Carbon dioxide is a big worry for the planet, but a little more of it may be good for our bodies in a direct way. I began writing about James Nestor’s intriguing book Breath two weeks ago, in “James Nestor on How Bad Mouth Breathing Is.” Here, I write about another theme in Breath: the role of carbon dioxide as a stimulant for respiratory function. (All the quotations in this post are from Breath.) One dimension of that stimulation of respiratory function is at the cellular level:Why did some cells get oxygen more easily than others? What directed billions of hemoglobin molecules to release oxygen at just the right place at the right time? How
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Carbon dioxide is a big worry for the planet, but a little more of it may be good for our bodies in a direct way.
I began writing about James Nestor’s intriguing book Breath two weeks ago, in “James Nestor on How Bad Mouth Breathing Is.” Here, I write about another theme in Breath: the role of carbon dioxide as a stimulant for respiratory function. (All the quotations in this post are from Breath.) One dimension of that stimulation of respiratory function is at the cellular level:
Why did some cells get oxygen more easily than others? What directed billions of hemoglobin molecules to release oxygen at just the right place at the right time? How did breathing really work?
He began experimenting. Bohr gathered chickens, guinea pigs, grass snakes, dogs, and horses, and measured how much oxygen the animals consumed and how much carbon dioxide they produced. Then he drew blood and exposed it to different mixtures of these gases. Blood with the most carbon dioxide in it (more acidic) loosened oxygen from hemoglobin. In some ways, carbon dioxide worked as a kind of divorce lawyer, a go-between to separate oxygen from its ties so it could be free to land another mate.
This discovery explained why certain muscles used during exercise received more oxygen than lesser-used muscles. They were producing more carbon dioxide, which attracted more oxygen. It was supply on demand, at a molecular level. Carbon dioxide also had a profound dilating effect on blood vessels, opening these pathways so they could carry more oxygen-rich blood to hungry cells. Breathing less allowed animals to produce more energy, more efficiently.
Meanwhile, heavy and panicked breaths would purge carbon dioxide. Just a few moments of heavy breathing above metabolic needs could cause reduced blood flow to muscles, tissues, and organs. We’d feel light-headed, cramp up, get a headache, or even black out. If these tissues were denied consistent blood flow for long enough, they’d break down.
High carbon dioxide is also the key to our subjective sense of being desperate for more air—more than low oxygen is:
We’d experienced the same confounding measurements during our bike workouts earlier in the week. The beginning of those workouts, like all workouts, sucked. We felt our lungs and respiratory system desperately trying to meet the needs of our hungry tissues and muscles: the dinner rush of the body. Normally, I’d open my mouth and huff and puff, trying to sate that nagging need for oxygen. But for the last few days, as I cranked the pedals harder and faster, I forced myself to breathe softer and slower. This felt stifling and claustrophobic, like I was starving my body of fuel, until I checked the pulse oximeter. Once again, no matter how slowly I breathed or how hard I pedaled, my oxygen levels held steady at 97 percent.
It turns out that when breathing at a normal rate, our lungs will absorb only about a quarter of the available oxygen in the air. The majority of that oxygen is exhaled back out. By taking longer breaths, we allow our lungs to soak up more in fewer breaths.
During that ride, I started playing around with my breathing. I tried to inhale and exhale slower and slower, from my usual exercising rate of 20 breaths a minute to just six. I immediately felt a sense of air hunger and claustrophobia. After a minute or so I looked down at the pulse oximeter to see how much oxygen I was losing, how starved my body had become.
But my oxygen hadn’t decreased with these very slow breaths, as I or anyone else might expect. My levels rose.
Take a sip of air through the nose or mouth. For this exercise, it doesn’t matter. Now hold it. In a few moments, you’ll feel a slight hunger for more. As this hunger mounts, the mind will race, the lungs will ache. You’ll become nervous, paranoid, and irritable. You’ll start to panic. All senses will zero in on that miserable, suffocating feeling, and your sole desire will be to take another breath.
The nagging need to breathe is activated from a cluster of neurons called the central chemoreceptors, located at the base of the brain stem. When we’re breathing too slowly and carbon dioxide levels rise, the central chemoreceptors monitor these changes and send alarm signals to the brain, telling our lungs to breathe faster and more deeply. When we’re breathing too quickly, these chemoreceptors direct the body to breathe more slowly to increase carbon dioxide levels. This is how our bodies determine how fast and often we breathe, not by the amount of oxygen, but by the level of carbon dioxide.
As humans evolved, our chemoreception became more plastic, meaning it could flex and shift with changing environments. It’s this ability to adapt to different levels of carbon dioxide and oxygen that helped humans colonize altitudes 800 feet below and 16,000 feet above sea level.
I speculate that high carbon dioxide levels may be part of the signal that stimulates the gradual increase in lung capacity from additional exercise. James Nestor has an interesting discussion of the various ways carbon dioxide is used already as a medical treatment. Breathing 7% carbon dioxide for any of these purposes is a relatively mild experience:
The most effective and safest blend they found was a few huffs of around 7 percent carbon dioxide mixed with room air. This was the “super endurance” level Buteyko found in the exhaled breath of top athletes. Breathing in this mixture had none of the hallucinogenic or panic-inducing effects. You hardly noticed it, and yet it offered potent results.
Breathing a few whiffs of 35% carbon dioxide is not especially dangerous, but James Nestor’s description of the experience makes it sound awful.
I find all of this intriguing. I can’t find 7% carbon dioxide on Amazon, so I can’t do an experiment with that. But the old treatment for hyperventilation of putting a paper bag over one’s head is probably also a safe way to experiment with mild carbon dioxide treatment. DO NOT USE A PLASTIC BAG: THAT COULD BE EXTREMELY DANGEROUS!!!!
The one thing I have done already is to use the app BreatheEasy Free to time myself for 9 second exhales and 6 second inhales (with 1 of the seconds each way a pause). That feels good.
I am curious, and would be glad to hear what any of you know about carbon dioxide treatment.