Respiratory sounds types and their characteristics

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Philip Kelley

The breath sounds are all those sounds that are heard in the chest during breathing using a stethoscope (also known as a stethoscope). These noises are of two classes: physiological (or normal) and pathological (abnormal)

Physiological breath sounds are present in all people and are produced by the vibration of the wall of the airway as air passes through it. In children they tend to be louder because the thorax is smaller and therefore the sound is produced closer to the stethoscope.

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Modification of the characteristics (intensity, tone) of physiological breath sounds is the first indication of lung disease, with pathological breath sounds, also known as aggregates, appearing within a few hours..

The aggregates always indicate that something is wrong in the lung, so much attention must be paid, not only to its presence but also to its characteristics and location, since using this information, a fairly accurate diagnostic approach can be made about the problem that afflicts the patient.

Article index

  • 1 Types of respiratory fluids 
    • 1.1 Physiological breath sounds or vesicular murmur
    • 1.2 Aggregated or pathological breath sounds
  • 2 Characteristics of breath sounds 
    • 2.1 Characteristics of the vesicular murmur 
    • 2.2 Characteristics of aggregated breath sounds 
  • 3 References 

Types of respiratory fluids

There are two large groups of breath sounds; those that are normal and should be present on the auscultation of any healthy person, and those that are pathological or aggregated, which are audible only in certain pathological conditions.

Physiological breath sounds or vesicular murmur

Vesicular murmur (or simply breath sounds in modern semiology) is the sound that air makes as it passes through the airway. This sound is due in part to the air molecules colliding with each other and in part to the vibration of the walls of the respiratory tree that vibrate when they come into contact with the moving column of air..

This movement is especially intense in the pulmonary alveoli (the final part of the airway) since they collapse a little during expiration and "inflate" again during inspiration..

This change in shape and volume makes the wall of each of the alveoli vibrate throughout the respiratory cycle, generating the vesicular murmur..

Aggregate or pathological breath sounds

Pathological breath sounds are called “aggregates” because they overlap with normal breath sounds. Whenever aggregates are auscultated, the cause should be sought since they are inexorably a consequence of a lung disease.

According to the production mechanism, the aggregates are called:

- Roncus

- Crackles

- Wheezing

- Rales

- Pleural rub

- Pectoriloquia

Each of them with peculiar characteristics and associated with specific pathological conditions.

Characteristics of breath sounds

Each respiratory noise has particular characteristics that differentiate it from the rest. However, in order to differentiate it, it is not enough just to read about it; Rigorous training with a trained professional is also necessary to develop the necessary dexterity to capture the subtle differences, not only between the various sounds, but also in their characteristics (intensity, tone, etc.).

Characteristics of the vesicular murmur 

The vesicular murmur is a low intensity noise, similar to a slight "blowing" that is heard both on inspiration and expiration, with a pause between them. This sound is heard throughout the area of ​​the chest that comes into contact with the lung and is usually a low-pitched, low-pitched noise..

In children it is usually more audible than in adults because the amount of lung tissue under the skin is less, therefore the sound is less attenuated.

When respiratory sounds (or vesicular murmurs) are heard with a lower intensity than normal, one should consider clinical conditions that increase the density of the tissues of the lung or the surrounding area, thus “attenuating” the vesicular murmur.

These conditions include pneumonia, pleural effusion, hemothorax, pneumothorax, and emphysema. The difference between each of them can be established based on the aggregated breath sounds..

When the vesicular murmur is normal, they are reported in the clinical history as “present, normophonic respiratory sounds”, while when they are decreased they are reported as “present, hypophonic respiratory sounds”.

In certain clinical conditions where the lung does not ventilate, that is, no air enters it as in lung collapse or massive pleural effusion, respiratory sounds are absent; in these cases it should be reported in the clinical history as "absent breath sounds" or "non-audible breath sounds".

Characteristics of aggregated breath sounds 

The characteristics of the aggregates are unique and individual, making it very easy to distinguish one aggregate from the other once it is trained. In general, each aggregate is associated with a particular clinical entity, although it is not uncommon to find several types of aggregate in the same patient at the same time, which somewhat complicates the diagnosis..

Roncus

The rhonchi are characterized by being of a serious tone and low intensity, similar to "hoarseness" when a person has laryngitis; but when it comes to "rhonchi" the sound comes from the lung.

It can be compared to a normal but more severe respiratory noise, and is generally associated with an increase in the amount of mucus on the respiratory epithelium, which makes the wall more dense and heavier, so it vibrates less frequently than the usual.

A particular characteristic of rhonchi is that they can change position after chest percussion as secretions are displaced. Regarding its relationship with the respiratory cycle, rhonchi can be heard both in inspiration and expiration, although they tend to be more intense in the first phase (inspiration)

Crackles

Crackles are low-intensity, discontinuous sounds that appear at the end of inspiration or early expiration. The classic semiological description compares them to the noise produced by tissue paper when rubbed between the fingers.

They are produced by the sudden opening of the alveoli at the end of inspiration or by their collapse during expiration, hence it is also sometimes compared to the sound that is produced when a vesicle of bubble wrap for packaging breaks.

The presence of crackles indicates that the amount of fluid within the lung parenchyma is greater than normal, being common to find them in cases of pneumonia, pneumonitis and bronchoaspiration.

Wheezing

As the name implies, they are a high intensity, high frequency “hiss”; they are the easiest aggregates to identify and are associated with a decrease in the diameter of the airway.

As the path through which the air passes becomes narrower, the sounds become more acute, producing the wheezing either during the inspiratory phase (asthma, bronchitis) or expiratory phase (emphysema).

Wheezing is usually synonymous with inflammation of the airway, either acute or chronic; for this reason they are frequent during asthma attacks, reactive bronchitis, acute bronchitis, bronchopneumonia and emphysema. In smokers it is usual to auscultate isolated wheezing due to the condition of chronic inflammation of the airway.

Rales

The rales are similar to the wheezing but of greater intensity, to the point that they can be heard without the need for a stethoscope. They generally occur when the larger airways (larynx, trachea, main bronchi) are inflamed and there is a decrease in their cross section.

It is heard as a “whistle” or “whistle” that is very easy to identify, its production mechanism being the same as that of wheezing, although its tone is much higher, due to the fact that it is the more superficial and larger sections of the respiratory tree..

Pleural rub

The pleural rub is a dry noise, of low intensity, present in inspiration and expiration that can be compared to the sound produced when passing sandpaper over the wood.

It occurs when the pleurae are inflamed and the friction between them is no longer soft and silent.

Pectoriloquia

It is not a respiratory noise in itself but an "induced noise". It is defined as the ability to hear through chest auscultation what the patient says in a whisper, almost inaudibly.

This is due to the fact that sound travels more easily through liquids than through air, therefore when there is pulmonary consolidation (pneumonia), when speaking in a whisper, the sound spreads more easily towards the chest than towards the environment, making it audible during auscultation.

References

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  2. Purohit, A., Bohadana, A., Kopferschmitt-Kubler, M. C., Mahr, L., Linder, J., & Pauli, G. (1997). Lung auscultation in airway challenge testing. Respiratory medicine91(3), 151-157.
  3. Loudon, R., & Murphy Jr, R. L. (1984). Lung sounds. American Review of Respiratory Disease130(4), 663-673.
  4. Murphy, R. L. (1981). Auscultation of the lung: past lessons, future possibilities. Thorax36(2), 99-107.
  5. Korenbaum, V. I., Tagil'tsev, A. A., & Kulakov, Y. V. (2003). Acoustic phenomena observed in lung auscultation. Acoustical Physics49(3), 316-327.
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