Abnormal lung sounds and causes

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abnormal breath sounds

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Merck Manual pulmonary auscultation crackles wheeze rhonchi stridor causes

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https://www.merckmanuals.com/professional/pulmonary-disorder…

Abnormal lung sounds and common causes

Sound	What it sounds like	Usual timing	Common causes
Fine crackles	Brief, high-pitched popping, like separating Velcro	Late inspiration	Interstitial lung disease/pulmonary fibrosis, early pulmonary edema/heart failure, atelectasis
Coarse crackles	Louder, lower-pitched bubbling or rattling	Inspiration, sometimes expiration	Pneumonia, pulmonary edema, bronchiectasis, COPD/chronic bronchitis, retained airway secretions
Wheeze	High-pitched musical whistle	Usually expiration	Asthma, COPD, bronchiolitis, allergic reaction, airway narrowing from edema or mucus. Heart failure can produce wheeze, sometimes called cardiac asthma. A localized one-sided wheeze raises concern for a foreign body or endobronchial tumor.
Rhonchi	Low-pitched, snoring or gurgling musical sound	Inspiration and/or expiration	Secretions in larger or medium airways, especially acute bronchitis, chronic bronchitis, COPD, and bronchiectasis. Often changes or clears after coughing.
Stridor	Loud, harsh, high-pitched sound, often audible without a stethoscope	Mainly inspiration	Upper-airway obstruction: croup, epiglottitis, anaphylaxis/angioedema, inhaled foreign body, laryngeal/tracheal stenosis, vocal-cord dysfunction, upper-airway tumor.
Pleural friction rub	Rough, grating, leathery sound	Both inspiration and expiration	Inflamed pleural surfaces: pleurisy from viral infection or pneumonia, pulmonary embolism with pleural involvement, autoimmune pleuritis, malignancy.
Reduced or absent breath sounds	Quiet or no air entry	Either phase	Pleural effusion, pneumothorax, emphysema/COPD hyperinflation, severe asthma with very poor airflow ("silent chest"), mucus plugging, or main bronchus obstruction.
Bronchial breath sounds in peripheral lung fields	Loud, harsh, tubular breathing where soft vesicular sounds should be heard	Inspiration and expiration	Lung consolidation, classically pneumonia. May accompany egophony and increased vocal resonance.

Quick clinical associations

Basal fine crackles + breathlessness + leg swelling: consider heart failure/pulmonary edema.
Focal crackles + fever/cough: consider pneumonia.
Diffuse expiratory wheeze: asthma or COPD, but do not automatically assume asthma.
Coarse crackles/rhonchi that improve after cough: secretions, bronchitis, or bronchiectasis.
Unilateral absent breath sounds: pneumothorax, pleural effusion, or main-airway obstruction.
Stridor at rest, especially with difficulty speaking, drooling, facial swelling, or cyanosis: emergency assessment is needed because it can reflect critical airway obstruction.

Textbook sources: Harrison’s Principles of Internal Medicine, 22nd ed., respiratory examination section; Goldman-Cecil Medicine, lung-auscultation table. The Merck auscultation overview also describes these sound patterns and includes audio examples.

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