Science tells us the human body
can only survive for a few minutes without oxygen. But some people are
defying this accepted truth.
There was a sickening crack when the
thick cable connecting Chris Lemons to the ship above him snapped. This
vital umbilical cord to the world above carried power, communications,
heat and air to his diving suit 100m (328ft) below the surface of the
sea.
Worst Case Scenario
This article is part of a new BBC Future column called Worst Case Scenario, which looks at the extremes of the human experience and the remarkable resilience people display in the face of adversity.
It aims to look at ways people have coped when the worst happens and what lessons we can learn from their experiences.
It aims to look at ways people have coped when the worst happens and what lessons we can learn from their experiences.
While his colleagues remember the terrible noise of this lifeline
breaking, Lemons himself heard nothing. One moment he was jammed against
the metal underwater structure they had been working on and then he was
tumbling backwards towards the ocean floor. His link to the ship above
was gone, along with any hope of finding his way back to it.
Most
crucially, his air supply had also vanished, leaving him with just six
or seven minutes of emergency air supply. Over the next 30 minutes at
the bottom of the North Sea, Lemons would experience something that few
people have lived to talk about: he ran out of air.
“I’m
not sure I had a full handle on what was happening,” recalls Lemons. “I
hit the sea bed 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 non-existent. A kind of
resignation came over me. I remember being taken over by grief in some
ways.”
Chris Lemons had been saturation diving for about a year and a half when the accident happened (Credit: Chris Lemons)
Lemons had been part of a saturation dive team
fixing piping on an oil well manifold at the Huntington Oil Field,
around 127miles (204km) east of Aberdeen on the east coast of Scotland.
To do this work, divers must spend a month living, sleeping and eating
in specially constructed chambers on board the dive ship, separated from
the rest of the crew by a sheet of metal and glass. In these 6m-long
tubes, the three divers acclimatise to the pressures they will
experience once underwater.
It is an unusual form of isolation.
The three divers can talk to and see their crewmates outside the
chamber, but they are otherwise cut off from them. The members of each
team are entirely reliant upon one another – it takes six days of
decompression before they can leave this hyperbaric chamber or help can
get inside.
A kind of resignation came over me, I remember being taken over by grief in some ways – Chris Lemons
“It
is a very strange situation,” says 39-year-old Lemons. “You are living
on the ship surrounded by lots of people who are just a sheath of metal
away, but you are completely isolated from them.
“It is quicker to get back from the Moon than it is from the depths of the sea in some ways.”
Decompression
is necessary because nitrogen gas from the air divers breathe while
underwater dissolves into their blood stream and tissues when they are
at depth. As they come to the surface, the pressure of the surrounding
water is lifted and the nitrogen bubbles out. If this happens too
quickly, it can cause painful tissue and nerve damage and even lead to
death if the bubbles form in the brain – a condition commonly known as
“the bends”.
Divers who spend long periods in deep water need to decompress for several days in a hyperbaric chamber (Credit: Getty)
The divers who do this work, however, take the
risks in their stride. For Lemons, he was most concerned about spending
such a long time away from his fiancée Morag Martin and the home they
shared on the west coast of Scotland.
The day of 18 September 2012
had started normally enough for Lemons and the two colleagues he was
diving with – Dave Youasa and Duncan Allcock. The three climbed into the
diving bell, which would be lowered from the ship, the Bibby Topaz, to the sea bed where they would carry out their repair work.
“In
many ways, it was just an ordinary day at the office,” says Lemons.
While not as experienced as the other two men, he had been a diver for
eight years and had been saturation diving for a year and a half, taking
part in nine deep-water dives. “The sea was a little rough on the
surface, but it was pretty clear underwater.”
Chris Lemons spent
30 minutes on the sea bed after the cable that was his lifeline to the
ship above him snapped in rough seas (Credit: Dogwoof)
That rough sea, however, would trigger a chain
of events that almost claimed Lemons’s life. Normally dive vessels use
computer-controlled navigation and propulsion systems – known as dynamic
positioning – to keep them over the dive site while they have people in
the water.
As Lemons and Youasa began repairing the piping underwater, with Allcock supervising them from the bell, the Bibby Topaz’s dynamic positioning system suddenly failed. The ship rapidly began drifting off course.
On
the sea floor, alarms sounded on the divers’ communications system.
Lemons and Youasa were instructed to get back to the bell. But as they
began following their umbilical cords, the ship had already drifted back
over the tall metal structure they had been working on, meaning they
had to climb over it.
We had this strange moment where we were looking into each other’s eyes – Chris Lemons
When
they neared the top, however, Lemons’s umbilical became snagged on a
piece of metal sticking out of the structure. Before he could free it,
the drifting ship pulled it tight, dragging him into the metal beams.
“Dave
realised something was wrong and turned to come back to me,” says
Lemons, whose story has been turned into a feature length documentary Last Breath.
