PaO2/FiO2 Ratio Calculator (PF Ratio)
Health & FitnessCalculate the PaO2/FiO2 ratio used to assess hypoxemia severity, including ARDS classification.
PF Ratio
PaO2/FiO2 ratio. Educational reference only, not a substitute for clinical judgment.
ARDS Severity (Berlin Criteria)
General severity category using the Berlin ARDS definition thresholds. ARDS diagnosis also requires other clinical criteria beyond this ratio alone. Over 300 - not consistent with ARDS
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Frequently Asked Questions
What is the PF ratio used for?
The PF ratio measures how well the lungs are transferring oxygen into the blood relative to how much oxygen is being delivered, used to assess the severity of hypoxemia, including classifying Acute Respiratory Distress Syndrome (ARDS).
What are the Berlin ARDS severity categories?
Under the Berlin definition, a PF ratio of 200-300 suggests mild ARDS, 100-200 suggests moderate ARDS, and 100 or below suggests severe ARDS, though a full ARDS diagnosis also requires additional clinical and imaging criteria.
Does a low PF ratio alone diagnose ARDS?
No. ARDS diagnosis requires the PF ratio plus additional criteria, including timing of onset, bilateral opacities on chest imaging, and ruling out cardiac failure as the primary cause of the hypoxemia.
Is this calculator a substitute for medical advice?
No. This is an educational reference implementation of the standard PF ratio formula, not a substitute for a physicians clinical assessment.
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