There are a few free apps that will teach it, I have used the “Advanced Buteyko” ios app.
If you demand extensive peer reviewed medical evidence of some specific quantified outcome before doing any activity in life you will miss quite a lot of valuable things that can’t be easily quantified or measured, or funded academically. There is however actually a lot of medical research on breathwork like this, they just will use the technical terms for what you are actually doing instead of a name like Buteyko.
I only did the basic free thing, and found it an interesting experience that calmed me down a lot. Personally I've moved on to other breathwork systems that I think accomplish the same things, but I like better- I practive several of Wim Hof's breathwork methods, as well as the breathwork training that freedivers use.
All of them involve intentionally and temporarily invoking hypercapnia (high CO2) and hypoxemia through slower breathing and/or breath holds.
Medical evidence costs money. What would look convincing costs sums few can pay. If you use only that medicine you basically use only Big Pharma. And they are set to produce only specific type of medicine: something you have to buy, preferably for life. A breathing technique is not like that so it will never amass that much "proof".
1. There are plenty of non-profitable non-financial things that do have scientific evidence backing them. Massage for example which can be performed by essentially anyone.
2. There needs to be some way to separate the wheat from the chaff, as it were. Otherwise we all drown beneath the waves of lying charlatans. So how do we differentiate what works? "Evidence" seems like a reasonable criterion.
Evidence is an excellent criteria, but only if you look more broadly so you're not ignoring most of the actual evidence available to you. All you really need to try something personally is decide that the likely benefit, given the limited information you have, outweighs the likely risk.
If you're sufficiently convinced it's not dangerous or difficult, the reasonable standard of evidence for some possible benefit needed to consider trying it might become correspondingly low.
Scientific studies are strong evidence of something really narrowly specific that they tested like "does X cause Y," but most decisions in life need to be made from things like direct observation, and anecdotes, because the scientific studies rarely exist to provide the full picture, even a good study on "does X cause Y" might tell you absolutely nothing about if "X causes Z" even if Z is more important than Y.
If there is something like a breathwork technique developed by a long dead soviet physician that regular people all around the world have been using for 60+ years and consistently reporting that it offered them some tangible benefits and didn't harm them, this is evidence that it might be worth a try. With the Buteyko method, most of its strongest advocates I have personally heard of are long dead from normal old age, and never had any plausible financial or personal motive to promote it.
For things like breathwork, I usually do carefully and broadly look at things like personal reports from regular people, on e.g. forums that are unlikely to have any motive to lie. If there's a strong consistent pattern of some harm or benefit, that can be quite useful evidence, even without any formal studies.
> the lack of medical evidence tells us that this is in fact not a valuable thing
Except almost none of the most valuable things I've encountered in life had any convincing medical evidence I could find beforehand.
I am an academic scientist that designs and reviews studies all day long, so I am very steeped in the practicalities and limitations of biomedical research, and as such have completely lost any illusion that biomedical research is in a state where it can guide most of my personal decisions in a useful way- maybe it will be someday. There are many things I know about as a scientist, but can't get funding to study or publish on because the funding agencies don't care about them, and/or there are practical constraints that make it impractical to study.
If all of your personal decisions are guided by peer reviewed literature in it's current state, you'll probably be sicker, and have an empty dull life compared to someone that just uses common sense, tries things, and pays attention. I say this from having seen it happen many times in the biohacking community, the people most steeped in attempting to translate research into life decisions often died young, or even got to be one of the only modern people to experience diseases of malnutrition.
For one, you have to pretty much assume there is some specific benefit you can physically quantify, and that it will apply to almost everyone in your study population, both very unlikely to be true in cases like studying breathwork.
For example, I'm a person that tends to be pretty uptight and overstressed, what you might assume in scientific terms is "sympathetic activation"- and there is a lot of breathwork research showing that almost anything that has an extended exhale can shift you into parasympathetic activation, where you calm down and relax. There is lots of research on this, and it arguably covers Buteyko, but they won't use that term in the article title, because it's more general than just Buteyko alone.
Now, I don't need some peer reviewed study to just try Buteyko for a few minutes, and immediately feel calm and relaxed, and see that I can suddenly notice the colors around me, and feel joy, when I couldn't before. If a massive peer reviewed study proved to me that this does not happen to most, or even any other people except me, why would I care about that at all? Does it mean I shouldn't do it? What if I have a problem not enough of those people have to make it show up in the statistical analysis, or my body responds in a way most of theirs do not?
There are huge limits to how meaningfully you can generalize from scientific studies about populations of other people, to yourself. Moreover, you have to choose up front what outcomes or effects you will look at in a study, and if our biological understanding can't even guess at the outcome that would have been useful to look at, the study is doomed to miss everything.
Sit down, and try it- or don't, but don't assume you can learn ahead of time if it will be worthwhile or not for you personally by looking on Google Scholar.
A lot of the Buteyko studies suffer from small sample sizes unfortunately. I have heard good things about Buteyko from athletes but I’m not well-read on this. I think myofunctional therapy has more Western research done on it and is strongly related
From the "Medical Evidence" section, it seems I'm not missing much.