“We had this strange moment where we were looking into each other’s
eyes. He was desperately flailing to get to me, but the boat was pulling
him away. Before I knew it, I didn’t have any gas because the cable was
stretched so tight.”
The crew on the
ship watched helplessly from the surface as a remotely operated vehicle
sent back live images of Lemons's fading movements 100m below (Credit:
Floating Harbour)
The strain on the cable must have been immense.
Composed of a tangle of hoses and electrical wires with a rope running
through the middle, it creaked as the drifting boat pulled it tighter
and tighter. Lemons instinctively turned the knob on his helmet to start
the flow of gas from the emergency tank on his back. But before he
could do anything else, the cable snapped, sending him tumbling back to
the sea bed.
Miraculously, in the pitch darkness, Lemons managed
to pull himself upright and feel his way back to the well structure,
climbing it again to the top in the hope of seeing the bell and getting
back to safety.
Without oxygen, the human body can only survive for a few minutes before the biological processes that power its cells begin to fail
“When I got there, the
bell was nowhere to be seen,” says Lemons. “I took a measured decision
to calm down and conserve what little gas I had left. I only had about
six to seven minutes of emergency gas on my back. I didn’t expect to be
rescued, so I just curled up into a ball.”
Without oxygen, the
human body can only survive for a few minutes before the biological
processes that power its cells begin to fail. The electrical signals
that power the neurons in the brain decrease and eventually stop altogether.
“Loss
of oxygen is right at the very sharp end of survival,” says Mike
Tipton, head of the extreme environments laboratory at Portsmouth
University in the UK. “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.”
The human body
should only be able to survive for a few minutes without oxygen at rest
and less if stressed or exercising (Credit: Dogwoof)
An adult at rest will typically use between a fifth and a quarter of a litre of oxygen every minute. This can rise to four litres every minute if they are exercising hard.
“If
someone is stressed or panicked, then this can raise their metabolic
rate too,” adds Tipton, who has studied people who have survived for
long periods without air underwater.
They watched helplessly as Lemons’s movements gradually stopped, his life fading away
Back
on board the Bibby Topaz, the crew desperately tried to manually
navigate back into position to save their lost colleague. As they
drifted further away, they launched a remote-controlled submarine in the
hope of finding him.
When it did, they watched helplessly on its cameras as Lemons’s movements gradually stopped, his life fading away.
“I
can remember pulling the last bits of air from the tank on my back,”
says Lemons. “It takes more effort to suck the gas down. It felt a bit
like the moments before you fall asleep. It wasn’t unpleasant, but I can
remember feeling angry and apologising a lot to my fiancée Morag. I was
angry about the damage this was going to do to other people. Then there
was nothing.”
The cold water and
extra oxygen that had dissolved in Lemons's blood while he was working
helped him to survive for so long without air (Credit: Dogwoof)
It took around 30 minutes before the crew of the
Bibby Topaz were able to regain control and restart the failed dynamic
positioning system. When Youasa reached Lemons on top of the underwater
structure, his body was still.
Through sheer will, Youasa dragged
his fallen colleague back to the bell and passed him up to Allcock. When
they removed his helmet, Lemons was blue and not breathing.
Instinctively, Allcock gave him two breaths of mouth to mouth
resuscitation.
Miraculously, Lemons gasped back into consciousness.
Common sense suggests he should have perished after so long at the bottom of the sea
“I
felt very groggy and there were some flashing lights, but I don’t have
many lucid memories of waking up,” says Lemons. “I recall Dave sitting
crumbled on the other side of the bell looking exhausted and not really
knowing why. It was only a few days later that I realised the gravity of
the situation.”
Nearly seven years later, Lemons is still
perplexed as to how he managed to survive for so long without oxygen.
Common sense suggests he should have perished after so long at the
bottom of the sea.
But it seems likely the cold water of the North
Sea may have played a role –around 100m (328ft) down, the water was
probably below 3C (37F). Without the hot water flowing through the
umbilical cord to heat his suit, his body and brain will have quickly
cooled.
A sudden loss of
pressure on an aircraft can leave passengers struggling to breathe in
the thin air which is why oxygen masks are provided (Credit: Alamy)
“Rapid cooling of the brain can increase
survival time without oxygen,” says Tipton. “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 (86F), it can increase
the survival time from 10 to 20 minutes. If you cool the brain to 20C
(68F), you can get an hour.”
The pressurised gas that saturation
divers usually breathe may have given Lemons an additional chance. When
breathing high levels of oxygen under pressure, it can dissolve into the
blood stream, giving the body additional reserves to draw on.
Going hypoxic
Divers
are perhaps the most likely people to experience a sudden loss of their
air supply. But there are many other situations where the oxygen supply
can be cut off. Firefighters often rely on breathing equipment when
entering smoke-choked buildings, while high-altitude fighter jet pilots
also use breathing masks.
