There was a nasty crack when the thick cable connecting Chris Lemons to the ship above him cracked. This vital umbilical cord to the world brought energy, communication, warmth and air to his diving suit 100 meters below the sea surface.
This article is part of a new BBC Future column called Worst Case Scenario that looks at the extremes of human experience and the remarkable resilience that people show in the face of adverse circumstances.
We will investigate how people have coped when the worst happens, and what lessons we can learn from their experiences.
His colleagues remember the terrible noise of this lifeline, Lemons himself heard nothing. In a moment, he pushed himself against the metal underwater structure they had been working on, then fell backwards onto the seafloor. His connection to the ship above had disappeared, and any hope of finding his way there was gone.
Above all, his air supply was gone, so that only six or seven minutes emergency air supply were available. For the next 30 minutes on the underside of the North Sea, lemons would experience something that few people lived to talk about: he had no more air.
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"I'm not sure I really got the hang of it," recalls Lemons. "I hit the ocean floor on my back and was surrounded by an all-encompassing darkness. I knew I had a very small amount of gas on my back and my chances of getting out of it were almost nonexistent. A kind of resignation passed over me. I remember that in a sense I was taken over by grief.
Lemons had been part of a saturation team that had attached piping to an oil well at Huntington Oil Field, about 1
It is an unusual form of isolation. The three divers can talk and see their crew members outside the chamber, but they are otherwise cut off from them. The members of each team are totally dependent on each other. It takes six days before they can leave this hyperbaric chamber or get help.
A sort of resignation passed over me, I remember being somehow taken over by grief – Chris Lemons
"It's a very strange situation," says 39-year-old Lemons. "They live on the ship, surrounded by many people who are just a metal scabbard, but they are completely isolated."
"It's faster to return from the Moon than from the depths of the sea in some ways."
Decompression is necessary because nitrogen gas from the air, which divers breathe, while underwater dissolves in their bloodstream and their tissues When they come to the surface, when they come to the surface, the pressure of the surrounding water increases and the nitrogen gushes out, which, if too fast, can cause painful tissue and nerve damage and even death if Forming blisters in the brain – a condition commonly known as "the bends."
However, the divers who do this work take the risks in their stride, and for Lemons, he was the most worried about it for so long To spend the day of September 18, 2012 for his fiancée Morag Martin and the house they shared on the west coast of Scotland.
The day of September 18, 2012 had begun for Lemons and his two colleagues Dave Youasa and Duncan Allcock. The three climbed into the diving bell, which was to be lowered from the ship Bibby Topaz to the seabed where they would carry out their repair work.
"In many ways, it was just an ordinary day at the office," says Lemons. Although he was not as experienced as the other two men, he had been a scuba diver for eight years and had completed saturation diving with nine deep-sea dives for a year and a half. "The sea was a bit rough on the surface, but underwater it was pretty clear."
However, this rough sea would trigger a chain of events that nearly took the lives of lemons. Typically, divers have computerized navigation and propulsion systems – known as dynamic positioning – to keep them above the dive site while humans are in the water.
When Lemons and Youasa began repairing the pipelines underwater, they overcame Allcock's bell, which failed Bibby Topaz's dynamic positioning system (19459011). The ship quickly got off course.
Alert messages were heard on the sea floor about the divers' communication system. Lemons and Youasa were ordered to return to the bell. However, as they followed their umbilicals, the ship had already drifted back over the high metal structure they had been working on, which meant they had to climb over it.
We had this strange moment when we looked each other in the eye – Chris Lemons
However, as they approached the tip, Lemons' umbilical cord caught on a piece of metal sticking out of the structure. Before he could free it, the driving ship pulled it tight and dragged it into the metal girders.
