Respiratory failure and COPD

1. Step 1 · Critical Care

   PaO₂/FiO₂ (P/F) Ratio

   Oxygenation severity (Berlin ARDS categories).

   Population

   Patients with ABG

   Key limitation

   PEEP-dependent.

   Inputs

   3

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2. Step 2 · Critical Care

   SpO₂/FiO₂ (S/F) Ratio

   Non-invasive oxygenation when no ABG is available.

   Population

   SpO₂ ≤ 97%

   Key limitation

   Oximetry bias.

   Inputs

   2

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3. Step 3 · Pulmonology

   A–a Oxygen Gradient

   Distinguish gas-exchange failure from hypoventilation.

   Population

   Patients with ABG

   Key limitation

   FiO₂-dependent normal range.

   Inputs

   5

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4. Step 4 · Pulmonology

   BODE Index for COPD

   Long-term prognosis in stable COPD.

   Population

   Stable COPD

   Key limitation

   Needs 6MWT.

   Inputs

   5

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The Navigator organises validated tools around a presentation. It does not recommend a diagnosis or treatment.