0:00:04 > 0:00:06At the cruising altitude of a jumbo jet,
0:00:06 > 0:00:098,500 metres above sea level,
0:00:09 > 0:00:14a team of climbers are about to take the final steps to the top of the world.
0:00:14 > 0:00:19Seeing Everest for the first time was incredible. It was almost like meeting a god.
0:00:20 > 0:00:24Once you're above 8,000 metres, you're considered to be inside the Death Zone.
0:00:24 > 0:00:30But this team know better than most just how dangerous the next few hours will be.
0:00:30 > 0:00:32This is a team of doctors.
0:00:32 > 0:00:37Oxygen saturation is 62%, figure 6, 2, over.
0:00:37 > 0:00:40And they are here to rewrite the medical textbooks.
0:00:42 > 0:00:46On the way to the summit, they will be tested as climbers, scientists,
0:00:46 > 0:00:52and in the deadly environment of Everest, they will be tested as doctors as well.
0:00:52 > 0:00:56In the last half hour, they've shown a complete disregard for human life.
0:00:56 > 0:01:00With respect to your doctor, he will die.
0:01:00 > 0:01:05There are guys on the mountain who are continuing to go up in bad shape.
0:01:05 > 0:01:09I wouldn't give them a cat's chance of living.
0:01:09 > 0:01:14This is the story of an expedition unlike any Everest has seen before.
0:01:14 > 0:01:18It's the story of a team of men and women willing to risk everything
0:01:18 > 0:01:21in the pursuit of knowledge.
0:01:23 > 0:01:28I'm here to do a job and I want to get it done and go home.
0:01:30 > 0:01:32I'm looking forward to getting home.
0:01:32 > 0:01:36This is the story of doctors in the Death Zone.
0:01:36 > 0:01:38'Mike, this is Denny, over.
0:01:40 > 0:01:42'Mike, this is Denny. Do you copy, over?'
0:01:58 > 0:02:00It's May 2007.
0:02:00 > 0:02:04Green, blue, ten. Green, red...
0:02:04 > 0:02:06Garden, hat, farmer...
0:02:06 > 0:02:11For the past two months, this barren landscape has been home to an extraordinary experiment.
0:02:13 > 0:02:18This is the largest medical research project ever to come to the Himalayas.
0:02:18 > 0:02:20MAN GROANS
0:02:20 > 0:02:22OK, swallow.
0:02:22 > 0:02:27Expedition leader, Dr Mike Grocott, believes it will ultimately
0:02:27 > 0:02:30transform our understanding of human physiology.
0:02:30 > 0:02:35We have an opportunity here to write the textbooks for the next 20, 30 years.
0:02:35 > 0:02:42This type of expedition with 200 volunteers coming to Base Camp, plus climbers going onto the mountain,
0:02:42 > 0:02:46and science, hopefully, up to the summit, doesn't come along very often,
0:02:46 > 0:02:49so it's important that when we're working and collecting data,
0:02:49 > 0:02:51that we really focus and we're careful.
0:02:51 > 0:02:56Make sure we calibrate everything, make sure we collect everything accurately.
0:02:56 > 0:02:58I can't stress that enough.
0:02:58 > 0:03:03Now, with five weeks of testing complete at Base Camp and Camp Two,
0:03:03 > 0:03:0814 of these doctors are going to go to even greater extremes -
0:03:08 > 0:03:11a bid for the summit.
0:03:16 > 0:03:18It's harder than I imagined.
0:03:21 > 0:03:26The point of going to the summit is to see
0:03:26 > 0:03:31just how far the body can be pushed to the extremes of its physiology.
0:03:34 > 0:03:41What is driving them to such lengths is the chance to study the one thing that gives life to us all...
0:03:41 > 0:03:43Breathe, breathe.
0:03:43 > 0:03:45..oxygen.
0:03:46 > 0:03:51Only if they can reach the summit will they be able to conduct their ultimate experiment -
0:03:51 > 0:03:56setting up a laboratory in the most extreme environment on Earth...
0:03:56 > 0:03:57I really don't want to fall here.
0:03:57 > 0:04:02..and taking blood from deep inside their own bodies.
0:04:03 > 0:04:05This better get easier.
0:04:10 > 0:04:12The reason lies a world away...
0:04:15 > 0:04:21..in the life-and-death environment of intensive care.
0:04:21 > 0:04:25Here, survival rarely hinges on the nature of an injury or illness.
0:04:25 > 0:04:27So, two units on the ninth.
0:04:27 > 0:04:33What kills Mike Grocott's patients is a lack of oxygen, also called hypoxia.
0:04:34 > 0:04:38That's why he's convinced Everest is a unique natural laboratory.
0:04:38 > 0:04:44At this extreme altitude, there are the lowest levels of oxygen on Earth.
0:04:44 > 0:04:49As these doctors climb higher, they are effectively putting their own bodies into intensive care,
0:04:49 > 0:04:55recreating in themselves the exact conditions they treat every day.
0:04:55 > 0:05:00We're doing some fundamental research that couldn't possibly be done anywhere else.
0:05:00 > 0:05:02It can't be done in a chamber.
0:05:02 > 0:05:04It can't be done in a simulated group.
0:05:04 > 0:05:09The only way of doing this sort of science is actually physically being here and doing it.
0:05:09 > 0:05:15But only if they reach the summit, will they be able to discover the ultimate limits of human survival.
0:05:16 > 0:05:22At 8,850 metres, Everest is not only the highest point on Earth,
0:05:22 > 0:05:25it also marks the boundary between life and death.
0:05:25 > 0:05:28The level of oxygen at the summit of Everest is close
0:05:28 > 0:05:32to the absolute limit of what humans can survive.
0:05:34 > 0:05:40It's the one place on Earth that can answer a fundamental question of human life.
0:05:40 > 0:05:41MONITOR BEEPS
0:05:41 > 0:05:43How little oxygen does the human body need
0:05:43 > 0:05:45to stay alive?
0:06:10 > 0:06:14The Caudwell Xtreme Everest Team have been climbing for four days.
0:06:14 > 0:06:17They are a few metres away from Camp Three.
0:06:20 > 0:06:23RADIO: 'Mike, good to see you, over.'
0:06:23 > 0:06:26At an altitude of more than 7,000 metres,
0:06:26 > 0:06:29they still have to climb over one-and-a-half kilometres
0:06:29 > 0:06:31to reach the summit.
0:06:31 > 0:06:34Hard going.
0:06:34 > 0:06:38Here, there is only 40% of the oxygen there is at sea level.
0:06:41 > 0:06:44We got up here. I mean, we weren't quick,
0:06:44 > 0:06:47but we got up here...
0:06:48 > 0:06:52..in an acceptable time. I feel good.
0:06:53 > 0:06:59Climbing with Mike is anaesthetist Andre Vercueil and Belfast GP Nigel Hart.
0:07:01 > 0:07:06The low oxygen is already affecting their ability to function.
0:07:06 > 0:07:09I reckon I can feel the altitude here.
0:07:09 > 0:07:10I just feel a little bit...
0:07:12 > 0:07:17..not quite on the... I've been going over my children's birthdays.
0:07:17 > 0:07:19I'm getting them reasonably quickly but...
0:07:20 > 0:07:26I don't believe that they come as quickly as they probably should.
