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Lung Sounds

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Breath sounds heard during auscultation of chest and their functional significance

Tracheal Sounds
Very loud, high pitched sound which originates in the large central airways, with a hollow/ “tubular” quality. The duration of inspiratory and expiratory phases are equal. Generally heard over the trachea.

Bronchovesicular Sounds
These have intermediate intensity and pitch with equal inspiratory and expiratory phase. Bronchovesicular sounds are best heard over the first and second intercostal space anteriorly and between scapula posteriorly.

Bronchial Breath Sounds
Loud, high pitched sound that are generated in larger airways (4mm or larger). This is seen in consolidated lung which conducts the high pitched soundsto the chest wall without modification. Other characteristics include distinct pause between inspiration & expiration, absent Alveolar phase and louder and longer expiratory phase. Bronchial breath sound are heard normally over manubrium of sternumBronchial breath sounds can be tubular or amphoric. Tubular breath sounds are heard in Consolidation, Compressed lung: pleural effusion (above the fluid), Thick fibrous scar extending from bronchi to periphery. Amphoric breath sounds are high pitched with distinctive “echo-like” or metallic quality i.e.  more resonant and harmonius timbre and are heard in large pulmonary cavity which is in communication with bronchial system and in bronchopleural fistula.

Vesicular Breath Sounds
Vesicular breath sounds are soft, low pitched sound heard in most parts of the chest wall. The lung tissues attenuates the high frequency sound and only low frequency sounds are transmitted. There is no pause between the inspiration and the expiration. The length of the inspiration is greater than expiration. The sound generated in the inspiratory phase is louder than the expiratory phase. The reason being during inspiration the air moves from the larger airways into the smaller airways and hence there is  more turbulence. On the contrary during expiration, the air moves from the smaller airways into the larger airways with less turbulence and less sound production.

Discontinuous, intermittent, nonmusical, brief sounds
Heard more commonly during inspiration
Can be normal at anterior lung bases
Heard on deep inspiration

Continuous (longer than 250ms) high pitched (dominant frequency >400Hz), musical sound
Hissing quality, heard > with expiration, however, can be heard on inspiration
When air flows through narrowed airways, the walls vibrate generating the wheeze
Velocity of air flow is important in causing vibration of obstructed airways

Low pitched (dominant frequency <200Hz), snoring quality, continuous, musical sounds
Caused by air flowing through narrow airway partially obs tructed by secretions
Similar to wheezes but coarser, lower pitched and sometimes localized
Often seen in obstructive lung disease; also in pneumonia, cystic fibrosis, etc.

Continuous, high-pitched monophonic sound heard throughout respiration; accentuated during inspiration
Like hiss, whistle or shriek
Loudest over trachea
Implies local obstruction to extra-thoracic airways (larynx or trachea), e.g. foreign body or tumour

Pleural Rub
Series of short explosive sounds
Heard during both inspiratory and expiratory phases
Grating, rubbing, creaky, leathery
Occurs when pleural surfaces are inflamed and rub against each other

Sequential inspiratory wheezes
High pitched, late inspiratory sound
Mechanism – reopening in inspiration of the narrow bronchiolar lumen
Heard in Bronchiolitis obliterans, pulmonary fibrosis, allergic alveolitis, consolidation

If you have any questions you  may post in the forum

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Last Updated on Monday, 23 August 2010 21:45  

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