Dead Space Fraction (Bohr) Calculator
Enter arterial and mixed-expired CO₂ to get the Bohr dead space fraction.
Result
How to use
- Enter your values in the fields above.
- Press Calculate to see your result instantly.
- Use the Share button to copy a link to your result.
About this calculator
This calculator applies the Bohr equation, the classic respiratory physiology formula for physiological dead space: Vd/Vt = (PaCO₂ − PeCO₂) ÷ PaCO₂, where PaCO₂ is arterial CO₂ tension and PeCO₂ is the mixed expired CO₂. It measures the fraction of each breath that ventilates the airways and alveoli without ever taking part in actual gas exchange.
Anesthesiologists and intensive-care clinicians use the Vd/Vt ratio to assess ventilation efficiency in mechanically ventilated patients — a normal ratio is roughly 0.2–0.4, and an elevated value points to conditions like pulmonary embolism or severe lung disease that waste ventilation.
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