Lung Auscultation – Adventitious Breath Sounds

Adventitious breath sounds are abnormal sounds heard during the auscultation. That represents all the sounds other than normal breath sounds or vocal resonance. Their nomenclature is very ambiguous and confusing and vary greatly from physician to physician. This can lead to misinterpretation and possibly medical errors. Clear and united nomenclature is therefore of great importance.

  1. Lung Auscultation – Normal Breath Sounds
  2. Lung Auscultation – Adventitious Breath Sounds
  3. Lung Auscultation – Vocal Resonance

History

The first one to describe auscultatory findings was René Laennec, the inventor of stethoscope, in his monography A Treatise on the Disease of the Chest and on Mediate Auscultation. He identified five adventitious sounds and all of them called rales (from French word râle – to rattle). To distinguish them he used adjectives like “moist”, “dry”, “crepitus” or “sibilus”, only to substitute it later for rhonchus so the patient would not mistake it for death rattle.

At later date terms wheeze and crackle were introduced, proposed for continuous musical and discontinuous sound, respectively, replacing the old rale and rhonchus. However, all the terms are still used today in medical textbooks and clinical practice as well. Studies show physicians use up to 16 different terms to describe similar sounds. This leads to obvious confusion.

In 1977 the American Thoracic Society proposed the terminology that was later in 1987 presented at the symposium of the International Lung Sounds Association and adopted for clinical practice. In 2000 the European Respiratory Society defined lung sounds based on their computerized analysis.

Clinical Vignette

To be added at later date.

Physical Examination

There are two methods of auscultation – the immediate and mediate auscultation.

Immediate auscultation. In this method the physician is listening to the body wall directly with the unaided ear. However, since the discovery of stethoscope this method was replaced by more accurate, convenient and hygienic mediate auscultation.

Mediate auscultation. It’s the method of auscultation as known today. The physician is listening to the body wall indirectly through the stethoscope which is composed of the bell or membrane, the tubing and the earpieces.

There is no best way of listening to the lungs. Some physicians prefer to listen back to front, top to bottom or vice versa. The key to detailed and correct examination is systematic approach. Any kind.

Except for the last step, the sequence is the same as in Lung Auscultation – Normal Breath Sounds.

  1. Room and patient setup. Room should be quiet and patient sitting up, decently exposed. Female patients should have only front or back of the chest exposed at once. If the patient is not able to sit up, roll the patient to each side to examine the back.
  2. Warming up. Warm up the cold stethoscope by rubbing the membrane. Even if it’s not cold it’s a nice gesture of special care.
  3. Breathing. Ask the patient to breathe deeply through the open mouth. When listening to the back, ask the patient to cross arms over the chest to evert the shoulder blades.
  4. Stethoscope placement. Listen to the front or back of the chest first, from apex to base or vice versa based on your preferences and clinical judgement. The key is to listen to the all of the chest. At each place listen to at least one complete breath cycle.
  5. Compare. Listen to and compare identical places on each sides. Focus on breath sounds first only then on adventitious sounds. Mind their pitch, number, continuity and musical quality, if present.

Interpretation

Adventitious sounds are classified by their quality and continuity into two main categories – musical and non-musical sounds. There is also mixed adventitious sound with musical and non-musical component – squawk.

Musical Non-Musical Mixed
Quality Continuous Discontinuous Both continuous and discontinuous component
Examples Stridor, wheeze, rhonchus Crackles, pleural friction rub Squawk

An excellent video with audio records of various adventitious lung sounds called “Essential Lung Sounds” by Easy Auscultation is available on YouTube.

Musical Adventitious Sounds

They are continuous sounds that can be high- or low-pitched. Two musical sounds are stridor and wheeze (and rhonchus, see later).

Stridor. It’s high-pitched, loud, musical sound produced by air flow through a narrowed segment of upper airways. Stridor is usually inspiratory sound although sometimes can be expiratory or both inspiratory and expiratory (biphasic). The most common cause of stridor is upper airway obstruction.

