Introduction
Breath sounds are an essential part of pulmonary examination and provide crucial information about lung pathology. They help differentiate normal vs. abnormal lung conditions and guide further diagnostic and therapeutic interventions in critical care settings.
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Classification of Breath Sounds
1. Normal Breath Sounds
These are heard in healthy lungs and vary based on location and airflow dynamics.
Vesicular: Soft, low-pitched, longer inspiratory phase; heard over most lung fields.
Bronchial: Loud, high-pitched, hollow sound, equal inspiratory and expiratory phases; heard over the trachea and large airways.
Bronchovesicular: Intermediate between vesicular and bronchial sounds, equal phases; heard over the mainstem bronchi.
Tracheal: Harsh, high-pitched sound; heard over the trachea.
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2. Adventitious (Abnormal) Breath Sounds
These are additional sounds heard over normal breath sounds, indicating pathology.
A. Discontinuous Sounds (Crackles/Rales)
Definition: Short, non-musical, intermittent sounds caused by collapsed alveoli reopening or airway secretions.
Types:
Fine Crackles: Soft, high-pitched, heard at the end of inspiration. Seen in interstitial lung disease, pulmonary fibrosis, early pulmonary edema.
Coarse Crackles: Loud, low-pitched, heard during inspiration and expiration. Common in pneumonia, bronchiectasis, congestive heart failure (CHF), and ARDS.
B. Continuous Sounds (Wheezes, Rhonchi, Stridor)
Definition: Continuous musical sounds due to airway narrowing or obstruction.
Types:
Wheezing: High-pitched, musical sound heard during expiration (sometimes inspiration). Causes include asthma, COPD, bronchospasm, and airway edema.
Rhonchi: Low-pitched, snoring-like sound, usually clears with coughing. Seen in conditions with excessive secretions like chronic bronchitis.
Stridor: High-pitched, inspiratory sound heard over the neck. Indicates upper airway obstruction, croup, laryngeal edema, or tracheal stenosis.
C. Pleural Friction Rub
Definition: Grating or creaking sound due to inflamed pleural surfaces rubbing against each other.
Best Heard: Over lower lateral chest during inspiration and expiration.
Causes: Pleuritis, pneumonia, pulmonary infarction.
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Clinical Significance of Breath Sounds in Critical Care
1. Differentiating Pulmonary Pathologies
Absent or Decreased Breath Sounds → Pneumothorax, pleural effusion, atelectasis, ARDS.
Fine Crackles → Pulmonary fibrosis, CHF, interstitial lung disease.
Coarse Crackles → Pneumonia, bronchiectasis, pulmonary edema.
Wheezing → Asthma, COPD, bronchospasm.
Rhonchi → Chronic bronchitis, excessive secretions.
Stridor → Upper airway obstruction, anaphylaxis, croup.
Pleural Rub → Pleuritis, pneumonia, pulmonary embolism.
2. Breath Sounds in Mechanically Ventilated Patients
Absent breath sounds on one side → Check for pneumothorax, mainstem intubation, or atelectasis.
Coarse crackles → Suggests retained secretions, requiring suctioning or physiotherapy.
Wheezing → Indicates bronchospasm, requiring bronchodilators.
Pleural rub → May indicate ventilator-induced lung injury or pleuritis.
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Approach to Auscultation in Critical Care
1. Systematic Examination
Use diaphragm of the stethoscope for high-pitched sounds (crackles, wheezes).
Use bell for low-pitched sounds (rhonchi, pleural rub).
Compare bilaterally: Listen at multiple lung zones.
Patient positioning: Ideally sitting upright; in ICU patients, supine or lateral positioning may be required.
2. Clinical Correlation
Crackles + Fever + Cough → Pneumonia.
Wheezing + Respiratory Distress → Asthma, COPD.
Stridor + Sudden Onset → Upper airway obstruction, anaphylaxis.
Absent Breath Sounds + Hypotension → Pneumothorax or large pleural effusion.