1. What is the PaO2/FiO2 Ratio?

The PaO2/FiO2 ratio is a clinical indicator used to assess pulmonary gas exchange and classify the severity of acute respiratory distress syndrome (ARDS). It's calculated by dividing the partial pressure of arterial oxygen (PaO2) by the fraction of inspired oxygen (FiO2).

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 (unitless, 0.21-1.0)

Explanation: This simple ratio provides a quick assessment of oxygenation efficiency that accounts for the oxygen concentration being delivered to the patient.

3. Importance of PaO2/FiO2 Ratio

Details: The PaO2/FiO2 ratio is crucial for diagnosing and classifying ARDS severity, guiding treatment decisions, and monitoring response to therapy in critically ill patients.

4. Using the Calculator

Tips: Enter PaO2 in mmHg and FiO2 as a decimal (e.g., 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. Lower values indicate impaired oxygenation.

Q2: How is the ratio used in ARDS classification?
A: ARDS is classified as mild (200-300), moderate (100-200), or severe (<100) based on the PaO2/FiO2 ratio.

Q3: When should this calculation be performed?
A: This calculation is typically performed in ICU settings for patients receiving supplemental oxygen or mechanical ventilation.

Q4: Are there limitations to this ratio?
A: The ratio doesn't account for PEEP levels or other ventilatory parameters that can affect oxygenation.

Q5: How does FiO2 affect the ratio?
A: Higher FiO2 values will decrease the ratio if PaO2 doesn't increase proportionally, indicating poorer oxygenation efficiency.