[drjasonharrison]

It's confusing to me too because if the blood is 99% saturated with oxygen is there only 1% CO2? Is hyperventilating getting to 100% or further?

Are we talking about the same numbers as a (calibrated) O2 optical saturation monitor reports or something else?

[nradov]

Hyperventilation doesn't significantly increase blood oxygen saturation. A healthy person near sea level will already be close to 100% so there's no room for increase. This is normally measured using an optical sensor.

Blood O2 and CO2 percentages don't sum to 100%. O2 saturation refers to the percentage of hemoglobin molecules which have oxygen bound. Only some CO2 is transported bound to hemoglobin.