Tuesday, March 31, 2009

Why is carbon dioxide so important?

It's ironic, really. Scientists tell us the planet is generating too much carbon dioxide (CO2) and here's me telling you many of us are retaining too little of it in our bodies. Perhaps there's some sort of "trade" deal big breathers can do with big industry!

If you read my last two blog posts you will have discovered that many people (at least 10% of the general population and probably almost everyone who has been diagnosed with asthma), overbreathe to some extent and suffer unpleasant symptoms as a consequence. Breathing more than the body needs for its metabolic requirements blows off too much carbon dioxide. Usually this overbreathing is not noticeable to an untrained observer and it is therefore often referred to as hidden hyperventilation. An overbreather is not sitting in a chair with heaving bosom or panting like a dog in summer, but he or she is likely to be heavy sighing or yawning a lot. So why does it matter if we breathe a little more than is necessary?

Ultimately this means your body keeps less of the CO2 it needs. CO2 is a waste gas i.e. it is an end product of metabolism, but it is a very important waste gas and it affects the functioning of all our bodily processes. "Carbon dioxide is the chief hormone of the entire body, it is the only one that is produced by every tissue and that probably acts on every organ." This quote is by Dr. Yandell Henderson from the Cyclopedia of Medicine, 1940, and it holds true today.

Our brain instructs us to breathe based on the levels of carbon dioxide in the blood and alveoli. If you hold your breath and swim underwater, eventually you feel a strong urge to breathe. It seems as though this is because you are short of oxygen. In reality it is the build up of carbon dioxide that triggers the respiratory center in your brain to say "Breathe, for goodness sake!" Your blood level of oxygen has to become very low (think asphyxia) before this will stimulate your respiratory drive. So if the level of carbon dioxide goes below what the brain's respiratory center perceives as normal, it will tell you to breathe less (i.e. stop blowing off more CO2). Conversely, if you hold your breath and let CO2 build up (there are other things that will also cause a build up of CO2 but we won't go into them here), then this also registers with the respiratory center and it tells you to breathe more. The respiratory center acts like a thermostat. Many of us have been quietly overbreathing (or perhaps noisily overbreathing in the case of asthma) for so long that the respiratory center has readjusted its thermostat to consider a lower level of CO2 as normal. It now feels normal for us to be pumping air in and out of the lungs at an increased rate and we maintain this low level of CO2. I talked about this in my last blog post.

Because CO2 is such an important gas, a lack of it is not without consequences. It is carbon dioxide that tells hemoglobin to release oxygen to the tissues. If you have a low level of CO2, hemoglobin will hang onto its oxygen molecules (this is called the Bohr effect) and your cells and tissues, including the brain, will suffer from a lack of vital oxygen.

CO2 is carried in the body as carbonic acid. If we lose it (breathe too much out), we have relatively less acid and the body's pH rises (becomes more alkaline). This causes some acute biochemical changes and is the reason why people who overbreathe often report pins and needles in their arms and around the mouth, muscle twitching and generalized weakness and muscle fatigue.

Just in case you hadn't heard enough, CO2 is also a very powerful dilator, or relaxer, of blood vessels and other smooth muscle e.g. breathing tubes. So once again, if you have low CO2 your body will respond by constricting these vessels. This will affect blood flow to the brain and heart, and air flow in and out of the lungs. You might experience chest pain and palpitations, faintness or dizziness (remember the blood is already not releasing as much oxygen and you're also not delivering as much blood as the vessels are squeezed), visual disturbances and auras, as well as air hunger and perhaps wheezing.

A lack of CO2 also stimulates cells in the lungs to produce more mucus. This may be a defence mechanism the body mounts in order to stop the further loss of CO2, but if you have asthma and are suffering from narrow airways, then an increase in mucus production is not helpful.

So this is why breathing too much does not in fact provide you with a lot of nice extra oxygen. Indeed it has the opposite effect and a handful of other unpleasant side effects as well. These hyperventilatory effects mimic other disorders (heart disease, migraine, for example). So it is often the case that people are sent from doctor to doctor, only to have these other possible causes ruled out, and are then labelled "anxious". Because of course anxiety does cause overbreathing, just as overbreathing can make us anxious! This is an unhelpful diagnosis for what is essentially a "diet" deficient in CO2 and there is something you can do about it beyond taking anti-anxiety medication. Breathe less!

I say that like it is a simple matter, but in fact it is not easy to reverse an ongoing habit, especially one related to your breathing, and you will need help. More about what you can do next time.

Legal Disclaimer: Unfortunately, because of the litigious world in which we live, I must remind you that this blog expresses my opinion only. Although my opinion is based on the most up to date, published research I can find, it has still been interpreted by me and remains an opinion, not fact. It takes a very long time for scientific theory to be classified as fact. Theories are 'proven' and 'disproven' for years before consensus is reached. So really, consider everything you read, here or anywhere else, as a theory and as information that may or may not apply to and/or assist you. I suggest you use any information you get here to start a discussion with a knowledgeable, compassionate health professional as to how it relates to your situation. I am not liable for any injury that you suffer supposedly as a result of anything you read here.

1 comment:

  1. Tell effect of breathing exercise, pranayama that involve breath retention, external means after expiration and internal means after inhalation. Pranayama helps reduce breathing rate and elongate length of breath.