Techniques for clarifying the acoustic profile
To increase diagnostic accuracy when auscultating lung fields, it is not enough to simply place a stethoscope on the chest. The physician must actively use refinement techniques.
Determining the boundaries of pathology To precisely outline the lesion zone, the method of dynamic auscultation is used. The physician asks the patient to breathe evenly while sequentially moving the stethoscope with each new breath from an area where completely normal breathing is heard to the area with an altered acoustic profile. This allows for the precise fixation of the moment the sound changes and the determination of the anatomical boundaries of the focus.
Cough test This is one of the most informative techniques, solving two clinical tasks at once:
- Differential diagnosis of adventitious sounds: If the physician doubts the nature of the sound, the patient is asked to cough. Rales (associated with secretion in the bronchi) change their tone, localization, or disappear completely after coughing. At the same time, crepitus and pleural friction rub remain unchanged, as their mechanism of formation does not depend on the patency of the bronchial tree.
- Exclusion of false breath attenuation: Sometimes a marked attenuation of breath sounds is not related to severe pathology of the lung tissue itself (consolidation) or the presence of fluid, but to simple obturation of the bronchial lumen by accumulated secretions. If after intensive coughing the transmission of breath sounds over the area improves, it means the cause of the "silence" was temporary airway obstruction.
Auscultation in pain syndrome
Examination of patients in whom deep breathing causes sharp pain (a typical situation in dry pleurisy) requires a special tactic. In such cases, the classic auscultation algorithm is modified to minimize the patient's suffering.
- Assessment of vocal transmission: Since forced breaths are not possible, at the first stage the physician uses methods that require only producing sounds. Vocal fremitus (fremitus vocalis) and bronchophony are assessed. These phenomena allow for the detection of areas of lung tissue consolidation or fluid effusion without the need for deep breathing.
- Local auscultation: Only after a suspicious area has been identified through voice assessment is the patient asked to take just 1–2 deep breaths. This is done precisely over the discovered lesion zone. Such a short test is sufficient to identify specific auscultatory phenomena (e.g., pathological bronchial breathing) while sparing the patient from prolonged pain stress.
Key points of the physical examination
Auscultation does not exist in a vacuum — it is the final chord of a sequential physical examination. The combination of data from four classical methods allows the physician to formulate a full-fledged pulmonary syndrome.
- Inspection: The baseline stage, the main goal of which is to find chest asymmetry. The physician assesses how evenly both halves participate in the act of breathing and records any lagging of one side.
- Palpation: Serves to confirm inspection data (palpatory assessment of excursion asymmetry) and analyze tissue density. Through the assessment of vocal fremitus (fremitus vocalis), areas of its enhancement (indicating lung tissue consolidation) or weakening (indicating fluid or air accumulation in the pleural cavity) are identified.
- Percussion: Assesses the baseline aeration of the lung tissue. Any deviations from the standard resonant pulmonary sound are identified: dullness indicates the predominance of dense elements, while hyperresonance or tympany indicates pathologically increased aeration.
- Auscultation: Finalizes the picture. The physician determines the main type of breathing (vesicular, bronchial, their pathological variants), evaluates the ratio of the duration of inspiration and expiration phases, and characterizes all adventitious sounds (rales, crepitus, pleural friction rub).
Briefly: answers to topical questions
In which specific diseases or syndromes are crepitus and pleural friction rub heard?
Crepitus is heard in the following conditions:
- Pneumonia — in the initial stage (crepitatio indux) and in the resolution stage (crepitatio redux); it is a manifestation of inflammatory infiltration syndrome.
- Diffuse alveolitis and interstitial fibrosis — heard throughout the course of the disease.
- Congestive heart failure.
Pleural friction rub is heard in the following conditions:
- Pleural irritation syndrome in lobar pneumonia.
- Dry pleurisy — often as the initial stage of exudative pleurisy.
- Subpleural processes — pneumonia/infiltrate, pulmonary infarction.
- Tumor processes — tumors of the lung parenchyma or pleura.
What pathological variants of vesicular and bronchial breathing exist?
Pathological changes in vesicular and bronchial breathing confirmed by sources:
- Weakened vesicular breathing / weakened breath sounds:
- in the initial and final stages of pneumonia;
- in hydrothorax or fluid accumulation in the pleura;
- in bronchial obturation by secretion as a cause of false breath attenuation, if breathing is transmitted better after coughing.
- Vesicular breathing with a bronchial tint:
- may be heard in the initial stage of lobar pneumonia.
- Pathological bronchial breathing:
- occurs with lung tissue consolidation and preserved patency of the ventilating bronchus;
- causes: lobar pneumonia, pulmonary tuberculosis, pulmonary infarction, compression atelectasis, initial stages of obturation atelectasis with preserved patency, a cavity or emptied abscess communicating with a bronchus and surrounded by consolidated tissue, large "dry" bronchiectasis;
- in lobar pneumonia, bronchial breathing is characteristic of the height of the disease.
What is the exact mechanism of formation of moist rales and crepitus?
The mechanisms of formation of moist rales and crepitus fundamentally differ in the localization of the process and the physical conditions of sound generation.
| Sign | Moist rales | Crepitation |
|---|---|---|
| Localization | Bronchi or lung tissue | Alveoli |
| Conditions of occurrence | Presence of secretion or mobile masses | Small amount of exudate in the alveoli |
| Mechanism of sound generation | Passage of air through liquids in the bronchi | Adhesion of alveolar walls and their separation at the height of inspiration |
Moist rales are heard in both phases of respiration and change with coughing, whereas crepitus is heard exclusively at the height of inspiration and does not depend on coughing.
Rales fear coughing (disappear or change), while crepitus and pleural friction rub do not.
What else to study on this topic
- Mechanisms of formation of vesicular and bronchial breathing
- Subtleties of differential diagnosis of crepitus and fine crackling rales
- Causes of changes in vocal fremitus: consolidation versus fluid accumulation
- Synthesis of physical examination data: algorithm for formulating pulmonary syndromes
- Topographic percussion: correlation with auscultatory borders
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