• High-pitched, fine, discontinuous inspiratory sounds resembling Velcro separation, best heard at the lung bases during mid-to-late inspiration.
• Generated by abrupt opening of fibrotic small airways and alveoli in ILD, particularly idiopathic pulmonary fibrosis (IPF).
• Brief, non-musical, repetitive sounds that persist after coughing and correlate with fibrotic changes on HRCT, including honeycombing.
• Classified as fine crackles, distinguished from coarse crackles by higher frequency, shorter duration, and basal predominance.
• Present in approximately 93% of IPF cases at diagnosis, exceeding the detection rates of dyspnea (80%) and restrictive pulmonary function tests (50–87%).

Reference

1. Sgalla G, Walsh SLF, Sverzellati N, et al. "Velcro-type" crackles predict specific radiologic features of fibrotic interstitial lung disease. BMC Pulm Med. 2018;18(1):103. Published 2018 Jun 18.
2. Moran-Mendoza O, Ritchie T, Aldhaheri S. Fine crackles on chest auscultation in the early diagnosis of idiopathic pulmonary fibrosis: a prospective cohort study. BMJ Open Respir Res. 2021;8(1):e000815.
3. Fukumitsu T, Obase Y, Ishimatsu Y, et al. The acoustic characteristics of fine crackles predict honeycombing on high-resolution computed tomography. BMC Pulm Med. 2019;19(1):153. Published 2019 Aug 17.
4. Do Fine Crackles on Chest Auscultation Indicate Idiopathic Pulmonary Fibrosis. Available from: https://www.pulmonologyadvisor.com/news/fine-crackles-on-chest-auscultation-as-an-early-indicator-of-idiopathic-pulmonary-fibrosis/