REVIEWS
PHYSIOLOGY 31: 216 –222, 2016. Published April 6, 2016; doi:10.1152/physiol.00057.2015
Oxygen Conditioning: A New Technique
for Improving Living and Working at
High Altitude
John B. West
Department of Medicine, University of California San Diego,
La Jolla, California
[email protected]
Large numbers of people visit, work, or reside at high altitude. The inevitable
hypoxia reduces physical performance and, in many instances, impairs neuropsychological function. The new technique of oxygen conditioning raises the
oxygen concentration in the air of buildings such as homes, schools, and
hospitals. The result is to decrease the equivalent altitude and improve both
physical and cognitive performance.
Deleterious Effects of the Hypoxia
of High Altitude
The physiological consequences of the hypoxia of
high altitude on the human body are legion. However, from the point of view of oxygen conditioning, they can be divided into impairment of
physical activity on the one hand, and cognitive or
neuropsychological impairment on the other. In
addition, it is useful to divide the people at high
altitude into three groups: visitors, sojourners, and
permanent residents.
Visitors
This group includes skiers, trekkers, tourists, and
climbers, who typically spend 1 or 2 wk, or perhaps
1 mo at high altitude.
Physical impairment. Everyone who has been to
high altitude is aware that physical performance is
reduced. The usual way to assess maximum aerobic activity is the maximal oxygen consumption
(V̇O2 max). FIGURE 1 shows V̇O2 max plotted against
altitude up to an altitude of ⬃6,000 m. There is
216
relentless fall in the V̇O2 max, with the result that, at
an altitude of 6,000 m, it is ⬃40% of the sea level
value (3). Measurements made on acclimatized
subjects breathing a gas with a PO2 corresponding
to the summit of Mt. Everest show that the V̇O2 max
is reduced to ⬃20% of the sea level value (16).
In FIGURE 1, the measurements made during
acute hypoxia are shown by open circles, and those
made in acclimatized subjects are shown by solid
circles. In these data assembled by Cerretelli, the
measurements for subjects acutely exposed to hypoxia and for those who are acclimatized fall on the
same line. In fact, in the text accompanying the figure, Cerretelli stated, “it is practically impossible to
find any difference in maximal performance between
subjects acutely exposed to mild hypoxia and those
acclimatized to it.” However, some studies have
shown that acclimatization does improve the V̇O2 max
to some extent (1, 12, 20).
Neuropsychological function. There is a large
body of data documenting impaired neuropsychological function in visitors to high altitude. For a
recent review, see Yan (23). Various tasks have
been tested, such as digit span, number and
letter sequence recognition, working memory
tasks, pattern completion tasks, card-sorting
tasks, word-association tasks, verbal fluency,
spatial working memory, and decision making (2,
9, 20, 24). In general, the impairments are found
to be more severe as the altitude is increased.
However, some neuropsychological impairment
has been identified at quite low altitudes, such as
1,500-2,500 m (2, 4).
Sojourners
This group is not as large as that of the visitors or
permanent residents. However, it is important because members of this group are likely to benefit
greatly from oxygen conditioning. By sojourners,
we mean people who come from low altitude but
find themselves at high altitude to work or to live.
Many are people connected with mines at high
1548-9213/16 ©2016 Int. Union Physiol. Sci./Am. Physiol. Soc.
Downloaded from http://physiologyonline.physiology.org/ by 10.220.32.246 on June 15, 2017
This article describes a novel technique that, in
effect, transports high-altitude personnel to a
lower altitude. It is called oxygen conditioning,
which emphasizes the analogy to air conditioning.
Air conditioning works by reducing the temperature of the air that is circulated to rooms where
people live and work. Oxygen conditioning does
the same, except that, instead of reducing the temperature of the air, it increases the oxygen concentration. This requires the generation of large
amounts of oxygen, but this technology is now
available. Oxygen conditioning promises to change
the living and working conditions of large numbers
of people at high altitude just as air conditioning
has done the same thing for millions of people who
live in hot climates. To understand the potential of
oxygen conditioning, it is first necessary to discuss
the negative effects of high altitude on the body.
