Respiratory sounds
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 and intensity of the sounds heard.
Abnormal breath sounds
Common types of abnormal breath sounds include the following:| Name | Continuous/discontinuous | Frequency/Pitch | Inspiratory/expiratory | Quality | Associated conditions | Example |
| Wheeze or rhonchi | continuous | high or lower | 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 | see New England Journal of Medicine, , Supplement to the N Engl J Med 2004; 350:2023-2026 |
| Crackles | discontinuous | high or low, 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 | discontinuous | neither | crunching, rasping | pneumomediastinum, pneumopericardium | not available |
Continued
- Rales: Small clicking, bubbling, or rattling sounds in the lungs. They are heard when a person breathes in. They are believed to occur when air opens closed air spaces. Rales can be further described as moist, dry, fine, and coarse. This term is no longer much in use.
- Rhonchi are coarse rattling respiratory sounds, usually caused by secretions in bronchial airways. The sounds resemble snoring. "Rhonchi" is the plural form of the singular word "rhonchus". Since the mid-1990s, it has no longer been considered appropriate terminology in auscultation of the thorax, as much confusion has been reported in the published literature which confuses this with crepitations and wheezes, so the exact nature of this term is unclear.
- Stridor: Wheeze-like sound heard when a person breathes. Usually it is due to a blockage of airflow in the windpipe or in the back of the throat.
- Wheezing: High-pitched sounds produced by narrowed airways. They are most often heard when a person breathes out. Wheezing and other abnormal sounds can sometimes be heard without a stethoscope.
Other tests of auscultation
History
In 1957, Robertson and Coope proposed the two main categories of adventitious lung sounds. Those categories were "Continuous" and "Interrupted". 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 last approximately 250 ms. Rhonchi are usually caused by a stricture or blockage in the upper airway. These are different from stridor.