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A-a O2 Gradient Calculator

13. Feb, 2012

Alveolar-arterial oxygen gradient

The alveolar-arterial oxygen tension difference (“A-a gradient”) is used in evaluating the causes of hypoxemia.

Enter Your Details
Pa_O₂(partial pressure of arterial O₂):	mmHg
Pa_CO₂ (partial pressure of arterial CO₂):	mmHg
Atmospheric Pressure:
Inspired Oxygen Concentration (Fi_O₂):	Room Air (21percent) Other:

Your Results
A-a Gradient	mmHg

A-a (O2) = (FiO2%/100) * (Patm – 47 mmHg) – (PaCO2/0.8) – PaO2
(units in mmHg)