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1. Buteyko claims that asthmatics are a subset of a group of people who breathe too much. The term hyperventilation would be confusing as it describes a well-known acute condition in medicine. Chronic over-breathing is not recognised in modern medicine.... no one ever checks for it. It is a grey area without the dramatic effects of acute hyperventilation. I believe that Buteyko's major contribution is to recognise this condition. It is the corner stone of his theory.
The question that must be asked, is whether it is reasonable to assume, as we do, that the set point about which respiration is regulated is immune from pathology.
If we assume for a moment that it is, indeed, possible for some people to breathe too much and that this condition goes undiagnosed, the rest of the pathophysiology follows quite logically.
2. Respiratory alkalosis resulting from over-breathing leads to renal pH compensation by dumping bicarb. The net result is a depletion of the Bicarb buffer, low pCO2 and a disruption of the electrolytic balance resulting from lost electrolytes which accompany the dumped bicarb.
3. In Kazarinov's Paper, Buteyko shows how every major metabolic process in the body is dependant on CO2 either directly or as a catalyst. Low CO2 therefore affects all the metabolic/anabolic processes from the tricarboxylic acid (Krebs) cycle to the synthesis of proteins and lipids. This is why Buteyko claims that over-breathing is the basis of many diseases, not only asthma.
4. Low CO2 in the blood reduces oxygenation of the tissues through a depressed Bohr effect. Hemoglobin is reluctant to release Oxygen under low CO2 concentrations. This affects peripheral Oxygen sensors leading to an Oxygen hunger, which tends to stimulate over-breathing. It is not part of the breathing regulation mechanism but it certainly does modulate it. The effect is that the more you breathe, the more CO2 you get rid of and therefore the more hungry you get for oxygen. It is understood that the respiratory center, under normal paO2, responds primarily to pCO2/pH and not to arterial oxygen tension. The respiratory centre eventually accommodates to pCO2 which is too low.
5. Over-breathing implies low alveolar CO2, leading to excessively alkaline lung linings. The smooth muscle in the bronchioles spasm when CO2 levels are too low. Apparently CO2 is required for Calcium diffusion across the muscle cell's membrane, in order to relax it.
6. According to all the texts I've read, the bronchioles constrict in response to local conditions rather than to CNS innervation. It makes teleological sense that the bronchioles should shunt air in order to even out ventilation. So overventilated bronchioles constrict in response to low CO2, while the under-ventilated bronchioles relax. Unfortunately for the asthmatics, all the bronchioles tend to be overventilated, so all the bronchioles to some extent are closer to shutting down than are the bronchioles of normal breathers. This is what makes them "twitchy". It only takes a little extra breathing to make those bronchioles still open to close up.
7. Buteyko therapy is simply an attempt to get the breathing normalised, i.e.: get the individual to breathe less. Once the respiratory centre is reset to a physiologically more normal level, the bronchioles will open up in response to more normal CO2 levels and broncho-constriction disappears.
8. I have not yet addressed the question of excessive sticky mucus we see in asthmatics , or the question of inflammation. I'm a little uncertain about these processes, because I find the lack of medical literature on Buteyko a problem. But the following is what I understand the position to be from what I've read and from discussions I've had.
Low CO2 in the lungs directly affects the stickiness of mucus in the same way as pH affects the viscosity of Albumin. I can't tell you the mechanism by which production of mucus is affected by low CO2.
Alkaline tissues develop erythema (alkaline burns), although I don't know if the degree of alkalinity associated with asthmatics is sufficient to be the cause of the erythema.
A more plausible explanation is that low CO2 affects the production of cortisol in the adrenal glands. That means that asthmatics tend to have lower natural cortisone levels, making them more vulnerable to allergens. That's why we often see eczema, hay fever and asthma all associated with each other. It also explains why Buteyko therapy in time is effective on these conditions.
9. Finally, what we have considered to be the cause of asthma, viz allergens, hyperventilation, anxiety etc, Buteyko says are all just triggers for asthma and not the cause.
10. The Buteyko theory makes sense of all the enigmas that have been confronting our classical understanding of asthma. According to Buteyko it is a single disease with multiple triggers, rather than a complex diseases with multiple causes.
11. Perhaps the strongest indicator of the correctness of the theory is the fact that the treatment which is developed by the theory works so spectacularly successfully.
Peter Kolb BSc(Eng),MSc(Med),CPEng(Biomed) BIOMEDICAL ENGINEER
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