Breathing has always been synonymous with life. Our speech is permeated with idioms and phrases relying on the idea that taking a breath is the surest sign of vitality, and we constantly compare things we need to our body’s ultimate necessity: oxygen. Our body can resist many forms of trauma, fight through a lack of nourishment, and take on harsh outer conditions, but without the ability to draw breaths, we’re effectively dead within a few moments.

Why is the air around us so critical to our existence? How long can we go without it before facing irreparable damage? And what about those miraculous times individuals seemingly bucked all expectations, and survived extended periods without air? Here’s a look at one of our body’s most vital systems, and what happens when we can’t find the breath we so desperately need.

Oxygen: The Body's Life Force

While blood may be the most important bodily fluid we possess, the main reason this is true revolves around the transport of oxygen. Humans are aerobic creatures, meaning we require oxygen to release energy and exist. Without oxygen, our cells wouldn’t be able to release the energy in the food we eat, and we would die.

We take in oxygen through respiration — we move air in and out of the lungs, and blood takes oxygen to the cells of the body. Carbon dioxide, a waste product in our bodies, is moved out of the body by the same system.

Respiration (breathing, as it is more commonly called) is normally a pretty unconscious activity. It’s controlled by the brainstem, which automatically regulates it, along with things like our heart rate, blood pressure, and digestion. Though we normally don’t have to worry about remembering to breathe, it is possible to consciously control our breathing rate. This can be done for relaxation, to maximize running efficiency, or simply to hold our breath for as long as possible.

It’s a dangerous line to approach, and a difficult one to even see sometimes. There are athletes whose success relies on holding their breath, and there are survival situations in which it is necessary. The amount of time it takes for the action to be permanently damaging is unclear, though there are a few cases researchers have looked at in order to determine when sport is in danger of turning into an emergency.

When You Lack Oxygen… On Purpose

The average untrained person doesn’t have a whole lot of reasons to hold their breath for risky amounts of time — we may hold it for a few seconds in the pool, or because we don’t want to smell something unpleasant. Most people don’t have a problem holding their breath for 30 to 60 seconds, and could probably go a bit further than that if necessary. It’s once a person deprives themselves of oxygen for a couple of minutes that they’re headed for trouble.

If someone has the willpower to push through the body’s clear requests for oxygen, they will eventually lose consciousness. Since the loss of consciousness was caused by a willful deprivation of oxygen, there is really no reason we wouldn’t start breathing again after we lose conscious control.

“Long before you die, you lose consciousness and your autonomic function would resume breathing,” Dr. Jordan Tishler, an attending emergency physician at the Department of Veterans Affairs, told Medical Daily in an email.

Again, the brainstem allows us to breathe without making a decision to. For this reason, it is impossible to commit suicide by refusing to breathe — you can refuse all you want, but your body will eventually veto your decision.

Unlike the majority of us, some people complete special training in controlling their breathing so they can hold their breath for extended periods. These people, mostly free divers, regularly spend more than a couple of minutes underwater. The current world record holder managed to hold his breath for 22 minutes in 2012 — an incredible feat helped along by preparation and physiology. Stig Severinsen, the Danish free diver holding the record, spent about 20 minutes hyperventilating pure oxygen before his attempt, an activity that saturated his body with oxygen and scrubbed him free of carbon dioxide.

Several studies have examined the physical adaptations that allow some to hold their breath for extended periods. One found that Brazilian fisherman who dove for their prey had significantly larger lungs than those who stayed on the surface. Another looked at Korean and Japanese pearl divers and found their bodies flood with an extra 10 percent of red blood cells during their dives.

Psychological state is also important when attempting extended breath holding: free divers often report reaching a place of great relaxation during dives in order to minimize their metabolic functions and preserve oxygen. Metabolic function is especially important in cases where going without oxygen isn’t quite so voluntary.

Death By Deprivation

Under relatively normal circumstances, we start struggling after a few minutes without oxygen. Without being able to convert energy and use it up, cells start to die. This happens throughout the entire body, but it is the brain’s lack of oxygen that is most urgent.

“The brain is a highly metabolically active organ,” Tishler said. “It needs oxygen to generate the energy to function. Without the energy (without oxygen) it dies.”

The brain normally takes up about 20 percent of the body’s oxygen. If it doesn’t get what it needs, cells begin dying off, putting a person at risk of permanent brain damage. If a person suffocates, or suffers another type of involuntary oxygen deprivation, they’ll ultimately suffer brain death: the utter, irreversible loss of brain function.

It’s a pretty unavoidable succession of events. However, there have been some unusual cases that gave researchers some insight into how to possibly avoid this virtually unavoidable chain of events.

The 1986 case of Michelle Funk is one of these unusual cases. The 2-year-old girl was submerged in icy water for over an hour but, in a turn of events described as “miraculous” by the American Medical Association, she survived. Even more incredible: She survived with all brain function seemingly intact. The case seems to refute all assumptions about oxygen deprivation, but scientists point to the extreme cold as the variable that allowed Michelle to survive.

Doctors reasoned that Michelle had become so profoundly hypothermic so quickly that she managed to stave off brain damage — sort of flash freezing her cells and allowing them to keep functioning once rewarmed. This case is by no means an indicator of how others would react in the same situation, since doctors aren’t sure which factors determine a favorable outcome in hypothermia.

It’s unlikely we’ll be able to freeze our brains and deprive them of oxygen anytime soon. So, in the meantime, it’s best not to play around with oxygen deprivation for too long — it really is your life force.