REVIEWS
logical function, much work remains to be done
(7, 21, 22).
Physical ability. Some permanent residents of
high altitude exhibit extraordinary physical prowess. For example, Sherpas in Nepal have reached
the summit of Mount Everest over 20 times. The
load-carrying ability of Sherpas at high altitude is
also often remarked on.
However, there is incontrovertible evidence that
high-altitude permanent residents are no different
from visitors in that they reduce their V̇O2 max at a
higher altitude, and, by the same token, they increase their V̇O2 max at a lower altitude. This is
indicated in FIGURE 1 where the crosses and the
asterisk near the bottom of the line show data from
permanent high-altitude residents. It can be seen
that the data fall on essentially the same line as
people acutely exposed to high altitude, as indicated by the open triangles.
In one of the studies included in FIGURE 1, the
V̇O2 max of nine young men who were permanent
residents of Morococha, Peru, altitude of 4,540 m,
was measured on a treadmill while they were
breathing ambient air. Measurements were also
made when the inspired PO2 was equivalent to an
altitude of 6,400 m and also to sea level. The results
were essentially the same as those reported in the
literature for sea-level residents (5) and are indicated by the cross near the bottom of the line in
FIGURE 1. Another more recent study on 50
healthy young men born and living in La Paz, altitude of 3,600 m, showed that they increased their
V̇O2 max when the inspired PO2 was raised to that of
sea level (6). Consistent with their studies, it is well
Downloaded from http://physiologyonline.physiology.org/ by 10.220.32.246 on June 15, 2017
altitude, particularly in Peru and Chile, where the
dormitories are as high as 4,200 m. Most of these
people are highly skilled because they are responsible for operating large pieces of equipment such
as enormous trucks and excavators. Essentially all
of these people come from low altitude, and they
will find sleeping at an altitude of 4,200 m very
difficult (15).
In addition to this group, there are many people
at high altitude who work in other places such as
telescope facilities, schools, hospitals, embassies,
banks, and other institutions. For example, the
ALMA telescope in north Chile at an altitude of
5,000 m employs ⬃400 people on the site. A few of
these people come from families living at high
altitude, but the majority are from low altitude.
Sojourners typically spend several years at high
altitude.
Physical impairment. There have been few
studies of sojourners at high altitude, but all the
evidence suggests that their physical abilities are
similar to those of acclimatized newcomers. As
noted earlier, FIGURE 1 shows that, on a plot of
V̇O2 max against altitude, people who are acclimatized fall on the same line as those who are acutely
exposed to hypoxia. Other anecdotal evidence supports this. For example, the physiologists who took
part in the Silver Hut Expedition of 1960 –1961 and
who spent up to 5 mo at an altitude of 5,800 m
showed essentially no improvement in their tolerance to high altitude in terms of physical activity
over the period of residence (10).
Neuropsychological function. Again, there are
few formal studies of this in sojourners at high
altitude, but the evidence indicates that it is similar
to acclimatized newcomers. For example, in one
investigation on Indian soldiers ranging in age
from 21 to 30 years who were taken from near sea
level to an altitude of 4,000 m and remained there
for 2 years, psychomotor performance was measured over the whole period. The measurements
included speed and accuracy by a hand-eye coordination test, in which a stylus was moved in a
narrow groove so that it did not touch the sides. It
was found that both speed and accuracy were impaired on arrival at high altitude and that this
finding remained over the whole period of 24 mo,
although there was some improvement toward the
end of that time (13).
Permanent Residents
It is often assumed that permanent residents of
high altitude are completely adapted to their situation. Many have been at high altitude for generations, and they carry on living and working much
as people do at low altitudes. However, recent
studies have questioned these assumptions, although, particularly in the area of neuropsycho-
FIGURE 1. V̇O2 max plotted against altitude
Open symbols, acute hypoxia; solid symbols,
chronic hypoxia; crosses, permanent residents of
high-altitude. The number of subjects is shown in
parentheses. Figure adapted from Ref. 3 and used
with permission from Academic Press.
