Regardless, it's still good to keep in mind that your nitrous balloon contains zero oxygen :)

I, the beneath signed, a long time reader, address my lonely plea to you, holding in view your massive expertise in cosmetic neuropsychopharmacy. Being the eminent field leader, indeed the mascot of neural cytoarchitectonics and brain metabolism research, I feel you will be best able to help me, with your luxuriously detailed medical training, at a distance and without having seen me. You see, I suffer from a bouquet of perplexing symptoms, these including dizziness, lack of concentration, occasional night terrors, the transcutaneous emission of a black tarry substance, and left-sided arse pain, now lasting over ten years. I am a long-term recreational user of, shall we say, heroic quantities of LSD, which (as you may well know) has no effect on ones' faculties of logic, scientific acumen or social competence. The most recent development in my condition has been a sudden onset of dull roaring in the background of my thoughts, followed by squealing, then followed by eldrich chanting and howling, whereupon I had found myself transported to a place of no fixed substance, and only of impression - the impression of terrifying pressure, ancient cold, hate, hunger, and a loathsome drooling anticipation of a victorious time when once again I and mine kind shall rise above the waves to avenge ourselves upon the mortals. In short, it was mildly disturbing, and having no further appointments that afternoon, I thought i should bring news of this phenomenon to your eminent attention. I understand that no topic is too trivial, and though I haven't asked a question per se, I am sure you will aim the ordinance of your intellect at finding for me the answer.

I thank you in advance for your immediate and undivided attention, and eagerly await your detailed response.

I only had the mask on for about a minute, maybe a minute and a half, but there was no dream-like sensation. I just felt sort of woozy, but constricted at the same time, like I couldn't take deep enough breaths. It sort of reminded me of how it feels before you pass out, which I've done a few times after getting blood drawn. I expressed my dislike, they stopped the flow, and soon I felt normal. The oral surgeon told me that although most folks enjoy nitrous a bad reaction is not unknown, and that he himself disliked the feeling quite a bit.

BTW, I recommend reading what the 19th century American psychologist and philosopher William James

I have one quibble with your nitrous page that I've wanted to bring up for a while. The gas itself is pretty harmless, but it easy to deprive yourself of oxygen (and expose yourself to a higher concentration of CO2) while using it. When you get the gas at the dentist, they mix it with oxygen. If you breath pure nitrous from a balloon, you aren't getting any oxygen in that breath. If you breath in and out of the same container repeatedly (don't do that), you are also getting C02, and prolonging your lack of oxygen. Nitrous doesn't "kill brain cells" but hypoxia does. If you black out while doing nitrous (which I have seen, usually huffing as described above), I'd wager it was mostly due to hypoxia, and that isn't a good thing.

I'm not saying you shouldn't use it, or that what you describe on your page is unsafe. However it is important to remember that you need oxygen. People occasionally do kill themselves by forgetting that in their pursuit of a bigger nitrous high. There is also fairly good evidence of long term harm due to reduced oxygen environments (i.e. high altitude climbers.) It's not a given that this applies to even the most extreme recreational nitrous use, but I wouldn't want to bet my brain that it doesn't.