Timing and character of the added sound localise the pathology
Expansion
Crackles, from the sudden opening of collapsed small airways
- Fine, late inspiratory, velcro-like, bibasal: pulmonary fibrosis
- Fine, late inspiratory, bibasal, with orthopnoea: pulmonary oedema
- Coarse, early inspiratory, change with cough: bronchiectasis, secretions
- Localised coarse: pneumonia
Wheeze, a musical sound from narrowed intrathoracic airways, mostly expiratory
- Polyphonic and widespread: asthma, chronic obstructive pulmonary disease
- Monophonic and fixed: localised obstruction such as a tumour or foreign body
- A silent chest in acute asthma is life threatening, not reassuring, because airflow is insufficient to generate sound
Stridor is inspiratory, harsh and loudest over the neck, indicating extrathoracic upper airway obstruction. It is an emergency.
Pleural rub: a creaking, leathery sound heard in both phases, from inflamed pleural surfaces. Causes are pneumonia, pulmonary infarction and pleurisy. It disappears when an effusion separates the surfaces.
Bronchial breathing is harsh, with equal inspiratory and expiratory phases and a gap between them, and is heard when solid lung conducts sound from the large airways. It occurs over consolidation, and at the upper level of an effusion.
Vocal resonance and whispering pectoriloquy follow the same logic as bronchial breathing, and are increased over consolidation and reduced over effusion or pneumothorax.