Alas, it is a very difficult move even for an experienced yogi (it's possible that I'll find a way to simplify it and make it more accessible). But if you suffer from reflux, you have lots of opportunity to practice! While you pop pills and/or prop yourself up on pillows, waiting for symptoms to subside, maybe work on the following. For a few decades! It can happen sooner if you're talented. (Me? I'm like an ant).
First, make sure your front abdomen is lithe and energized. This itself will likely be a multi-year ordeal, especially if you're older. Young people don't get reflux because their front abdomen is lithe and energized! Cause/effect is all interwoven with this stuff!
The best way is by practicing nauli (rolling abdominal muscles up and down and - more difficult - side to side). I could do nauli like a champ as a child, but when I tried in my 40s, I couldn't even begin. Because I’d lost that supple connection. I essentially had gone dead there.
Most middle-aged people end at the bottom of their rib cage, just beneath their diaphragm. We know that below this there's elimination stuff and sex stuff and walking stuff, but that machinery is akin to the underside of a trolley, not well-integrated with one's sense of corporeality...which, once again, ends, for middle-aged people, just beneath the diaphragm.
See, I told you this wouldn't be easy. I know, I know...."What the hell is he talking about???" etc etc. But (please, world, hear this plea) just because you don't understand doesn't make me crazy!So when you can do a nice responsive nauli all the way down to the top of the pubic bone (where there's not a lot of actual muscle to contract, but that doesn't mean you can't activate what's there) then you're good to begin working on my suggested fix. That's the prerequisite. Also: a few years of meditation (I do this stripped-down, simple, efficacious practice, but I do not recommend the rest of the web site) will help develop your concentration and body awareness to the point where the following will seem less daunting.
Ok, here goes: Be a crocodile. That's it. But it's hard to be a crocodile.
If you lack deep visualization and concentration skills, you'll need to practice while lying prone on your stomach, ala crocodiles. But it can be done while in any body position. This is an entirely internal action, not external. You can do it (I have done it) while playing basketball. But that's way, way harder. I'm apparently one of the few in the world able to do so (I didn't realize this until a celebrated Taoist master explained it to me).
What is the fundamental body charateristic of a crocodile? From one end to the other, it's all a straight line. Food hovers magically in empty space which passes - like a tube - through the body. And crocodiles understand this at some deep level.
Humans don't conceive of our digestive track as a tube, largely because we have a weird and un-animal-like right angle at the throat, which is great because it lets us walk erect, but problematic because it creates a sensation of complication which makes our digestive tract seem like some remote terrain "down there".
We need to learn to disregard the complication of the throat's right angle, and visualize a straight empty tube from mouth (gaping open, and filled with scary sharp teeth - remember, you're a crocodile!) to your body's end, i.e. the soles of your feet. That way, we can integrate it. This is an integration practice.
Foot-wise, there's a certain point just above the arch and roughly in the center of the sole. You'll discovery this point experientially, because as you practice, it will sparkle a little. Watch for that. It will be reminiscent of the sparkly sensation of a body part "falling asleep", but more subtle and more pleasant.
So, again, be a crocodile, with one straight line going from scary open mouth/maw to the other end - the mid-soles of the feet, just above the arch.
Stretch this line. Unify it - make it one. It's hard, because of that stupid right angle at the throat that you need to utterly disregard. You're not a bent human being with a complicated relationship with its digestive tube. You're a crocodile with one line from beginning to end. Stretch the line, unify it, making the soles of your feet sparkle, and then locate your stomach and join it in the line. Maw (scary!), stomach (sour), and feet (sparkly), all as one single unbroken straight line.
If you can't feel your stomach, then you don't have reflux and this is all unnecessary! Just locate the unpleasant sensation, and let that sourness stream down inside your thighs, into your feet (to the sparkly place). Maintain the linearity. Keep it one thing. You're a crocodile. Mouth ajar. Scary teeth. One line. All the way. Include the stomach. Let the acid fill your feet.
I'm repeating myself incessantly because that's how you'll need to practice. It's many things to bear in mind, so you'll need to self-coach, constantly self-reminding the various elements. A straight line really should be easy and all one thought. But often simplicity requires the most conscientious effort. This is exactly why spaghetti aglio e olio is the hardest dish to master. Simplicity makes the mind wander!
If you can learn to actually do this, you can shut down a reflex attack. Don't ask me what's physiologically happening while you're doing it. Perhaps you’re somehow closing that damned flap separating esophagus and stomach. I can't really say. I'm actually a scientific-minded guy, but you can't translate yoga moves into coherent science (though lord knows yogis try). Better to render unto Caesar what is Caesar's - "Caesar" being your GP. Let doctors do the things doctors are good at. But reflux sure ain't one of those things. And necessity is the mother of invention. So welcome to my invention!
I said of crocodiles that "food just hovers magically in empty space which passes - like through a tube - through the body." But it's even more magical for us, because people are vertically-configured whereas crocodiles are horizontal. Our food essentially levitates amid this long hole/tube running through us. It's no wonder that it sometimes wants to reverse course when we lie down. That's why this whole practice is about establishing a unified downward flow.
Connect down to feet from the mouth, via the stomach. Let the sourness shower down through the thighs, pooling in the soles of the feet and making them sparkly. Reading those two sentences might, alone, bring some iota of relief. Maybe memorize them.
There's no stomach acid in your feet, of course, silly! The sparkle is vital energy (which always follows attention). This is why acolytes for millennia have grabbed their guru's feet. It's not supplication, they're getting a charge from the sparkliness. Can I explain any of that scientifically? Of course not! But I'm grateful not to suffer from agita quite as badly these days. Good luck!