Breath Sounds

• Normal Breath Sounds:

  • Generated by turbulent airflow in the trachea and large airways
  • Transmitted through air, fluid and tissue to get to the chest wall/stethoscope
  • Normal BS are faint, muffled, low pitched and absent during the latter half of expiration (expiration quieter and shorter than inspiration)
  • BS are quieter at the base of the lung than the apex
• Decreased / Absent Breath Sounds:

  • BS are created by flow-related turbulence so reduced flow causes less sound
  • Causes:
  • Atelectasis e.g. bibasal post-op atelectasis or lobar atelectasis from sputum plug
  • Emphysema (hyperinflation)
  • Asthma (silent chest)
  • Pneumothorax
  • Obesity
  • Pleural effusion
• Bronchial Breath Sounds:

  • Loud and harsh sounding
  • Expiration is as loud as inspiration
  • There is a pause in-between inspiration and expiration
  • Sounds like a deep sea diver breathing through a regulator or Darth Vader
  • Sound is better transmitted through something solid
  • Causes:
  • Consolidation (pneumonia)
  • Fibrotic lung