Missing Titanic submersible: How would the Titan crew be conserving oxygen?

The Titan submersible - pictured here on a previous expedition - is missing with five people aboard. Credit: PA

Search and rescue teams are in a desperate race against time to locate a submersible missing in the Atlantic, as the number of hours of breathable air the crew is estimated to have left dwindles.

Operated by OceanGate, the tourist vessel, named Titan, has five people on board - including a British billionaire and a British-Pakistani father and son.

The submersible was on a voyage to the shipwreck of the Titanic, which rests on the seabed at a depth of nearly 12,000ft deep.

ITV news health and science correspondent Martin Stew explains the complexity of the search mission

How much oxygen supply does the Titan have left?

Similar to a plane or rocket, the air inside the Titan is recycled.

When it began its descent early on Sunday morning, the sub had a capacity of approximately 96 hours of oxygen between the passengers.

Several estimates have been suggested of when exactly the amount of breathable air will run out within the Titan.

The US Coast Guard has estimated "breathable air” could run out shortly after 10am BST (5am ET).

On Wednesday afternoon, US Coast Guard Rear Admiral John Mauger told the BBC there was estimated to be less than 20 hours off oxygen left aboard the Titan.

As the search intensifies the US coastguard confirmed it has detected "banging sounds" through sonar technology.

The allotted supply would deplete according to a range of variables - such as how cold the crew are and how heavily they are breathing.

The pilot on board, Paul-Henry Nargeolet, has decades of deep-sea diving experience and would be well aware of the risks posed by the limited air supply in a tight space.

The ex-French Navy commander of more than 25 years is known among many as Titanic's "greatest explorer" and helped supervise the recovery of more than 5,000 Titanic artefacts.

Alongside Mr Nargeolet is experienced deep-sea diver and OceanGate CEO, Stockton Rush, as well as three-time Guinness World Record holder and billionaire Hamish Harding, who has been described as "the quintessential British explorer".

Mr Rush (left) is described as 'highly professional'. Credit: AP

How would the crew be conserving oxygen?

Mike Tipton, now the Professor of Human and Applied Psychology at Portsmouth University, spent 40 years working in the areas of thermoregulation, environmental and occupational physiology.

He was based at the Institute of Naval Medicine for over 20 years, and told news outlet Insider that oxygen is best conserved when resting.

Doing as little as possible uses a third of a litre of oxygen a minute, whereas exercising on a bike, for example, uses 2L of oxygen a minute, according to Professor Tipton said.

They might try to sleep, as sleeping slows the metabolism, and therefore decreases the need for oxygen.

It will also depend, however, on how cold the crew is - the ocean floor temperature is near freezing.

A glimpse inside the Titan submersible

If power is lost and the vessel is losing heat, staying warm either with blankets or any other means is vital.

"Shivering is a form of exercise that consumes up to about a litre of oxygen per minute," Professor Tipton explained.

The crew might even be meditating or doing some exercises to remain calm and keep their breathing measured.

Dr Glenn Singleman, an Australian physician and professional adventurer, has travelled to the Titanic's wreck before.

"The oxygen and the carbon dioxide - they're the critical things because every submersible has only got a fixed amount of oxygen and a fixed amount of CO2 scrubber," Dr Singleman told the BBC on Wednesday.

"In any submersible after a long dive, these are the things that you really worry about.

"What they have is always based on a standard oxygen usage schedule that's for a seated human.

"If they know they're in trouble, it's very likely that they'll be trying to sleep, trying to calm themselves down, trying to meditate, trying to relax, trying to breathe a bit slower so that maybe they can extend out that limited oxygen supply that they have."

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