Acute Respiratory Distress Syndrome Calculator

PaO₂/FiO₂ Ratio Formula:

\[ PaO_2/FiO_2 = \frac{PaO_2}{FiO_2} \]

PaO₂/FiO₂ Ratio:

ARDS Severity:

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1. What is the PaO₂/FiO₂ Ratio?

The PaO₂/FiO₂ ratio is a clinical measurement used to assess the severity of acute respiratory distress syndrome (ARDS). It represents the ratio of arterial oxygen partial pressure to fractional inspired oxygen concentration and serves as an indicator of lung function and oxygenation efficiency.

2. How Does the Calculator Work?

The calculator uses the PaO₂/FiO₂ ratio formula:

\[ PaO_2/FiO_2 = \frac{PaO_2}{FiO_2} \]

Where:

\( PaO_2 \) — Partial pressure of arterial oxygen (mmHg)
\( FiO_2 \) — Fraction of inspired oxygen (decimal)

ARDS Severity Classification:

Mild ARDS: PaO₂/FiO₂ ≤ 300 mmHg
Moderate ARDS: PaO₂/FiO₂ ≤ 200 mmHg
Severe ARDS: PaO₂/FiO₂ ≤ 100 mmHg

3. Importance of PaO₂/FiO₂ Ratio

Details: The PaO₂/FiO₂ ratio is crucial for diagnosing ARDS severity, guiding mechanical ventilation strategies, monitoring treatment response, and predicting patient outcomes in critical care settings.

4. Using the Calculator

Tips: Enter PaO₂ in mmHg (typically 80-100 mmHg in healthy individuals) and FiO₂ as a decimal fraction (0.21 for room air to 1.0 for 100% oxygen). Ensure values are within physiological ranges.

5. Frequently Asked Questions (FAQ)

Q1: What is the normal PaO₂/FiO₂ ratio?
A: Normal ratio is typically >400 mmHg. Values below 300 mmHg suggest impaired oxygenation and potential ARDS.

Q2: How does PEEP affect the PaO₂/FiO₂ ratio?
A: Positive end-expiratory pressure (PEEP) can improve oxygenation and thus increase the ratio, which should be considered when interpreting results.

Q3: When should this calculation be performed?
A: This calculation is essential in ICU settings for patients with acute respiratory failure, suspected ARDS, or those requiring mechanical ventilation.

Q4: Are there limitations to using this ratio?
A: The ratio may be affected by altitude, barometric pressure, and patient factors like cardiac output. It should be interpreted in clinical context.

Q5: How does this relate to oxygen saturation?
A: While SpO₂ provides continuous monitoring, PaO₂ from arterial blood gas gives more precise oxygenation assessment for this calculation.