• Upper airway signs: inspiratory stridor, suprasternal retractions, drooling
  • e.g., laryngospasm, angioedema, anaphylaxis, tumors, croup, epiglottitis, diphtheria, drowning, OSA
  • Above the level of the vocal cords: nasal cavity, nasopharynx, oropharynx, hypopharynx, larynx
• Lower airway signs: expiratory wheezing, rhonchi, prolonged exhalation
  • e.g., AECOPD, acute asthma exacerbation, bronchiolitis, aspiration, bronchiectasis, cystic fibrosis
  • Below the vocal cords (subglottic): trachea, bronchi, bronchioles, alveoli

Stridor

• E → I (inhalation closes upper airways = sound)
• Inspiratory stridor → glottis or supraglottis
• Expiratory stridor → obstruction at the level of alveoli