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Calculate the P/F ratio using PaO2 and FiO2 to assess ARDS risk and pulmonary oxygenation function.
Enter PaO₂ and FiO₂ for calculation.
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When a patient experiences respiratory distress, quickly calculating the P/F ratio (the ratio of arterial oxygen partial pressure to fractional inspired oxygen) is a critical step in assessing ARDS risk. By entering the PaO2 (mmHg) and FiO2 (%) values, this tool automatically calculates the ratio and compares it against the Berlin definition to output a clinical assessment: "Normal" (P/F ≥ 400), "Mild ARDS" (300 ≤ P/F < 400), "Moderate ARDS" (200 ≤ P/F < 300), or "Severe ARDS" (P/F < 200).
Should I enter FiO2 as 21% or 0.21?
Simply enter the percentage value (e.g., 21). The tool will automatically convert it to a decimal for the calculation.
At what P/F ratio should mechanical ventilation be considered?
A P/F ratio < 150 indicates severe oxygenation impairment, requiring clinical evaluation for the necessity of ventilatory support. However, the final decision should be based on a comprehensive assessment of blood gas analysis, imaging, and other clinical indicators.
Before using, please confirm: 1. PaO2 is the measured value from an arterial blood gas test; 2. FiO2 is entered based on the actual oxygen therapy concentration (defaults to 21% for patients not on oxygen therapy); 3. The calculation results are not applicable to patients in high-altitude areas.
Typical scenario example: A patient has a PaO2 of 58 mmHg (Type I respiratory failure) and is receiving oxygen via a non-rebreather mask (FiO2 = 60%). The calculated P/F ratio is 96.7, which meets the criteria for severe ARDS. Note that the P/F ratio should be measured after 30 minutes of stable oxygen therapy, and the reliability is higher when FiO2 > 50%.
