A-a Gradient Calculator

This advanced calculator is designed for healthcare professionals to compute the alveolar-arterial (A-a) gradient, an important measure for assessing lung function.

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A-a Gradient: N/A

Data Source and Methodology

This calculator uses standard formulas for the A-a gradient based on medical research. View full details.

All calculations are based strictly on these formulas and data provided by this source.

The Formula Explained

The A-a gradient is calculated as follows:

A-a Gradient = (FiO2 × (760 - 47) - (PaCO2 / 0.8)) - PaO2

Glossary of Terms

How It Works: A Step-by-Step Example

Consider a patient with PaO2 of 85 mmHg, FiO2 of 0.21, and PaCO2 of 40 mmHg. The A-a gradient can be calculated as follows:

A-a Gradient = (0.21 × (760 - 47) - (40 / 0.8)) - 85 = 10.7 mmHg

Frequently Asked Questions (FAQ)

What is the A-a gradient used for?

The A-a gradient is used to identify issues with oxygen transfer from the alveoli to the blood.

Is a higher A-a gradient concerning?

Yes, a higher A-a gradient may indicate issues such as pulmonary embolism or fibrosis.

Can this calculator be used for all patients?

This calculator is intended for healthcare professionals and may not be suitable for all patient situations.

What units should be used?

PaO2 and PaCO2 should be entered in mmHg, and FiO2 as a decimal (e.g., 0.21 for 21%).

How often should the A-a gradient be checked?

The frequency depends on the clinical scenario; consult with a healthcare provider for guidance.

Tool developed by Ugo Candido. Content reviewed by healthcare experts. Last reviewed for accuracy on: October 10, 2023.