The first few times Miss H and I played around with choking we both enjoyed it immensely. I totally got off on the power trip of choking her and she was near orgasmic from the head rush and thrill of it all. As time passed and we started to settle into our more comfortable roles of me being the submissive and her the dominant, the choking continued but now it was me on the receiving end of things. At first I was kind of nervous about doing it but that fear quickly subsided as the turn on increased. The feeling of being so helpless and completely under someone else's power is a complete adrenaline rush with a huge dose of sexual excitement thrown in for good measure.
Miss H used to almost exclusively just use her hand around my throat as a means to control my breathing. She would squeeze, I would start to struggle, and eventually she would let go. The only problem is that maintaining a consistent pressure and level of oxygen deprivation can be tough. If I start to thrash around she can loose a good grip and fortunately/unfortunately depending on how you look at it, Miss H doesn't actually want to kill me so she always presses more lightly then she could or I would like. That's probably for the best as I prefer my trachea in an uncrushed state, but still.
We've also used a really wicked looking inflatable hood that I bought at Demask in NYC a few years ago. There aren't any eye holes, nose holes, or mouth opening per se other then a roughly six inch tube that is placed in the mouth and extended outside the hood. I'll take a pic and try to post it later but for now just try to use your imagination. It's a great item and provides for a safer means of breath control (if there is such a thing, talk about an oxymoron) because it only takes a hand over the end of the tube to totally shut off all breathing in an instant.
More recently however we've moved into something new. Miss H will push my head between her breasts, which are huge, or between her ass or sometimes her pussy and just wrap her arms around it with a death lock preventing me from pulling away. Then she'll sit there calmly and watch as I begin to freak out and desperately try to pull away. She'll do this without warning so some times I have a chance to take a breath before hand, other times not at all. If I have a hand free I'll "tap out" on her thigh when I start to panic as I sign that I can't take much more. I think she really enjoys this because she's never once stopped when I tried signaling her. She always takes things a bit further, makes it a bit scarier, and gets me that much closer to cumming. She lets me free when she wants to, not when it would suit me. The feeling I get from these experiences is amazing. People say they like bondage because it allows them to give up control. Well nothing can compare to giving up control of your breathing.
The first time Miss H let me loose after smothering me between her breasts she was a bit concerned by the fact I was sort of flopping around like a fish and grunting loudly. She thought I was suffering from lack of oxygen and spazzing out to breath once again. In fact, I was struggling to keep myself from cumming all over the place. With even the slightest bit of penis stimulation, the combination of physical and mental turn on is immense and gets me to the edge almost every time. Those first few seconds when your brain goes ballistic with fear from you not being able to breath and you realize that you're not getting another breath until she allows you to is the ultimate in submission.