I was bringing my very tired 6 month old into his house and barley bumped the back of his head on the door as I walked in. It was like a light brushing against the back of his head. I knew because he was so tired he was going to cry, he did cry, big time! It escalated very quickly and after a couple cries he absolutely could not catch his breath, he turned blue! I was freaking out, I put him upside down and gave him a wack on his back and he caught his breath. It took him a few minutes to calm down. I have never been so scared. Does anyone have experience with this? I have read that it's an involuntary holding of the breath and that he will grow out of it, I will definitely be taking an infant CPR class.