GUEST EDITORIAL
Recognising and mitigating the risk of altitude-related illness
only approach 6 kPa (Fig. 1). This is less
than half of the sea level value, despite adequate acclimatisation. Values <3 kPa have been
recorded in healthy climbers on Everest.[9]
The only reliable preventive measure to
combat HAI is a slow rate of ascent to altitude,
allowing adequate time for physiological
acclimatisation. While most healthy individuals can acclimatise up to 5 500 m, HAI
can be induced in any individual if the rate
of ascent is sufficiently rapid. Contrary to
common beliefs, youth, physical and aerobic
fitness, gender and previous ascent to high
altitudes offer no protection.[7] Medications
such as acetazolamide (Diamox) may hasten
acclimatisation, but still require a suitably slow
ascent profile to have a protective effect.[3]
Numerous evidence- and consensus-based
guidelines for safe ascent rates and acclimatisation exist,[8,10,11] but are not uniformly applied.[5]
Typically, above 3 500 m, an increase in sleeping altitude of ≤500 m/day is recommended,
with a rest day for each 3 - 4 days’ climb. The
old climber’s adage ‘climb high, sleep low’
may confer an advantage, but this has not
been proven in the literature. While most
of the world’s highest peaks lie deep within
wilderness areas and require a lengthy trek
to reach (and therefore time for acclimatisation), Kilimanjaro is a particularly important
exception. As the world’s highest free-standing mountain, it allows rapid ascent from the
surrounding lowlands (<700 m). Conversely,
the absence of requirement for technical
climbing skills to gain the 5 895 m summit,
combined with the allure of one of the Seven
Summits, draws >30 000 aspirant summiteers
every year – many of whom have never before
experienced extreme altitudes. While the
trekking distances required make reaching
the summit in 3 - 4 days easily achievable,
acclimatising to nearly 6 km above sea level
cannot occur in such a short time. Itineraries
of 4 - 5 days have rates of AMS >75%,[4] while
Metres
above
sea level
9 000
Alveolar
partial
pressure of
oxygen (kPa)
Minimum
ascent
rate (days)
3
30
4
10
5
7
6
2
7
2
Everest
Extreme altitude
8 848 m
8 000
Aconcagua
6 961 m
7 000
Very high altitude
6 000
Kilimanjaro
5 895 m
5 000
Mont Blanc
4 808 m
4 000
Thabana Ntlenyana
3 482 m
High altitude
The recent tragic and widely publicised death
of South African (SA) celebrity Gugu Zulu
on Mount Kilimanjaro has drawn significant
public interest and speculation about the
risks of high-altitude trekking and climbing.[1] It has also demonstrated numerous
myths and misconceptions with regard to
safe high-altitude ascents among not only
the lay public, but also medical professionals.
Kilimanjaro is of particular relevance, as it
has a very high incidence of altitude-related
illnesses.[2-5] Regardless of the details of the
Zulu tragedy, a great number of southern
Africans undertake treks on Kilimanjaro each
year. We have a responsibility to improve
understanding and access to medically sound
advice for prospective adventurers, and to
encourage tour operators to plan and market
adventure activities that mitigate the risks to
participants.
While the proportional composition of the
atmosphere remains remarkably consistent,
ambient pressure decreases logarithmically
with ascent, causing a corresponding decrease
in the partial pressure of oxygen (PO2).[6]
The physiological effects of altitude are
predominantly due to the resultant hypoxia
and hypobaria. High altitude is defined as
>1 500 m above sea level, where the physiological effects of altitude may first be
consistently observed, but pathological
consequences are very rare.[7] At this level,
the alveolar partial pressure of oxygen (PAO2)
is ~10 kPa, compared with the sea level value
of 13 kPa. It is worth noting that large areas
of SA, including the extensive metropolitan
areas in Gauteng, therefore qualify as highaltitude areas. Above 3 500 m is referred to
as very high altitude, above which immediate
compensatory mechanisms no longer suffice,
acclimatisation over time is required, and the
incidence of acute high-altitude illness (HAI)
due to rapid ascent increases dramatically. This
can include the syndrome complex known
as acute mountain sickness (AMS), or the
more severe and life-threatening conditions,
high-altitude cerebral or pulmonary oedema
(HACE or HAPE). While uncommon, cases
have occurred in the Drakensberg mountains
(authors’ experience). Altitudes >5 500 m are
referred to as extreme altitudes. Exposure to
these levels without gradual acclimatisation
will almost certainly result in severe illness.[8]
At the top of Kilimanjaro (5 895 m, barometric
pressure ~47 kPa), atmospheric air has a
PO2 of only 9.4 kPa and the alveolar gas
equation predicts that even with maximal
hyperventilation and hypocarbia, the PAO2 can
3 000
Drakensberg
3 000 m
2 000
8
Johannesburg
1 760 m
1 000
10
Table Mountain
1 084 m
11
13
Sea level
Fig. 1. Relative heights of well-known African and international peaks in comparison to Kilimanjaro,
with approximate PAO2 values and minimum duration of safe ascents (drawing by the authors, PAO2
values calculated).
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September 2016, Vol. 106, No. 9
GUEST EDITORIAL
HACE incidence has been reported as 18%.[2] Indeed, consensus
statements in the wilderness medical literature indicate that ascents
of <7 days carry very high risks.[10] In contrast to this lies the commercial imperative: every day on Kilimanjaro incurs additional guiding, porter, camping, national park and rescue fees, all of which create
a perverse incentive to hurry, imposed by the almighty dollar. This is
further compounded by the pressure placed on the guides by companies and climbers alike, for whom summit success is paramount.
