Download - Society for Cardiothoracic Surgery

July 2010 23
Professor Chris Imray PhD FRCS FRCP
UHCW NHS Trust, Coventry and Warwick Medical School
Lhotse Face
acclimatise
elsewhere on
safer ground, so
that we could
move through
the icefall more
quickly.
‘Coffee, tea or French onion soup?’ was the
question Sundeep asked me, as we settled
into Camp 3, perched halfway up the
Lhotse Face at about 7,100m. The Face is a
1,500m (4,500ft) ice and snow slope
angled at between 40-50 degrees. Our
campsite (!) was a narrow strip of
horizontal space and had been carved out
of the steep ice and snow slope by our
sherpas. On the one side blocks have been
cut out of the slope, and on the other the
blocks have been used to build up a ramp
to give a six foot wide horizontal terrace to
place our tent.
South Col
On first arrival, the South Col had a
deceptively benign appearance. In the sun
and without any wind, it was warm enough
for T shirts. It was only later when the sun
set and the wind picked up that we began
to appreciate the true harshness of the
place. Temperatures plummeted to as low
as -35C, and with oxygen levels 1/3 of
those found at sea level, we began to
appreciate what was meant by the term the
‘death zone’. At this altitude, the body is
deteriorating all the time, and life is
unsustainable for any length of time.
Without oxygen even the simplest of tasks
such as brushing ones teeth took on
gargantuan proportions, requiring a rest to
complete the task.
Most teams arrive at the South Col in the
early afternoon, they then spend a few
hours rehydrating and
sleeping before setting off
on their summit attempt
somewhere between
9.00pm and midnight. Our
plan was different; we had
the most ambitious range
of scientific experiments
ever undertaken at this
altitude to undertake in the
world’s highest ‘laboratory’
on the South Col (8000m).
We spent a day setting up
equipment, followed by two days of
experiments ranging from cerebral
perfusion studies to maximal bicycle
exercise tests. At rest and off supplemental
oxygen our blood oxygen saturations were
between 48-56%, (normally 99%) and with
exercise these levels dropped further,
understandably our bodies were
deteriorating continuously. In total, we
spent 5 nights on the South Col- we believe
this is the longest anyone has ever spent
there.
The results so far
One of the questions asked is ‘Have we
learnt any lessons for critically ill patients?’
Although much data is still in the process
of being analyzed there are some
interesting and potentially important
messages emerging from the preliminary
data.1,2,3 Perhaps the most notable being
expedition leader Mike Grocott’s paper in
the NEJM on arterial blood gases and
oxygen content in climbers on Mount
Everest. It demonstrated that individuals
appear to be able to function reasonable
normally (!) with exceptionally low arterial
blood oxygen levels. Four of us underwent
femoral arterial stabs at 8,400m, and a
sherpa ‘ran’ these down to Camp 2 at
6,400m for analysis. This descent took us
two days, but Pasang managed it in two
hours -with time for tea at the South Col!
‘‘In four samples taken at 8400 m (27,559
ft)-at which altitude the barometric
pressure was 272 mm Hg (36.3 kPa)-the
mean PaO2 in subjects breathing ambient
air was 24.6 mm Hg (3.28 kPa), with a
range of 19.1 to 29.5 mm Hg (2.55 to 3.93
kPa). The mean PaCO2 was 13.3 mm Hg
(1.77 kPa), with a range of 10.3 to 15.7 mm
Hg (1.37 to 2.09 kPa).’’1
Conclusions
The mountain was climbed, everyone
returned home safely, and
great friendships were forged.
Judged by conventional
criteria Mike Grocott has lead
one of the most successful
Everest expeditions ever. On
the research side, tantalizing
initial insights into the
pathophysiology of hypoxic
‘healthy’ individuals and the
critically ill are beginning to
emerge. However, perhaps
the most remarkable aspect
of the expedition were the incredible
sherpas. With enormous good grace and
humour they performed amazing physical
feats often in a very dangerous
environment under extreme hypoxia.
Surely their genetic and physiological
adaptation offers the most obvious line of
research in trying to understand to the
response of humans to extreme hypoxia?
Acknowledgements
The expedition was supported by Mr. John
Caudwell, BOC Medical (now part of Linde Gas
Therapeutics), Eli Lilly, the London Clinic, Smiths
Medical, Deltex Medical, and the Rolex Foundation,
the Association of Anaesthetists of Great Britain
and Ireland, the United Kingdom Intensive Care
Foundation, and the Sir Halley Stewart Trust.
Caudwell Xtreme Everest is a research project
coordinated by the Centre for Altitude, Space, and
Extreme Environment Medicine, University College
London. Membership, roles, and responsibilities of
the Caudwell Xtreme Everest Research Group can
be found at: www.caudwell-xtremeeverest.co.uk/team.
1. Grocott MP, Martin DS, Levett DZ, McMorrow R,
Windsor J, Montgomery HE; Caudwell Xtreme
Everest Research Group. (Collaborator and
Subject 3) Arterial blood gases and oxygen
content in climbers on Mount Everest. New
England Journal of Medicine. 2009 Jan
8;360(2):140-9.
2. Firth PG, Zheng H, Windsor JS, Sutherland AI,
Imray CH, Moore GW, Semple JL, Roach RC,
Salisbury RA. Mortality on Mount Everest, 1921-
2006: descriptive study. British Medical
Journal. 2008 Dec 11; 337: a2654. doi:
10.1136/bmj.a2654.
3. Wilson MH, Newman S, Imray CH. The cerebral
effects of ascent to high altitudes. Lancet
Neurology. 2009 Feb; 8(2):175-91.