Article #5 Describing the Pathophysiology of
Altitude Sickness and Comparing the
Efficacy of Prophylactics – A Review
Describing the
Pathophysiology of
Altitude Sickness
and Comparing
the Efficacy of
Prophylactics – A
Review Abstract
The primary effects of high altitude on humans are the result of
a reduction in available oxygen concomitant with decreased air
pressure. When oxygen partial pressure drops below 60mmHg,
there is a steep decline in oxygen saturation potentially
compromising oxygen delivery to tissues. Reduced uptake of
oxygen in the tissues due to rapid ascent to high altitude often
results in the development of altitude sickness. Acclimatisation
can allow time for physiological adaptations to take place to
sustain adequate oxygen levels in the body to meet metabolic
demands. Chemo-prophylactics such as acetazolamide and
dexamethasone can also be used to reduce the risk of developing
altitude sickness, and supplementary oxygen can be used to
maintain higher oxygen partial pressures outside the body. This
paper explores the key pathophysiology of altitude sickness, and
compares the efficacy of some available prophylactic treatments
for altitude sickness prevention.
Author: Nea Sneddon-
Jenkins
Keywords:
oxygen delivery;
altitude sickness;
acclimatisation;
hypobaric hypoxia
Key Words: oxygen delivery; altitude sickness; acclimatisation;
hypobaric hypoxia
Introduction
Altitude sickness is defined as the maladaptive physiological
effects of high altitude that can develop in individuals shortly after
ascent. Whilst the precise elevation at which onset of altitude
sickness occurs is widely disputed, the Lake Louise Consensus
Group provides a definition in which altitudes of above 2500m
may result in the onset of acute mountain sickness (AMS) – the
most-mild form of altitude sickness (Williamson et al., 2018). In
one 1993 study, questionnaires were administered to 3158 adult
travellers within 48hrs of arrival at elevations of 2000-3000m
in order to determine the incidence of altitude sickness. and
an incidence of 25% for AMS was observed in the participants.
The data also suggested that incidence of altitude sickness
was increased 3.5-fold in individuals travelling from permanent
residences at elevations lower than 1000m and that individuals
with a previous history of altitude sickness have an increased
susceptibility to future episodes of 2.8 times the susceptibility
of the general population (Honigman et al., 1993). The more
severe forms of altitude sickness – high-altitude pulmonary
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