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a pathological respiratory sound arising in the bronchi, trachea, or cavities formed in the lungs (abscesses, caverns).
Dry and moist rales are distinguished. Dry rales are caused by the whirling movement of air in places where a bronchial cavity narrows owing to spasm, swelling of the mucous membrane, or accumulation of viscid secretion. They have a whistling or buzzing quality and can be heard in auscultation, sometimes from a distance, for example, during an attack of bronchial asthma. Moist rales are caused by the passage of a stream of air through mucus and sound like bursting bubbles. They occur in bronchi, in the trachea, and in pathological cavities in a lung. Depending on the order of the bronchus or size of the cavity, rales may be smallbubbling, medium-bubbling, or large-bubbling. Consonanting (clear) and nonconsonanting (unclear) moist rales are also distinguished.
The presence, type, and sound of rales are important in the diagnosis of bronchitis, pneumonia, and other disorders.