0:07:26 > 0:07:30At this extreme altitude, the climbers are breathless, even at rest.
0:07:30 > 0:07:34You feel slightly better than you expect to, I think,
0:07:34 > 0:07:38but it's pretty a bleak and hostile environment out there.
0:07:39 > 0:07:44It was here yesterday that the expedition faced its biggest test so far...
0:07:44 > 0:07:46Get the oxygen down here, as well.
0:07:47 > 0:07:51..an advance team were confronted with a climber from another expedition
0:07:51 > 0:07:53in desperate need of medical attention.
0:07:53 > 0:07:56He needs to be up here.
0:07:56 > 0:08:01To save his life, the doctors wanted him to descend immediately, but his team refused to act.
0:08:01 > 0:08:06We believe that if he stays the night here, he has a very high chance of dying.
0:08:06 > 0:08:09In the last half hour, I've seen a complete disregard for human life.
0:08:09 > 0:08:11But the climber was lucky.
0:08:11 > 0:08:16Surrounded by some of the world's leading high-altitude doctors, they were able to keep him alive
0:08:16 > 0:08:20and he returned to Base Camp this morning.
0:08:20 > 0:08:25The experience has left the whole team critically aware of the dangers they face.
0:08:25 > 0:08:29Things can very quickly deteriorate and...
0:08:29 > 0:08:31you know, it was a warning to us all.
0:08:31 > 0:08:36A wake-up call, not to be so bold to think that any of us
0:08:36 > 0:08:41are beyond that risk. We're not. It goes with the territory.
0:08:44 > 0:08:47To complete their science, they must push on.
0:08:47 > 0:08:51Only five days of clear weather remain to attempt the summit.
0:08:53 > 0:08:56But to reach Camp Four on the South Col,
0:08:56 > 0:09:00they must first complete one of the most challenging parts of the climb.
0:09:00 > 0:09:05In front of them is a near-vertical one kilometre wall of ice,
0:09:05 > 0:09:07the Lhotse Face.
0:09:17 > 0:09:23The Lhotse Face was both more frightening and more beautiful than I expected it to be.
0:09:26 > 0:09:29And it's...
0:09:29 > 0:09:32an utterly amazing environment -
0:09:32 > 0:09:37better than any day you could have in the mountains anywhere else.
0:09:38 > 0:09:41RADIO EXCHANGES: 'Camp Three, this is Camp Two, over.'
0:09:41 > 0:09:45'Reading you loud and clear, Denny. Go ahead, over.'
0:09:46 > 0:09:50'Have you got any idea what time they're leaving, over?'
0:09:50 > 0:09:54'That's a good question. How many people can you see standing on Lhotse, over?'
0:09:55 > 0:09:57'Camp Four, this is Camp Three.'
0:10:02 > 0:10:06If you fell from the Lhotse Face, you would stand no chance.
0:10:06 > 0:10:10When the ice is that hard, you wouldn't be able to stop.
0:10:10 > 0:10:12You'd go all the way to the bottom.
0:10:20 > 0:10:23It has taken the team a day of gruelling climbing
0:10:23 > 0:10:25to get to Camp Four.
0:10:28 > 0:10:33Well done. Well done. You deserve it.
0:10:39 > 0:10:42An advance party has already reached this landmark.
0:10:43 > 0:10:46It is led by the only member of the team
0:10:46 > 0:10:48with previous experience of the mountain,
0:10:48 > 0:10:51military doctor Sundeep Dhillon.
0:10:51 > 0:10:56One of the questions I'm asked the most often is why am I coming back here to a place
0:10:56 > 0:10:59that is inherently dangerous when I've already summited?
0:10:59 > 0:11:06The answer to that really has to be that the project we're involved in is so unique,
0:11:06 > 0:11:10but I really hope that the results it will bring will justify that.
0:11:11 > 0:11:17Sundeep's team have brought with them all the contents of a medical laboratory.
0:11:17 > 0:11:22Just getting this far has fulfilled a long-held dream for Dr Dan Martin.
0:11:22 > 0:11:26I've looked forward to being on the South Col since I was at school,
0:11:26 > 0:11:28many, many years, and I never thought I'd get here.
0:11:28 > 0:11:32I've been looking forward to seeing this bicycle test for about a year,
0:11:32 > 0:11:3618 months now, so it's difficult to say which is more exciting.
0:11:36 > 0:11:37It gets all muddled up.
0:11:37 > 0:11:42It's exciting to be here, but I think the research has sort of taken over now.
0:11:42 > 0:11:46The lab stands at the threshold of the Death Zone,
0:11:46 > 0:11:50where there is simply not enough oxygen to sustain human life.
0:11:52 > 0:11:59Every moment spent here is so suffocating, the cells in their bodies are slowly dying.
0:11:59 > 0:12:01Thumbs up if you are OK.
0:12:04 > 0:12:09For the doctors, it is the ultimate location for their research.
0:12:10 > 0:12:15But in this deadly environment, it's their medical skills that are needed once again.
0:12:15 > 0:12:19RADIO: 'OK, Mike, the situation up here as far as we know it,
0:12:19 > 0:12:22'I can see one, two, three, four, five,
0:12:22 > 0:12:26'six people on the triangular face, over.
0:12:28 > 0:12:31'A rescue party dealing with a Nepali woman.'
0:12:31 > 0:12:35Can we revise that time? The guys have moved fast. We can see them over the ice bulge.
0:12:35 > 0:12:42High on the mountain, a female Nepali climber, Usha Bista, has succumbed to the lack of oxygen.
0:12:42 > 0:12:46She has been found by another team, delirious and alone at 8,500 metres.
0:12:46 > 0:12:50We need someone to come in here who speaks... Someone who speaks
0:12:50 > 0:12:53very good Nepali and good English.
0:12:54 > 0:12:57Here was a person on their own getting into
0:12:57 > 0:13:00that situation where they get sick,
0:13:00 > 0:13:03no-one with them to realise they are becoming unwell,
0:13:03 > 0:13:07becoming confused, and the outcome of all that is that
0:13:07 > 0:13:11she ends up unconscious at 8,500 metres.
0:13:11 > 0:13:14Not a great place to become unconscious with no-one around.
0:13:17 > 0:13:22Mike knows if they don't act immediately, this could be fatal.
0:13:23 > 0:13:25What did you drag her on?
0:13:25 > 0:13:27Stretcher or no stretcher?
0:13:27 > 0:13:28Does she know what day it is?
0:13:28 > 0:13:32TRANSLATOR SPEAKS NEPALI
0:13:32 > 0:13:35She says she is in a tent.
0:13:35 > 0:13:37Whereabouts?
0:13:37 > 0:13:39Summit. She went to summit.
0:13:39 > 0:13:42The radio link is beginning to falter.
0:13:42 > 0:13:47Mike uses the summit team's cameras to relay a message to Base Camp.
0:13:47 > 0:13:53OK, so the key things are cerebral oedema, mild hypothermia, frostbite - ten digits.
0:13:53 > 0:13:55She needs dexamethasone, high-flow oxygen,
0:13:55 > 0:13:59passive re-warming, and get her to Base Camp as fast as possible.
0:13:59 > 0:14:02Camp Two may be the safest place overnight. Have you got that?