At the less extreme end, a lack of
oxygen – known as hypoxia – can affect many other people. Mountain
climbers experience low levels of oxygen when they are on high
mountains, a condition which often has been blamed for accidents. When
levels of oxygen drop, brain function can suffer, leading to poor decisions and confusion.
Chris Lemons's
extraordinary story of survival has been turned into a feature length
documentary called Last Breath (Credit: Dogwoof)
Patients undergoing surgery will also often undergo mild hypoxia, which is thought to impact their recovery.
Strokes are also caused by a patient’s brain being starved of oxygen,
leading to cell death and damage that can have lasting effects on their
lives.
“There are a lot of diseases where the final stage is
hypoxia,” says Tipton. “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.”
Children and women are more likely to survive because they are smaller and their bodies tend to cool much faster – Mike Tipton
Lemons himself survived his time without oxygen unscathed. He found only a couple of bruises on his legs after his ordeal.
But
his survival is not unheard of either. Tipton has examined 43 separate
cases in the medical literature of people who have been submerged in water for long periods. Four of these recovered, including a two-and-a-half-year-old girl who survived being under water for at least 66 minutes.
“Children and women are more likely to survive because they are smaller and their bodies tend to cool much faster,” says Tipton.
Mountaineers on the
world's highest mountains, such as Everest, need to use supplimentary
oxygen supplies due to the thin air (Credit: Alamy)
The training of saturation divers like Lemons
may also be inadvertently teaching their bodies to cope with extreme
situations. Researchers at the Norwegian University of Science and
Technology (NTNU) in Trondheim have found that saturation divers adapt
to the extreme environment they work in by altering the genetic activity of their blood cells.
“We
saw a marked change in the genetic programs for oxygen transport,” says
Ingrid Eftedal, head of the barophysiology research group at NTNU.
Oxygen is carried around our bodies in haemoglobin, a molecule found in
our red blood cells. “We found the activity of genes at all levels of
oxygen transport – from haemoglobin to the production and activity of
red blood cells is turned down during saturation diving,” Eftedal adds.
Since the accident,
saturation divers now carry supplies of emergency air that can last 40
minutes rather than six or seven (Credit: Dogwoof)
She and her colleagues believe this might be a
response to the high concentrations of oxygen they breathe while
underwater. It is possible that the slow-down of oxygen transport in
Lemons’s body allowed it to make the meagre supplies it had last longer.
Exercising before diving has also been shown to help reduce the risk of developing the bends.
Studies
of indigenous people who habitually free dive without additional air
have also shown just how much the human body can adapt to life without
oxygen. The Bajau people in Indonesia can reach depths of up to 70m
(230ft) while holding their breath as they hunt for food with spears.
Lemons says he
remembers nothing from the moment he took his last breath to when he
regained conciousness, bewildered, on board the diving bell (Credit:
Floating Harbour)
Melissa Ilardo, an evolutionary geneticist at the University of Utah, has found that the Bajau have genetically evolved to have spleens that are 50% larger than the their land-dwelling neighbours, the Saluan.
With larger spleens, it is thought the Bajau benefit from a greater injection of oxygenated blood and so can hold their breath for longer
The spleen is thought to play a key role in enabling humans to free dive.
“There
is something called the mammalian dive reflex, which in humans is
triggered by the combination of holding your breath and submerging
yourself in water,” says Ilardo. “One of the effects of the dive reflex
is contraction of the spleen. The spleen acts as a reservoir for
oxygen-rich red blood cells, and when it contracts these red blood cells
are pushed into circulation, providing an oxygen boost. It can be
thought of as a biological scuba tank.”
Traditional free
divers of the Bajau people in Indonesia have evolved enlarged spleens to
help them spend longer underwater (Credit: Alamy)
With larger spleens, it is thought the Bajau
benefit from a greater injection of oxygenated blood and so can hold
their breath for longer. One Bajau diver that Ilardo met told her he had
spent 13 minutes underwater.
Lemons himself returned to diving
about three weeks after his accident – at the very spot where it had
happened, to finish the job they had started. He has also married Morag
and they have a daughter together.
Reflecting on his brush with death and his miraculous survival, he doesn’t take much credit for his own actions.
“One
of the greatest reasons I survived was the quality of the people around
me,” he says. “In truth, I did very little. It was the professionalism
and the heroics of the two in the water with me and everyone on the
ship. I was very lucky.”
As he ran out of
air, Lemons's main thoughts were of his fiancée Morag, who he promptly
married after the accident (Credit: Chris Lemons)
His accident has triggered a number of changes
in the diving community. They now use emergency tanks that carry 40
minutes of air rather than five. The umbilical cords are now festooned
with fairy lights so they can be seen more easily under water.
The changes in his own life have not been so dramatic.
“I’ve
still got to change the nappies,” he jokes. But he does find himself
thinking about death differently. “I don’t see it as something to be
feared any more. It is more about what you leave behind.”
* Last Breath is available to watch on demand now.
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