Rales, crackles or crepitation, are the clicking, rattling, or crackling noises heard on auscultation of the lungs with a stethescope during inhalation. The sounds are caused by the "popping open" of small airways and alveoli collapsed by fluid, exudate, or lack of aeration during expiration.

Rales can be heard in patients with pneumonia, atelectasis, acute bronchitis, and severe bronchitis. Pulmonary edema secondary to left-sided congestive heart failure can also cause rales.

The sound of rales

Crackles (or rales) are caused by fluid in the small airways or atelectasis. Crackles are referred to as discontinuous sounds; they are intermittent, nonmusical and brief. Crackles may be heard on inspiration or expiration. The popping sounds produced are created when air is forced through respiratory passages that are narrowed by fluid, mucus, or pus. Crackles are often associated with inflammation or infection of the small bronchi, bronchioles, and alveoli. Crackles that don't clear after a cough may indicate pulmonary edema or fluid in the alveoli due to heart failure or adult respiratory distress syndrome (ARDS).

• Crackles are often described as fine, medium, and coarse.
• Fine crackles are soft, high-pitched, and very brief. You can simulate this sound by rolling a strand of hair between your fingers near your ear, or by moistening your thumb and index finger and separating them near your ear.
• Coarse crackles are somewhat louder, lower in pitch, and last longer than fine crackles. They have been described as sounding like opening a Velcro fastener.

See also

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• Wheeze
• Ronchi

External links

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• Audio file of rales