0:14:02 > 0:14:08Most severe is a cerebral oedema, a swelling of the brain brought on by the high altitude.
0:14:08 > 0:14:14Drugs and oxygen can help, but unless she is taken to a lower altitude she is likely to die.
0:14:14 > 0:14:17She needs a doctor to go down with her.
0:14:17 > 0:14:21We've just got here, but we're going to turn around and go back down to Camp Three with her.
0:14:21 > 0:14:24It's the right thing to do, you know.
0:14:26 > 0:14:32Andre volunteers to turn around and attempt the treacherous descent of the Lhotse Face.
0:14:34 > 0:14:35Nick, this one here.
0:14:35 > 0:14:39No hand-warmers. Not hand-warmers.
0:14:39 > 0:14:45There's not enough people here that are in good enough shape to take her down on a stretcher.
0:14:45 > 0:14:48To rescue somebody on a stretcher, ideally...
0:14:49 > 0:14:51..you need 16 people.
0:14:51 > 0:14:53We're going to try and do it with seven...
0:14:54 > 0:14:56..because we think she's got a chance.
0:14:56 > 0:15:00The crew are going to help you get her to the spur.
0:15:00 > 0:15:05The rescue party are set to go when news breaks of further casualties.
0:15:05 > 0:15:09Mike, there are four people in worse shape coming down.
0:15:09 > 0:15:12Mike is faced with an agonising choice.
0:15:12 > 0:15:15So it's a question of which people are most salvageable.
0:15:15 > 0:15:17She is definitely salvageable.
0:15:17 > 0:15:20Well, they're still up high.
0:15:20 > 0:15:24- There's no telling. - If they're up high, we ain't gonna get them out of here today.
0:15:24 > 0:15:26There's nobody going back up to get them.
0:15:26 > 0:15:30So, one, who's up there, and these are not nice decisions.
0:15:30 > 0:15:35If one person is up there close to death and no-one's rescuing them, there's nothing we can do.
0:15:35 > 0:15:39- What we can do is rescue her. - When we get down to two, we'll talk to people.
0:15:39 > 0:15:42We can save her life, so I'm going to go down with her.
0:15:42 > 0:15:43Because we can save her life.
0:15:43 > 0:15:46- Absolutely. - And those guys may or may not die.
0:15:46 > 0:15:49- These guys?- Yes, these two guys.
0:15:49 > 0:15:52It was a real reminder for us
0:15:52 > 0:15:58who had yet still to go further up that this was indeed a difficult and dangerous place
0:15:58 > 0:16:04and again, another warning of not to become complacent about the environment.
0:16:04 > 0:16:06We have two guys.
0:16:06 > 0:16:08Two guys for rescue.
0:16:10 > 0:16:14Usha is to be evacuated down 1,500 metres to the Western Cwm,
0:16:14 > 0:16:17where the expedition has a support team at Camp Two.
0:16:17 > 0:16:21'I've said they can have anything they want of ours at two. Now, they may choose
0:16:21 > 0:16:23'to go to their own camps...'
0:16:23 > 0:16:25Mike radios his wife, Dr Denny Levett,
0:16:25 > 0:16:29the team's Chief Medical Officer, to alert her to the incoming casualty.
0:16:29 > 0:16:33We've offered to take care of the lady on her way down
0:16:33 > 0:16:36and our doctors on the South Col have assessed her there.
0:16:36 > 0:16:40At the moment, she is being transported down the Lhotse Face.
0:16:46 > 0:16:50Usha is a stark reminder of just how little they understand
0:16:50 > 0:16:53about the effects of high altitude on the human body...
0:16:54 > 0:16:58..and the life-threatening symptoms it can produce.
0:16:58 > 0:17:02It's been a very dramatic day, so we've split ourselves into a medical rescue team
0:17:02 > 0:17:05and a scientific team here, such that we can do our work
0:17:05 > 0:17:08and we can also rescue people safely from the mountain.
0:17:10 > 0:17:13Off we go. 60rpm, please.
0:17:14 > 0:17:20At this altitude, even the simple things don't come easily.
0:17:20 > 0:17:21This neuropsychological test
0:17:21 > 0:17:26is straightforward to complete at sea level but here, Nigel is struggling.
0:17:27 > 0:17:29That doesn't look right.
0:17:34 > 0:17:39The brain is so badly affected, many climbers return with permanent damage.
0:17:44 > 0:17:50To counter these effects, all those conducting the tests used supplementary oxygen.
0:17:50 > 0:17:53VJ, you can see, is on oxygen and the reason for that
0:17:53 > 0:17:58is we want the person running the test to really know what they're doing.
0:17:58 > 0:18:04We don't want somebody who is hypoxic and mad to control what is going on.
0:18:04 > 0:18:10This test is the most ambitious and difficult experiment the team are attempting at Camp Four.
0:18:11 > 0:18:18So Sundeep is the first person to do a maximal cycle exercise test at 8,000 metres.
0:18:18 > 0:18:19SUNDEEP GROANS
0:18:19 > 0:18:22- First person ever. - First person ever, yeah.
0:18:22 > 0:18:23THEY CHUCKLE
0:18:23 > 0:18:28The doctors hope it will reveal why some people suffer so badly
0:18:28 > 0:18:31from lower levels of oxygen, when others are unaffected.
0:18:34 > 0:18:37Breathing just the thin air, Sundeep is pushing his body to its limit
0:18:37 > 0:18:44as they analyse exactly how much oxygen he is using to do a precise amount of exercise.
0:18:45 > 0:18:50The team have performed this test all the way from sea level,
0:18:50 > 0:18:53but only here in Camp Four will they get their ultimate result.
0:18:54 > 0:18:59It could explain why Sundeep is able to perform so well in this environment
0:18:59 > 0:19:02when the levels of oxygen leave others on the edge of death.
0:19:02 > 0:19:09And it could be that some people, with a given amount of oxygen delivered to the cell,
0:19:09 > 0:19:12they use that oxygen in a much more efficient way
0:19:12 > 0:19:15and we're really trying to measure that oxygen efficiency
0:19:15 > 0:19:18in a lot of the experiments we're doing up here now.
0:19:18 > 0:19:19What we would love to see
0:19:19 > 0:19:23is that some people are much more efficient at using oxygen than others.
0:19:29 > 0:19:33- How do you feel, mate? - Good.- There we are. Fantastic. Absolutely superb.
0:19:36 > 0:19:41It's interesting, because, like you say, your heart rate goes up, your respiratory rate goes up
0:19:41 > 0:19:47to 60 fairly quickly and you think you can maintain it. I don't know.
0:19:47 > 0:19:51It's like most things. You think you can go for a few minutes longer.
0:19:51 > 0:19:53I was...
0:19:53 > 0:19:55starting to feel sick more than anything else.
0:19:57 > 0:20:01Although all the data will be analysed over many months,
0:20:01 > 0:20:06the potential of this experiment to save lives is enormous.
0:20:06 > 0:20:11It might, for the first time, reveal how the body becomes more efficient when faced with a lack of oxygen,
0:20:11 > 0:20:18allowing a treatment to be developed that could recreate this life-saving effect in critically ill patients.
