Foreign body inhalation series (pediatric)

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The suspected foreign body inhalation series although not a primary port of investigation aims to detect and identify both foreign bodies or the secondary signs of inhaled foreign bodies . It involves a frontal chest radiograph in both the inspiration and expiratory phases and, in some cases, bilateral-lateral decubitus chest views.

Note: Each institution will have different protocols when approaching this radiological investigation. All protocols have a common goal, to demonstrate lung volume that does not change during the respiratory cycle .

Patient position

Patient positioning will depend on patient age. The frontal chest radiograph can be performed erect or supine, conditional to the patients’ needs. The lateral decubitus radiographs will follow the same position advice as to the lateral decubitus view.

Technical factors
  • chest inspiration and expiration
  • bilateral lateral decubitus (can be done to increase sensitivity) 

Image technical evaluation

  • entire lung fields should be visible; post-processing collimation is not advisable in pediatric imaging (if it is exposed it should be examined).
    • full inspiratory effort 
      • ensure 8 visible posterior ribs in children aged 0-3 years old
      • ensure 9 posterior ribs in children aged 3-7 years old
      • ensure 10 posterior ribs in children aged 7 years old and above
  • due to ossification centers in children, the medial ends of clavicles are difficult to visualize; therefore measuring the medial ends of the clavicle to the spinous process is not advised
  • the head of clavicles to lie at the level between T2 and T4 

Practical points

  • it is important to obtain a true inspiration and expiration radiograph as this will better demonstrate the secondary signs of the ball-valve phenomenon evident in inhaled foreign bodies
  • bilateral decubitus views should demonstrate hyperinflation of the affected lung on both radiographs; in the obstructive foreign body there will be air-trapping and therefore hyperlucency of the dependent lung