PHYSIOLOGY • Volume 31 • May 2016 • www.physiologyonline.org
217
REVIEWS
but had relocated to the lower altitude of ⬍400 m for
at least 1 year. The low-altitude group resided at an
altitude of ⬍400 m where the measurements were
made. Considerable effort was made to match the
two groups. First, they were all from the Han ethnic
group and matched for age. Both groups had the
same socio-economic status in that they were both
from middle-class families. The hemoglobin levels
were the same.
Studies included a verbal working memory task
involving block letters that the participants were
very familiar with and basically consisted of
whether each presented letter was the same as the
one presented two stimuli previously. The results
showed that, using an independent two-sample
t-test, the high-altitude group had a significantly
longer reaction time and lower accuracy than the
sea-level group, as seen in FIGURE 2. Measurements were also made using fMR to determine the
activation in the precentral gyrus and other parts
of the brain. Group comparisons showed that the
high-altitude subjects had decreased activation in
various regions on the left side of the brain. Significant correlations were found between the neuropsychological measurements and the BOLD data
from the fMRI (22). Further studies on the same
groups of subjects showed that the high-altitude
residents also had reduced performance accuracy in a spatial working memory task (21). Another study showed that, when a lower-altitude
group spent about 7 mo at an altitude of 2,260 m,
this did not result in significant cognitive impairments (24).
An interesting study of a large group of 168 subjects consisting of infants, children aged 6 –10
years, and adolescents aged 13 -16 years was carried out in Bolivia at altitudes of 500, 2,500, and
3,700 m (7). The participants were well matched for
age and gender in their group. Socio-economic
status was thought to be comparable, with the
majority of participants being from families in the
middle to high social strata. A series of neuropsy-
FIGURE 2. Reaction times and response accuracy from a verbal working memory test in two
groups of college students who lived at high altitude (2,616 – 4,200 m) or near sea level
**Differences were significant at the P ⬍ 0.05 level. Figure adapted from Ref. 22 and used with permission
from Springer.
218
PHYSIOLOGY • Volume 31 • May 2016 • www.physiologyonline.org
Downloaded from http://physiologyonline.physiology.org/ by 10.220.32.246 on June 15, 2017
known that, when permanent residents of high
altitude move to a higher altitude, the amount of
work that they can do decreases. For example, this
is clearly seen when Sherpas carry loads at extremely high altitudes in the Himalayas.
The fact that the amount of physical work that
permanent residents of high altitude can do increases when they move to a lower altitude or
decreases when they move to a higher altitude is
hardly surprising. Any change in altitude will alter
the PO2 of the body tissues, with other things being
equal, and this includes exercising muscle.
Neuropsychological function. We have seen
that the physical work capacity of permanent residents of high altitude is reduced compared with
that of low-altitude residents and that when highaltitude residents moved to a lower altitude, this
increases. Whether the same is true for neuropsychological function is one of the most challenging
issues that we need to consider.
First, it is obvious that neuropsychological function is much more difficult to measure than physical function. Also, assessing neuropsychological
function often raises issues of whether two populations are adequately matched. Factors such as
educational level and cultural background become
important. These considerations do not enter into
a comparison of physical ability. Finally, it is easy
to see that this topic could be controversial. To
argue that the millions of people who live permanently at high altitude would have improved cognitive function if they lived lower is obviously likely
to raise hackles.
Nevertheless, there is some evidence that people
who are born and raised at high altitude have reduced neuropsychological function compared with
a matched group at a lower altitude. In one study,
28 high-altitude residents were matched with 30
residents of low altitude, and some cognitive differences were detected (22). The high-altitude
group had been born and raised on the Tibetan plateau for ⬎18 years at an altitude of 2,616 – 4,200 m
REVIEWS
mo after descent from the Jungfraujoch, and the
impairment of function was no longer detectable.
The investigators summarized the principal findings as 1) short-term 24-h exposure to high altitude
markedly impairs verbal short-term memory, episodic memory, and executive functions in healthy
children; and 2) similar or even greater impairment
of these functions were detectable in children who
had been living at high altitude for at least 3 years.
