We need Carbon Dioxide.

When we first learn about breathing, we learn that humans inhale in oxygen and exhale out carbon dioxide. While that isn’t wrong, it’s not completely correct either. We actually exhale most of the oxygen we inhale. We don’t exhale out all of the carbon dioxide we produce. The stimulus or urge to breathe is typically created by the levels of carbon dioxide in our body, not the level of oxygen.

Our bodies produce carbon dioxide when they convert food or glucose and oxygen into energy through cellular respiration. By measuring how much carbon dioxide we exhale, we can determine exactly how many calories we burned or how much glucose (food) our cells turned into energy. When you lose weight you are technically exhaling the weight in the form of carbon dioxide through your breath. We need to get rid of excess carbon dioxide; we do this by exhaling carbon dioxide out through our lungs and airways.

Yet carbon dioxide is more than a waste gas. Your red blood cells will only let go of oxygen when carbon dioxide is around. Carbon dioxide is needed in order for oxygen to get into our muscles, organs, brain, and cell tissues. Carbon dioxide is part of the signaling system that tells your body where to send oxygen, which cell tissues need more oxygen.

This carbon dioxide requirement was discovered in 1904 by Dr. Bohr and is known as the Bohr effect. If we exhaled all the carbon dioxide we produced, we wouldn’t be able to oxygenate our body and cells. Ideally 5-7% of the air in our lungs would be carbon dioxide. Even with climate change, the air we breathe is only 0.04% carbon dioxide. Therefore we maintain 5-7% of the air in our lungs and a similar amount in our blood, by letting carbon dioxide accumulate slightly in our blood and our lungs before we get rid of it.

We have special sensors in our blood, called chemoreceptors that measure the amount of carbon dioxide in our blood. These sensors create our sensation or desire to breathe. When our carbon dioxide levels rise higher than normal, we have the desire to breathe. In general it’s our level of carbon dioxide not the level of oxygen that triggers our need to breathe. Like most aspects of the body, individuals have a unique carbon dioxide tolerance that has resulted upon their life experiences.

If you have a room full of people, there will be a range of breathing patterns and rates in the room. If you have a group of scuba divers and they all dive for an hour, they will have used different amounts of the air in their tanks, some scuba divers will empty a tank much earlier than others. Our bodies continue to adapt, you can change your tolerance to carbon dioxide and therefore the amount of air you breath overtime. In general a higher tolerance of carbon dioxide increases your breathing efficiency and resiliency. If you want to access your carbon dioxide tolerance, check out this blog post.

Carbon Dioxide plays many important roles in our body. Carbon dioxide…

• Is produced during cellular metabolism (when food and oxygen turn into energy, our body makes carbon dioxide)
• Regulates our blood pH
• Is a Vasodilator – Dilation of smooth muscles in the walls of blood vessels
• Allows Oxygen to be released from blood to the cell tissues (doorway which lets oxygen reach your muscles and organs)
• Is our primary stimulus to breathe

TEST YOURSELF:

You can get a rough sense of how tolerant to carbon dioxide you are by holding your breath out after an exhale and walking. Ideally you’d be able to walk 50 – 100 steps without breathing.