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* [[SpO2|SpO<sub>2</sub>]] at altitude may be slightly misleading as the oxygen deliver to the muscles may be modified by O<sub>2</sub> dissociation curve shifts caused by changes in pH, PCO<sub>2</sub>, and blood temperature<ref name="DempseyWagner1999"/>. However, [[SpO2|SpO<sub>2</sub>]] is cheap and easy to monitor and should not be ignored.
* There is great individual variability in the response to altitude<ref name="ChapmanStray-Gundersen1998"/>. Some studies have classified subjects as 'responders' and 'non-responders' due to the significance of this variability. This variability can change over time within an individual. I met someone in Tanzania who had been a porter on Kilimanjaro (19,334 ft) until he lost his ability to cope with the altitude.
* Some variability may be due to differences in iron intake/availability. Low blood iron (serum ferritin < 20 ng/ml female, < 30 ng/ml male) may limit the body's ability to generate new red blood cells, which is part of the altitude adaptation. Studies in the USSR and CIS have shown genetic factors as well. See below for more detailson iron supplementation.
* Generally, 'live high, train low' seems to work better than 'live high, train high'. [[Intermittent Hypoxic Exposure]] may have additional benefits over other [[Altitude Training Approaches]].
* Altitude acclimatization takes time, with 2 weeks being a point of diminishing returns. This is based on a study of athletes traveling to 2340m/7,766' that showed a performance decrease of 26% on arrival, they recovered by 6.0% after 7 days, another 5.7% after 14 days, but only another 1.4% after 21 days<ref name="Schuler-2007"/>. These findings seem broadly similar for those sleeping in an altitude tent (normobaric hypoxia) <ref name="Townsend-2002"/>.
# "I had to be evacuated to a lower altitude."
=Effects of hypoxia=
Low levels of SpO<sub>2</sub> effect effect brain functioning as shown in the following table<ref name="Anesthesia"/>.
{| class="wikitable" style="margin-left: auto; margin-right: auto; border: none;"
! style="background-color: #F2F2F2;" |SpO<sub>2</sub>
| style="background-color: #F9F9F9;" |60-40%
| style="background-color: #F9F9F9;" |Severe hypoxia
| style="background-color: #F9F9F9;" |[[Muscle]] paralysis paralysis
| style="background-color: #F9F9F9;" |Apparent unconsciousness.
|-
! style="background-color: #F2F2F2;" |'''Air Pressure(mmHg)'''
! style="background-color: #F2F2F2;" |'''Oxygen Pressure(mmHg)'''
! style="background-color: #F2F2F2;" |''' % of sea level Oxygen'''
! style="background-color: #F2F2F2;" |'''Equivalent O2 partial
pressure at sea level'''
| style="background-color: #F9F9F9;" |68
| style="background-color: #F9F9F9;" |14.2
| style="background-color: #F9F9F9;" |86.4 4 % (+/- 4.8%)
| style="background-color: #F9F9F9;" |90.2% (+/-2.7%)
|-