Medical Calculator – SonDoctor.com
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P/F ratio (PaO₂ / FiO₂) Calculator
Used for lung function assessment and risk classification in ARDS
※ Berlin definition of ARDS (Ranieri et al., 2012)
PaO₂/FiO₂ 200 ~ 299 : Mild
PaO₂/FiO₂ 100 ~ 199 : Moderate
PaO₂/FiO₂ < 100 : Severe

FiO₂ values according to types of oxygen inhalation therapy
(1) Nasal cannula
| 100% O₂ flow rate (L/min) | FiO₂ |
|---|---|
| 1 | 0.24 |
| 2 | 0.28 |
| 3 | 0.32 |
| 4 | 0.36 |
| 5 | 0.40 |
(2) Simple mask
| 100% O₂ flow rate (L/min) | FiO₂ |
|---|---|
| 5~6 | 0.4 |
| 6~7 | 0.5 |
| 7~8 | 0.6 |
(3) Reservoir mask
| 100% O₂ flow rate (L/min) | FiO₂ |
|---|---|
| 6 | 0.6 |
| 7 | 0.7 |
| 8 | 0.8 |
| 9 | >0.8 |
| 10 | >0.8 |
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