Quickly calculate the Alveolar Partial Pressure of Oxygen (PAO2) and the Alveolar-arterial (A-a) gradient with our free online tool. Essential for assessing pulmonary gas exchange, understanding causes of hypoxemia, and aiding in clinical diagnosis for various respiratory conditions. Simplify complex medical calculations.
Formula:
Formulas Used:
Alveolar Partial Pressure of Oxygen (PAO2):
PAO2 = FiO2 * (Patm - PH2O) - (PaCO2 / R)
Alveolar-arterial (A-a) Gradient:
A-a Gradient = PAO2 - PaO2
Variable Explanations:
- FiO2: Fraction of Inspired Oxygen (decimal, e.g., 0.21 for room air)
- Patm: Atmospheric Pressure (in mmHg, typically 760 mmHg at sea level)
- PH2O: Partial Pressure of Water Vapor (in mmHg, typically 47 mmHg at 37°C)
- PaCO2: Arterial Partial Pressure of Carbon Dioxide (in mmHg, from ABG)
- R: Respiratory Quotient (ratio of CO2 production to O2 consumption, typically 0.8)
- PaO2: Arterial Partial Pressure of Oxygen (in mmHg, from ABG)