Calculates alveolar oxygen tension using the alveolar gas equation.
Overview
Calculates alveolar oxygen tension using the alveolar gas equation.
Clinical Significance
Estimates alveolar oxygen tension for gas-exchange assessment. Interpretation depends on inspired oxygen, altitude, ventilation and the paired arterial oxygen tension.
How It Is Calculated
- PAO₂ = FiO₂ × (PB − 47) − PaCO₂/RQ.
Interpretation
- Estimates alveolar oxygen tension for gas-exchange assessment. Interpretation depends on inspired oxygen, altitude, ventilation and the paired arterial oxygen tension.
Worked Example
Enter a clinically consistent set of values in the displayed units. MedicalC applies: PAO₂ = FiO₂ × (PB − 47) − PaCO₂/RQ.
Limitations
- This tool does not establish a diagnosis or mandate treatment.
- Published cut-offs may vary between cohorts and measurement methods.
- Calculation precision cannot compensate for poor source data.
Clinical Pearls
- Trend the result over time where clinically appropriate.
- Record the source values and units alongside the calculated result.
Common Mistakes
- Using the wrong unit.
- Combining measurements obtained at different times.
- Applying a research-derived threshold as a universal treatment trigger.
Frequently Asked Questions
What does this calculator provide?
Calculates alveolar oxygen tension using the alveolar gas equation.
Can this result be used alone?
No. It must be interpreted with clinical context and appropriate investigations.
What equation is used?
PAO₂ = FiO₂ × (PB − 47) − PaCO₂/RQ.
What is the main limitation?
The result depends on valid inputs and may not be calibrated for every population or setting.
References
- West JB. Respiratory Physiology: The Essentials. Wolters Kluwer. — Formula, physiological or validation reference.
Reviewed by: MedicalC Clinical Editorial Team
Last reviewed: July 2026