The vagus nerve, also called the 10th cranial nerve, is the longest nerve in the human body, and runs from our brainstem to the colon in a kind of erratic, meandering fashion, which is why the latin word for 'wanderer' was assigned to it. It's the same word that is the basis of our word, 'vagabond'.
There's a lot of hype about the vagus nerve, which has become the new darling of the "What can I sell you today" club of holistic wellness.
Don't get me wrong, I'm a big fan of finding, or trying to find, the most natural way to deal with whatever needs dealing with, and in the most expeditious way possible.
There's a lot of research of varied quality about the manipulation, 'toning', stimulation, and healing of the vagus nerve. I'm not sure how reliable much of it is, and I'm not up to diving deep right now. The vagus is a mysterious and talented multi-tasker that would require more than a quick peek.
Recent (within the last decade or so) research indicates that the vagal nerve is the communication pathway between our gut and our brain and the basis for the enteric nervous system, sometimes referred to as our 2nd brain, which is constantly updating the first brain on whazzup in various areas of the body, often on request from that first brain.
When you say you feel something in your gut, it's probably input from your second brain. That's the mysterious part.
There. Pedantic intro over.
All of those areas would be consonant with the various pathways of the vagus nerve. One of the functions of the vagal nerve system is to provide sensation in the more or less external areas, like the skin and muscles. It also provides sensation in your internal organs, like lungs, kidneys, liver, etc.
Or it could be that you're irritating your vagus nerve in the area where you're feeling discomfort.
The Sensate explanation reminds me of cures that you're warned will make you feel worse in the early stages because of the Herxheimer reaction, or 'die-off', which is often largely a fable. But it suits the seller's purpose better than any other, so the myths persist.
The two vagal nerves run on either side of it usually, altho given it's wandering ways, how close to the breastbone will probably vary from one person to another.
The vagus nerve is actually two nerves that start at your brainstem, separate, and run down either side of your neck, roughly parallel to your trachea and just beneath your earlobe, wandering this way and that, all the way to your colon.
The lymphatic system is absolutely everywhere in your body. There are two primary ducts, the Right Lymphatic duct, which drains most of the right upper quadrant, and the Thoracic Duct, which drains the lower body including the extremities and abdomen. One or both (I cant recall right now) seem to hover around the jugular vein(s) on their way thru your body.
If you enjoy using it and it helps you sleep, or soothes your nerves, or regulates your heart rate, or whatever benefit you derive from it, maybe turn down the volume, as it were, and keep using it. I'm all for any shortcuts or assists that speed the positive natural processes without harming the overall housing, as it were.
Alternatively, you can stimulate and 'tone' your vagus nerve, which is connected to both your vocal cords and the muscles at the back of your throat, by singing or humming or chanting, which can activate those muscles and sites, and stimulate your vagal nerve. It will also probably increase your HRV and vagal tone nicely.
But you might want to find sources of info independent of whoever is selling the Sensate, because their interests and yours could possibly diverge at some point ...
Good luck, and I hope this has helped. God knows, it's long. Sorry. Couldn't think of a way to pass along the info in a shorter format ....