Emergency Medicine

5yoF with shortness fo breath for 12 hours. Was found to be choking the evening prior to presentation which resolved at home after the Heimlich maneuver. This morning was able to eat breakfast without difficulty but was still short of breath. Sent to the ED by her pediatrician for hypoxia to 86%. On exam, no respiratory distress, comfortable appearing. Decreased left breath sounds, normal sounds on the right. No stridor or other upper airway sounds. Prior to obtaining the x-ray, what items would be on your differential? What are your next steps with this image? What if the object was not visualized?