Finally, it was speculated that learning new information at high altitude may be particularly difficult because not only the encoding but also the
retrieval processing is altered. The authors concluded that “based on these findings, the study of
the learning abilities of children born and permanently living at high altitude appears to be of utmost importance” (11).
Downloaded from http://physiologyonline.physiology.org/ by 10.220.32.246 on June 15, 2017
chological tests was carried out appropriate to the
age of the subjects. The tests included Wechsler
intelligence scale, visual-motor abilities; finger tapping test, and a behavioral screening questionnaire
for children aged 3–16 years. The conclusion was
that there was a minor reduction in motor and
cognitive processing speed with increasing altitude, with no effect of age. It was suggested that
this was due to a reduced cerebral blood flow velocity with increasing altitude.
An important study to determine whether exposure to high altitude results in cognitive dysfunction in young healthy European children was
recently carried out by a Swiss group (11). Three
groups of children and adolescents were tested.
One group was comprised of 48 healthy, non-acclimatized European children and adolescents who
were tested 24 h after ascending by train from an
altitude of 568 m to the Jungfraujoch (altitude of
3,450 m). The second group consisted of matched
Europeans living permanently at high altitude in
La Paz, Bolivia (altitude of 3,500 m). These children
had been living in La Paz for over 3 years, with the
high-altitude exposure beginning between the ages
of 6 mo and 6 years. A third control group consisted of children and adolescents living at the
altitude of ⬃580 m. It was stated that all participants had a similar educational level, and cultural
and socioeconomic background. In La Paz, the
parents of the children were mainly businessmen,
engineers, or embassy personnel.
The battery of neuropsychological tests included
assessment of executive functions (inhibition,
shifting, and working memory), memory (verbal
short-term, verbal episodic, and visual spatial
memories), and verbal speed processing ability.
Additional measurements include a trail making
test, a digit span task, a California verbal learning
test, and a Corsi block tapping test. The original
publication should be consulted for technical details (11).
The results were of great interest. It was found
that short-term hypoxia, that is the effect of the
ascent to the Jungfraujoch, induced significant impairment of five of the seven abilities that were
tested. Only the visual spatial memory and processing speed were not significantly changed. Remarkably, the alterations of cognitive function
were also present, or even significantly more severe, in children permanently living at high altitude. It was also found that executive functions
were markedly impaired at high altitude in La Paz.
For example, on the trail making test, the time
taken to complete part of this was ⬃20% longer.
Long-term high-altitude exposure in La Paz had
even more severe effects on memory abilities.
Measurements were also made on the children 3
Oxygen Conditioning at High
Altitude
Principle of Oxygen Conditioning
Oxygen is generated from atmospheric air using a
synthetic zeolite that preferentially adsorbs the nitrogen, and the oxygen that is obtained is added to
the air that is circulated in the building. Large
amounts of oxygen are required, but the technology has been developed in various industries such
as paper mills, wastewater treatment, fish farming,
and industrial chemistry. Modern oxygen concentrators can produce several thousand liters per
minute of 93% oxygen.
Power of Added Oxygen
A key feature of oxygen conditioning is the surprisingly large extent to which the equivalent altitude
can be reduced by adding oxygen to the air. The
equivalent altitude is that which has the same inspired PO2 during air breathing. For every 1% increase in oxygen concentration, that is, for
example, from 21 to 22%, the equivalent altitude is
reduced by ⬃300 m. In other words, if the oxygen
concentration is increased from 21 to 28%, the
equivalent altitude is reduced by ⬃2,100 m. As an
example, someone in La Paz (altitude of 3,650 m)
can have the altitude reduced to 1,610 m, that is
the altitude of Denver, by raising the oxygen concentration to 27%, as shown in Table 1. Details on
how to calculate the equivalent altitude from the
actual altitude and oxygen concentration have
been published (19).