"Dave realized something was wrong and came back to come back to me," says Lemons, whose story has turned into a feature-length documentary Last Breath. "We had that strange moment when we looked each other in the eye. He scrambled to me desperately, but the boat pulled him away. Before I knew it, I had no gas, because the cable was so taut. "
The load on the cable must have been enormous. Consisting of a tangle of hoses and electric wires with a rope running through the middle, it creaked as the drifting boat pulled it tighter and tighter. The lemons instinctively turned the button on his helmet to trigger the gas flow from the emergency tank on his back. But before he could do anything else, the cable snapped and dropped it back to the bottom of the sea.
Miraculously, in the pitch darkness, Lemons managed to pull himself upright and head back to the Well Building in the hope of seeing the bell and moving back to safety.
Without oxygen, the human body can survive only a few minutes before the biological processes that drive its cells begin to fail.
"When I arrived there, the bell was nowhere to be seen," says Lemons. "I made a modest decision to calm down and save the little gas I still had. I only had emergency gas on my back for about six to seven minutes. I did not expect to be rescued, so I just rolled myself into a ball. "
Without oxygen, the human body can survive only a few minutes before the biological processes that drive its cells begin to fail. The electrical signals that drive the neurons in the brain diminish and eventually stop altogether.
"The loss of oxygen is at the very end of survival," says Mike Tipton, head of the Extreme Environmental Laboratory at Portsmouth University in the UK. "The human body does not have a lot of oxygen – maybe a few liters. How you use it depends on your metabolic rate. "
A dormant adult usually consumes between a fifth and a quarter liters of oxygen per minute. This can increase with hard training to every minute to four liters.
"If someone is stressed or panicked, it can also increase their metabolic rate," adds Tipton, who has studied humans who have survived long periods of time without air underwater.
They watched helplessly as Lemon's movements gradually came to a standstill and his life dwindled.
Back on board the Bibby Topaz, the crew desperately tried to manually navigate to their position to rescue their lost colleague. As they continued to drive off, they launched a remote-controlled submarine hoping to find it.
As they did so, they watched helplessly on their cameras as Lemon's movements gradually ceased and his life dwindled.
"I can remember to pull the last pieces of air out of the tank on my back," says Lemons. "It costs more effort to suck the gas. It felt a bit like the moments before falling asleep. It was not uncomfortable, but I can remember being angry and apologizing a lot to my fiancé Morag. I was angry at the damage this would do to other people. Then there was nothing.
It took about 30 minutes for the crew of the Bibby Topaz to regain control and restart the failed dynamic positioning system. When Youasa reached Lemons on the underwater construction, his body was still calm.
By sheer will, Youasa pulled his fallen colleague back to the bell and handed him over to Allcock. When they removed his helmet, Lemons was blue and did not breathe. Instinctively, Allcock breathed two breaths from mouth to mouth.
Miraculously, lemons panted back into consciousness.
Common sense says he should have died on the ocean floor after such a long time
"I felt very lethargic and there were a few flashing lights, but I do not have many clear memories of waking up," says Lemons. "I remember Dave collapsed on the other side of the bell and looked exhausted and did not know why. Only a few days later, I realized the severity of the situation. "
Nearly seven years later, Lemons is still perplexed about how he managed to survive without oxygen for so long. Common sense suggests that he should have died on the ocean floor after such a long time.
But it seems that the cold waters of the North Sea played a role: at a distance of 100 m (328 ft), the water was probably below 3 ° C (37F). If the hot water does not flow through the umbilical cord to warm his suit, body and brain will have cooled down quickly.
"Rapid cooling of the brain can prolong survival without oxygen," says Tipton. "If you lower the temperature by 10 degrees, the metabolic rate drops by a half to a third. If you lower the brain temperature to 30 ° C (86 ° F), the survival time may increase from 10 to 20 minutes. If you cool the brain down to 20 ° C, you can have one hour to spare. "
The pressurized gas that saturation divers normally breathe may have given lemons an extra chance. Inhaling high levels of oxygen under pressure can dissolve it in the blood, giving the body extra reserves to fall back on.
Divers are probably the most likely people to suddenly lose their airflow. However, there are many other situations where oxygenation can be interrupted. Firefighters often rely on breathing apparatus when entering smoke-clogged buildings, while jet-fighter pilots also use breathing masks at high altitudes.
