Skip directly to content

Crackles

Author: Dr. Subrahmanyam KaruturiMD

  • Crackles are short, explosive, disconitnous, nonmusical sounds that punctuate the underlying breath sound. (<230 msec).
  • Synonyms: Rales (USA), Crepitation (British)
  • Of all the adventitious sonds, carckles are probably the most clinicallly valuable.
  • Laennec's vividly compared crackles to "gurgling water" and "crackling salt".
  • Underlying Breath Sounds : For early and mid-inspiratory crackles it is vesicular, whereas late-inspiratory crackles it is either vesicual or bronchial.
  • Mechanism behind Crackles:
    • Early and mid-inspiratory crackles - Coarse sounds produced by bubbling of air through thin secretions in large and medium-sized airways as in bronchitis and bronchiectasis.
    • Late-inspiratory crackles - Fine sounds that occur during the reopening of distal airways that have become partially occluded as a result of high interstitial pressure as in pneumonia, pulmonary hemorrhage or congestive heart failure.
  • Characteristics of Crackles:
    • Early and mid-inspiratory crackles - Coarse, loud, low pitched, scanty, gravity independent and strongly associated with ostructuve physiology. They resolve with coughing and cannot be extinguished with posture.
    • Late-inspiratory crackles - Fine, soft, high pitched, profuse, gravity dependent and strongly associated with restrictive physiology. They can be extinguished by a change in postire but not by coughing.
  • DD of Crackles:
    • Early crackles - originate in large central airways - Acute or Chronic Bronchitis
    • Mid-inspiratory crackles - originate in medium-sized airways - Bronchiectasis
    • Late crackles - originiate in peripheral airways - Pneumonia, Pulmonary Hemorrhage, Pulmonary Edema, Pulmonary Fibrosis
  • Crackles in Normal Healthy Subjects
    • May occur
    • Typically end inspiratory, high pitched and fleeting
    • Usually resolve after a few deep inspirations
    • They indicate reopening of atelectatic lung units, which occurs normally in most healthy subjects after a deep inspiration follows periods of quiet breathing and especially in subjects that have been recumbent for prolonged time.
  • In asbestosis, the number of crackles correlates directly with severity of the underlying disease.
  • Crackles in Expiration:
    • Crackles are primarily inspiratory
    • 10% occur in expiration
      • Obstructive process - Bronchitis ir Bronchiectasis - Early Expiratory Crackles. Decrease in number with coughing
      • Restrictive process - Pulmonary Fibrosis, Connective Tissue Disease - Mid or Late Expiratory Crackles. Do not resolve with coughing. They are produced by the closure of stiff and fibrotic small airways. in ILD, number of expiratory crackles has been shown to correlate directly with a reduction in diffusing capacity
  • Crackles in Pneumonia
    • Depend on stage of Pneumonia
    • In acute setting - Crackles are predominantly coarse and mid-inspiratory
    • During recovery - Crackles are shorter, more end-inspiratory
  • Crackles in Congestive Heart Failure
    • Profuse, fine, high pitched and late inspiratory
    • More in posture dependent regions
    • Bibasilar fine crackles suggest heart failure
  • Posturally Induced Crackles (PICs)
    • If late-inspiratory crackles are absent in the sitting position but become audible in the supine or leg-elevated position, the test is positive for PICs.
    • Clinical Significance of PICs - both diagnositcally and prognostically indicate higher PCWP, lower pulmonary venous compliance, higher mortality, important predictor or recovery after acute myocardial infarction
  • References
    • Pasterkamp H, Kraman SS, Wodicka GR: Respiratory sounds. Advances beyond the stethoscope.  Am J Respir Crit Care Med  1997; 156:974-987.
    • Piirila P, Sovijarvi AR: Crackles: Recording, analysis and clinical significance.  Eur Respir J  1995; 8:2139-2148.
    • Nath AR, Capel LH: Inspiratory crackles and mechanical events of breathing.  Thorax  1974; 29:695-698.
    • Piirila P, Sovijarvi AR, Kaisla T, et al: Crackles in patients with fibrosing alveolitis, bronchiectasis, COPD, and heart failure.  Chest  1991; 99:1076-1083.