Pulmonary Shunt Fraction (Qs/Qt)
Pulmonary shunt fraction Qs/Qt (Berggren 1942): from hemoglobin and the alveolar, arterial, and mixed-venous O₂ saturations and tensions, the fraction of cardiac output bypassing gas exchange; normal ~4–10%.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Hemoglobin
- 15 g/dL
- Alveolar / end-capillary O₂ tension
- 110 mmHg
- Arterial SaO₂
- 99 %
- Arterial PaO₂
- 95 mmHg
- Mixed-venous SvO₂
- 75 %
- Mixed-venous PvO₂
- 40 mmHg
Result: Shunt fraction 4.7% — within the ~4–10% normal range.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Reference
- Normal ~4–10%; rising with true shunt.
What you enter
- Hemoglobin
- Alveolar / end-capillary O₂ tension
- Arterial SaO₂
- Arterial PaO₂
- Mixed-venous SvO₂
- Mixed-venous PvO₂
How this is calculated
- Formula
- CxO₂ = 1.34 × Hb × SxO₂ + 0.0031 × PxO₂ (end-capillary saturation 100%); Qs/Qt = (CcO₂ − CaO₂) / (CcO₂ − CvO₂).
Berggren SM. The oxygen deficit of arterial blood caused by non-ventilating parts of the lung. Acta Physiol Scand. 1942;4(Suppl 11):1-92. Restated in Nunn’s Applied Respiratory Physiology (Lumb AB, ed.). Search PubMed for this source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.