Objective Lung Sound Analysis Techniques

Because of the large degree of observer variability in clinical auscultation there has been considerable interest in more objective methods of utilizing the information provided by lung sounds. Summaries of the work done to date can be found in two state of the art papers published by the American Thoracic Society (16, 17). An extensive bibliography is also available on the International Lung Sounds Association Web site (18). Some of the more clinically relevant reports are mentioned below.
Tape recordings and acoustic analysis have helped to clarify the previously confused nomenclature (19). This has been facilitated by International groups, particularly the International Lung Sound Association and the CORSA group of the European Economic Community. Tape recordings have been particularly useful in the educational process and a number of tapes are commercially available.
There has also been a good deal of interest in computerized analysis of lung sounds since the initial report in 1973 (14). Several clinical applications have resulted. Screening for occupationally related diseases has been demonstrated to be feasible using acoustic techniques (20, 21). Screening for sleep apnea can be done using lung sounds (22). Long term monitoring of wheezing is now feasible and the instrumentation to do this is now commercially available (23, 24). Lung sound analysis has been demonstrated to show the effects of bronchoconstrictors and allergen induced asthmatic responses in patients with asthma (25-28). This has distinct advantages in subjects unable to perform pulmonary function tests properly, particularly children. A detailed discussion of the numerous studies showing the usefulness of this approach as well as its pitfalls has been presented (29). Numerous investigators have presented computerized methods for detection and quantification of lung sounds (30-32). Some of these have been validated (33). Pattern differences among the common lung diseases have been demonstrated to be documented objectively with the aid of computers (34). Despite the enormous potential, the applications of lung sound technology, that are currently proven to be clinically useful, however, are relatively few. In view of the recent advances in computer technology it is likely that powerful diagnostic and monitoring devices will be available in the near future.

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15. Baughman, RP, Shipley, RT, Loudon, RG, Lower, EE. Crackles in Interstitial Lung Disease Comparison of Sarcoidosis Fibrosing Alveolitis Chest 1991;100:96-101.

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18. www.ILSA.cc

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23. Beck, RU, Dickson, MD, Montgomery, Mitchell, I. Histamine challenge in younge children using computerized lung sounds analysis. Chest 1992;102:759.

24. Malmberg, LP, Sorva, R, Sovijarvi, ARA. Frequency distribution of breath sounds as an indicator of bronchoconstriction during histamine challenge test in asthmatic children. Pediatr Pulmonol 1994;18:170.

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32. Murphy, RLH, Del Bono, E, Davidson, F. Validation of an automatic crackle (rale) counter. Am Rev Respir Dis 1989;140:1017.

33. Kaisla, A. R. Sovijärvi, P. Piirilä, H. M. Rajala, S. Haltsonen and T. Rosqvist Validated method for automatic detection of lung sound crackles. Med. Biol. Eng. Comput. 29, 517-521 (1991).

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