SpO<sub>2</sub> is the measure of the amount of oxygen in the blood. It stands for '''S'''aturation of '''p'''eripheral '''O'''xygen (O<sub>2</sub>) and is normally measured with a [[Pulse Oximeter]].
=Effects of hypoxia=
Low levels of SpO<sub>2</sub> effect brain functioning<ref name="anweb"/>, as shown in the following table.
{| class="wikitable"
!SpO<sub>2</sub>!!Description!!Effect!!Notes
|-
|100-80% ||Mild Hypoxia||Normal brain functioning||This mild level of hypoxia does not affect the functioning of the brain, but some people can be sensitive enough to detect changes.
|-
|80-60%||Moderate Hypoxia||Decreasing brain function||Vision can be altered, including tunnel vision. Coordination is impaired in things like handwriting will deteriorate. Below 80% the skin may become blue (cyanosis). Mental functioning is impaired, sometimes creating euphoria or tranquility, including indifference to everything including pain. At this level some people become fixated on whatever they were doing when the hypoxia began, which can be dangerous. Memory and speech can also be impaired. There may be older treat visual hallucinations, feelings of depersonalization and even out of body experiences.
|-
|60-40% ||Severe hypoxia||[[Muscle]] paralysis||Apparent unconsciousness.
|-
|<40%||Extreme hypoxia||Unconsciousness and eventually death||
|-
|}
=Hypoxia at altitude=
The following table<ref name="anwebgo2"/> gives an idea of different SpO<sub>2</sub> levels at different altitudes. However, [[Intermittent Hypoxic Exposure]] can increase SpO<sub>2</sub> levels at a given altitude<ref name="ihtspo2"/>, which are specified in the table below for some altitudes.
{| class="wikitable"
! Altitude(feet)
! Altitude(meters)
! Air Pressure(mmHg)
! Oxygen Pressure(mmHg)
! % of sea level Oxygen
! Equivalent O2 partial<br/>pressure at sea level
! SpO<sub>2</sub><br/>Unconditioned
! SpO<sub>2</sub><br/>Conditioned
|-
| 0
| 0
| 760
| 159
| 100
| 20.9
| 98%
|
|-
| 5,000
| 1,524
| 639
| 134
| 84
| 17.6
| 95%
|
|-
| 7,500
| 2,286
| 584
| 122
| 77
| 16.1
| 93%
|
|-
| 9,000
| 2,740
| 554
| 116
| 73
| 15.3
| 90.3% (+/-3.4%)
| 93.8% (+/-2%)
|-
| 10,000
| 3,048
| 534
| 112
| 70
| 14.6
| 89%
|
|-
| 11,000
| 3,360
| 514
| 107
| 68
| 14.2
| 86.4 % (+/- 4.8%)
| 90.2% (+/-2.7%)
|-
| 12,500
| 3,810
| 487
| 102
| 64
| 13.4
| 87%
|
|-
| 14,000
| 4,267
| 460
| 96
| 61
| 12.7
| 83%
|
|-
| 15,000
| 4,570
| 443
| 93
| 58
| 12.1
| 81.7% (+/-6%)
| 89.1% (+/-3%)
|-
| 16,500
| 5,029
| 418
| 87
| 55
| 11.5
| 77%
|
|-
| 18,000
| 5,490
| 395
| 83
| 52
| 10.9
|
| 84.9% (+/-4%)
|-
| 20,000
| 6,096
| 365
| 76
| 48
| 10.0
| 65%
|
|-
| 21,000
| 6,400
| 351
| 73
| 46
| 9.6
|
| 79.2% (+/-6%)
|-
| 25,000
| 7,620
| 299
| 62
| 39
| 8.2
| <60%
|
|}
=References=
<references>
<ref name="anwebgo2">anesthesia and hypoxia http://www.anesthesiaweb.org/hypoxia.php Originally from "The Pilot: An Air Breathing Mammal," Mehler, Stanley R. MD, Human Factors Bulletin, Flight Safety Foundation, 1981.</ref>
<ref name="anweb">anesthesia and hypoxia http://www.anesthesiaweb.org/hypoxia.php </ref>
<ref name="ihtspo2">The Effect of Dynamic Intermittent Hypoxic Conditioning on Arterial Oxygen Saturation http://www.wemjournal.org/article/S1080-6032%2809%2970080-8/abstract </ref>
</references>