From the Guidelines
Pulmonary fibrosis lungs typically exhibit bilateral inspiratory crackles, described as "fine" or "dry" and sounding like Velcro being pulled apart, primarily at the lung bases and posterior lung fields. These crackles are usually most prominent during inspiration, especially at the end of inspiration, as air enters the stiffened, fibrotic alveoli 1. The characteristics of these crackles can be attributed to the progressive scarring of lung tissue, creating stiff, non-compliant lungs with impaired gas exchange. Key features of these sounds include:
- Being "dry" and "Velcro-like" in quality
- Primarily heard during inspiration, particularly at the end of inspiration
- Most prevalent in the lung bases and posterior lung fields, though they can extend to other areas as the disease progresses
- Can be accompanied by decreased breath sounds in severely affected areas due to reduced air movement
- Occasionally, a pleural friction rub may be detected if there is pleural involvement, and some patients may exhibit wheezing if there is concurrent airway disease 1. The presence and characteristics of these auscultation sounds are crucial for the clinical assessment and diagnosis of pulmonary fibrosis, as highlighted by the American Thoracic Society and the European Respiratory Society 1.
From the Research
Auscultation Sounds of Lungs with Pulmonary Fibrosis
- The auscultation sounds of lungs with pulmonary fibrosis are characterized by the presence of crackles, which can be fine or coarse 2, 3.
- Fine crackles on chest auscultation are a sensitive and robust screening tool for early diagnosis and treatment of patients with idiopathic pulmonary fibrosis (IPF) 2.
- The distribution of crackles in patients with IPF is typically higher at the bases than the apices and higher during inspiration than during expiration 3.
- Upper zone crackles during inspiration and lower zone crackles during expiration have been shown to correlate with measures of poorer lung function 3.
- The use of independent component analysis (ICA) and time variant autoregressive model (TVAR) can help to characterize and recognize adventitious lung sounds, including crackles, and provide a 2D spatial distribution imaging to help diagnose pulmonary diseases such as fibrosis 4.
- Automated systems for diagnosing pulmonary fibrosis using crackle analysis in recorded lung sounds have been developed and shown to have strong potential for diagnostic support, especially in assisting general practitioners in the auscultatory assessment of lung sounds 5, 6.