Possible Fire Hazard
People who first hear about this procedure often
raise the issue of fire hazard. This is an important
topic and has been extensively studied by the National Fire Protection Association (8). However, it
should be emphasized that, although the PO2 in the
PHYSIOLOGY • Volume 31 • May 2016 • www.physiologyonline.org
219
REVIEWS
Table 1. Some of the highest towns or cities in the world, with examples of how the equivalent altitude can be reduced by
oxygen conditioning
Name
Country
Approximate
Population
Altitude, m
Equivalent Altitude With
Oxygen Conditioning, m
O2 Concentration, %
La Rinconada
Cerro de Pasco
El Alto
Lhasa
La Paz
Leadville
Peru
Peru
Bolivia
China
Bolivia
U.S.
7,000
75,000
1,000,000
370,000
850,000
2,580
5,100
4,300
4,150
3,650
3,650
3,094
2,400
2,000
2,000
1,610
1,610
1,610
30
28
28
27
27
24
The equivalent altitude is that where the PO2 is the same during air breathing. The first four columns are self-explanatory; the fifth column shows
examples of lower equivalent altitudes; and the last column shows the oxygen concentration in the air to produce these. The altitude of Denver,
CO is 1,610 m, where the hypoxia of high altitude is easily tolerated.
Oxygen Enrichment of Room Air
Oxygen conditioning on a small scale has been in
use for some 20 years. This procedure is called
oxygen enrichment of room air and consists of
adding oxygen to the ventilation of one or several
rooms (18). For example, some astronomers at an
altitude of 5,000 m in north Chile are living and
working in an atmosphere of 28% oxygen, which
reduces the equivalent altitude to ⬃2,900 m. The
same technique is used in some luxury hotels and
ski resorts at high altitude (19). Oxygen conditioning as described here can be regarded as an enhanced form of oxygen enrichment.
Chinese Train to Lhasa
There is already one remarkable example of oxygen
conditioning at high altitude, which is in the Chinese train from Golmud in Qinghai Province to
Lhasa, the capital of Tibet. The train passes
through an altitude of 5,072 m, which would result
in severe hypoxia for the passengers in the absence
of added oxygen. However, each passenger car has
an oxygen generator that raises the concentration
in the air to 24 –25%. There are 16 passenger cars in
a typical train, with a total of over 900 passengers,
so this is oxygen conditioning on a large scale.
However, the procedure is not central oxygen conditioning as promoted in this article but rather
conditioning of individual passenger cars. It is
analogous to using window air conditioners in an
apartment block rather than a central air conditioning system as in large institutions.
Economics of Oxygen Conditioning
FIGURE 3. Oxygen conditioning diagram
Equivalent altitudes are shown for the actual altitudes and the
oxygen concentration in the air. Note that the bottom section
of the diagram below the broken line is not available because
of the National Fire Protection Agency guidelines. Figure
adapted from Ref. 17.
220
PHYSIOLOGY • Volume 31 • May 2016 • www.physiologyonline.org
An important issue is the cost of oxygen conditioning, especially for large institutions such as schools
and hospitals. This is a complex issue that needs
more space than is available here. However, an
example will show the feasibility on a smaller scale.
Suppose we wish to oxygen condition an embassy
in La Paz, altitude of 3,650 m. (On a personal note,
I met several people from the U.S. Embassy in La
Paz some years go, and they all complained about
the altitude.) The equivalent altitude can be reduced to that of Denver by raising the oxygen
concentration to 27.3%. Equipment is now available to generate up to 1,500 or even 5,000 l/min of
93% oxygen (PCI Gases, Riverside, CA, models
DOCS 1500 and 5000). When this oxygen is mixed
with air, the resulting ventilation is more than
enough to provide any reasonably sized building
with the required oxygen concentration, and the
running costs are apparently not much greater
Downloaded from http://physiologyonline.physiology.org/ by 10.220.32.246 on June 15, 2017
air is increased by oxygen conditioning at altitude,
it is always less than the PO2 in air at sea level. The
reason for this is that the barometric pressure is so
low. The important message is that the equivalent
altitude can be safely reduced substantially. Table
1 lists the altitudes of several high cities in the
world, with the oxygen concentrations required to
reduce the equivalent altitude to acceptable levels
while not incurring a fire hazard. FIGURE 3 shows
the equivalent altitudes plotted against the actual
altitudes for different acceptable oxygen
concentrations.
