I started carrying a pulse oximeter on airplanes because I wanted to see what happened to my oxygen levels at altitude.
Airplanes don’t contain less oxygen by percentage. The cabin air still contains about 21% oxygen, just like the air at sea level. The difference comes from pressure. As altitude increases, atmospheric pressure drops, so the partial pressure of oxygen drops with it. Aircraft pressurization keeps the cabin far more comfortable than the outside environment, but cabin pressure still sits below sea-level pressure.
That lower pressure means less oxygen pressure with every breath. Your lungs have less pressure pushing oxygen into your blood, which helps explain why SpO₂ can fall during a flight.
On some flights, my SpO₂ would be around 94 or 95%. But I noticed that when I drank carbonated water, the number would go higher.
Most people think of carbon dioxide as a waste product that your body needs to get rid of. But your body also uses CO₂ to regulate oxygen delivery. When CO₂ rises in your blood, blood pH falls (becomes more acidic) and hemoglobin releases oxygen more readily. That’s the Bohr effect.
Your muscles use this system every time you exercise. Working muscles produce more CO₂ as they use energy. The rise in CO₂ helps hemoglobin release oxygen where your tissues need it.
Carbonated Water and Oxygen
Researchers have tested what happens when you add CO₂ to a low-oxygen environment.
In one human study, healthy adults breathed low-oxygen air with or without added CO₂. Adding CO₂ increased arterial oxygen tension, oxygen saturation, and cerebral oxygenation. In other words, adding CO₂ helped more oxygen get into the blood and increased oxygen delivery to the brain, even though the participants were breathing low-oxygen air.
A separate 2021 study looked specifically at CO₂-containing drinking water. Researchers gave 39 healthy adults about a liter per day during the treatment period. After the treatment period, their SpO₂ increased.
That finding lines up with what I saw on airplanes.
In the full article, I’ll show you exactly how to test this on your next flight.
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