Alveolar-Arterial (A-a) Gradient

Distinguishes hypoxemia from impaired gas exchange (elevated gradient) versus hypoventilation alone (normal gradient).

For healthcare professionals.These calculate a score or a measurement from values you enter. They do not diagnose, and they are no substitute for clinical judgement. If you are a patient, discuss any result with your own doctor rather than acting on it.

Ageyears

FiO₂21% = room air. Most reliable on room air.%

PaCO₂mmHg

PaO₂mmHg

Enter the values above to see the result.

Source

Mellemgaard K. The alveolar-arterial oxygen difference: its size and components in normal man. Acta Physiol Scand. 1966;67(1):10-20.

Shown for reference and checked against the source above. Confirm against current guidance before acting on it, and use your own clinical judgement.

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Specialists get the full set, including dosing and infusion calculators, alongside virtual chambers and board consultations.

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