At a less extreme end, hypoxia – known as hypoxia – can affect many other people. Climbers experience low levels of oxygen in high mountains, a condition that is often blamed for accidents. When the oxygen content decreases, the brain function may suffer, leading to misjudgment and confusion.
Patients undergoing surgery often experience mild hypoxia that affects their recovery. Strokes are also caused by the fact that the brain of a patient suffers from oxygen and leads to cell death and damage that can have a lasting effect on life.
"There are many diseases in which the end-stage is hypoxia," says Tipton. "One of the things that happens is that people who are hypoxic start losing their peripheral vision and end up looking at a point. It is believed that this is the reason why people report seeing a light at the end of the tunnel near death. "
Children and women survive better because they are smaller and their bodies tend to cool faster – Mike Tipton
The lemons themselves survived their time without oxygen. After his ordeal, he found only a few bruises on his legs.
But his survival is not uncommon. Tipton has studied 43 different cases in the medical literature of individuals immersed in water for extended periods of time. Four of them recovered, including a two-and-a-half-year-old girl who lived underwater for at least 66 minutes.
"Children and women survive survival as they are smaller and the body tends to cool down much more quickly," says Tipton.
Training for satiety divers like Lemons can also cause the body to accidentally teach in extreme situations Researchers at the Norwegian University of Science and Technology (NTNU) in Trondheim have found that satiety divers adapt to the extreme environment in which they work by altering the genetic activity of their blood cells.
"We have a significant change Ingrid Eftedal, head of the barophysiology research group at NTNU, says oxygen is transported in our bodies in hemoglobin, a molecule found in our red blood cells. "We found the activity of genes at all levels oxygen transport – from hemoglobin to P red blood cell production and activity is attenuated during saturation, "adds Eftedal.
She and her colleagues believe that this could be an answer to this. The high oxygen concentrations breathe them under water. It is possible that the slowing down of oxygen transport in Lemons' body resulted in the lean supplies being able to last longer.
Pre-dive training has also shown it reduces the risk of bends.
Indigenous people, who usually dive without extra air, have also shown how much the human body can adapt to life without oxygen. The Indonesian Bajau people can reach a depth of 70 meters while holding their breath while searching for food with spears.
Melissa Ilardo, an evolutionary geneticist at the University of Utah, has discovered that the Bajau have developed genetically The spleen is 50% larger than its land-dwelling neighbor, the Saluan.
Larger spleens assume that the Bajau benefits from a larger injection of oxygen-rich blood, allowing them to hold their breath longer
It is believed that the spleen plays a key role in allowing humans to dive freely.
"There is a so-called mammalian diving reflex that is triggered in humans by the combination of breath and immersion in water," says Ilardo. "One of the effects of the dive reflex is the contraction of the spleen. The spleen serves as a reservoir for oxygen-rich red blood cells. When it contracts, these red blood cells are pushed into the bloodstream, causing an oxygen boost. It can be thought of as biological diving bottles.
Larger spleens assume that the Bajau benefits from a larger injection of oxygen-rich blood, allowing them to hold their breath longer. A Bajau diver whom Ilardo had met told her that he had spent 13 minutes underwater.
Lemons himself returned to diving about three weeks after his accident – exactly where it had happened to finish the work they had started. He also married Morag and they have a daughter.
Due to his contemplation of death and his miraculous survival, he does not put up with much for his own actions.
"One of the main reasons I survived was the quality of the people around me," he says. "In truth, I have done very little. It was the professionalism and the heroic deeds of the two in the water with me and everyone on the ship. I was very lucky. "
His accident has sparked some changes in the diving community. They now use emergency tanks that transport 40 minutes instead of five minutes. The umbilical cords are now decorated with fairy lights, so they are better visible under water.
The changes in his own life were not that dramatic.
"I have to change the diapers," he said jokes But he thinks differently about death. "I do not see it as something to fear. It's more about what you leave behind.
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