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By Dr. Artour Rakhimov, Buteyko breathing teacher and educator

Breathing education
Part 4-A. Properties of CO2: Vasodilation

Those people who breathe less have longer breath holding time and more oxygen in tissues. Those people who breathe heavier (or deeper/bigger) have much less oxygen and shorter breath holding time. Why? This video clip provides the answer. Video clip "Physiology of oxygen transport" (it will open in a new window).

CO2 is a dilator of blood vessels (arteries and arterioles). Arteries and arterioles have their own tiny muscles that can constrict or dilate depending on CO2 concentrations. At the same time, according to physiological research, the dilation of these blood vessels is the main factor that define total resistance to blood flow in the body.

Normal CO2 parameters make resistance to blood flow in the cardiovascular system small. Hence, breathing directly participates in regulation of the heart rate.

When the CO2 level is low, total resistance becomes greater and vital organs (like the brain, heart, kidneys, liver, stomach, spleen, colon, etc.) get less blood due to the constriction of small blood vessels. As physiological studies found, blood flow to these organs is proportional to blood CO2 concentrations.

Be observant. When you get a small bleeding cut or a wound, deliberately hyperventilate and see if that can help stop the bleeding. It should. As an alternative, perform comfortable breath holding and breathe less and accumulate CO2. What would happen with your bleeding? (It should increase.) Now you know what to do after dental surgeries, brain traumas, and other accidents involving bleeding. It is natural for humans and other animals to breathe heavily in such conditions. Hence, hyperventilation can be life-saving in cases of severe bleeding.

What about brain blood flow? According to the Handbook of Physiology (Santiago & Edelman, 1986), cerebral blood flow decreases 2% for every mm Hg decrease in CO2 pressure. When people have 20 mmHg CO2 in their blood (half of the official norm), they have about 40% less blood supply to the brain in comparison with normal conditions. Only skeletal muscles can get more blood in conditions of hyperventilation.

“…cerebral blood flow decreases 2% for every mm Hg decrease in CO2”
Professor Newton, University of Southern California Medical Center, Hyperventilation Syndrome, 2004 June 17, Topic 270, p. 1-7 (www.emedicine.com).

Experiment. Take 100 deep and fast breaths through the mouth and you can pass out due to ... lack of oxygen
and poor blood supply for the brain. Why? Because CO2 is a vasodilator (dilator of blood vessels).

Consider these physiologial results:

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* Illustrations by Victor Lunn-Rockliffe