Wheeze. It’s high-pitched, continuous, musical sound produced by vibrations of the opposing walls of narrowed airways, not by resonance of air. Wheezes are always associated with airflow limitation. However, airflow can be limited even in the absence of wheeze (severe asthma).

Rhonchus. Considered to be variant of wheeze, rhonchus is a low-pitched, continuous, musical sound sometimes referred to as low-pitched wheeze. On auscultation it resembles the sound of snoring. The cause is sometimes attributed to the excessive airway secretions and can be confused for coarse crackles. Therefore it’s probably best to be avoided and replaced by low-pitched wheeze instead.

Stridor Wheeze Rhonchus
Pitch High High Low
Respiratory cycle Inspiratory, although can be expiratory or biphasic Inspiratory, expiratory or biphasic Inspiratory, expiratory or biphasic
Common cause Upper airway obstruction Airflow limitation Airflow limitation, secretions
British term Stridor High-pitched wheeze Low-pitched wheeze

Non-Musical Adventitious Sounds

They are discontinuous sounds like crackles and pleural friction rub.

Crackles. These are short, non-musical, discontinuous sounds heard mostly on inspiration. The sound is likened to rubbing strands of hair in fingers or gently separating strips of Velcro. Some textbooks use word rale or crepitus as a synonym for crackle. There are two categories of crackles that have distinct pathophysiology. Fine crackles are soft, higher pitched and usually heard during mid-to-late inspiration or early expiration. They are unrelated to secretions and associated with pulmonary fibrosis or congestive heart failure. Coarse crackles are loud and lower pitched, heard only on inspiration and possibly related to secretions. They are commonly associated to airway inflammation like COPD or pneumonia.

Fine crackles Coarse crackles
Quality Discontinuous, soft Discontinuous, loud
Pitch High Low
Respiratory cycle Inspiration and/or early expiration Only inspiration
Related to secretions No Yes
Associated pathology Pulmonary fibrosis, congestive heart failure COPD, pneumonia

Pleural friction rub. It’s non-musical, loud, rubbing sound that is predominantly expiratory or biphasic. It’s associated with inflammation of the pleura.

Mixed Adventitious Sound

The only example of this is squawk which contains musical as well as non-musical component.

Squawk. It’s a mixed sound with musical as well as non-musical component. It is associated with hypersensitivity pneumonia, interstitial lung disease. However, it has been described in pneumonia as well.

Caveats and Errors

Common errors are the same as in Lung Auscultation – Normal Breath Sounds.

Breathing through the nose. Common error of the examiner is to listen to the lungs while patient is breathing through the nose which could diminish the intensity of the breath sounds. Instruct the patient to breathe deeply through the open mouth.

Listening through clothing. To accurately assess the lung sounds physician should never listen to the chest through the clothing. The patient should be exposed just enough to protect his or her modesty while having access to the bare chest.

Sitting up straight. Patients use to sit up straight when listening to the back of the chest. This retracts the shoulder blades covering the lungs. Ask them to cross their arms over the chest to evert the shoulder blades.

Clinical Significance

To be added at later date.

References

Chi, J., Artandi, M., Kugler, J., Ozdalga, E., Hosamani, P., Koehler, E., … Verghese, A. (2016). The Five-Minute Moment. The American Journal of Medicine, 129(8), 792–795. https://doi.org/10.1016/j.amjmed.2016.02.020

McGee, S. R. (2018). Evidence-based physical diagnosis (4th edition). Philadelphia, PA: Elsevier.

Bohadana, A., Izbicki, G., & Kraman, S. S. (2014). Fundamentals of Lung Auscultation. New England Journal of Medicine, 370(8), 744–751. https://doi.org/10.1056/NEJMra1302901

Pasterkamp, H., Brand, P. L. P., Everard, M., Garcia-Marcos, L., Melbye, H., & Priftis, K. N. (2016). Towards the standardisation of lung sound nomenclature. European Respiratory Journal, 47(3), 724–732. https://doi.org/10.1183/13993003.01132-2015