0:20:18 > 0:20:22Even a minor improvement in oxygen efficiency could have a major impact
0:20:22 > 0:20:25on the most oxygen-sensitive organ - the brain.
0:20:31 > 0:20:35Chris Imray, a vascular surgeon, is examining the most dangerous
0:20:35 > 0:20:38effect of high altitude, a lack of oxygen going to the brain.
0:20:38 > 0:20:42This is phenomenal. I've never seen such a large artery.
0:20:42 > 0:20:45It's, um... This is amazing.
0:20:45 > 0:20:50The scan reveals an astonishing change inside Nigel's skull.
0:20:50 > 0:20:53We're now at 8,000 metres. You can see this massive artery,
0:20:53 > 0:20:56which is roughly twice the diameter that one would expect.
0:20:56 > 0:21:01This, I guess, must be this sort of size because we're trying to get
0:21:01 > 0:21:04a lot more oxygen there because there's so little oxygen around.
0:21:04 > 0:21:07This is fantastic. This is really exciting stuff.
0:21:07 > 0:21:11As long as it gets me to the summit of Everest, I'm excited.
0:21:11 > 0:21:13At the moment, Nigel is OK.
0:21:13 > 0:21:16Only when this process runs out of control
0:21:16 > 0:21:19can it lead to a potentially fatal form of brain swelling.
0:21:19 > 0:21:24It's called high altitude cerebral oedema, or HACE.
0:21:24 > 0:21:29This is the exact condition that is affecting the Nepali climber, Usha.
0:21:29 > 0:21:31OK, just come with me.
0:21:31 > 0:21:33My name's Denny. Well done.
0:21:33 > 0:21:35Just sit down here.
0:21:35 > 0:21:39That's right, sweetheart. OK. Just get her into the middle.
0:21:42 > 0:21:44Very tired-looking. All right.
0:21:44 > 0:21:46How is she now? Any pain?
0:21:46 > 0:21:48TRANSLATOR SPEAKS IN NEPALI
0:21:48 > 0:21:49- No?- No.
0:21:49 > 0:21:52OK, just pop the head forwards.
0:21:52 > 0:21:57- Different mask.- 110 over 70. - Excellent.
0:21:57 > 0:22:00The swelling of the brain has been arrested,
0:22:00 > 0:22:03but it may be too late to save her from the frostbite.
0:22:05 > 0:22:08Dehydration would make the injury from the frostbite worse,
0:22:08 > 0:22:12so we're going to help things along by giving her some fluids into her vein.
0:22:12 > 0:22:17I think tonight we need to keep her here to make sure the pain is under control.
0:22:17 > 0:22:20She needs oxygen, one, to try and improve
0:22:20 > 0:22:24the oxygen supply to the fingers and salvage any cells
0:22:24 > 0:22:27that are just short of oxygen and not dead yet and, secondly,
0:22:27 > 0:22:30because she's had the altitude sickness,
0:22:30 > 0:22:32it's important that she stays on oxygen.
0:22:32 > 0:22:35Despite her injuries, Usha is fortunate.
0:22:35 > 0:22:41Others exposed to such low levels of oxygen do not survive the ordeal.
0:22:42 > 0:22:48And it is this question, of who lives and who dies, that stands at the centre of the expedition.
0:22:57 > 0:23:00In their largest experiment, the Caudwell Xtreme Everest Team
0:23:00 > 0:23:04have recruited an army of guinea pigs to make their way to Base Camp.
0:23:09 > 0:23:11Each of the 200 volunteers has given up
0:23:11 > 0:23:16nearly a month of their lives to subject themselves to the effects of altitude.
0:23:16 > 0:23:21Waiting for them at the end of the 60 kilometre journey is Dr Paul Gunning.
0:23:21 > 0:23:25It's hard to think of a body system not affected by altitude.
0:23:25 > 0:23:28We treat changes in altitude quite casually,
0:23:28 > 0:23:31but the consequences to every system in the body are considerable
0:23:31 > 0:23:35and we've seen that already on the trek with people becoming unwell
0:23:35 > 0:23:39and feeling symptomatic from altitude.
0:23:40 > 0:23:44Some will be affected more than others...
0:23:45 > 0:23:50..and with this many volunteers being tested, the doctors believe they can find out why.
0:23:57 > 0:23:59Today's a 600 metre gain,
0:23:59 > 0:24:02so I'm pretty sure that some people
0:24:02 > 0:24:08will get some splitting headaches and be suffering a bit.
0:24:11 > 0:24:13The trekkers come from all walks of life,
0:24:13 > 0:24:16ranging from 18 to 73 years old,
0:24:16 > 0:24:19fit and unfit, men and women.
0:24:19 > 0:24:22Just keep turning them, turning them, turning them.
0:24:25 > 0:24:31Technically, I'm on my way to suffering a very large, large amount.
0:24:31 > 0:24:36Top thing is the blood oxygenation, which usually is 98%
0:24:36 > 0:24:40at around sea-level, which is why I'm breathing quite hard.
0:24:40 > 0:24:41Keep that going.
0:24:41 > 0:24:48Andy Walker is 34 years old and is already finding coping with the decreasing levels of oxygen hard.
0:24:48 > 0:24:49ANDY COUGHS
0:24:49 > 0:24:53Keep going, keep going, keep going. OK.
0:24:53 > 0:24:55I am on vacation.
0:24:55 > 0:25:00Taking leave from work, I sit back, a man of leisure(!)
0:25:01 > 0:25:05Most intriguingly, what makes some of them do better than others
0:25:05 > 0:25:08doesn't seem to depend on fitness or youth.
0:25:10 > 0:25:13Yeah, I'm just feeling a bit ropey,
0:25:13 > 0:25:16a bit nauseous when we first arrived. Not doing the walk.
0:25:16 > 0:25:20I felt fine doing the walk. Maybe the adrenalin keeps you going,
0:25:20 > 0:25:23like you have to get somewhere, but once we sat down,
0:25:23 > 0:25:25not too good.
0:25:25 > 0:25:32It seems that some people are simply born with a better ability to deal with low levels of oxygen.
0:25:32 > 0:25:35What we're specifically trying to do here is not just look at
0:25:35 > 0:25:40what the effects of altitude are, but who gets the changes in altitude, who doesn't,
0:25:40 > 0:25:46and how they cope with changes in altitude and how they acclimatise to changes in altitude.
0:25:47 > 0:25:52On the mountain, not adapting well to a lack of oxygen makes climbing difficult.
0:25:55 > 0:26:01But in intensive care, it could be the difference between life and death.
0:26:01 > 0:26:05It's a lottery the doctors are confronted with every day.
0:26:09 > 0:26:13Somebody who appears to be very fit may become very seriously unwell
0:26:13 > 0:26:15and, against all odds, they may die,
0:26:15 > 0:26:22whereas a more frail patient may surprise us all and survive the most terrible of illnesses.
0:26:24 > 0:26:28And it may be that the things that predict
0:26:28 > 0:26:31how people do at high altitude will be the same things
0:26:31 > 0:26:35that predict whether they would survive a critical illness.
0:26:36 > 0:26:42The team are convinced the answer to this mystery lies in the data they are collecting from the trekkers.
0:26:44 > 0:26:47Just pop your chin on the block and look down there for us.
