Titanic sub’s oxygen is dwindling. How can passengers prolong survival?

Rescuers are racing against the clock to find a missing submersible that was set to tour the Titanic wreckage off the coast of Newfoundland.

The stakes are life and death for the five people on board OceanGate Expeditions’ underwater submersible Titan, which lost contact with its support ship shortly after it began its dive Sunday morning.

An estimated four days of oxygen supply is feared to run out Thursday morning around roughly 6 a.m. Eastern, raising concerns about the passengers’ survival, assuming the vessel is still intact and had not already suffered a devastating decompression.

A lot depends on how much oxygen can be preserved, which is no easy task in the cramped and nerve-wracking conditions, says Dr. Samir Gupta, a respirologist at the University of Toronto.

“They have a fixed amount of oxygen available to them and we’re hearing about a 72 to 96 hour window around how long that will last,” he said in TikTok video Wednesday.

The body uses up more oxygen when it’s active. For example, while exercising a person takes in five to six times more air than resting, Gupta explained.

“So, the key will be for them to be as still as possible and to use as little oxygen as possible,” he said. “And that is going to be very challenging because it’s a very cramped environment. It’s very anxiety-provoking.”

Temperature could also be a big factor.

Depending on how deep the sub is, it maybe be very cold down there, causing the passengers to shiver. That muscle movement would use around three times more oxygen than if they were resting, said Gupta.

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Bill Milsom, a professor emeritus in the University of British Columbia’s zoology department, told Global News in an interview that lowering one’s body temperature can help slow their metabolic rate, which can reduce the need for oxygen.

“Anything that will slow your metabolic rate and slow the O2 demands will prolong survival time,” he said. “If people panic, they’ll use up oxygen faster. If they go into a meditative-like state, they can slow their metabolism, prolonging the period of time that they’ll be able to get by.”

Achieving that meditative state and avoiding panic will pose a “mental game” to the passengers, Milsom said.

If the temperature dips too low, he added, the passengers will pass through hypothermia and may even die from the cold.

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The submersible had a four-day oxygen supply when it put to sea around 6 a.m. Sunday, according to David Concannon, an adviser to OceanGate Expeditions, which oversaw the mission.

Frank Owen, a submarine search and rescue expert, told the Associated Press that the estimated 96-hour oxygen supply is a useful “target” for searchers, but is only based on a “nominal amount of consumption the average human might consume in doing certain things.”

Owen said the diver on board Titan would likely be advising passengers to “do anything to reduce your metabolic levels so that you can actually extend the 96 hours.”

The first few symptoms when a person runs of oxygen — especially in a cramped environment — are shortness of breath, headaches and impaired judgement, leading to a coma.

As the brain gets less and less oxygen, there is a chance of seizure that can ultimately lead to brain death.

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Milsom says those symptoms can occur very quickly after oxygen is fully depleted.

“For most individuals, they will lose consciousness within, say, three to five minutes and usually die within five to 10 minutes,” he said.

The average human can only hold their breath for 30 to 90 seconds. While it’s possible to train the body to hold one’s breath for longer, that can come with medical risks as well.

The U.S. Coast Guard on Wednesday said a Canadian military surveillance aircraft detected underwater noises in the area of the Titanic wreck, which might indicate that at least someone is alive on the Titan and trying to signal for help.

Although search and rescue crews remain hopeful the passengers will be found alive, the challenge is both to locate the Titan in the deep sea and to find a vessel that can descend to those depths for a rescue.

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Even when there is no hope of any occupants surviving because their oxygen is depleted, recovery of the vessel will be difficult.

The best chance to reach the submersible could be to use a remotely operated robot on a fiber optic cable, Jeff Karson, a professor emeritus of earth and environmental sciences at Syracuse University, told the Associated Press.

But he also said debris from the Titanic is spread out over a kilometer and some could be as big as the submersible itself, making its location and recovery difficult.

The submersible, if in the debris field, would be essentially “another lump down there,” he said.

— With files from the Associated Press.