The prevalence of auscultatory crackles in subjects without lung disease

Crackles heard during auscultation of the lungs are generally considered an abnormal physical finding. This study was done to see if crackles could be induced to occur in the lungs of normal subjects. We studied 52 nonsmoking normal subjects by listening at the right and left posterior bases and over the lower right anterior chest during inspiration from functional residual capacity (FRC) and then during inspiration from residual volume (RV). Crackles were recorded on magnetic tape for subsequent time-expanded waveform analysis. No crackles were heard at any of the three sites during inhalation from FRC. Of 52 subjects, 26 had crackles over the anterior site when inhaling from RV. These crackles were often profuse, loud, and easily recorded. Waveform analysis revealed these crackles in normal subjects to be similar to those occurring in patients with interstitial lung diseases. We conclude that crackles, heard over the anterior chest during inspiration from low lung volumes, are not necessarily adventitious sounds.