Calculate Alveolar–arterial gradient
| A-g gradient | 14.7 |
| PAO2 | 99.7 |
Formula:
PAO2 = (FiO2 * (Patm - 47)) - (PaCO2/0.8)
A-a gradient = PAO2 - PaO2
Note: Water vapor pressure (Partial pressure of water, PH2O) at body temperature of 37C when fully humidified is 47 mmHg.
Normal PaO2 on room air: 80 - 100 till age 60.