0:26:47 > 0:26:51With this many subjects, they hope to hunt down the genes
0:26:51 > 0:26:56that not only make people natural-born climbers, but also natural-born survivors.
0:27:01 > 0:27:05I think in our wildest dreams, what we would love to see is that some people
0:27:05 > 0:27:10have certain genes which allow them to use oxygen more efficiently than others
0:27:10 > 0:27:15and so, what we're really, really hoping from this trip
0:27:15 > 0:27:19is that we could target treatment to poor oxygen users.
0:27:19 > 0:27:23They already know one of the genes that controls
0:27:23 > 0:27:26how well someone responds to low oxygen. It's called the ACE gene.
0:27:26 > 0:27:30This is one of the reasons why, for this study, we have a huge sample size
0:27:30 > 0:27:36and this is so that we can see, overall, who are the people that perform well
0:27:36 > 0:27:40and then we can relate that to underlying genes.
0:27:40 > 0:27:43If they can pinpoint the other genes involved, they might be able
0:27:43 > 0:27:47to develop a drug that could turn poor oxygen users into strong ones.
0:27:47 > 0:27:53The ideal scenario would be that we could switch yourselves into a more efficient mode of functioning
0:27:53 > 0:27:59so that whilst you're exposed to these low levels of oxygen, you use the oxygen most efficiently
0:27:59 > 0:28:01and should hopefully survive and, for me,
0:28:01 > 0:28:05that would be the best possible outcome of Xtreme Everest.
0:28:06 > 0:28:10But the team are hoping one test will have a more immediate effect.
0:28:12 > 0:28:16High on Everest, the doctors at Camp Four have a single goal.
0:28:20 > 0:28:25They want to find out how little oxygen the human body requires to survive.
0:28:30 > 0:28:32It's the extreme physiology
0:28:32 > 0:28:34which we're interested in here.
0:28:34 > 0:28:38How much oxygen is there in someone standing on the top of Mount Everest
0:28:38 > 0:28:41who is able to function in a reasonably normal way?
0:28:43 > 0:28:47That will be useful to us in intensive care, just to know
0:28:47 > 0:28:52how low an oxygen level people can tolerate and still survive.
0:28:52 > 0:28:55In the next 24 hours, they will attempt to take a sample of blood
0:28:55 > 0:28:59from deep within an artery on the summit of Everest.
0:29:03 > 0:29:05Mac, Mike, over.
0:29:05 > 0:29:10RADIO: 'Have an updated weather forecast for you. Everything remains stable.'
0:29:10 > 0:29:11Copy that, over.
0:29:11 > 0:29:13'There is a but.
0:29:13 > 0:29:18'The wind is moderate to strong and increases more and more.
0:29:18 > 0:29:24'At the summit, the wind speeds range between 30 and 80 kilometres per hour.
0:29:24 > 0:29:26'Received so far, over?'
0:29:26 > 0:29:28Copy that, over.
0:29:29 > 0:29:34The smallest of windows in the weather brings the summit in reach.
0:29:34 > 0:29:38This evening, everybody in this tent will be
0:29:38 > 0:29:42hopefully climbing to the summit of Everest, which is 8,850 metres.
0:29:42 > 0:29:46Ascending the 900 metres from Camp Four to the summit
0:29:46 > 0:29:51will take the team over some of Everest's most infamous landmarks.
0:29:51 > 0:29:56First, they must overcome the steep ice slope that leads to the plateau called the Balcony.
0:29:58 > 0:30:03From here, a perilously narrow ridge leads to the summit.
0:30:03 > 0:30:08To avoid the approaching gales, the team has to reach the top by midday tomorrow.
0:30:10 > 0:30:13It means leaving the South Col in the dead of night.
0:30:19 > 0:30:22Further down the mountain at Camp Two,
0:30:22 > 0:30:24Denny will face an agonising wait.
0:30:24 > 0:30:27Mike is my husband and my other half.
0:30:27 > 0:30:30I've thought about it quite a lot, it's not going to be an easy time
0:30:30 > 0:30:34and it will be a nerve-racking time, waiting for him to come back down.
0:30:37 > 0:30:40'I think it's the fear of the unknown and the knowledge
0:30:40 > 0:30:45'that people have come a cropper in the past and not made it up and down,
0:30:45 > 0:30:50'so it's a combination of excitement and feeling on the edge of your seat
0:30:50 > 0:30:54'and also really wanting to hear Mike's voice.'
0:30:59 > 0:31:03The departure time is nearing for the summit team.
0:31:09 > 0:31:12But there's a troubling development.
0:31:12 > 0:31:14We're a bit worried - the weather forecast changed
0:31:14 > 0:31:17and it's a bit windier than we hoped.
0:31:17 > 0:31:23And it's been windy this afternoon on the South Col, so I think the guys are a bit nervous setting out.
0:31:23 > 0:31:25WIND HOWLS
0:31:29 > 0:31:33Risking the weather could be a life or death decision,
0:31:33 > 0:31:37but at this altitude, the climbers are in no fit state to make it.
0:31:41 > 0:31:44The air that they are breathing is so thin
0:31:44 > 0:31:49that it's affecting their ability to think clearly and may even be making them delirious.
0:31:49 > 0:31:53So the team has agreed that any decision made high on the mountain
0:31:53 > 0:31:56has to be referred to those further down.
0:31:59 > 0:32:02At Base Camp, this responsibility
0:32:02 > 0:32:05falls to expedition manager, Mac Mackenny.
0:32:05 > 0:32:08We're going to give them a call in one hour.
0:32:08 > 0:32:09So that will be 22.30.
0:32:09 > 0:32:13And then just get a check in, asking them a series of questions,
0:32:13 > 0:32:18so we can basically establish what state they are in, how they're doing.
0:32:18 > 0:32:20That's critical.
0:32:20 > 0:32:22Absolutely critical.
0:32:24 > 0:32:28Mac has to repeat the checklist every hour to ensure each climber is
0:32:28 > 0:32:32mentally and physically fit enough to endure the rigours of Everest.
0:32:32 > 0:32:35Denny Levett, Denny Levett, this is Mac at Base Camp, over.
0:32:35 > 0:32:38Heh heh heh heh.
0:32:38 > 0:32:43If not, he has the authority to order them off the mountain.
0:32:43 > 0:32:50It's a heavy responsibility, as for every 15 people who summit, one person dies trying.
0:32:50 > 0:32:51OK, standing by.
0:32:56 > 0:32:59Everyone OK? Michael, how are you doing?
0:32:59 > 0:33:03Despite the volatile conditions, the team get the go-ahead.
0:33:07 > 0:33:09Denny, this is Mike. Do you read?
0:33:09 > 0:33:12Reading you loud and clear, hun, go ahead.
0:33:12 > 0:33:14OK, we're heading off in it.
0:33:14 > 0:33:18Very best of luck from all of us and be careful.
0:33:18 > 0:33:21And come back safely. I love you.
0:33:21 > 0:33:24I love you too and we'll be very careful, over.
0:33:27 > 0:33:29There is that anticipation.
0:33:29 > 0:33:31This is it, this is really it.
0:33:31 > 0:33:33We're going to be able to go after all.
0:33:35 > 0:33:38I just remember butterflies in my stomach,
0:33:38 > 0:33:42wondering how difficult it would be and would we make it,
0:33:42 > 0:33:44but then, finally, you're off.
