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P/F Ratio Formula:
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The P/F Ratio (PaO2/FiO2 Ratio) is a clinical measurement used to assess lung function and oxygenation status. It compares the partial pressure of arterial oxygen (PaO2) to the fraction of inspired oxygen (FiO2) to evaluate the efficiency of oxygen exchange in the lungs.
The calculator uses the P/F Ratio formula:
Where:
Explanation: The ratio provides a standardized measure of oxygenation that accounts for the amount of oxygen being delivered to the patient.
Details: The P/F Ratio is crucial for diagnosing and monitoring respiratory conditions, particularly acute respiratory distress syndrome (ARDS). It helps clinicians assess the severity of lung injury and guide treatment decisions.
Tips: Enter PaO2 in mmHg and FiO2 as a fraction between 0.01 and 1. All values must be valid (PaO2 > 0, FiO2 between 0.01-1).
Q1: What is a normal P/F Ratio value?
A: A normal P/F Ratio is typically above 300-500 mmHg. Values below 300 may indicate mild ARDS, below 200 moderate ARDS, and below 100 severe ARDS.
Q2: How is FiO2 measured?
A: FiO2 is the fraction of oxygen in the inspired air. Room air is 0.21 (21%), while supplemental oxygen can increase this value up to 1.0 (100%).
Q3: When should P/F Ratio be measured?
A: P/F Ratio should be measured when assessing patients with respiratory distress, monitoring ARDS patients, or evaluating oxygenation status during mechanical ventilation.
Q4: Are there limitations to P/F Ratio?
A: The ratio may be affected by factors such as positive end-expiratory pressure (PEEP), patient position, and underlying cardiac function.
Q5: How does P/F Ratio differ from other oxygenation indices?
A: P/F Ratio is simpler than other indices like the Oxygenation Index (OI) or Oxygenation Saturation Index (OSI), but provides a quick assessment of oxygenation efficiency.