Adventitious breath sounds

Rhonchi: dry and moist

Rhonchi are formed in bronchi of various calibers, as well as in pathological cavities (abscess, cavern) if they communicate with the bronchial tree. The sound is produced by the rapid movement of air, which is why rhonchi are best auscultated at the beginning of inspiration and at the end of expiration.

Dry rhonchi Occur during narrowing of the airway lumen (mucosal edema, smooth muscle spasm, tumor growth) or when thick, viscous sputum is present. They are heard throughout the respiratory cycle and are classified by pitch:

• High-pitched (sibilant) — rhonchi sibilantes. Indicate obstruction of the small bronchi.
• Low-pitched (sonorous) — rhonchi sonori. Occur when medium and large bronchi are affected.

Localized dry rhonchi indicate a focal process (e.g., at the lung apex — a sign of a cavern), while bilateral ones indicate a generalized lesion (bronchial asthma, bronchitis).

Moist rales Form when liquid contents accumulate in the lumen (liquid sputum, blood, transudate). Air passes through the liquid, creating a foaming effect (the sound of bursting bubbles). Depending on the caliber of the affected bronchus, they are classified as fine, medium, and coarse bubbling rales.

It is critically important to assess the sonority of moist rales:

1. Non-sonorous (dull) — typical of bronchitis or resolving asthma. The sound is muffled by the heterogeneous air environment of the lungs.
2. Sonorous (consonating) — always indicate consolidation of the lung tissue around the bronchus (infiltration, pneumonia). Dense tissue acts as a resonator, excellently conducting sound to the surface. Coarse sonorous rales are often a sign of a fluid-filled cavity.

Crepitation: alveolar phenomenon

Crepitation (crepitatio) fundamentally differs from rales by the site of its origin — it occurs exclusively in the alveoli. Acoustically, this phenomenon resembles light crackling or the sound of rubbing a lock of hair between fingers near the ear.

Mechanism of formation: When a small amount of exudate is present in the alveoli, their walls stick together. During inspiration, as pressure changes, they abruptly separate. This is precisely why crepitation is heard only at the height of inspiration.

Dynamics in pneumonia:

• Crepitatio indux — initial stage. There is little exudate, the alveoli can expand.
• Stage of gray hepatization (peak) — alveoli are completely filled with fibrin, air does not enter them. Crepitation (like normal breathing) disappears.
• Crepitatio redux — stage of resolution of pneumonia. Exudate is resorbed, alveoli begin to fill with air again and separate.

There is also "chronic" crepitation, which is auscultated over a prolonged period in fibrosing alveolitis and pneumofibrosis. Subcutaneous (gas) and bone crepitation are palpation rather than auscultation phenomena.

Pleural friction rub

This is a coarse sound phenomenon, sometimes even detected by palpation. It occurs due to the mutual friction of roughened, inflamed visceral and parietal pleural leaves. Causes may include dry pleurisy, subpleural pneumonia, pulmonary infarction, or tumor involvement.

Pleural friction rub can be confused with rales, but it has strict distinctive features:

1. Auscultated with equal intensity during both inspiration and expiration.
2. Does not change or disappear at all after coughing.
3. The sound intensifies when the stethoscope membrane is pressed against the chest wall (bringing the pleural leaves closer together).
4. Persists if the patient holds their breath but continues to mimic respiratory movements with the abdomen (diaphragm).

A pleuropericardial rub is distinguished separately. It occurs with inflammation of the pleura adjacent to the heart and is triggered by cardiac contractions. The main difference from a true pericardial friction rub is clear synchrony not only with the pulse, but also with the phases of respiration.

Pathological changes in basic breath sounds

For completeness of the auscultatory picture, it is necessary to take into account changes in the basic sounds, which create the background for additional phenomena.

Pathological bronchial breathing Occurs where vesicular breathing should normally be. Two conditions are required for its appearance: consolidation of lung tissue (pneumonia, tuberculosis, pulmonary infarction) and preserved patency of the bronchus ventilating this area. If the bronchus is blocked (e.g., by a tumor), bronchial breathing will not occur. A special variant is amphoric breathing (metallic tint of the sound), which is auscultated over large smooth-walled cavities or in pneumothorax.

Phenomenon of prolonged expiration Normally, expiration is shorter than inspiration. If the duration of expiration equals inspiration or exceeds it, this is a sure sign of bronchial obstruction. When determining the forced expiration time (phonendoscope on the trachea), a value greater than 4 seconds confirms airway obstruction (typical of emphysema and COPD).

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Topical diagnostics of moist rales by caliber
• Mechanism of amphoric breath sounds
• Specifics of auscultating the pleuropericardial friction rub
• Stages of lobar pneumonia and changes in the auscultatory pattern
• Methodology for assessing forced expiratory time

Other topics in the "Respiratory System" section

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