The aim of this study was therefore to assess the diagnostic value of early vs late, and coarse vs fine inspiratory crackles heard at the lung bases, for the identification of COPD. The possible role of crackle characteristics (early/late and coarse/fine) when identifying obstructive lung conditions could now be re-evaluated in a non-selected general population. In the seventh Tromsø study (2015–2016), lung sound recordings from six chest locations were classified in more than 4000 participants, 11 and the presence of COPD could be evaluated in most of these. 10 Yet these conclusions have been mainly based on small datasets, and we hypothesise that the distinction between ‘early’ and ‘late’ will generate higher agreement and possibly also be more useful in clinical practice. 1 7 The clinical usefulness of differentiating coarse from fine crackles has however been questioned due to low agreement between clinicians in identifying these crackle characteristics. 1 7–9 Coarse and early crackles are related to each other, since coarse crackles tend to appear early during inspiration 9 and both coarse and early crackles are commonly heard in obstructive lung diseases. 1 Coarse crackles may be caused by sudden opening of obstructed central bronchii, while fine crackles are related to opening of distal airways. These crackle types are defined by the duration of each single crackle. Instead, another subdivision based on crackle characteristics is frequently referred to, namely ‘coarse’ versus ‘fine’. 4 This difference could be explained by the site of airway closure, that is, central airways in obstructive and peripheral airways in restrictive defects.Īlthough Nath and Capel proposed that the timing of crackles could be clinically helpful, which was also supported by Piirilä et al, 1 recent guidelines for diagnosing COPD 5 and heart failure 6 do not mention the distinction between early and late crackles. Few years after Forgacs published his findings, Nath and Capel observed clear differences in the timing of crackles between patients with bronchial obstruction, in whom early crackles usually were heard, and patients with restrictive lung defects, who had late crackles. 2 Since the inflation of the lungs happens sequentially, and the basal parts inflate later during inspiration than the central parts, 3 crackles may be described by time of appearance. 1 Forgacs proposed that crackles heard during inspiration were related to sudden opening of airways.
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