Home / Clinician Tools / Alveolar-Arterial (A-a) Oxygen Gradient

Alveolar-Arterial (A-a) Oxygen Gradient - Scientific Formula

Pulmonology Equation

Standard Calibration Equation:

PIO₂ = (P_barom - 47) * (FiO₂/100); PAO₂ = PIO₂ - (PaCO₂ / RQ); G = PAO₂ - PaO₂; Expected = (Age/4) + 4

Accuracy Bounds & Limits:

While mathematical calculators evaluate demographic models, extreme variance (hyperthyroidism, dialysis cases, muscular bodybuilders, pregnancy) can trigger output errors. Weight and clearance assessments must follow separate personalized titration grids.