It is important to recognise that AMS symptoms are nonspecific
(headache, nausea, vomiting, gastrointestinal upset, fatigue and
poor sleep) and mimic common conditions such as influenza.[12]
HAI is very rare below 2 500 m, but any new symptoms occurring
after ascent above 3 500 m should be presumed to be altitude
related until proven otherwise. Mild AMS can be managed
by temporarily halting ascent, simple analgesia and hydration.
Moderate to severe AMS (or any evidence of HACE or HAPE)
should result in immediate descent until symptoms subside.
Adherence to these simple guidelines should minimise the risk of
an altitude-induced death.
Mountaineers on expeditions on remote peaks traditionally
make provision for the risk of altitude illness by allowing time for
acclimatisation, and carrying suitable supplies for treatment if such
illness should occur. While medication and descent are the mainstay
of altitude illness, supportive therapy with supplemental oxygen and
portable hyperbaric chambers can be lifesaving, especially in cases
where descent is delayed or impossible owing to weather or logistical
difficulties. Despite the relative accessibility of Kilimanjaro, and while
many tour operators claim to offer their services, the varying level
of medical skills and number of groups spread across the mountain
make availability questionable. Reliance on helicopter rescue in this
region, even without the limits of altitude, weather, and darkness, is
inadvisable.
Historically, mountaineering expeditions have been medically
supported by recreational mountaineers who are doctors and
who may have very varied backgrounds and medical skills. In
recent times, however, the importance of providing high-quality,
evidence-based practice in wilderness, remote and austere settings
has driven the development and rapid growth of the disciplines
and formal education in wilderness, expedition and extreme
medicine.[13] Examples include the Fellowship of the Academy
of Wilderness Medicine (FAWM)[14] under the auspices of the
Wilderness Medical Society (WMS), and the Diploma in Mountain
Medicine (DiMM),[15] under the auspices of the International
Climbing and Mountaineering Federation (UIAA). As practice
has evolved, published standards for the education, skills and
proficiencies of expedition medics have emerged.[16,17] Until very
recently, these educational opportunities have not been available
in SA. Currently, however, internationally accredited training
courses are being offered, and a Wilderness and Expedition
Medicine Society of Southern Africa (WEMSSA) has been formed.
Owing to the accessibility and popularity of climbing Kilimanjaro
and other African peaks, practitioners should recognise the significant
risks of very high altitude ascents and refer participants to accepted
guidelines and expedition or altitude experts. Doctors wishing to
serve as expedition medics should undertake formal training and
obtain experience in the field, whether their role is voluntary or for
remuneration. Large or specialist groups (such as charity events) are
encouraged to request the services of an experienced and qualified
expedition doctor, who can oversee planning, screening, equipment
835
and the health of participants on the expedition. Finally, the medical
fraternity should continue to advocate that individuals do not shy
from the health benefits to be
gained from the wilderness, while
promoting adequate acclimatisation
for high-altitude adventures and
actively campaigning against
itineraries placing participants at
heightened risk.
Ross Hofmeyr
Department of Anaesthesia and
Perioperative Medicine, Faculty of
Health Sciences, University of Cape
Town; and WildMedix, Cape Town,
South Africa
Walther Meyer
WildMedix, and Venture Forth International, Cape Town, South Africa
Mike James
Department of Anaesthesia and Perioperative Medicine, Faculty of
Health Sciences, University of Cape Town, South Africa
Rik De Decker
Division of Paediatric Cardiology, University of Cape Town, and Red
Cross War Memorial Children’s Hospital, Cape Town, South Africa;
and International Commission for Alpine Rescue, Kloten, Switzerland
Corresponding author: R Hofmeyr (ross.hofmeyr@uct.ac.za)
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bbc.com/news/world-africa-36823937 (accessed 10 August 2016).
2. Karinen H, Peltonen J, Tikkanen H. Prevalence of acute mountain sickness among Finnish trekkers
on Mount Kilimanjaro, Tanzania: An observational study. High Alt Med Biol 2008;9(4):301-306.
DOI:10.1089/ham.2008.1008
3. Davies AJ, Kalson NS, Stokes S, et al. Determinants of summiting success and acute mountain sickness on Mt
Kilimanjaro (5 895 m). Wilderness Environ Med 2009;20(4):311-317. DOI:10.1580/1080-6032-020.004.0311
4. Jackson SJ, Varley J, Sellers C, et al. Incidence and predictors of acute mountain sickness among
trekkers on Mount Kilimanjaro. High Alt Med Biol 2010;11(3):217-222. DOI:10.1089/ham.2010.1003
5. Shah NM, Windsor JS, Meijer H, Hillebrandt D. Are UK commercial expeditions complying with
wilderness medical society guidelines on ascent rates to altitude? J Travel Med 2011;18(3):214-216.
DOI:10.1111/j.1708-8305.2011.00511.x
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2015;115(6):824-826. DOI:10.1093/bja/aev151
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DOI:10.1016/j.emc.2004.02.001
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NEJM200107123450206
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Everest. N Engl J Med 2009;360(2):140-149. DOI:10.1056/NEJMoa0801581
10. Luks AM, McIntosh SE, Grissom CK, et al. Wilderness Medical Society practice guidelines for the
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Suppl):S4-S14. DOI:10.1016/j.wem.2014.06.017
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treatment. Prog Cardiovasc Dis 2010;52(6):467-484. DOI:10.1016/j.pcad.2010.02.003
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S, Roach RC, eds. Hypoxia and Molecular Medicine. Burlington, VT: Queen City Printers, 1993:272-274.
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15. International Climbing and Mountaineering Federation/International Commission for Alpine Rescue/
International Society for Mountain Medicine. UIAA Diploma in Mountain Medicine 2016. http://
theuiaa.org/mountain-medicine-diploma.html (accessed 10 August 2016).
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DOI:10.1186/s13728-015-0041-x
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