Rescuers are holding out hope the five people missing on the Titanic tourist sub could still be alive, surviving by prolonging their oxygen beyond the 96-hour air supply window, which ran out Thursday morning.

OceanGate Expeditions, the private company that owns the Titan submersible, estimated the vessel had four days of life support available after it vanished Sunday. However, the US Coast Guard said the metric wasn’t a direct indicator of the fate of the missing passengers.

Frank Owen, a submarine search and rescue expert, told The Post there was still hope the passengers could survive beyond the 96-hour window if they reduced their metabolic levels and body activity through “breathing slowly and sleeping.”

Inversely, other experts warned the passengers stuck inside the cramped, 22-foot-long sub could’ve actually shortened their oxygen supply by panicking.

Dr. Ken Ledez, a hyperbaric medicine specialist at Memorial University of Newfoundland, told the BCC Thursday prolonged levels of low oxygen would cause irreversible damage “to the nervous system or heart.”

With a dwindling air supply, people can experience restlessness, headaches, confusion, shortness of breath, blue fingertips, increased heart rate, and eventually loss of consciousness.

Within five minutes of low oxygen, cell death occurs and can lead to brain injury, coma or death, according to the Cleveland Clinic. After ten minutes without oxygen, total brain death occurs.

Despite the bleak estimations, Ledez echoed the Coast Guard’s call for the families of the passengers —Sulaiman Dawood, 19, his business tycoon father Shahzada, 48; British billionaire Hamish Harding, 58; famed Titanic explorer Paul-Henri Nargeolet, 77; and OceanGate founder and CEO Stockton Rush, 61.— to remain hopeful.

“I don’t think [rescuers] should give up,” he said.

Notably, the Guiness World Record for longest breath held voluntarily underwater was a whopping 24 minutes and 37 seconds, held by Croatia’s Budimir Šobat, who completed the amazing feat in 2021 to raise awareness over an earthquake that struck the city of Sisak.

Under the effects of cerebral hypoxia, the medical term for lack of oxygen to the brain, people younger than 25 stand a better chance to recover.

That would mean 19-year-old Sulaiman Dawood, the youngest person aboard Titan, could have the best chances if the submersible is quickly recovered.

Along with the lack of oxygen, Mike Tipton, head of the extreme environments laboratory at the UK’s Portsmouth University, told Insider that passengers aboard Titan could have also faced carbon dioxide poisoning inside the sub if its filtration system had been damaged or ran out of power.

Ledez echoed the warning, adding that the passengers also faced risks of hypothermia floating in the cold Atlantic Ocean if something happened with the submersible’s heating system.

“[After a while] you won’t have movement or muscle strength,” Ledez said. “Your reasoning will decline and you will lose consciousness the colder you get.”