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David Payne on hypoxia, Everest-style

17 Nov, 09 | by BMJ Group

Dan Martin undresses in 20-knot winds beneath the Everest summit to prepare for a femoral artery blood sample and muscle biopsy while a team of sherpas look on, entertained by what they see. The critical care anaesthetist and his three colleagues ended up on the top of the world’s highest peak two years ago as part of their research project to quantify the limit of human tolerance for hypoxia.

Describing the experiment so far at a Wellcome Collection event in London last week, Martin said he and his three colleagues recorded an average blood oxygen level of 54% (3.28 kilopascals or kPa). His was the lowest, at 34% (2.55 kPa). Patients with a level below 8 kPa are considered critically ill.

The samples were put into non-permeable glass syringes, which are very difficult to handle, and transferred to ice-filled vacuum containers, which the sherpas quickly deposited at a lab 200m below.

The research team’s bid to discover “how low can you go” via Everest was seen as preferable to putting a large number patients on a round of low oxygen in a hypobaric setting. Martin said: “Hypobaric is unpleasant. It’s a windowless steel tube. We were at altitude for 72 days I would not have liked to sit in a tube for 72 days.”

Neither was it practicable. A large chamber study would have risked some people suffering the bends, he added. Even so, the team spent two years using this environment to measure their equipment’s efficiency in preparation for the trip.

They encountered scepticism along the way. The team was thought to be “a bit mad,” so they could not seek funding through the normal routes. Eventually the gas/oxygen company BOC provided finance, even through, ironically, their research was about the lack of it.

Martin’s “madness” extends to his physiological reaction to hypoxia. It’s very rare to gain weight at altitude. Most people shed kilograms, mainly due to a dramatic loss of muscle density (often 30%), despite a daily diet of up to 6000 calories, including eating neat butter to keep the weight on.

But Martin, as well as recording a 34% arterial blood sample hypoxia reading (something most doctors would never see in a hospital patient), gained 3kg.

The team also hauled exercise bikes up the mountain, to test metabolic efficiency, in a similar way to Olympic athletes training at high altitudes to make them more efficient when the perform closer to sea level.

The research team’s goal, given that oxygen is highly toxic, is to see if a hypoxic patient’s physiology can somehow be altered to enable them to survive better in a critical care setting.

Elsewhere in the animal kingdom, for example, mammals “switch their bodies into different modes” to handle low-oxygen environments.

So what’s the next step? For Martin, it’s moving beyond an observational study to an intervention or pharmacological one.

But might sherpas, who regularly function at high altitudes, hold the key?

Martin told the meeting: “From the few experiments that have been done on sherpas they don’t carry any more oxygen than we do. If sherpas become ill in ITU we expect them to do better.

Why was their arterial blood and muscule tissue not sampled on the summit? “They were very keen for us to take their blood but we couldn’t for ethical reasons,” explained Dan.

David Payne is editor, bmj.com and doc2doc.bmj.com

Everest also featured in the Christmas 2008 BMJ:

Mortality on Mount Everest, 1921-2006: descriptve study

Voices in the air

Christmas 2008 BMJ podcast

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  • Matiram Pun

    Hi David,

    Thanks about feature the research on Everest and Hypoxia from third in the history and so far most technically sophistical medical and physiological research expedition on Everest (http://www.xtreme-everest.co.uk/)!

    The arterial blood gas that you talked was published in New England Journal of Medicine (http://content.nejm.org/cgi/content/abstract/360/2/140) last year.

    The expedition was all featured in BBC Horizon where team leader Mike Groccott and other many prominent and important research team members lik Dan, Sandeep, Jeremy are seen all the way up, down and research interventions.

    The spectrum of hypoxia research and implications is really broad. As you pointed out people from there likes of Sherpa could give some clue.

    Obviously, we need more research in the field to understand physiology and pathophysiology. Then the interventional studies will provide some direct implications as well.

    Thanks,
    mati

    Competing Interest: I’m the research group member of the Expedition.

  • Matiram Pun
  • http://www.bmj.com David Payne

    Thanks Mati – they mentioned the Horizon programme at the event. I’ll check out the link.

  • Siddhartha Yadav

    Hi David,

    Interesting blog.

    Coincidently, Jeremy Windsor, who is one of the researchers of the Extreme Everest Study published in NEJM and the Everest mortality study published in BMJ, was here in Kathmandu this week and I was able to listen to his talk on these studies. Fascinating research that could hold answer to a lot of questions on hypoxia. And indeed, Everest can serve as one of the biggest natural labs for research on hypoxia.

    Thanks for sharing this.

    Best wishes,
    Siddhartha

  • Matiram Pun

    Hi Sid,

    That’s great Jeremy was there and the Mountain Medicine Society of Nepal (www.mmsn.org.np) did great job for that UIAA Medcom meeting there (http://www.mmsn.org.np/index.php?option=com_content&view=article&id=67:15th-to-17th-nov-the-international-mountaineering-and-climbing-federations-uiaa-medical-committees-meeting-in-nepal&catid=36:activities&Itemid=55).

    Excellent work!

    Best wishes,
    mati

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