Use of zonal distribution of lung crackles during inspiration and expiration to assess disease severity in idiopathic pulmonary fibrosis

Purpose of the study To measure the number and distribution of crackles in patients with idiopathic pulmonary fibrosis (IPF) and assess how this relates to measures of disease severity. Study design Fourteen patients with IPF had both the number of crackles per litre of lung volume and lung function measured every 3 months for 1 year. Crackle counts were expressed according to position (upper and lower zones) and whether they occurred during inspiration and expiration. Results At baseline, crackle count per unit volume was higher at the bases than the apices and higher during inspiration than during expiration. There was a significant relationship between lung function and number of crackles per unit volume. Upper zone crackles during inspiration (crackle count vs forced vital capacity (FVC): r=0.69, p=0.007) and lower zone crackles during expiration (crackle count vs FVC: r=0.55, p=0.04) demonstrated the strongest relationship with lung function. Conclusions Number and distribution of crackles in IPF relate to physiological measures of disease severity. Inspiratory lower zone crackles were universal and extensive but the presence, hence, development of inspiratory upper zone crackles and expiratory lower zone crackles correlated with measures of poorer lung function. The presence or appearance of these assessed using chest auscultation provides a clinician with simple measure of disease severity, and possibly progression, prompting further physiological assessment and review of treatment.