Characterisation of lung sounds for early identification and monitoring of fibrotic interstitial lung disease

Abstract

Chronic Interstitial Lung Diseases (ILD) are characterised by the interstitial involvement of the lungs, often resulting in the aberrant deposition of fibrotic tissue which causes progressive impairment of lung function. Earlier diagnosis of Idiopathic Pulmonary Fibrosis (IPF), the most frequent and severe among Idiopathic Interstitial Pneumonias, is warranted for a timely start of effective antifibrotic treatment. New tools for a more accurate prediction of disease progression and poor outcome are also required to improve the management of the individual patients. Audible “Velcro-type” crackles on chest auscultation represent a typical finding in patients with fibrotic ILD. Although non-specific, their assessment performed by healthcare practitioners is invaluable to prompt the diagnostic work up and limit the diagnostic delay in these patients. Nevertheless, their value toward the early identification and the monitoring of fibrotic ILD has never been explored. Despite the modern advances in the field of electronic auscultation and computerised analysis of lung sounds offer a reliable, objective characterisation of normal and adventitious lung sounds, such methods have never been successfully translated into clinical practice. This thesis provides a comprehensive characterisation of lung sounds recorded in patients with fibrotic ILD using a digital stethoscope, and tries to clarify whether this approach may valuably inform the diagnostic process and the management of these patients in the clinical practice. A prospective case-control study investigated the association between the presence of “Velcrotype” crackles, evaluated by respiratory physicians, and radiologic signs of pulmonary fibrosis in three consecutive large cohorts of patients undergoing a High-Resolution Computerised Tomography (HRCT) scan of the chest. The presence of “Velcro-type” crackles predicted the presence of ILD patterns on HRCT and was independently associated with distinct radiologic features suggestive of pulmonary fibrosis. Such evidence indicates that lung sounds have potential to improve early identification of ILD, while future work is needed to determine the real diagnostic accuracy of “Velcro-type” crackles, either assessed subjectively or via quantitative computerised analysis. A longitudinal cohort study collected serial recordings of lung sounds from a cohort of 19 patients with IPF and 10 healthy controls over a 12-month observation period. Computer-aided lung sound analysis was used to extract almost 500 different acoustic features from each recording. A narrow set of acoustic features of lung sounds recorded via a digital stethoscope was found to be highly reproducible, distinctive of pulmonary fibrosis and responsive to disease progression assessed via validated clinical and functional parameters. As such, this study provided the first evidence on the longitudinal changes occurring in the acoustic features of lung sounds from IPF patients, and paves the way to further research aimed to determine the validity of lung sounds as a new prognostic marker in patients with progressive ILD.

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ORCID for Donna Davies: orcid.org/0000-0002-5117-2991

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