PaO2/FiO2 Ratio Calculator

The PaO2/FiO2 ratio is a key clinical measure used to assess the severity of hypoxemia and is particularly important in diagnosing acute respiratory distress syndrome (ARDS). This ratio compares arterial oxygen pressure (PaO2) to the fraction of inspired oxygen (FiO2) to provide an indication of lung function.

Background

The PaO2/FiO2 ratio is commonly used in intensive care units (ICUs) to evaluate oxygenation levels in critically ill patients. A lower ratio indicates more severe lung impairment and can guide clinical decision-making regarding respiratory support.

Calculation Formula

The formula to calculate the PaO2/FiO2 ratio is:

\[ \text{PaO2/FiO2 Ratio} = \frac{\text{PaO2 (mmHg)}}{\text{FiO2 (expressed as a decimal)}} \]

For example, if the PaO2 is 80 mmHg and the FiO2 is 40%, the ratio would be:

\[ \text{PaO2/FiO2 Ratio} = \frac{80}{0.40} = 200 \]

Clinical Significance

• Normal Range: >300
• Mild ARDS: 200-300
• Moderate ARDS: 100-200
• Severe ARDS: <100

Importance

This ratio is essential in assessing the severity of respiratory failure and determining appropriate treatment strategies. Accurate and timely calculation can be life-saving, particularly in critical care settings.