Intensity of breath sounds, in general, is a good index of ventilation of the underlying lung. If the intensity increases there is more ventilation and vice versa. Breath sounds are markedly decreased in emphysema.
Symmetry: If there is asymmetry in intensity, the side where there is decreased intensity is abnormal.
Any form of pleural of pulmonary disease can give rise to decreased intensity.
Bronchial breathing anywhere other than over the trachea, right clavicle or right interscapular space is abnormal. Presence of bronchial breathing would suggest:
In all these conditions, there are no ventilation into alveoli and the sound that is heard originates from bronchi and is transmitted to the chest wall.
Experienced physicians could discriminate between consolidation and cavitation by noting the quality of bronchial breathing. In consolidation, the bronchial breathing is low pitched and sticky and is termed tubular type of bronchial breathing. In cavitary disease, it is high pitched and hollow and is called cavernous breathing. You can simulate this sound by blowing over an empty coke bottle. In tension pneumothorax bronchial breath sounds has a metallic quality and is called amphoric breathing.
Adventitious sounds