Sound the alarm for the sound of ILD

Early identification of symptoms of fibrotic interstitial lung diseases (ILDs), most tellingly ‘Velcro-like’ crackles on auscultation, should trigger prompt referral1–4



Inspiratory ‘Velcro-like’ crackles at the lung bases can be a key indicator of interstitial lung disease (ILD)5,6

Diagnosis of ILD can be delayed, making early recognition in the primary care setting a high priority7,8

Initial symptoms of fibrotic ILDs, such as dry cough and dyspnea, can be nonspecific, which can lead to misdiagnosis.1,2 Misdiagnosis of ILD can lead to frequent physician visits, repeated diagnostic tests, and exposure to ineffective treatment1,8

Initial ILD symptoms are often mistaken for symptoms of other common disease like:1,9






Congestive heart failure

50% of patients with IPF are initially misdiagnosed with other common respiratory diseases10

Initial symptoms of fibrotic ILDs can be similar to some common conditions6,7,11–14


*Common (high pitch, low amplitude and short duration) in the base of the lungs

ILD should be considered in all patients with chronic cough and exertional dyspnea16

Most tellingly, ‘Velcro-like’ crackles on auscultation should trigger prompt referral1–4

The presence of ‘Velcro-like’ crackles on lung auscultation is valuable in identifying fibrotic ILD early, as it has excellent sensitivity and good specificity for pulmonary fibrosis3,17

  • Bilateral fine crackles (‘fine crackles’ are discontinuous, high-pitched, 
    low-amplitude, short-duration crackles18) on chest auscultation have a distinctive ‘Velcro-like’ character and are heard during middle to late inspiration5
  • The sounds may be gradually or suddenly extinguished by having the patient bend forward, thus removing the effect of gravity19
  • They tend to be heard almost exclusively over the dependent (+/-basal) lung regions and are changed very little by coughing5

Hear the difference in lung auscultation for:20,21

COPD recording 1
Audio file


COPD recording 2
Audio file

Healthy recording 1
Audio file


Healthy recording 2
Audio file

Fibrotic ILDs recording 1
Audio file


Fibrotic ILDs recording 2
Audio file


Fibrotic ILDs recording 3
Audio file


Fibrotic ILDs recording 4
Audio file


Fibrotic ILDs recording 5
Audio file


Fibrotic ILDs recording 6
Audio file


Fibrotic ILDs recording 7
Audio file


Fibrotic ILDs recording 8
Audio file

COPD, asthma, bronchiectasis22,23

*The obstructive auscultation audio file used represents COPD.

It is possible to use the sounds of ILDs in tandem with flow-volume loops to help differentiate fibrotic ILD

View flow-volume loops

‘Velcro-like’ crackles (e.g. fibrotic ILDs)

Coarse crackles (e.g. chronic bronchitis and severe pulmonary edema)



High pitched

Low pitched

Low amplitude

High amplitude

Short duration

Long duration

Heard during mid to late inspiration

Occurs in both phases of respiration

Usually starts in the basal part of the lungs

No predilection for any particular area of lungs

Altered by body position change — sounds may gradually or suddenly be extinguished by having the patient bend forward19

Unaltered by body position change

Unaltered by coughing

Altered by coughing

It is not transmitted to mouth

It can be transmitted to mouth

Produced by sudden inspiratory opening of small airways which were held closed during the previous expiration

Produced by gas passing through airways which undergo intermittent opening and closing


Recognize the distinctive sound of ‘Velcro-like’ crackles on auscultation of fibrotic ILDs as a trigger for prompt referral1

Perform lung auscultation on your patients with existing CTD and in patients with a pulmonary symptom, so you can promptly refer patients with ‘Velcro-like’ crackles to a lung specialist1,25,26


CHF, congestive heart failure; COPD, chronic obstructive pulmonary disease; CTD, connective tissue disease; ILD, interstitial lung disease; IPF, idiopathic pulmonary fibrosis.

