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>Dr.A.A Buhlmann, a medical type, in is published book, "Decompression -
>Decompression Sickness," Rev.2 provides the following table in regards
>to O2 at altitude.
>
>
>                            0 to 150meters  3500meters  7500meters
>Ambient Pressure                1.0 Bar       .68 Bar     .38 Bar
>Pressure of Inspired Oxygen     .196 Bar      .129 Bar    .066 Bar
>Pressure of Inspired Nitrogen   .74 Bar       .487 Bar    .250 Bar
>1 Bar = 1.01325 ATA
>
>The fraction of O2 can be calculated from the data provided.
>                            0 to 150meters  3500meters  7500meters
>Fraction of Oxygen              .196          .189        .173
>

Buhlmann is interested in the situation in the lungs. The air coming down
to the lungs is saturated with water at 37 deg C. The PP for steam at
this temperature is 0,063 bar. Then Buhlmans figures makes perfect sense:

P Tot   1,00    0,68    0,38
-----------------------------
P 02    0,196   0,129   0,066
P N2    0,740   0,487   0,250
P H2O   0,063   0,063   0,063
-----------------------------
Sum     0,999   0,679   0,379


F gas   20,9%   20,9%   20,9%

Fgas is PO2/(PO2+PN2)

This shows that Buhlman used the same air as the rest of us.

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