1. What is the PaO2/FiO2 Ratio?

The PaO2/FiO2 ratio is a clinical indicator used to assess pulmonary gas exchange and oxygenation status. It's particularly useful in critical care settings for evaluating respiratory function and diagnosing conditions like acute respiratory distress syndrome (ARDS).

2. How Does the Calculator Work?

The calculator uses the PaO2/FiO2 ratio equation:

Where:

• \( PaO_2 \) — Partial pressure of arterial oxygen (mmHg)
• \( FiO_2 \) — Fraction of inspired oxygen (unitless, range 0.21-1.0)

Explanation: The ratio provides a simple yet effective measure of oxygenation efficiency, normalizing the arterial oxygen partial pressure to the inspired oxygen concentration.

3. Importance of PaO2/FiO2 Ratio Calculation

Details: This ratio is crucial for assessing respiratory function, diagnosing and classifying ARDS severity, monitoring treatment response, and guiding ventilator management in critically ill patients.

4. Using the Calculator

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).

5. Frequently Asked Questions (FAQ)

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 is this ratio most commonly used?
A: It's primarily used in intensive care units for patients receiving supplemental oxygen or mechanical ventilation to assess oxygenation status and ARDS classification.

Q3: Are there limitations to this ratio?
A: The ratio doesn't account for factors like PEEP levels, patient position, or cardiac output. It should be interpreted in clinical context alongside other parameters.

Q4: How does FiO2 affect the ratio?
A: Higher FiO2 values typically result in lower ratios for the same PaO2, making it a useful normalization tool across different oxygen delivery methods.

Q5: Can this ratio be used for non-intubated patients?
A: Yes, it can be used for patients receiving supplemental oxygen via various devices, though accuracy may vary with different oxygen delivery systems.