  1. Zibrak JD, Price D. Interstitial lung disease: raising the index of suspicion in primary care. NPJ Prim Care Respir Med.2014;24:14054.
  2. Molina-Molina M, Aburto M, Acosta O, et al. Importance of early diagnosis and treatment in idiopathic pulmonary fibrosis. Exp Rev Resp Med. 2018;12(7):537–539.
  3. Cottin V, Cordier J-F. Velcro crackles: the key for early diagnosis of idiopathic pulmonary fibrosis? Eur Respir J. 2012;40(3):519–521.
  4. Manfredi A, Cassone G, Cerri S, et al. Diagnostic accuracy of a velcro sound detector (VECTOR) for interstitial lung disease in rheumatoid arthritis patients: the InSPIRAtE validation study (INterStitial pneumonia in rheumatoid ArThritis with an electronic device). BMC Pulm Med. 2019;19(1):111.
  5. Kraman SS. Lung sounds for the clinician. Arch Intern Med. 1986;146(7):1411–1412.
  6. Raghu G, Remy-Jardin M, Myers JL, et al; on behalf of the ATS/ERS/JRS/ALAT. Diagnosis of idiopathic pulmonary fibrosis. An Official ATS/ERS/JRS/ALAT clinical practice guideline. Am J Respir Crit Care Med. 2018;198(5):e44–e68.
  7. Cottin V, Hirani N, Hotchkin D, et al. Presentation, diagnosis and clinical course of the spectrum of progressive-fibrosing interstitial lung diseases. Eur Respir Rev. 2018;27(150):180076.
  8. Cosgrove GP, Bianchi P, Danese S, Lederer DJ. Barriers to timely diagnosis of interstitial lung disease in the real world: the INTENSITY survey. BMC Pulm Med. 2018;18(1):9.
  9. Ryu JH, Daniels CE, Hartman TE, Yi ES, et al. Diagnosis of interstitial lung diseases. Mayo Clin Proc. 2007;82(8):976–986.
  10. Collard HR, Loyd JE, King TE Jr, Lancaster LH, et al. Current diagnosis and management of idiopathic pulmonary fibrosis: a survey of academic physicians. Respir Med. 2007;101:2011–2016.
  11. Fischer A, Distler J. Progressive fibrosing interstitial lung disease associated with systemic autoimmune diseases. Clin Rheumatol. 2019;38(10):2673–2681.
  12. Johnson MJ, Bland JM, Gahbauer EA, et al. Breathlessness in elderly adults during the last year of life sufficient to restrict activity: prevalence, pattern, and associated factors. J Am Geriatr Soc. 2016;64(1):73–80.
  13. Theander K, Hasselgren M, Luhr K, Eckerblad J, Unosson M, Karlsson I. Symptoms and impact of symptoms on function and health in patients with chronic obstructive pulmonary disease and chronic heart failure in primary health care. Int J Chron Obstruct Pulmon Dis. 2014;9:785–794.
  14. Niimi A. Cough and asthma. Curr Respir Med Rev. 2011;7(1):47–54.
  15. Dubé B-P, Vermeulen F, Laveneziana P. Disnea de esfuerzo en las enfermedades respiratorias crónicas: de la fisiología a la aplicación clínica. Arch Bronconeumol. 2017;53:62–70.
  16. Raghu G, Remy-Jardine M, Richeldi L, et al; on behalf of the ATS/ERS/JRS/ALAT Committee on Idiopathic Pulmonary Fibrosis. Am J Respir Crit Care Med. 2011;183(6):788–824.
  17. 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.
  18. Mikami R, Murao M, Cugell DW, et al. International symposium on lung sounds. Synopsis of proceedings. Chest. 1987;92:342–345.
  19. Forgacs P. The functional basis of pulmonary sounds. Chest. 1978;73:399–405.
  20. Al-Ashkar F, Mehra R, Mazzone PJ. Interpreting pulmonary function tests: recognize the pattern, and the diagnosis will follow. Cleve Clin J Med. 2003;70(10):866, 868,871–87.
  21. Wood KL. Airflow, lung volumes, and flow-volume loop. In: MSD Manual April 2022. Available at:,-lung-volumes,-and-flow-volume-loop. Accessed: May 2023.
  22. Moore VC. Spirometry: step by step. Breathe. 2012;8:233–240.
  23. Johnson JD, Theurer WM. A stepwise approach to the interpretation of pulmonary function tests. Am Fam Physician. 2014;89(5):359–366.
  24. Sarkar M, Madabhavi I, Niranjan N, et al. Auscultation of the respiratory system. Ann Thorac Med. 2015;10(3):158–168.
  25. Molina-Molina M, Castellví I, Valenzuela C, et al. Management of progressive pulmonary fibrosis associated with connective tissue disease. Expert Rev Respir Med. 2022;16(7):765–774.
  26. Castelino FV, Moua T. Detection and management of interstitial lung diseases associated with connective tissue diseases. ACR Open Rheumatol. 2021;3(5):295–304.

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