Crackles are discontinuous, brief sounds heard more commonly on inspiration.
They can be classified as
* fine (high pitched, very brief) or
* coarse (low pitched, less brief).
Crackles can be produced by two common mechanisms.
* When previously closed small airways suddenly open. To see how this can happen, gently close your wet lips and open them suddenly. You will hear a 'plop'. When this happens in the terminal bronchioles, fine crackels are produced.
* Another explanation is that air bubbles through secretions as in pulmonary edema and resolving pneumonia.
Causes:
1. bronchiectasis
2. pulmonary edema
3. ARDS
4. consolidation
5. fibrosis
6. asthma
7. chronic bronchitis
8. interstitial lung disease
