[Respiratory sounds].

Abstract

After having invented the stethoscope, Laennec published his treatise on auscultation in 1819, describing the acoustic events generated by ventilation and linking them with anatomopathological findings. The weak points of his semiology lay in its subjective and interpretative character, expressed by an imprecise and picturesque nomenclature. Technical studies of breath sounds began in the middle of the twentieth century, and this enabled the American Thoracic Society to elaborate a new classification of adventitious noises based on a few physical characteristics. This terminology replaced that of Laennec or his translators (except in France). The waveforms of the different normal and adventitious noises have been well described. However, only the study of the time evolution of their tone (frequency-amplitude-time relationship) will enable a complete analysis of these phenomena. This approach has been undertaken by a few teams but much remains to be done, in particular in relation to discontinuous noises (crackles). Technology development raises hope for the design, in near future, of automatic processes for respiratory noise detection and classification. Systematic research into the production mechanisms and sites of these noises has progressed equally. It should, in time, reinforce their semiological value and give to auscultation, either instrumental or using the stethoscope or instrumentally, an increased diagnostic power and the status of respiratory function test.