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P/F Ratio Formula:
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The P/F Ratio (PaO2/FiO2 ratio) is a measure of oxygenation that compares arterial oxygen partial pressure (PaO2) to the fraction of inspired oxygen (FiO2). It is commonly used to assess the severity of acute respiratory distress syndrome (ARDS) and other respiratory conditions.
The calculator uses the P/F Ratio formula:
Where:
Explanation: The ratio provides a standardized measure of oxygenation that accounts for the amount of oxygen being delivered to the patient.
Details: The P/F Ratio is crucial for diagnosing and classifying the severity of ARDS, guiding treatment decisions, and monitoring patient response to therapy in critical care settings.
Tips: Enter PaO2 in mmHg and FiO2 as a decimal (e.g., 0.21 for room air, 1.0 for 100% oxygen). Both values must be valid positive numbers.
Q1: What is a normal P/F Ratio?
A: A normal P/F Ratio is typically >400 mmHg. Values between 300-400 indicate mild ARDS, 200-300 moderate ARDS, and <200 severe ARDS.
Q2: How does P/F Ratio differ from oxygenation index?
A: While both assess oxygenation, P/F Ratio is simpler and doesn't account for mean airway pressure, making oxygenation index more comprehensive for ventilated patients.
Q3: When should P/F Ratio be measured?
A: P/F Ratio should be measured when assessing patients with suspected respiratory failure, during mechanical ventilation, and when monitoring response to oxygen therapy.
Q4: Are there limitations to P/F Ratio?
A: Yes, P/F Ratio doesn't account for positive end-expiratory pressure (PEEP) levels and may be less accurate at extreme FiO2 levels or with significant ventilation-perfusion mismatch.
Q5: Can P/F Ratio be used for non-intubated patients?
A: Yes, P/F Ratio can be used for both intubated and non-intubated patients receiving oxygen therapy, though interpretation may vary based on the delivery method.