Legend of Sleepy Hollow

Halloween comes but once a year to Sleepy Hollow and this year an inventive high-school senior, Joel who lives in a rural district, is determined to reenact the famous legend. Instead of going as a headless-horsemen, he modifies his costume by hollowing out a pumpkin which Joel sets on his head.  He cuts out eyes to see through. As the clock strikes midnight, our imaginative high schooler sets out on his trusty steed to terrify his friends. He gallops to the entrance of the first farm house and makes his horse rear up several times before wailing and generally causing a ruckus, then he rides away. Unfortunately, the pumpkin sat loosely on his head and when the horse reared up it blocked his vision. The horse rides close to a tree and Joel catches one of the branches with his chest, falls to the ground and hears a loud “bone cracking sound”. He cannot get up. By now the parents of his friends have given chase and see the spectacle of Joel on the ground with a pumpkin on his head, writhing in pain.  The friend’s father immediately thinks of the pumpkin pie martini he was enjoying, but immediately jumps into action. The dad calls an ambulance and Joel is taken to the ED where paradoxical respiration is observed. He clearly broke his ribs during the fall. Which of the following conditions does the ER clinicians fear will take place initially in individuals experiencing such injuries?

Which condition is most likely ensue immediately upon the rib fracture?