Partial Airway Obstruction
Anatomy/Physiology/Pathology
  • Intrathoracic airway dilates during inspiration and becomes smaller during expiration.
  • Air enters and exits each lung simultaneously. In unilateral lung disease this will be altered.
  • In lateral decubitus position the dependent lung is smaller than top lung at resting position. However there is more ventilation to dependent lung. Breath sounds increase with ventilation.
  • Size of airways is smallest in the bottom lung.
Chest x-ray of a patient with aspirated tooth in right main bronchus causing partial airway obstruction.

Focused physical examination
Localized expiratory rhonchi will be heard overlying the site of obstruction.
Palpable rhonchi: A rhonchi becomes palpable whenever they unite from larger bronchi.
Decubitus evaluation: When the decreased side is dependent either the breath sounds will become completely absent - if the occlusion becomes complete - or the wheezing can dramatically increase in intensity. These findings will change once you roll patient to the opposite side. The size of airways becomes smaller on the dependent lung thus the obstruction either becomes complete or significantly worsen accounting for the findings.
On simultaneous auscultation one can appreciate a lag in inspiration compared to normal side. During expiration normal side will empty early while the diseased side will have delayed expiration.
Swinging of mediastinum during deep inspiration and expiration can be elicited by wedging trachea with fingers on either side and asking patient to take deep inspiration and expiration. Trachea will move toward the side with partial obstruction during inspiration and towards normal side during expiration.  
Hyper-resonance on the side of partial obstruction during expiration due to air trapping can be elicited.  
Bag-pipe sign: Have the patient take a deep breath and expire and stop in the middle of expiration with glottis open. A continuous expiratory rhonchi will be heard even though patient has stopped expiring. The trapped air deflates creating the rhonchi.