As a med student who just learned about this I feel somewhat qualified to answer, even though the anatomy of the subject receiving the injection is a little different. It is true that tiny air bubbles, if injected into a vein could cause an air embolism. Muscular injections do not suffer from this problem. The key is to make sure you havent mistakenly injected into a vein. After inserting the needle draw back GENTLY on the plunger. If you see blood sucked back into the syringe just reposition and try again. If there is no blood after pulling back, you are okay to inject the small air bubbles. Hope that helps.