1. What is the PaO₂/FiO₂ Ratio?

The PaO₂/FiO₂ ratio is a key indicator used to assess oxygenation impairment and diagnose acute respiratory distress syndrome (ARDS). A ratio < 300 mmHg is one of the diagnostic criteria for ARDS according to the Berlin definition.

2. How Does the Calculator Work?

The calculator uses the PaO₂/FiO₂ ratio formula:

Where:

• \( PaO_2 \) — Partial pressure of arterial oxygen (mmHg)
• \( FiO_2 \) — Fraction of inspired oxygen (0-1)

ARDS Classification:

• Mild ARDS: 200 < PaO₂/FiO₂ ≤ 300 mmHg
• Moderate ARDS: 100 < PaO₂/FiO₂ ≤ 200 mmHg
• Severe ARDS: PaO₂/FiO₂ ≤ 100 mmHg

3. Importance of PaO₂/FiO₂ Calculation

Details: The PaO₂/FiO₂ ratio is crucial for diagnosing and classifying ARDS severity, guiding treatment decisions, monitoring disease progression, and predicting patient outcomes in critical care settings.

4. Using the Calculator

Tips: Enter PaO₂ in mmHg (typically 80-100 mmHg in healthy individuals) and FiO₂ as a fraction between 0.21 (room air) and 1.0 (100% oxygen). Ensure values are within valid ranges for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the normal PaO₂/FiO₂ ratio?
A: A normal ratio is typically > 400 mmHg. Values below 300 mmHg indicate impaired oxygenation and potential ARDS.

Q2: When is this calculation most useful?
A: This calculation is essential in ICU settings for patients with acute respiratory failure, pneumonia, sepsis, or other conditions that may lead to ARDS.

Q3: Are there limitations to the PaO₂/FiO₂ ratio?
A: Yes, the ratio can be affected by PEEP levels, patient position, and underlying lung pathology. It should be interpreted in clinical context.

Q4: How does FiO₂ affect the ratio?
A: Higher FiO₂ values will result in lower ratios if oxygenation is impaired, making it a sensitive indicator of lung function.

Q5: What other factors should be considered with this ratio?
A: Clinical context, chest imaging findings, and exclusion of cardiac failure or fluid overload are essential for accurate ARDS diagnosis.