0:33:49 > 0:33:53Already, the safeguards are looking fragile.
0:33:53 > 0:33:56- Mike, this is Denny, over. - STATIC
0:34:00 > 0:34:03We've got some pretty bad communications at the moment.
0:34:03 > 0:34:06We're getting comms with Camp Two,
0:34:06 > 0:34:10but unfortunately we have no communication at all with Camp Four.
0:34:10 > 0:34:13I don't know if they can hear us, but we can't hear them.
0:34:13 > 0:34:15Mike, this is Denny, over.
0:34:16 > 0:34:18FUZZY RESPONSE
0:34:21 > 0:34:23Mike, you're breaking up.
0:34:23 > 0:34:25FUZZY RESPONSE
0:34:25 > 0:34:28Sorry, could you repeat, please, Mike.
0:34:28 > 0:34:30CRACKLING
0:34:35 > 0:34:39I just have to sit here and wait for the next 12 hours, I guess.
0:34:41 > 0:34:46- Scary, though.- Yeah, scary. It's not a nice feeling, is it?
0:34:48 > 0:34:51And it's his birthday today. He's 41 today.
0:34:51 > 0:34:56Anyway, a good thing to do on your 41st birthday, get to the summit of Everest, I guess.
0:34:58 > 0:35:01The team have to move fast.
0:35:02 > 0:35:08If they have not reached the Balcony by daybreak, they could be too late to reach the summit.
0:35:09 > 0:35:13But there's a more pressing reason to keep to the schedule.
0:35:13 > 0:35:16The climbers have entered the Death Zone.
0:35:16 > 0:35:19The air they are breathing is simply too thin to sustain life.
0:35:22 > 0:35:26Even just a few hours' exposure to these low levels of oxygen
0:35:26 > 0:35:29can result in irreparable damage to their body tissue.
0:35:37 > 0:35:41- Mike, this is Denny. - Hello, this is Mike, over.
0:35:41 > 0:35:46Another hour passes and Mac is still out of range.
0:35:46 > 0:35:48Are you all still together?
0:35:50 > 0:35:53Are you all still together?
0:35:55 > 0:35:57Excellent, that sounds brilliant.
0:35:57 > 0:36:00So frustrating that we can't hear ourselves.
0:36:06 > 0:36:11- Mac, Base Camp, this is Denny, over. - Denny, this is Mac at Base Camp.
0:36:11 > 0:36:14Quite keen, if possible, when they get the chance,
0:36:14 > 0:36:18to try another frequency with you being the only one who can hear them, over.
0:36:20 > 0:36:25Well, to try and change radio stations means removing gloves etc
0:36:25 > 0:36:30and I don't think that's necessarily wise since we have got a signal, over.
0:36:30 > 0:36:33OK, I'm starting to lose you as well now, Denny.
0:36:33 > 0:36:37But I understand you say to wait until light,
0:36:37 > 0:36:40so Mac, standing by.
0:36:42 > 0:36:45- She's got a point.- Yep, absolutely.
0:36:45 > 0:36:49It's all right when it's all going well, but if there's trouble...
0:36:51 > 0:36:55I don't like working off luck. I'd sooner know.
0:36:57 > 0:37:02Despite losing half of their lifeline, the summit team clamber further into the night.
0:37:05 > 0:37:08We climbed and climbed and climbed and for the first,
0:37:08 > 0:37:13it must be about three hours, it was really, really hard work
0:37:13 > 0:37:16and I think quite a lot of us were thinking,
0:37:16 > 0:37:20perhaps we'd like to turn around and go back to the South Col.
0:37:20 > 0:37:23At that stage, it starts to feel a lot more difficult.
0:37:23 > 0:37:26The rhythm, not just coming so well
0:37:26 > 0:37:30and your feet were quite cold.
0:37:30 > 0:37:32Wondering, you know, is it frostbite?
0:37:32 > 0:37:39And if it's frostbite, should we move on? Will I have to turn back?
0:37:43 > 0:37:46- Mike, this is Denny, over. - CRACKLES
0:37:47 > 0:37:50Mike, Mike, this is Denny, over.
0:37:50 > 0:37:54That's everything, hun. Will you call again in an hour?
0:37:59 > 0:38:02OK, thinking of you then, lots of love.
0:38:03 > 0:38:06Standing by.
0:38:08 > 0:38:10Mac at Base Camp, this is Denny, over.
0:38:10 > 0:38:13Yes, this is Mac, go ahead.
0:38:13 > 0:38:16I've just had contact from the climbers.
0:38:16 > 0:38:20Location, just between Balcony and South Summit.
0:38:28 > 0:38:32One of the most exciting things about climbing through the night
0:38:32 > 0:38:36so high on Everest is seeing dawn, which just takes for ever.
0:38:36 > 0:38:39It also brings with it the promise of warmth,
0:38:39 > 0:38:42which makes it seem that forever is taking even longer.
0:38:46 > 0:38:50Dawn, really, when you look back at what you've just climbed
0:38:50 > 0:38:54and you think, oh my goodness, how am I ever going to get down there?
0:38:54 > 0:38:57It looked really frightening to look back and see what you'd done.
0:39:02 > 0:39:05The team have been climbing for eight hours.
0:39:05 > 0:39:08The summit is tantalisingly close.
0:39:13 > 0:39:17But they are yet to face one of Everest's greatest perils,
0:39:17 > 0:39:19the Ridge.
0:39:22 > 0:39:26You are going into an area which is littered with bodies,
0:39:26 > 0:39:28so many people have died on that ridge.
0:39:30 > 0:39:34At just half a metre wide, there is no room for error.
0:39:37 > 0:39:39You are wondering why you're doing it,
0:39:39 > 0:39:43but you're pushing yourself forward, because you know this is it.
0:39:43 > 0:39:47You're only going to get one chance at this mountain, despite the danger.
0:39:55 > 0:39:57You have to be lucky on Everest.
0:39:57 > 0:40:01You have to be lucky for every step that you take,
0:40:01 > 0:40:06because a lot of the things that happen up there are outwith your control.
0:40:13 > 0:40:18As the climbers go further, the odds against them all surviving get shorter.
0:40:24 > 0:40:28More than 30 people have lost their lives climbing this exposed track.
0:40:33 > 0:40:36But high on Everest, the Ridge is not the biggest threat,
0:40:36 > 0:40:40it is the phenomena these doctors have come here to try and understand,
0:40:40 > 0:40:44the desperate shortage of oxygen called hypoxia.
0:40:46 > 0:40:53Climbing high up on the mountain when there is so little oxygen is almost a dreamlike state.
0:40:53 > 0:40:57You feel like you're drunk, you feel soporific.
0:40:57 > 0:41:02You just want to sit down in the snow and lie down and do nothing
0:41:02 > 0:41:08and every footstep is an effort of will and physically pushing the body.
0:41:14 > 0:41:18Without additional oxygen, the climbers could be overcome by hypoxia,
0:41:18 > 0:41:21their body systems shutting down one by one,
0:41:21 > 0:41:26leading to a loss of consciousness and, eventually, death.
0:41:32 > 0:41:37Using the bottled gas only increases the amount of oxygen they breathe by two per cent,
0:41:37 > 0:41:41but this tiny fraction is enough to make a vital difference.
