Retraction is exactly what you are looking at. If when your son breathes in, you can see the skin going into the ribs, that is retraction...also look for his use of accessory muscles (around the neck) when he is breathing...you'll see his muscles tense up. But yes, if doc told you to watch for this, I would notify them immediately. Not sure exactly his history, but different breathing treatment, etc might be needed...and that is a sign of respiratory distress. Good luck!