REVIEWS
than those of air conditioning a similar building in
a hot climate such as that of Houston in the summer. For example, assuming an electricity cost of
$0.1/kWh, the cost of running the concentrator
producing 1,500 l/min for an 8-h day is less than
$40.
Who Would Benefit From Oxygen
Conditioning?
Downloaded from http://physiologyonline.physiology.org/ by 10.220.32.246 on June 15, 2017
We need to separately consider visitors, sojourners,
and permanent residents. The earlier discussion
indicated that visitors to high altitude would certainly benefit from oxygen conditioning. For example, high-end condominiums or hotels in ski
resorts with oxygen conditioning would ensure a
better night’s sleep for guests. A particularly important category is the sojourners who come from
low altitude but have located at high altitude to live
or work. Many of these are people associated with
high-altitude mines. For example, the new mine at
Toromocho, where the living accommodation is at
⬃4,200-m altitude, would benefit greatly from oxygen conditioning. However, definite benefit also
would be obtained at more moderate attitudes
such as that of La Paz at 3,650 m. Also, people from
low altitude who are working in corporations such
as banks and embassies would certainly benefit.
When we turn to permanent residents of high
altitude, the situation is less clear. As discussed
earlier, there is evidence that some high-altitude
residents have reduced cognitive function compared with a matched group living at a lower altitude. However, this does not necessarily mean that
oxygen conditioning homes and workplaces at
high altitude will improve the neuropsychological
function of permanent residents. It is possible that
growing up at high altitude is an important factor
in the reduced cognitive function. Furthermore,
even if moving to a lower altitude results in improvement, we have no data yet on how long this
process takes.
However, it seems that schools would be an important group if, as indicated above, cognitive
function for children of school age is accelerated at
a lower altitude. Hospitals also would be obvious
candidates because it is reasonable to assume that
essentially all sick patients would benefit from being at a lower altitude with an increase in their
tissue PO2. We can also expect that a surgeon’s
dexterity would be improved in some instances. In
general, since the evidence shows that cognitive
function is improved, at least in sojourners, all sites
where important decisions are being made would
be appropriate. This would include the boardrooms of corporations, embassies, banks, and legal
institutions. The application of this new technology appears to be very extensive. All people who
live or work in very hot climates expect to have the
advantages of air conditioning. Perhaps in the future the same will be true of oxygen conditioning
in high altitudes.
In summary, recent advances in technology
make it possible to raise the oxygen concentration
in the air in whole buildings and thus reduce the
equivalent altitude. Visitors to high altitude such as
skiers can expect a better night’s sleep in hotels
with oxygen conditioning. Sojourners such as people from low altitude who are working in mines,
telescopes, or embassies at high altitude will have
enhanced physical and neuropsychological function. Children in schools can expect to have improved cognition. Permanent residents of high
altitude will have enhanced physical ability, but
whether their neuropsychological function can be
improved needs further research. 䡲
No conflicts of interest, financial or otherwise, are declared by the author(s).
Author contributions: J.B.W. conception and design of
research; J.B.W. performed experiments; J.B.W. analyzed
data; J.B.W. interpreted results of experiments; J.B.W.
prepared figures; J.B.W. drafted manuscript; J.B.W. edited and revised manuscript; J.B.W. approved final version
of manuscript.
References
1.
Balke B, Daniels JT, Faulkner JA. Training for maximal performance at altitude. In: Exercise at Altitude, edited by Margaria R. Amsterdam: Excerpta Med. Foundation, 1967, p.
179 –186.
2.
Cahoon R. Simple decision making at high altitude. Ergonomics 15: 157–163, 1972.
3.
Cerretelli P. Gas exchange at high altitude. In: Pulmonary Gas
Exchange. Vol. 2, edited by West JB. NewYork: Academic,
1980.
4.
Denison D, Ledwith F, Poulton E. Complex reaction times at
simulated altitudes of 5000 and 8000 feet. Aerospace Med
37: 1010 –1013, 1966.
5.
Elsner RW, Bolstad A, Forno C. Maximum oxygen consumption of Peruvian Indians native to high altitude. In: The Physiological Effects of High Altitude, edited by Weihe WH. New
York: Macmillan, 1964217–223.
