Respiratory Physiology of Pranayama
At an ashram in India, I and fellow yoga practitioners were discussing why we felt so good after pranayama…the pranayama high. “It’s because pranayama produces more oxygen”, our teacher told us. That is what I heard time and time again, and passed this knowledge on to my students. With yoga we must be careful to check our resources when making these claims. Early yogis didn’t have the scientific research on respiratory physiology, but now we do. We must educate ourselves on this evidence…
Myth: We are consuming more oxygen due to pranayama.
Fact: The physiological effects of fast pranayama compared to slow pranayama are very different.
Fact: Fast breathing “lowers body stores of carbon dioxide,” the Navy’s diving manual states, “without significantly increasing oxygen stores.” Producing a drop in carbon dioxide influences mood in many ways.
"One is through respiratory alkalosis. It heightens the excitability of nerves and muscles—so much so that many circuits short out, producing tingling in the hands and spasms in the muscles. While exhilaration and nerve excitement go up, fast breathing does something else that has critical repercussions for mood, mental outlook, and potentially health—it robs the brain of oxygen.
The reason is that the surge in carbon dioxide causes blood vessels in the brain to contract, reducing the flow of oxygen and producing lightheadedness and perhaps blurred vision. Other symptoms include dizziness and giddiness. In extreme cases, a person can hallucinate or pass out.
What this means in plain English—as crazy as it sounds, as counterintuitive as it seems, as contrary to the teachings of popular yoga as it appears—is that fast breathing lowers the flow of oxygen to the brain, and does so dramatically. Scientists have found that it cuts levels roughly in half. That plunge is why people faint."
Practitioners who are new to fast pranayama techniques should begin slowly. As you train your body you will be able to perform this exercises without light headedness if done properly.
Fact: Fast styles of pranayama tend to excite.
Fact: Slow styles of pranayama tend to calm. The process starts with such varieties as Ujjayi. The consequences again center on carbon dioxide—only this time its rise in the bloodstream, not its fall.
Today, a standard figure is that cutting lung ventilation in half prompts blood levels of carbon dioxide to double. And the ensuing dilation of cerebral blood vessels means the brain now gets more oxygen, not less.
Slow breathing turns out to have deep mental ramifications, with increases in calm alertness and raw awareness. In 2001, Luciano Bernardi, a medical internist at the University of Pavia, in Italy, reported on a study of nearly two dozen adults. His team found that the repetition of a mantra cut the normal rate of respiration by about half, reinforcing mental calm and producing an enhanced sense of well-being.
Broad, William J. (2012). The Science of Yoga.