[Question] Why is capnometry biofeedback not more widely known?

What capnometry biofeedback is and why it seems important

A capnometer is a device that measures levels of carbon dioxide in your blood in a non-invasive way (think of it sort of like a pulse oximeter for carbon dioxide, except that the most common type of capnometer uses a nasal cannula to collect your breath instead of just clipping onto your finger). Capnometry biofeedback does biofeedback using a capnometer: you breathe while you are hooked up to a capnometer and looking at a monitor that tells you your carbon dioxide levels, and adjust your breathing style to try to get your carbon dioxide levels in the “good” range. You might even intentionally breathe in a “wrong” way to get carbon dioxide levels out of range, so that you can practice getting back into range. Over time (across multiple sessions), you learn what good breathing feels like, and automatically start to breathe in that way.

Certain health thinkers (e.g. Buteyko method practitioners) make a big deal out of carbon dioxide levels. They argue that low carbon dioxide levels (also known as hypocapnia) lead to a variety of health problems (shortness of breath, asthma, and much more).

My own impression is that while people like Buteyko practitioners often make wild claims, and the theory of why the method works is not known in much detail, the method does actually work (here is my own experience report). Having a capnometer seems useful for confirming that one’s breathing (or other health) problems are due to carbon dioxide levels and for practicing better breathing. In my own experience trying nasal breathing/​Buteyko-lite breathing without a capnometer, it feels like groping around in the dark, and I feel continually unsure if I am even doing the right thing (and also feel that my improvements have plateaued after just 2-3 months of experimentation); I imagine having a capnometer would feel like turning the lights on.

There are also a bunch of academic writing and even experimental studies on using a capnometer, but I have mostly not read these. My own interest and confidence in Buteyko-esque stuff/​capnometry comes from my own experience playing around with such breathing techniques. (I realize this won’t be convincing to many people. I’m just trying to be honest about my process for coming to this conclusion.)

Evidence for the assertion that capnometry biofeedback is not more widely known

I live in the Seattle area. In the last 1.5 years I have gone to two pulmonologists as well as one allergist-immunologist in the area, none of whom mentioned anything about carbon dioxide levels or capnometry or Buteyko breathing when I presented with shortness of breath. I have called a respiratory clinic in my area asking if they rented out any capnometers, and they did not even know what a capnometer was. I contacted my sleep doctor (with whom I did a sleep study, during which they did measure my carbon dioxide levels) asking if his office rented out capnometers and his office replied saying they did not, and that it is not a common practice to do so. I reached out to three biofeedback practitioners in my area asking if they used a capnometer in their practice; none of them did (one of them said they were familiar with how to use the device, but did not actually have one in their office).

Looking around online, I was able to find just a few people offering such services. The 20 that are listed on this page (most of them not even in the US), plus one in Texas and one in maybe Australia.

From the above I conclude that capnometry biofeedback is virtually unknown by the world.

Some guesses for why capnometry biofeedback is not more widely known

Here is my attempt to answer my own question. I can think of two reasons:

  • Capnometers are really expensive: From looking online, legit capnometers seem to cost somewhere in the $1,000 to $5,000 range. There are some cheaper used ones on eBay but many of them come with disclaimers that the device’s accuracy has not been tested and the device is sold as-is. Could there be a chicken-and-egg problem where devices are expensive because not many people want them, and not many people want them because they’re expensive? I will address this point in the next section (my take: this is not what’s happening).

  • Maybe capnometry biofeedback doesn’t work that well: It is possible that doing Buteyko-like breathing “blind”, without a capnometer, is basically sufficient. I am possibly somewhat unique in wanting external feedback as I practice breathing. Buteyko breathing does not seem all that well-known either, but certainly more people know about Buteyko breathing than capnometry biofeedback.

I am interested to hear thoughts on my reasons, or any other reasons people can think of.

Some discussion about why capnometers are so expensive

As best as I can make out, the chicken-and-egg problem where devices are expensive because not many people want them, and not many people want them because they’re expensive, does not hold for capnometers. Hospitals seem to make use of capnometers (especially in emergency situations), so it is not just wacky quantified self/​”pulmonaut”/​mysteriously chronically ill people on the internet who want such devices. Also, capnometers don’t seem to be inherently difficult to manufacture (although I know basically nothing about how to build one, so I am interested in hearing thoughts on this!). So why are they so expensive? It seems that there is a patent on one or more of the crucial components, so only one company is allowed to manufacture those components.

Samuel Kordik (who seems to have a lot of experience working in emergency medical services) on Twitter here says:

2) the patents on quantitative clinical ETCO2 monitoring are much newer than on pulse oximetry; Oridion (bought by Covidien than Medtronic) was the inventor and they seem to be the only manufacturer at this time; everyone uses their tech.

I was not able to find a “1)” in the replies. Not sure if the “2)” was a typo. I have also not fact-checked the comment so can’t comment on its accuracy. I do not have experience looking up patent filings, and I expect it to take quite a bit of time to do this well, so I did not attempt it. Googling does produce a few filings, at least one of which has expired already, but I don’t know if that’s the most relevant patent. I would appreciate any help in trying to figure this out.

Muonium1 on this YouTube video:

I would really, really, reaaaaly like to see a teardown of one of these. It has to be using infrared absorption of CO2 as the detection mechanism but it can’t be using an incandescent light source because the batteries last too long for that at 8 hours. So it has to be an LED, but what kind of LED are they using to produce the mid-infrared light where CO2 strongly absorbs? Anyway, there’s definitely nothing super expensive in there justifying the greater than $1,000 cost, so that’s got to be a consequence of it being a very new and totally patent covered technology. I would expect these to become as cheap and almost ubiquitous as pulse oximeters in a few years.

I can’t comment on the accuracy of the comment; I’d be interested in hearing people’s thoughts!

LV Kusch comments in this Facebook thread:

MAInly because the sensors are medical grade tech and expensive to manufacture.

Not very informative, but consistent with the above two quotes.

So here is a weak prediction I have: assuming non-expired patents really are the reason, this could mean that in the near future capnometers may become very cheap, allowing people to have easy access to do capnometry biofeedback and improve their breathing (and possibly other aspects of their health).

Acknowledgments: Thanks to Vipul Naik for feedback on a draft of this post!