Respiratory sounds

Respiratory sounds, breath sounds, or lung 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^[1] with a stethoscope. These include normal breath sounds and adventitious or "added" sounds such as rales, wheezes, pleural friction rubs, stertor and stridor.

Description and classification of the sounds usually involves 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.

Types of normal breath sounds

Vesicular - heard over most of the lungs. Often described as similar to a soft rustle (of leaves). The inspiratory sounds are faster and louder and longer than expiratory sounds. The expiratory intensity is soft, the pitch is low, and the sound dies away after the first third of the expiratory phase.

Bronchovesicular - heard over the 1st and 2nd intercostal spaces and the interscapular area. The inspiratory and expiratory phases are roughly equal in length.

Bronchial - may be normally heard over the manubrium. Expiratory phase is greater than inspiratory. The expiratory pitch is high and intensity is loud.

Tracheal - heard directly over the trachea. Inspiratory phase equals the expiratory phase. The sound is very loud and the pitch very high.

Types of adventitious breath sounds

Common types of abnormal breath sounds include the following:^[2]

Name	Continuous/discontinuous	Frequency/Pitch	Inspiratory/expiratory	Quality	Associated conditions	Example
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.	Wheezing The sound of wheezing as heard with a stethoscope. Problems playing this file? See media help.
Stridor	continuous	high	either, mostly inspiratory	whistling/sibilant, musical	epiglottitis, foreign body, laryngeal oedema, croup	Stridor Inspiratory and expiratory stridor in a 13-month child with croup. Problems playing this file? See media help.
Inspiratory gasp	continuous	high	inspiratory	whoop	pertussis (whooping cough)	not available
Crackles (aka crepitations or rales)	discontinuous	high (fine) or low (coarse), nonmusical	inspiratory	cracking/clicking/rattling	pneumonia, congestive heart failure	Crackles Crackles heard in the lungs of a person with pneumonia using a stethoscope. Problems playing this file? See media help.
Pleural friction rub	continuous	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

Other tests of auscultation

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.

References

External links

• Audio Breath Sounds - Multiple case studies with audio files of lung sounds.
• R.A.L.E. Repository - sound files of breath sounds
• MEDiscuss - Respiratory auscultation with audio examples
• Wilkins R, Dexter J, Smith J (1984). "Survey of adventitious lung sound terminology in case reports". Chest 85 (4): 523–5. doi:10.1378/chest.85.4.523. PMID 6705583. 
• Lehrer, Steven. Understanding Lung Sounds. Elsevier 2002.
• Lung Sounds - 20 recordings and waveforms