0:41:42 > 0:41:49It is not uncommon to have to take 15 huge breaths
0:41:49 > 0:41:52between each pace and despite that,
0:41:52 > 0:41:56every 10 to 15 steps, you just want to collapse down into the snow.
0:41:59 > 0:42:04Eight hours in the Death Zone is taking the climbers to the brink of their physical ability.
0:42:07 > 0:42:11At sea level, they would be taking ten breaths every minute.
0:42:13 > 0:42:18But here, in the critically thin air, their breathing rate has soared to 80 breaths a minute.
0:42:27 > 0:42:33And their oxygen-starved minds will struggle to make sense of the world around them.
0:42:33 > 0:42:35Essentially, you're climbing by yourself.
0:42:35 > 0:42:41Once you've got your oxygen mask on, the person who's four yards in front of you could be on another planet,
0:42:41 > 0:42:46and you hear your own breathing, you hear blood rushing in your ears,
0:42:46 > 0:42:52you hear your own feet on the snow and that's about it.
0:42:55 > 0:43:00The summit is just 50 metres away, but they will be some of the hardest to overcome.
0:43:06 > 0:43:09Ahead of the team stands a sheer face of rock
0:43:09 > 0:43:14named after Everest's first summiteer, Sir Edmund Hillary.
0:43:20 > 0:43:24The Hillary Step is the most technical part of the climb.
0:43:27 > 0:43:32And however well you've done up to that point, there's always a certain amount of fear
0:43:32 > 0:43:35that you might not be able to negotiate it.
0:43:39 > 0:43:44You can sort of climb up on to the top of the step, almost,
0:43:44 > 0:43:48and then round another little block and you're right on the edge there
0:43:48 > 0:43:54on a tiny little step and as you look down, it's just miles down into Tibet
0:43:54 > 0:43:59and you're quite careful about your footing at that point as you edge your way round.
0:44:06 > 0:44:11At that altitude, just hauling yourself up a rock face is hard work.
0:44:11 > 0:44:16You're really out of breath, gasping as if someone's strangling you.
0:44:31 > 0:44:34Once you've got to the Hillary Step and you've managed to get over it,
0:44:34 > 0:44:37that's it, the climb's done and you just walk to the summit.
0:44:41 > 0:44:46We knew that no-one was going to stop us getting to the summit then, I think.
0:45:00 > 0:45:05It went on for what seemed like an eternity,
0:45:05 > 0:45:09because, you know it's not that far, you know it's not that further up,
0:45:09 > 0:45:15but it seemed to go on and on and on and you can't actually initially see the summit.
0:45:28 > 0:45:32You really just come round a corner and suddenly the summit is there.
0:45:37 > 0:45:43The mountaineering challenge may be over, but the science is yet to begin.
0:45:44 > 0:45:47The team have subjected themselves to this ordeal
0:45:47 > 0:45:51to quantify what the extreme limits of human survival are.
0:45:52 > 0:45:57Once they reach the summit, they will take blood from deep within their arteries
0:45:57 > 0:46:00and measure just how little oxygen there is keeping them alive.
0:46:13 > 0:46:15Pasang, Pasang, is that you, over?
0:46:15 > 0:46:20At last, the radio silence is broken.
0:46:20 > 0:46:23Pasang, Pasang, is that you, over?
0:46:24 > 0:46:27Yes, it is Pasang, over.
0:46:29 > 0:46:33This is Denny at Camp Two. Are you at the summit, over?
0:46:35 > 0:46:39Yeah, we have arrived at the summit, over.
0:46:39 > 0:46:41Congratulations!
0:46:41 > 0:46:44Who else is with you?
0:46:44 > 0:46:49Ah, we are all of us in the summit, over.
0:46:49 > 0:46:53Fantastic news.
0:46:53 > 0:46:54That's excellent.
0:46:54 > 0:46:57Mac at Base Camp, this is Denny.
0:46:57 > 0:47:00Denny, this is Mac at Base Camp. Go ahead, over.
0:47:00 > 0:47:04I'm pleased to report that Mike, Dan...
0:47:06 > 0:47:11Uh, Sundeep, Nigel, Chris, Dave and all the Sherpas are on the summit.
0:47:11 > 0:47:14WHOOPING
0:47:22 > 0:47:25Five years of planning, preparation and, ultimately,
0:47:25 > 0:47:29sheer determination, finally get their reward.
0:47:30 > 0:47:33It's a great moment when you get to the top.
0:47:36 > 0:47:38The views are...
0:47:38 > 0:47:41everything that you would imagine they would be,
0:47:41 > 0:47:43and we had a pretty clear day.
0:47:53 > 0:47:56The scale on Everest is almost incomprehensible.
0:47:56 > 0:47:59The way I try and explain it to people who've never been
0:47:59 > 0:48:05is that next time you fly, have a look out the window and imagine trying to walk up to that altitude.
0:48:07 > 0:48:11Just to stand on the top and look from the top
0:48:11 > 0:48:14is an amazing sense of achievement,
0:48:14 > 0:48:17but there's an odd feeling you can't explain
0:48:17 > 0:48:21when you're standing on the top of the mountain looking down on everything else.
0:48:21 > 0:48:24And then there's nothing really to compare to it.
0:48:24 > 0:48:28You instantly forget about the horror of getting to the top,
0:48:28 > 0:48:31and for a while you forget about the long journey down.
0:48:31 > 0:48:35And you're just sort of held in time,
0:48:35 > 0:48:38looking from the summit. You don't want to leave.
0:48:38 > 0:48:43You just want to stand there and make the most of it, having spent weeks getting there.
0:48:46 > 0:48:50- Mike, over.- Mike, I love you.
0:48:52 > 0:48:56I am very, very proud of you, honey.
0:48:56 > 0:48:59Thanks, angel.
0:48:59 > 0:49:02Standing by.
0:49:02 > 0:49:03Standing by.
0:49:05 > 0:49:08Really good news.
0:49:14 > 0:49:18At Base Camp, word of the team's success has spread.
0:49:19 > 0:49:22But the climbers are already off the summit.
0:49:25 > 0:49:29The team's ultimate ambition has hit a problem.
0:49:31 > 0:49:36The fierce winds have driven them 400 metres down the mountain
0:49:36 > 0:49:38to set up their final laboratory.
0:49:40 > 0:49:43Mike was obviously thinking clearly,
0:49:43 > 0:49:46because I think it was the right decision,
0:49:46 > 0:49:49and before we'd even realised it,
0:49:49 > 0:49:52he was saying, "Right, it's time to go."
0:49:52 > 0:49:54VJ, Sundeep, over.
0:49:55 > 0:50:01With their oxygen masks removed, the climbers are breathing some of the thinnest air in the world.
0:50:01 > 0:50:07Oxygen saturation for Chris Imray, is 62 per cent. Figure 6 - 2, over.
0:50:07 > 0:50:09I've just had one of the best days of my life.
0:50:12 > 0:50:17At sea level, this is a routine procedure, but at this altitude,
0:50:17 > 0:50:20it requires all the doctor's skills.
0:50:20 > 0:50:23The result is equally unusual.
0:50:23 > 0:50:24The colour is blue.
