Inside the missing Titanic exploration sub
A search is currently underway for a tourist submersible set to explore the wreck of the Titanic that went missing in the Atlanic Ocean on Sunday (June 18).
Five people are believed to be on board the OceanGate submarine, including British billionaire and explorer Hamish Harding.
The sub was reported overdue on Monday, however, the coast guard said contact with the vessel was lost just under two hours into its dive on Sunday, more than 400 miles off the coast of Newfoundland.
An underwater sonar search is being carried out, while two aircraft are scanning the surface of the water in the area.
It has been estimated by the US coast guard that the sub would have had between 70 and 96 hours of emergency oxygen – or up to four days’ worth.
How long can the human body survive without air?
The average person can only hold their breath for between 30 to 90 seconds, and this will depend on their fitness levels and lung capacity.
At the three-minute mark some people will begin to lose consciousness.
If the brain is starved of oxygen for longer than five minutes you could start to experience brain damage as cells begin to die.
If this goes on for longer it will result in brain death, and without immediate medical attention this will ultimately lead to death.
However, all of this is dependent on many factors, including a person’s size, health, gender and how warm or cold you are.
Speaking to the BBC, Mike Tipton, from the extreme environments laboratory at the University of Portsmouth, explained: “Loss of oxygen is right at the very sharp end of survival.
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“The human body doesn’t have a great store of oxygen – maybe a couple of litres. How you use that up depends on your metabolic rate.”
He said that an adult at rest will usually use between a fifth and a quarter of a litre of oxygen every minute.
But this can increase to four litres every minute if they are exercising hard.
Mr Tipton, who has studied people who have survived for long periods without air underwater, said: “If someone is stressed or panicked, then this can raise their metabolic rate too.”
Hypoxia is the medical term for a lack of oxygen.
It affects many people including mountaineers at high altitude. When oxygen levels drop brain function is reduced, leading to symptoms of confusion and poor decision making.
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“There are a lot of diseases where the final stage is hypoxia,” Mr Tipton said.
“One of the things that happens is that people who are hypoxic start to lose their peripheral vision and they end up looking at a point.
“It is thought to be the reason why people report seeing a light at the end of the tunnel in near death experiences.”
Beating the odds
Despite all of this, it is not unheard of for people to survive underwater for much longer periods of time.
Mr Tipton has studied 43 separate medical cases of people who have been submerged in water for long periods.
Of these, four cases were of people who survived being underwater for at least 66 minutes – including a girl aged just two-and-a-half.
“Children and women are more likely to survive because they are smaller and their bodies tend to cool much faster,” Mr Tipton added.
“Rapid cooling of the brain can increase survival time without oxygen.
“If you reduce the temperature by 10 degrees the metabolic rate drops by a half to a third.
“If you lower the brain temperature down to 30C, it can increase the survival time from 10 to 20 minutes. If you cool the brain to 20C, you can get an hour.”
Research has also shown that the body can adapt to longer periods without oxygen.
As an example, the Bajau people in Indonesia are known to reach depths of up to 70 metres while holding their breath as they hunt for food – with one diver claiming to have spent 13 minutes underwater.
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