Definition of Breath Sounds

Breath Sounds – Characteristic noises the flow of air makes as it courses through the trachea and bronchi. The doctor listens to breath sounds using the diaphragm (flat) side of a stethoscope placed at various sites on the outside of the chest and the back, a diagnostic method called auscultation. There are four normal breath sounds, heard with inhalation and exhalation:

  • Tracheal breath sounds, hollow sounds heard over the throat as air passes through the trachea
  • Bronchial breath sounds, harsh sounds heard near the sternum as air passes through the bronchi (large airways in the lungs)
  • Vesicular breath sounds, rustling sounds heard in most locations on the chest and back as air moves in and out of the alveoli
  • Bronchovesicular breath sounds, a mix of harsh and rustling sounds heard just to the sides of the upper sternum on the chest and below the shoulder blades on the back

Normal breath sounds are of nearly equal duration with inhalation and exhalation and are particular to specific locations. Normal breath sounds heard elsewhere are abnormal and indicate the possibility of pulmonary conditions such as atelectasis (collapsed segment of lung), fibrosis (SCAR tissue in the lungs), or other circumstances that cause the lung to shift its physical or functional presence within the thoracic cavity. The absence of normal breath sounds indicates that the segment or lobe of the lung is not receiving air, usually as a result of a significant bronchial occlusion (blockage of a bronchus), severe atelectasis, or lung collapse.

Other breath sounds the doctor can hear through the stethoscope are abnormal and indicate infection or disease. Doctors call these adventitious breath sounds. Among them are

Stridor is a life-threatening emergency that requires immediate medical attention.

  • pleural rub, brushing sounds that indicate inflammation of the pleura (membrane covering the outer surfaces of the lungs) such as occurs with pleural effusion or pleural fibrosis

Breath sounds present important diagnostic information that helps the doctor determine the health status of the lungs as well as assess the progress of conditions under treatment.

See also EPIGLOTTITIS; HEART SOUNDS.

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