1. Classify PaO₂
Recognize normal oxygenation, graded hypoxemia, and hyperoxemia from arterial oxygen tension.
Free Oxygenation Practice Tool
OxyGenius
Practice PaO₂ classification, P/F ratio severity, and Berlin ARDS criteria with a fast clinical reasoning simulator.
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Cases
Step 1 · Oxygenation
Clinical CaseEasy
Clinical scenario
Massive Aspiration
58-year-old male aspirated gastric contents during emergency intubation.
Arterial Oxygen Tension
34
PaO₂ mmHg
New to oxygenation assessment? Start with the P/F Ratio Guide or review oxygenation physiology with the A–a Gradient Calculator.
Continue Building Oxygenation Reasoning
Pair OxyGenius with PulmTools guides and calculators for ABG interpretation, hypoxemia workups, and ARDS review.
Oxygenation Study Guide
P/F Ratio Practice, Hypoxemia Classification, and ARDS Cases
OxyGenius is a free clinical oxygenation quiz that moves from PaO₂ interpretation to P/F ratio calculation and then asks whether the complete case meets ARDS criteria. The sequence helps learners separate a number from a diagnosis.
2. Calculate PaO₂/FiO₂
Convert FiO₂ to a decimal, calculate the P/F ratio, and classify the oxygenation deficit.
3. Apply ARDS criteria
Integrate timing, imaging, edema origin, oxygenation, and positive airway pressure before labeling ARDS.
Oxygenation and P/F Ratio FAQ
How do you calculate the P/F ratio?
Divide arterial oxygen tension (PaO₂) by inspired oxygen expressed as a decimal (FiO₂). For example, PaO₂ 80 mmHg on FiO₂ 0.40 gives a P/F ratio of 200.
What is a normal P/F ratio?
A P/F ratio above 300 generally indicates oxygenation outside the Berlin ARDS severity ranges. Healthy lungs often produce a higher value, but the result must be interpreted with oxygen support and the full clinical picture.
What P/F ratio indicates mild, moderate, or severe ARDS?
Under the Berlin definition, mild ARDS corresponds to a P/F ratio of 201–300, moderate ARDS to 101–200, and severe ARDS to 100 or less, with the required PEEP or CPAP and the other diagnostic criteria present.
Can a low P/F ratio diagnose ARDS by itself?
No. ARDS assessment also requires acute timing, bilateral opacities, respiratory failure not fully explained by cardiac failure or fluid overload, and qualifying oxygenation impairment with positive airway pressure.
Who should use OxyGenius?
OxyGenius is designed for respiratory therapy and nursing students, medical trainees, respiratory therapists, and critical care learners practicing PaO₂ interpretation, hypoxemia classification, P/F ratio calculation, and ARDS reasoning.