Alveolar-Arterial Gradient Equation

Question 1

Alveolar- Arterial Gradient Equation:

Answer 1

((Barometric pressure-47)FiO2 - PaCO2/0.8)-PaO2

Or at sea level: default barometric pressure is 760mmHg
0.8 is the respiratory quotient

So, equation can be:

(150-PaCO2/0.8)-PaO2

Results:
0-10 is normal, no need for supplemental O2
11-20 is questionable, use physical exam to decide if 02 needed
21-30 bordering on inappropriate oxygenation, O2 will benefit
>31 oxygen indicated, patient may be developing respiratory distress syndrome