Foreign Body, Trachea

Michael P. D'Alessandro, M.D.
Peer Review Status: Internally Peer Reviewed

Etiology/Pathophysiology:
An aspirated foreign body causes a spectrum of airway obstruction, depending on its size and how long it has been present. When the foreign body is much smaller than the airway you have a bypass valve effect giving you normal aeration - air gets in and out on inspiration and expiration. When the foreign body is only a little bit smaller than the airway you have a check valve effect giving you air trapping - air gets in during inspiration but does not get out on expiration. When the foreign body is as large as the airway you have a stop valve effect - air does not get in or out during inspiration or expiration. A foreign body is more common in the right main bronchus than left main bronchus (55% versus 33% ) because the foreign body has a straighter shot down the right main bronchus once aspirated.

Pathology:
Not applicable

Imaging Findings:
Ninety-five percent of foreign bodies are non opaque. Inspiratory and expiratory PA chest films or airway fluoroscopy are most helpful in making the diagnosis. On an expiratory film there is air trapping on the affected side and mediastinal shift to the unaffected side. Then on the inspiratory film there is mediastinal shift back to affected side as the other lung aerates normally. On decubitus films the affected side does not collapse when it is placed in a dependent position. Pneumomediastinum and pneumothorax may be rarely seen.

DDX:

• Congenital lobar emphysema
• Congenital pulmonary airway malformation

References:
See References Chapter.

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