0:50:24 > 0:50:27It is very dark, as if it was in an artery.
0:50:27 > 0:50:30It is flowing into the syringe of its own accord.
0:50:30 > 0:50:35Arterial blood coming from the heart is usually bright red.
0:50:35 > 0:50:38The uncharacteristic colour can only mean one thing.
0:50:38 > 0:50:41Severe oxygen depletion.
0:50:41 > 0:50:44That is an amazing piece of science.
0:50:44 > 0:50:48No one has ever done blood gases above 8,000 metres.
0:50:48 > 0:50:51What altitude are we? 86 or something?
0:50:53 > 0:50:55It is outrageous science.
0:51:00 > 0:51:04One of the team's Sherpas, Pasang, takes these blood samples to Camp Two
0:51:04 > 0:51:08for an exact measurement of the oxygen content.
0:51:08 > 0:51:10For him, it's a familiar journey.
0:51:14 > 0:51:19For the doctors, it's fraught with peril.
0:51:19 > 0:51:21Whenever you summit a mountain of any size,
0:51:21 > 0:51:24your celebration of reaching the summit
0:51:24 > 0:51:28shouldn't really begin until you're back down safely.
0:51:33 > 0:51:37It's almost universally true that most climbing accidents happen on the way down,
0:51:37 > 0:51:42when you may have taken your focus off why you are there.
0:51:42 > 0:51:47You've got to the summit, you're now coming down, you're on ground that you've already been over.
0:51:47 > 0:51:51It's now daylight, rather than dark, so you might feel more comfortable with where you are,
0:51:51 > 0:51:55but both physically and mentally, you're far more exhausted.
0:52:13 > 0:52:18The team have made it to the relative safety of the South Col.
0:52:20 > 0:52:25At under 8,000 metres, it is just out of the Death Zone.
0:52:25 > 0:52:27Congratulations.
0:52:27 > 0:52:31OK, Mac, we have all climbers and all Sherpas back in camp.
0:52:31 > 0:52:34Everybody fully intact and feeling well, over.
0:52:36 > 0:52:38I think that's it.
0:52:38 > 0:52:40Well done.
0:53:01 > 0:53:03Carried by the Sherpa Pasang,
0:53:03 > 0:53:08the precious blood samples arrive at Camp Two in record time.
0:53:09 > 0:53:11Pasang!
0:53:13 > 0:53:15Very well done.
0:53:15 > 0:53:17Give me a hug.
0:53:17 > 0:53:20Well done. Very fast. Two hours.
0:53:20 > 0:53:22Two hours from the summit.
0:53:22 > 0:53:25Amazing.
0:53:25 > 0:53:27- He summited...- 10.30.
0:53:27 > 0:53:3010.30. Two hours exactly.
0:53:30 > 0:53:32Very quick.
0:53:32 > 0:53:37The team already believe that the blood samples will be low in oxygen,
0:53:37 > 0:53:40but now Denny hopes to back it up with some solid figures.
0:53:40 > 0:53:43We knew from preliminary work that the numbers
0:53:43 > 0:53:45that we were going to get are those
0:53:45 > 0:53:49which most of our colleagues would say are not compatible with life.
0:53:49 > 0:53:52Thank you very much. This is very precious.
0:53:52 > 0:53:56And we wanted to demonstrate that not only are they compatible with life,
0:53:56 > 0:54:01but actually you can make very rational thoughts up there and effectively,
0:54:01 > 0:54:06you can function to pretty near sea-level norms.
0:54:06 > 0:54:09It was vital that we got this data as high up the mountain as we could,
0:54:09 > 0:54:11because the higher up we were,
0:54:11 > 0:54:14the more outrageous the results would seem.
0:54:14 > 0:54:17X08. So this is Sundeep's arterial.
0:54:17 > 0:54:21PC02, 1.77. Woah.
0:54:21 > 0:54:26P02, 4.9. I have never seen a carbon dioxide that low.
0:54:26 > 0:54:29The preliminary results are amazing.
0:54:29 > 0:54:35Ordinarily, the P02 number, meaning oxygen content, would be around 13.
0:54:35 > 0:54:39Anything less than eight would place someone in Intensive Care.
0:54:39 > 0:54:45In a clinical situation, you would never see an alive patient with gases anything like that.
0:54:46 > 0:54:49Very, very low.
0:54:49 > 0:54:52Somehow, Dan has managed to summit Everest
0:54:52 > 0:54:56with the lowest blood oxygen level ever measured in a living human.
0:54:56 > 0:54:58P02, 3.50.
0:54:58 > 0:55:01Dan should definitely be dead.
0:55:10 > 0:55:15In a stroke, they have re-written our understanding of the limits of survival.
0:55:15 > 0:55:20It's incredibly satisfying to have climbed Everest
0:55:20 > 0:55:24and to know that I don't really have to go back again is good.
0:55:26 > 0:55:30From all sorts of perspectives, we achieved what we wanted to do.
0:55:30 > 0:55:32CHEERS
0:55:44 > 0:55:46I'm really happy.
0:55:46 > 0:55:48They all look so well, don't they?
0:55:50 > 0:55:52They all look so well.
0:55:57 > 0:56:01Well done. I am so glad you're back!
0:56:06 > 0:56:11I don't have a huge drive to go back now, but I guess
0:56:11 > 0:56:14I've only been home a couple of months, so we'll see how things go.
0:56:25 > 0:56:28It's a good feeling to be home. Everybody else is home.
0:56:28 > 0:56:32The nervousness about impending disaster doesn't really go away
0:56:32 > 0:56:34until you're back in Kathmandu or even back in London.
0:56:34 > 0:56:40As we said earlier, the haemoglobin's gradually been coming down. Any signs of infection?
0:56:41 > 0:56:46Mike is living proof that the human body can survive the condition
0:56:46 > 0:56:49that kills many of his patients in Intensive Care.
0:56:52 > 0:56:55And now the team can find out why.
0:56:55 > 0:56:58Guys, all right?
0:56:59 > 0:57:04First, they will have to analyse the tens of millions of pieces of data.
0:57:06 > 0:57:12Once complete, it will be the most comprehensive study of hypoxia in the human body.
0:57:12 > 0:57:17And that could unlock the secret of life in the most critically ill.
0:57:17 > 0:57:19I think it's a fantastic achievement.
0:57:19 > 0:57:24This is the most ambitious project that's ever been carried out at altitude, certainly.
0:57:24 > 0:57:28Over 90 per cent of what we planned to do, we've done,
0:57:28 > 0:57:31and that is a fantastic achievement and I think that data
0:57:31 > 0:57:34will be very powerful in terms of giving us information
0:57:34 > 0:57:39about adaptation to hypoxia that will hopefully help our patients in the future.
0:57:40 > 0:57:43By taking themselves to the highest point on Earth
0:57:43 > 0:57:48and risking their own lives, the doctors may one day save many more.
0:57:48 > 0:57:51There wasn't much time whilst we were away
0:57:51 > 0:57:55to actually take pleasure in what we'd achieved.
0:57:55 > 0:58:00And it's actually quite nice at the moment, when you come back and see your friends
0:58:00 > 0:58:03you haven't seen for a while and they say, "How was it?"
0:58:03 > 0:58:05And you think, "That was really good, actually."
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