If the brain can only survive 4-6 minutes without oxygen, how can freedivers hold their breath for 8+ minutes?

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And what about people like David Blaine or Tom Sietas? Sietas held his breath underwater for over 22 minutes (world record). I know they train for it like months and even years, but doesn’t holding your breath = no oxygen to brain?

Permanent brain damage apparently occurs just after 4 minutes of lack of oxygen to the brain, so why are freedivers left generally unscathed after 8 or 10 minutes without air?

In: Biology

34 Answers

Anonymous 0 Comments

As you dive down, the water pressure increases and the Partial Pressure of oxygen in your lungs and blood also increase, keeping it at sustainable level. Even as you metabolise O2 to CO2, the remaining O2 is still at sustainable partial pressure. As you swim up, the pressure drops and there’s risk of shallow water blackout.

Anonymous 0 Comments

Your blood has oxygen in it. You have a lot of blood. You do not use up all the oxygen immediately. Picture a teabag placed in a cup of water. It takes a while for all of the tea to get infused into the water, it doesn’t just instantly turn the water into tea.

Anonymous 0 Comments

Because all the oxygen in your blood isn’t used up immediately once you start holding your breath. Free divers train and perform exercises to increase their lung capacity and lower their heart rates so their bodies use up less oxygen.

Anonymous 0 Comments

When the human body stops breathing, it does not lose its access to oxygen. The average human only consumes about 5% of the oxygen we intake. This means your average breath has a fair bit of excess oxygen that our body consumes. Once you max out how much oxygen you can store in your lungs the next step is minimizing how much oxygen you use. Minimize all function you dont need. David Blaine trained for months to drop his heart rate to ridiculously low levels, the lower your heart rate the less oxygen you need. After that you are left with no oxygen. Min Max that last 4 minutes to avoid brain damage.

Anonymous 0 Comments

The athletes inhale before holding their breath, and trap a large amount of air in their lungs. Heart continues to pump blood through the lungs (loading up oxygen) and to the brain (oxygenating the brain) and back to the lungs (unloading carbon dioxide and loading oxygen again). This slowly replaces the oxygen in the air in the lungs with carbon dioxide in the air in the lungs, so they will run out of oxygen eventually, but as you can see it can take some time.

When you breathe normally, only [a small percentage](https://www.sharecare.com/health/air-quality/oxygen-person-consume-a-day) of the oxygen in the air you inhale actually gets into the blood. You could take several breaths of the same air, and it would still have sufficient oxygen for you.

Athletes train to improve their circulation (blood flow, blood effectiveness at transporting oxygen) and lung capacity (how much air is held per breath) to maximize the process of “breathing” and getting oxygen to their brain.

You should know that the other cells in your body require oxygen too. Muscles, for example, will consume a lot of it if you exercise them. So part of the training is also to minimize muscle effort during the dive, in order to reserve as much of the oxygen as possible for the brain.

Anonymous 0 Comments

When you hold your breath there is still a lot of oxygen in your blood and that gets carried to your brain.

For example when choking someone and you apply too much pressure on their neck so the blood can’t flow to the brain anymore then the choked person will be unconscious after just a few seconds because of the lack of oxygen. You don’t get unconscious from holding your breath though because your blood is still flowing and carrying oxygen into your brain.

Of course, if you hold your breath long enough then there will be no oxygen left in your blood and you will lose conscience and eventually your brain will die off.

Anonymous 0 Comments

If you take a deep breath first, you fill your lungs with air. When you hold your breath, you still extract oxygen from the air in your lungs, so the oxygen supply to your brain isn’t cut off immediately.

The number of minutes you survive without oxygen is based on a cut off. E.g. empty lungs or a cut off blood flow so the oxygen rich blood can’t be transported to the brain.

At least that is what I recall.
Feel free to correct or educate me if necessary.

Anonymous 0 Comments

They are literally holding breath.

Some people have a weird thing they can do where they basically close their throat, but can still pull air into their mouth and then force cheekfuls of air down into their lungs so they end up with way more air in their lungs than is normal for breathing.

Enough for 20 or more minutes, if they also work on doing things that make them use less and less oxygen.

Anonymous 0 Comments

Divers can breathe in as much air as possible before diving. That air will supply them with oxygen for a while. Also they can hyperventilate (breathe in and breathe out strongly and rapidly for a while) before diving, so that their blood will become saturated with oxygen, keeping the brain oxygenated even if there’s no more air.

If the brain stops getting its oxygen the person usually loses conscience within mere seconds (like if an airplane depressurizes while at high altitude). Obviously divers don’t want that to happen, so their brain keeps getting oxygen. If a diver has lost conscience they’d quickly drown. The 4-6 minutes survival time means that oxygen supply to the brain has to be restored within that timeframe to avoid death.

Anonymous 0 Comments

The level of oxygen in the body is dependent on two things – how much oxygen is in the bloodstream, and how fast it can be used by the body.
So in the case of David Blaine, he breathed pure oxygen for good period before his record attempt, and through practice increased the time that oxygen could last for by slowing down how much he uses that oxygen.

Free divers also are helped by the body slowing down in cold water their pulse rate, and how their body uses energy. These all slow down so free divers (after much practice) can hold their breath for longer than people on dry land.