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Midinspiratory and expiratory crackles are heard in bronchiectasis but are not specific for this diagnosis. Wheezes and rhonchi may be associated.
Wheezes occur when air flows rapidly through bronchi that are narrowed nearly to the point of closure. They are often audible at the mouth as well as through the chest wall. Causes of wheezes that are generalized throughout the chest include asthma, chronic bronchitis, COPD, and congestive heart failure (cardiac asthma). In asthma, wheezes may be heard only in expiration or in both phases of the respiratory cycle. Rhonchi suggest secretions in the larger airways. In chronic bronchitis, wheezes and rhonchi often clear with coughing.
Occasionally in severe obstructive pulmonary disease, the patient is no longer able to force enough air through the narrowed bronchi to produce wheezing. The resulting silent chest should raise immediate concern and not be mistaken for improvement.
A persistent localized wheeze suggests a partial obstruction of a bronchus, as by a tumor or foreign body. It may be inspiratory, expiratory, or both.
A wheeze that is entirely or predominantly inspiratory is called stridor. It is often louder in the neck than over the chest wall. It indicates a partial obstruction of the larynx or trachea, and demands immediate attention.
Inflamed and roughened pleural surfaces grate against each other as they are momentarily and repeatedly delayed by increased friction. These movements produce creaking sounds known as a pleural rub (or pleural friction rub).
Pleural rubs resemble crackles acoustically, although they are produced by different pathologic processes. The sounds may be discrete, but sometimes are so numerous that they merge into a seemingly continuous sound. A rub is usually confined to a relatively small area of the chest wall, and typically is heard in both phases of respiration. When inflamed pleural surfaces are separated by fluid, the rub often disappears.
A mediastinal crunch is a series of precordial crackles synchronous with the heart beat, not with respiration. Best heard in the left lateral position, it is due to mediastinal emphysema (pneumomediastinum).
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