6.
Favier R, Spielvogel H, Desplanches D, Ferretti G, Kayser B,
Hoppeler H. Maximal exercise performance in chronic hypoxia and acute normoxia in high-altitude natives. J Appl
Physiol 78: 1868 –1874, 1995.
7.
Hogan AM, Virues-Ortega J, Botti AB, Bucks R, Holloway JW,
Rose-Zerilli MJ, Palmer LJ, Webster RJ, Baldeweg T, Kirkham
FJ. Development of aptitude at altitude. Develop Sci 13:
533–544, 2010.
8.
National Fire Protection Association. National Fire Protection
Association Standard for Hypobaric Facilities (1999 ed.).
Quincy, MA: National Fire Protection Association, 1999.
9.
Pavlicek V, Schirlo C, Nebel A, Regard M, Koller EA, Brugger
P. Cognitive and emotional processing at high altitude. Aviat
Space Environ Med 76: 28 –33, 2005.
10. Pugh LGCE. Physiological and medical aspects of the Himalayan Scientific and Mountaineering Expedition, 1960-61.
BMJ 2: 621– 633, 1962.
11. Rimoldi S, Rexhaj E, Duplain H, Urben S, Billeux J, Alleman Y,
Romero C, Ayavin A, Salinas C, Villena M, Scherrer U, Sartori
C. Acute and chronic altitude-induced dysfunction in children
and adolescents. J Pediatr 169: 238 –243, 2016.
12. Schuler B, Thomsen JJ, Gassmann M, Lundby C. Timing the
arrival at 2340 m for aerobic performance. Scand J Med Sci
Sports 17: 588 –594, 2007.
PHYSIOLOGY • Volume 31 • May 2016 • www.physiologyonline.org
221
REVIEWS
13. Sharma V, Malhotra M, Baskaran A. Variations in
psychomotor efficiency during prolonged stay at
high altitude. Ergonomics 18: 511–516, 1975.
18. West JB. Oxygen enrichment of room air to relieve the hypoxia of high altitude. Respir Physiol
99: 225–232, 1995.
14. Virues-Ortega J, Buela-Casal G, Garrido E, Alcazar B. Neuropsychological functioning associated
with high-altitude exposure. Neuropsychol Rev
14: 197–224, 2004.
19. West JB. Potential use of oxygen enrichment of
room air in mountain resorts. High Alt Med Biol
3: 59 – 64, 2002.
15. Weil JV. Sleep at high altitude. High Alt Med Biol
5: 180 –189, 2004.
16. West JB, Hackett P, Maret K, Milledge J, Peters
R, Pizzo C, Winslow R. Gas exchange on the
summit of Mt. Everest. J Appl Physiol 55: 678 –
687, 1983.
17. West JB. A strategy for oxygen conditioning at
high altitude: comparison with air conditioning. J
Appl Physiol 119: 719 –723, 2015.
20. Wihite DP, Mickleborough TD, Laymon AS,
Chapman RF. Increase in V̇O2 max with “live hightrain low” altitude training: role of ventilatory
acclimatization. Eur J Appl Physiol 113: 419 – 426,
2013.
22. Yan X, Zhang J, Gong Q, Weng X. Prolonged
high-altitude residence impacts verbal working
memory: an fMRI study. Exp Brain Res 208: 437–
445, 2011.
23. Yan X. Cognitive impairments at high altitudes
and adaptation. High Alt Med Biol 15: 141–145,
2014.
24. Zhang J, Liu H, Yan X, Weng X. Minimal effects
on human memory following long term living at
moderate altitude. High Alt Med Biol 12: 37– 43,
2011.
21. Yan X, Zhang J, Gong Q, Weng X. Adaptive
influence of long term high altitude residence on
spatial working memory: an fMRI study. Brain
Cogn 77: 53–59, 2011.
Downloaded from http://physiologyonline.physiology.org/ by 10.220.32.246 on June 15, 2017
222
PHYSIOLOGY • Volume 31 • May 2016 • www.physiologyonline.org