|Other names||Breath sounds, lung sounds|
|1) area for normal tracheal sound, 2) area for ascultation of upper lung fields, 3) area for normal bronchial sound. Blue marks ascultation area and red line marks heart.|
Respiratory sounds refer to the specific sounds generated by the movement of air through the respiratory system. These may be easily audible or identified through auscultation of the respiratory system through the lung fields with a stethoscope as well as from the spectral chacteristics of lung sounds. These include normal breath sounds and adventitious or "added" sounds such as crackles, wheezes, pleural friction rubs, stertor, and stridor.
Description and classification of the sounds usually involve auscultation of the inspiratory and expiratory phases of the breath cycle, noting both the pitch (typically described as low, medium or high) and intensity (soft, medium, loud or very loud) of the sounds heard.
Common types of abnormal breath sounds include the following:
|Wheeze or rhonchi||continuous||high (wheeze) or lower (rhonchi)||expiratory or inspiratory||whistling/sibilant, musical||Caused by narrowing of airways, such as in asthma, chronic obstructive pulmonary disease, foreign body.|
|Stridor||continuous||high||either, mostly inspiratory||whistling/sibilant, musical||epiglottitis, foreign body, laryngeal oedema, croup|
|Inspiratory gasp||continuous||high||inspiratory||whoop||pertussis (whooping cough)||see New England Journal of Medicine, Classic Whooping Cough sound file, Supplement to the N Engl J Med 2004; 350:2023-2026|
|Crackles (aka crepitations or rales)||discontinuous||high (fine) or low (coarse), nonmusical||inspiratory||cracking/clicking/rattling||pneumonia, pulmonary edema, tuberculosis, bronchitis|
|Pleural friction rub||discontinuous||low||inspiratory and expiratory||nonmusical, many repeated rhythmic sounds||inflammation of lung linings, lung tumors||not available|
|Hamman's sign (or Mediastinal crunch)||discontinuous||neither (heartbeat)||crunching, rasping||pneumomediastinum, pneumopericardium||not available|
Pectoriloquy, egophony and bronchophony are tests of auscultation. For example, in whispered pectoriloquy the person being examined whispers - typically a two syllable number as the clinician listens over the lung fields. The whisper is not normally heard over the lungs, but if heard may be indicative of pulmonary consolidation in that area. This is because sound travels differently through denser (fluid or solid) media than the air that should normally be predominant in lung tissue. In egophony, the person being examined continually speaks the English long-sound "E" . The lungs are usually air filled, but if there is an abnormal solid component due to infection, fluid, or tumor, the higher frequencies of the "E" sound will be diminished. This changes the sound produced, from a long "E" sound to a long "A" sound .
In 1957, Robertson and Coope proposed the two main categories of adventitious (added) lung sounds. Those categories were "Continuous" and "Interrupted" (or non-continuous). In 1976, the International Lung Sound Association simplified the sub-categories as follows:
Several sources will also refer to "medium" crackles, as a crackling sound that seems to fall between the coarse and fine crackles. Crackles are defined as discrete sounds that last less than 250 ms, while the continuous sounds (rhonchi and wheezes) last approximately 250 ms. Rhonchi are usually caused by a stricture or blockage in the upper airway. These are different from stridor.
Mansy, H.A., Royston, T.J., Balk, R.A. et al. Med. Biol. Eng. Comput. (2002) 40: 526. https://doi.org/10.1007/BF02345450