Normal Breathing Sounds

Respiratory sounds that can be heard through a stethoscope are of two kinds: the normal breathing sounds that occur when no respiratory problems exist and abnormal or adventitious sounds.

The normal breath sounds are both inspiratory and expiratory. They occur as the air moves in and out of the chest when a person breathes normally. There are two important types. The differences can be easily distinguished by listening to examples of each. The first is the tracheal or bronchial breath sound, heard over the large airways or respiratory passages. This recording (as well as all subsequent ones) starts in the beginning of inspiration. It sounds like this:

This sound can be readily recognized by placing the stethoscope over the trachea and listening as the subject breathes in and out with mouth open. What you hear is a "tubular" sound, similar to air being blown through a tube.

The other major type of breath sound is vesicular. The name comes from a Latin word for "little vessels". Sounds of this kind can be heard in the chests of most people as they breathe normally:

Bronchial and vesicular breathing have several characteristics that make them simple to identify. Bronchial breath sounds are loud when the breath is exhaled. Vesicular sounds, in contrast, are relatively quiet during expiration. Listen now to the difference, paying particular attention to the sound made during expiration. This is the vesicular breath sound:

and this is the bronchial:

Vesicular breathing is said to resemble the sound of wind blowing through trees, causing the leaves to rustle. Listen again to the vesicular sound. Note that the tubular sound is not present:

Now listen to an example of sound with a tubular quality; it is air being blown through a cardboard roll:

What is the practical importance of being able to distinguish the difference between bronchial and vesicular breath sounds when the chest is examined? To answer this question, it is important first of all to understand where the sound of bronchial breathing is normally heard: near the large airways. It is heard normally when the stethoscope is placed over the trachea or in the midline of the upper anterior chest, both to the right and left of the sternum. It is also heard, in normal persons, in the right upper anterior chest and on the back between the scapulae.

It is important to point out that, in normal persons, the sound is not heard in any other places on the chest. Therefore, when bronchial breath sounds are heard at the bases of the lungs, this is abnormal. In such a case, bronchial breath sounds are probably being more efficiently transmitted to places where vesicular breath sounds would normally be found. Either that or the normal vesicular sounds are not occurring because a disease is present. Whatever the reason, when the lung tissue becomes solid, it is common to hear bronchial breath sounds.

What kinds of things make the lung tissue solid? Pneumonia, or any situation in which the alveoli and the small airways are filled with fluid, will produce bronchial breath sounds in abnormal locations. These will be found immediately over the area where the disease process is taking place.

It is, then, quite important to be able to recognize bronchial breath sounds. In fact, these sounds are often an early clinical finding of a pneumonia in someone who has a fever and a cough. They may be heard up to one day before the chest x-ray shows any clearcut evidence of the disease.

If the disease can be recognized more quickly, treatment can begin more promptly.

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