I am certain that not only Buteyko practitioners but also some of our students and outside researchers can benefit from this information related to end-tidal CO2 vs alveolar CO2 in measuring health and estimating the Buteyko CP (Control Pause) test result. Here are a couple of the recent messages that I posted on Facebook’s Buteyko Practitioners Discussion Forum. Facebook may disappear or even close our group, while the group is closed making it impossible to easily access these details:
- Posted by Artour Rakhimov on 4th of September 2020:
End-tidal CO2 has never been a part of the original or classical Buteyko method since none of the Soviet/Russian patents, trials, or approbations used this value. Instead, you can collect all expired air and measure total CO2 content as it was done in the cancer trial by Dr. Sergey Paschenko. More about which CO2 to measure:
YouTube video: Alveolar vs. End-tidal, CO2 in Exhaled Air (Buteyko Method):
etCO2 can be particularly misleading when students progress from below 15-20 s CP to 25-30 due to the transition to diaphragmatic breathing.
2. Posted by Artour Rakhimov on 7th of September 2020:
From what I read in his 60’s and 80’s medical articles, it follows that he used capnography and measured expired CO2 together with air velocity (mentioned as “spirography”) in real time to define alveolar CO2. It seems that he did not measure chest/torso displacement for better accuracy. Probably, it was enough for him.
From his papers, it is clear that he considered alveolar CO2 as the most accurate CO2 parameters that correlated with states of airways and blood vessels (there are more publications about the effects of the cardiovascular system). That is why alveolar CO2 is the key factor in many of his papers.
When someone relies only on the capnography, the information about airflow speed distribution is missing. There can be the same CO2 curve or graph, but with very different airflow velocity distributions and different alveolar CO2 content.
When the whole graph is further reduced to one value (end-tidal CO2), there is a further loss of information about what is going on in the lungs. That is likely why Rosalba’s paper did not find any correlation between etCO2 and CP, while the alveolar CO2-CP link is the key claim of one of the Buteyko’s patents.
From his papers, it is clear that he considered alveolar CO2 as the most accurate CO2 parameters that correlated with states of airways and blood vessels (there are more publications about the effects of the cardiovascular system). That is why alveolar CO2 is the key factor in many of his papers.
When someone relies only on the capnography, the information about airflow speed distribution is missing. There can be the same CO2 curve or graph, but with very different airflow velocity distributions and different alveolar CO2 content.
When the whole graph is further reduced to one value (end-tidal CO2), there is a further loss of information about what is going on in the lungs. That is likely why Rosalba’s paper did not find any correlation between etCO2 and CP, while the alveolar CO2-CP link is the key claim of one of the Buteyko’s patents.
PS. September 10, 2020. It follows from the above that, for most Buteyko breathing students (or those who progress from Health Level 2 of 10-20 s MCP to Health Level 3 of 20-30 s MCP), measuring etCO2 would not provide any consistent or positive information. It is likely that, for this step in health improvement, one may get a better correlation when measuring their own pulse (heart rate) or breathing frequency. Both these parameters are included in the Buteyko Table of Health Zones.
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