FIO 2
These two graphs explain the percentage of nasal cannula oxygen in the inspired volume, and the minimal effect that O2 purity has on FIO2. Also this is provided with the scientific source that has produced the statistics.
Nasal cannula oxygen represents only 3-7% of inspired volume

RR 20-30/min, 2-3 LPM, I:E 1:2
O2 purity has little influence on FIO2
OXYGEN SOURCE | ROOM AIR | LIQUID OXYGEN (2LPM) |
---|---|---|
FIO 2 | ![]() |
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O2 purity | 21% | 99,6% |
nasal cannula FIO2 equation | 21% x 500ml = 105ml | 99,6% x 33ml = 33ml 21% x (500-33)ml = 98ml 131ml |
Calculated FIO | 105/500 = 21% | 131/500 = 26.2% |
Nasal cannula FIO2 equation. Clinical Application of Blood Gases. Shapiro BA. 5th ed RR/20min, I:E, inspiration 2s, 2 LPM = 33ml/s105/500 = 21%