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Sound Advice

A Quick Update on Lung Sounds


In 2000, ERS published a committee consensus group guidance on computerized respiratory sound analysis. Since then publications have been found in ATS and Respiratory care.


Key takeaways:


Breath sound classifications consists of sound frequency and duration. It has been modified with the advent of better and sensitive listening tools (stethoscopes).


Adventitious Lung sounds are those found by the listener in addition to the normal or expected sounds. This umbrella covers continuous and discontinuous sounds.


Formerly called Rales – Crackles are an example of discontinuous adventitious respiratory sounds (DARS). They are explosive and short in duration <20ms. They are transient and can have frequencies between 100 to 2000 Hz. They are heard during inspiration.


Continuous adventitious respiratory sounds (CARS) examples include Rhonchus that is now classified as a Wheeze.


Rhonchus, now classified as a wheeze, occupies the sound domain of 300 Hz – essentially a low pitch wheeze. It must be greater than 100 ms. It falls into the CARS classification.


Traditional Wheeze remains but is a more catch all term. It is a continuous adventitious musical sound that occupies frequencies of >100 Hz to 1600 Hz. It also must be greater than 100 ms. Typically wheeze is heard on exhalation.


So in summary, Respiratory sounds emminating from the Chest, Trachea, or mouth are now reclassified because of the advent of more sensitive auscultation technology. We have two buckets to put sounds in - CARS and DARS, Wheeze and Crackles respectively.


References:


  1. A.R.A. Sovijärvi et al., Standardization of computerized respiratory sound analysis. Eur Respir Rev 2000; 10: 77, 585




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