I came across a video to do with vagal tone and the vagus nerve. The part that stands out is to do with the mammalian dive reflex. It's been several years since I thought about it. Now I dont feel the sensations on my face anymore but I do try to lower the heart rate and hold my breath sometimes too. Here's some links:
Hacking the vagus nerve
Mammalian dive reflex
Thanks for the little nudge :)