Why Can’t We Breathe 100% Oxygen?
The science behind what sustains us
Our chest expands as air fills our lungs, it sustains us and it’s all we’ve known. Breathing is an unconscious action our bodies instinctually do. It’s unfathomable to think we started as single-cell organisms nearly 3.5 billion years ago and now life on Earth has proliferated and expanded. Human bodies now house 36 trillion cells, each with highly specialized roles. The ability to aspirate is just one of these roles, the result of multiple different cell interactions and specializations.
The ability to breathe in oxygen is the result of millions of years worth of evolution. Earth first had to develop oxygen, those levels needed to stabilize, and then somewhere in our evolutionary tree, it had to be beneficial (or at least not detrimental) for our ancestors to breathe air.
How Do We Breathe?
Breathing is a complex cycle sustained by air and blood. When we inhale, air fills our lungs and alveoli, specialized cells located in the lungs, pull the oxygen out of the air and equip red blood cells with fresh O2. These red blood cells then transport the fresh oxygen through the veins to other cells within the human body.
When the red blood cells reach the lungs again, they have carbon dioxide. The alveoli exchange this carbon dioxide for new oxygen. The red blood cells then continue through the cycle again, constantly taking new oxygen and depositing old carbon dioxide. The alveoli push this into the oxygen we previously breathed in, causing humans to exhale carbon dioxide.
Every exhale is again followed by an inhale, restarting the cycle once more. The circulatory system is an evolutionary marvel and this is only a brief summary of the complex process. A video by the Amoeba Sisters goes further into this topic.
Raising The Concentration Of Oxygen
But air is not oxygen, or rather it’s not entirely oxygen. The air we breathe is primarily nitrogen, at 78%, and contains 21% oxygen. Trace gases, like argon, carbon dioxide, and neon make up the remaining 1%. Oxygen masks and scuba tanks mimic this and are only comprised of around 21% to 40% oxygen.
Because our bodies have evolved for the specific concentration of oxygen in the atmosphere, breathing in 100% oxygen can be incredibly dangerous. Breathing in too concentrated oxygen can result in oxygen toxicity, a form of lung damage.
The alveoli of the lungs are calibrated to handle pulling in additional oxygen when needed, but at higher concentrations, they become overwhelmed. 100% oxygen can cause these air sacs to fill with fluid or collapse. In both circumstances, the lung’s ability to take in oxygen and diffuse it to the blood is reduced. The inability to absorb enough oxygen can cause:
- Painful breathing
- Coughing
- Dizziness
- Confusion
- Ringing in the ears
Because of air, and the concentrations of different gasses, higher concentrations of oxygen aren’t naturally occurring. Oxygen toxicity typically occurs when an individual breathes in artificial air from a scuba tank, hospital oxygen mask, or hyperbaric oxygen therapy.
Can Lungs Recover?
Most people recover from oxygen toxicity with time, but it can take weeks or months. Cell recovery and body healing can take a while.
The simplest treatment is to reduce high oxygen-level exposure. If from a scuba tank, this means replacing or adjusting the tank’s settings. In a hospital setting, medical professionals can adjust oxygen levels when necessary. Worse symptoms, like a collapsed lung, can require hospitalization and intubation.
For most people, oxygen toxicity isn’t a worry. Hospital levels are closely monitored by medical professionals. Scuba tanks are used under professional supervision or by those trained to operate and identify symptoms of oxygen toxicity.
While breathing in 100% oxygen sounds more efficient, our lungs have evolved to function precisely given our environment. Air is plentiful already and living beings have perfected the oxygen-carbon dioxide exchange.
