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PaO2/FiO2 Ratio Formula:
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The PaO2/FiO2 ratio is a clinical measurement used to assess pulmonary gas exchange and oxygenation status. It's commonly used in critical care settings to evaluate respiratory function and diagnose conditions like acute respiratory distress syndrome (ARDS).
The calculator uses the PaO2/FiO2 ratio formula:
Where:
Explanation: The ratio provides a simple way to assess oxygenation efficiency by comparing the amount of oxygen in arterial blood to the amount of oxygen being inspired.
Details: The PaO2/FiO2 ratio is crucial for diagnosing and classifying ARDS severity, monitoring respiratory status in critically ill patients, and guiding oxygen therapy decisions.
Tips: Enter PaO2 in mmHg and FiO2 as a decimal value (e.g., 0.21 for room air, 0.4 for 40% oxygen). Both values must be valid (PaO2 > 0, FiO2 between 0.21-1.0).
Q1: What is a normal PaO2/FiO2 ratio?
A: A normal ratio is typically >400 mmHg. Ratios below 300 indicate mild ARDS, below 200 moderate ARDS, and below 100 severe ARDS.
Q2: When should PaO2/FiO2 ratio be measured?
A: It should be measured in patients with respiratory distress, those on mechanical ventilation, or when assessing oxygenation status in critical care settings.
Q3: Are there limitations to this ratio?
A: The ratio doesn't account for PEEP levels, patient position, or other factors affecting oxygenation. It should be interpreted in clinical context.
Q4: How does FiO2 affect the ratio?
A: Higher FiO2 values typically result in lower ratios for the same PaO2, as the denominator increases while numerator may not increase proportionally.
Q5: Can this ratio be used for non-intubated patients?
A: Yes, but FiO2 estimation is less precise in non-intubated patients receiving oxygen via nasal cannula or mask.