PF Ratio Calculator
PaO2/FiO2 Ratio for ARDS Assessment
Calculate the PF ratio (PaO2/FiO2) to assess oxygenation status and ARDS severity using Berlin criteria.
Respiratory Parameters
From arterial blood gas (ABG) analysis
21% = room air, 100% = pure oxygen
PF Ratio Formula
PF Ratio = PaO2 (mmHg) / FiO2 (decimal)
Example: PaO2 = 80 mmHg, FiO2 = 40% (0.4)
PF Ratio = 80 / 0.4 = 200
Berlin ARDS Criteria
Normal
PF ratio ≥ 300
Mild ARDS
PF ratio 200-300
Moderate ARDS
PF ratio 100-200
Severe ARDS
PF ratio < 100
Medical Use Only
This calculator is for healthcare professionals only. ARDS diagnosis requires clinical correlation, imaging, and exclusion of cardiac causes. Always use measured ABG values when available.
Understanding PF Ratio
The PF ratio (PaO2/FiO2) is a key metric for assessing oxygenation and diagnosing Acute Respiratory Distress Syndrome (ARDS) using the Berlin Definition.
Key Components:
- PaO2: Partial pressure of oxygen in arterial blood (mmHg)
- FiO2: Fraction of inspired oxygen (0.21-1.0 or 21-100%)
- Normal PF ratio: 400-500 mmHg on room air
- ARDS threshold: PF ratio < 300 mmHg
Berlin ARDS Definition
Complete ARDS criteria (all must be met):
- Timing: Within 1 week of known clinical insult
- Imaging: Bilateral opacities on chest X-ray or CT
- Origin: Not fully explained by cardiac failure or fluid overload
- Oxygenation: PF ratio < 300 with PEEP ≥ 5 cmH2O
- Severity: Based on PF ratio (mild, moderate, severe)
Lung-Protective Ventilation Strategy
Tidal Volume:
- 6 mL/kg predicted body weight
- Plateau pressure < 30 cmH2O
- Driving pressure < 15 cmH2O
- Permissive hypercapnia acceptable
PEEP Strategy:
- Minimum 5 cmH2O for ARDS
- Mild ARDS: 5-10 cmH2O
- Moderate ARDS: 10-15 cmH2O
- Severe ARDS: 15-20 cmH2O
- Titrate to oxygenation and compliance
Adjunctive Therapies:
- Prone positioning (12-16 hrs/day)
- Neuromuscular blockade (early)
- Conservative fluid management
- Recruitment maneuvers
- ECMO for refractory cases
You Might Also Like
Explore more tools in this category