Pao2 Fio2 Ratio Calculator

P/F Ratio Formula:

\[ P/F\ Ratio = \frac{PaO_2}{FiO_2} \]

P/F Ratio:

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1. What is the P/F Ratio?

The P/F Ratio (PaO2/FiO2 Ratio) is a clinical measurement used to assess pulmonary function and oxygenation status. It's particularly useful in diagnosing and monitoring acute respiratory distress syndrome (ARDS) and other respiratory conditions.

2. How Does the Calculator Work?

The calculator uses the P/F Ratio formula:

\[ P/F\ Ratio = \frac{PaO_2}{FiO_2} \]

Where:

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

Explanation: The ratio compares the oxygen level in arterial blood to the oxygen concentration being inhaled, providing a measure of how efficiently the lungs are oxygenating the blood.

3. Importance of P/F Ratio Calculation

Details: The P/F Ratio is crucial for diagnosing ARDS severity, guiding ventilator management, monitoring treatment response, and assessing prognosis in critically ill patients with respiratory failure.

4. Using the Calculator

Tips: Enter PaO2 in mmHg and FiO2 as a fraction between 0.21 and 1.0. Both values must be positive and valid for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What are normal P/F Ratio values?
A: Normal P/F Ratio is typically >400 mmHg. Values between 300-400 indicate mild impairment, 200-300 moderate impairment, and <200 severe impairment (consistent with ARDS).

Q2: How is P/F Ratio used in ARDS diagnosis?
A: P/F Ratio is a key criterion for ARDS diagnosis: mild (200-300), moderate (100-200), and severe (<100) when measured with PEEP ≥5 cm H2O.

Q3: When should P/F Ratio be measured?
A: It should be measured during arterial blood gas analysis, particularly in patients receiving oxygen therapy, mechanical ventilation, or with suspected respiratory dysfunction.

Q4: Are there limitations to P/F Ratio?
A: Yes, it can be affected by altitude, barometric pressure, and doesn't account for ventilation efficiency or CO2 elimination. It's best interpreted in clinical context.

Q5: How does P/F Ratio differ from oxygenation index?
A: Oxygenation index incorporates mean airway pressure, making it more comprehensive for mechanically ventilated patients, especially children.