Craquements pulmonaires: que perçoit le clinicien ?

Introduction. - The overall duration of a pulmonary crackle is usually less than 20-30 ms butpsychoacoustics demonstrates that an acoustical event with a duration of less than 20-40 mscannot be estimated in terms of pitch and duration. We pose the hypothesis that the mainresonant information is contained into the breath sounds following the crackle.Methods. - Eight patients with COPD, viral pneumonia, bronchiectasis, congestive heart fai-lure, hypoproteinemia and fibrosing alveolitis were recruited for this study. Thirty-six crackleswere analyzed in time and frequency domains; 12 in each category of low, medium and highfrequencies. The acoustic features of the crackles, their segments (initial deflection width,first cycle duration, two cycles duration, decay segment) and the breath sounds following thecrackles were compared.Results. - The study confirms the differences between the three crackles categories in timeand frequency domains. No statistical differences were found between the decay segments andbreath sounds in each category.Conclusions. - Breath sounds modified by lung tissue density could be the main resonatorsdetermining the fundamental transmission frequencies of crackle signals. Combined acousticanalysis of crackles and breath sounds could replace single analysis of isolated crackles.