and pulmonary gas exchange impairment in workers exposed to asbestos — A. Sette, J.A. Neder, et al. (2004)
• Correlation between respiratory symptoms and pulmonary function in asbestos-exposed workers — C.A. Brodkin, S. Barnhart, et al. (1993)
• Lung function impairment as a guide to exercise limitation in work-related lung disorders — J.E. Cotes, J. Zejda, et al. (1988)
• Lung and pleural CT signs predict deaths: 10-year follow-up after lung cancer screening of asbestos-exposed workers — T. Vehmas, P. Oksa, et al. (2012)
• Pulmonary abnormalities as a result of exposure to Libby amphibole during childhood and adolescence-The Pre-Adult Latency Study (PALS) — J. Szeinuk, C.W. Noonan, et al. (2017)

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