Normal (vesicular) breath sounds are louder/longer on inspiration and continuous with expiratory sounds
Bronchial breath sounds occur due to large-airway turbulence and are louder and higher pitched on expiration, with a gap between inspiratory and expiratory sounds (heard over areas of consolidation)
Intensity of breath sounds may be reduced symmetrically or asymmetrically depending on location of pathology
Adventitious sounds
Continuous (wheeze) → occur due to significant airway narrowing; most commonly heard during expiration (as airways normally narrow during expiration) but inspiratory wheeze can also occur
Interrupted (crackles) → occur due to opening and closing of small airways
Early inspiratory crackles → COPD
Late/pan-inspiratory
Fine crackles → interstitial lung disease
Medium crackles → LV failure
Coarse crackles → bronchiectasis
Pleural rub → continuous/intermittent grating sound due to pleura rubbing together