The thought has crossed my mind...
I sweat pretty much all over except for my head, but anyway...Same thing with the breathing and heart rate really. It's a feeling like your holding your breath eventhough you don't do that conciously. Some pressure on my chest is involved sometimes, too.
I have always had problems with breathing through my nose, a combination of allergies coupled to small nostrils (deviated septum, too) doesn't help. When I was younger during tests at school people would tell me to breathe less loudly (this happened just once but still) and also don't speak 'through your nose' so much'. Makes you a little self-concious, but still I kind of neglected it further on, it wasn't really a debilitating factor in my life enough for me to do something about it (as opposed to HH) and I didn't think it would affect my general health.
But then I read that breathing deeply triggers the parasympathetic nervous system, which counters the sympathetic nervous system.
So recently I got a prescription corticosteroid nasal spray and I'm trying that out now, since last thursday coincidentally. I'll let you know if it helps me a little.
On a unrelated note. I get this weird pain and bloating of my abdomen sometimes, particularly at parties, which means a a situation of a couple hours of continuous sweating and drinking (not necessarily alcohol), the doc checked it out but didn't find anything (when I wasn't feeling this pain), but is that familiar at all to you? I'm thinking maybe kidneys...