What Happens To Your Brain When You Hold Your Breath?

When we go to a high altitude, have a tough workout, or hold our breath, we feel that we’re running out of oxygen. But what goes on inside our body when we experience this feeling? This recent study in the European Journal of Applied Psychology holds some answers to the question.

The study is very straightforward, taking measurements of heart rate and oxygen levels while volunteers hold their breath, and it offers a revealing picture of how the body copes with a shortage of oxygen—and what can go wrong.

The research was performed at Ghent University in Belgium, by Janne Bouten, Jan Bourgois, and Jan Boone… They asked 31 volunteers (17 men, 14, women) to hold their breath for as long as possible three times in a row, with two minutes break each time. Typically people get better and better in repeated breath holds, in part because their spleens are squeezing more oxygen-carrying red blood cells into circulation. During the third and final breath hold, they took continuous measurements of parameters including heart rate, oxygen levels in the brain, and oxygen levels in the leg muscles.

Humans, like other mammals, have a “diving response” that kicks in when you hold your breath, with the goal of making sure your brain always has enough oxygen. As the researchers point out, if your circulation stops abruptly, you’ll be unconscious within 30 seconds and suffer irreversible damage within two to ten minutes. The diving response is enhanced if your face is submerged in water, but it happens even on dry land. Your heart rate drops, and the blood vessels leading to non-essential parts of the body like your leg muscles constrict in order to redirect crucial blood (and oxygen) to the brain.