Alveolar-arterial (aa) Gradient (Maa) calculator Formula:
aag = FiO2 * (Atm - 47) - PaCO2 * 1.25 - PaO2
Where:
FiO2: fraction inspired O2, room air is 21%
Atm: Atmospheric Pressure, 760mmHg at sea level
PaO2: Arterial O2
PaCO2: Arterial CO2
aag: A-a O2 Gradient