1. What is the Fio2 Pao2 Ratio?

The PaO2/FiO2 ratio is a measure used in critical care medicine to assess the efficiency of oxygen exchange in the lungs. 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 simple formula:

Where:

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

Explanation: This ratio provides a standardized measure of oxygenation that accounts for varying levels of supplemental oxygen.

3. Importance of PaO2/FiO2 Ratio

Details: The PaO2/FiO2 ratio is a key parameter in diagnosing and classifying acute respiratory distress syndrome (ARDS). It helps clinicians assess the severity of lung injury and guide treatment decisions.

4. Using the Calculator

Tips: Enter PaO2 in mmHg and FiO2 as a decimal between 0.21 (room air) and 1.0 (100% 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 greater than 300-500 mmHg. Values below 300 indicate mild ARDS, below 200 moderate ARDS, and below 100 severe ARDS.

Q2: How is FiO2 measured?
A: FiO2 is typically measured using oxygen analyzers at the patient interface. For patients on room air, FiO2 is 0.21 (21%).

Q3: When is this ratio most useful?
A: This ratio is particularly valuable in critical care settings for monitoring patients with respiratory failure and for ARDS diagnosis and classification.

Q4: Are there limitations to this ratio?
A: The ratio may be less accurate at very high FiO2 levels and doesn't account for positive end-expiratory pressure (PEEP) or other ventilatory parameters.

Q5: How does this compare to other oxygenation indices?
A: The PaO2/FiO2 ratio is simpler than the oxygenation index (OI) or alveolar-arterial oxygen gradient but provides a quick assessment of oxygenation status.