Physiologic Dead-Space Fraction (Bohr-Enghoff Vd/Vt)
Physiologic dead-space fraction (Vd/Vt) by the Bohr-Enghoff equation; above 0.6 carried independent mortality risk in ARDS (Nuckton 2002).
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Arterial PaCO2
- 60 mmHg
- Expired CO2 source
- Mixed-expired PĒCO2 (volumetric capnography)
- Expired CO2 value
- 20 mmHg
Result: Vd/Vt 0.67 (67%), over 0.6: elevated dead-space fraction.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Vd/Vt 0.6 or below
- At or below the cited threshold.
- Vd/Vt over 0.6
- Carried independent mortality risk in ARDS (Nuckton 2002).
- End-tidal surrogate
- Using EtCO2 in place of mixed-expired PĒCO2 underestimates true dead space.
What you enter
- Arterial PaCO2
- Expired CO2 source
- Expired CO2 value
How this is calculated
Enghoff modification of the Bohr equation. Prognostic value in ARDS: Nuckton TJ, Alonso JA, Kallet RH, et al. Pulmonary dead-space fraction as a risk factor for death in the acute respiratory distress syndrome. N Engl J Med. 2002;346(17):1281-1287. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.