🫁 Physiologic Shunt Fraction (Qs/Qt)
UseWhen to use: hypoxemia workup with arterial and mixed-venous (or content) data.
StrataHigher Qs/Qt → larger shunt physiology cue; interpret with FiO₂ and cardiac output.
LimitsWhen not to use: no venous sample / unreliable sats. · Pitfall: substituting ScvO₂ for SvO₂ without caveat. · High FiO₂ may inflate apparent shunt.
SourceClassic Berggren physiologic shunt equation
This-shift next steps
After scoring: open the scene pack, peer scores, and the matching pathway. Local reference — no HIS write.
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Methodology · worked example, guidelines & full notes
Berggren equation.
When to use
When to use: hypoxemia workup with arterial and mixed-venous (or content) data.
How it works
Qs/Qt = (CcO₂ − CaO₂) / (CcO₂ − CvO₂).
Key points
- Berggren equation.
- Contents or gas mode.
- Next: vent / imaging review.
References
- Classic Berggren physiologic shunt equation
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Input mode | Direct O₂ contents (mL/dL) |
|---|---|
| CcO₂ (end-pulmonary ideal) | 20.5 mL/dL |
| CaO₂ (arterial) | 18.5 mL/dL |
| CvO₂ (mixed venous) | 14.0 mL/dL |
| Haemoglobin (gas mode) | 12 g/dL |
| FiO₂ (gas mode) | 0.50 fraction or % |
| PaCO₂ (gas mode) | 40 mmHg |
| PaO₂ (gas mode) | 80 mmHg |
| SaO₂ (gas mode) | 92 % |
| PvO₂ (gas mode, optional) | 40 mmHg |
| SvO₂ (gas mode) | 70 % |
| Barometric pressure | 760 mmHg |
| RQ | 0.8 |
→Qs/Qt30.8%
- CcO₂：20.50 mL/dL
- CaO₂：18.50 mL/dL
- CvO₂：14.00 mL/dL
| Input mode | Hb + sats/gases (compute contents) |
|---|---|
| CcO₂ (end-pulmonary ideal) | 20.5 mL/dL |
| CaO₂ (arterial) | 18.5 mL/dL |
| CvO₂ (mixed venous) | 14.0 mL/dL |
| Haemoglobin (gas mode) | 12 g/dL |
| FiO₂ (gas mode) | 0.50 fraction or % |
| PaCO₂ (gas mode) | 40 mmHg |
| PaO₂ (gas mode) | 80 mmHg |
| SaO₂ (gas mode) | 92 % |
| PvO₂ (gas mode, optional) | 40 mmHg |
| SvO₂ (gas mode) | 70 % |
| Barometric pressure | 760 mmHg |
| RQ | 0.8 |
→Qs/Qt35.2%
- CcO₂：17.03 mL/dL
- CaO₂：15.04 mL/dL
- CvO₂：11.38 mL/dL
Verification & sources · governance
FAQ
Frequently asked questions
- Does Physiologic Shunt Fraction (Qs/Qt) upload patient data? Where is it calculated?
- Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.
- How is Physiologic Shunt Fraction (Qs/Qt) calculated in practice? Can you show a worked example?
- Inputs: Input mode Direct O₂ contents (mL/dL), CcO₂ (end-pulmonary ideal) 20.5 mL/dL, CaO₂ (arterial) 18.5 mL/dL, CvO₂ (mixed venous) 14.0 mL/dL, Haemoglobin (gas mode) 12 g/dL, FiO₂ (gas mode) 0.50 fraction or %, PaCO₂ (gas mode) 40 mmHg, PaO₂ (gas mode) 80 mmHg… → Result: Qs/Qt 30.8 %（CcO₂: 20.50 mL/dL, CaO₂: 18.50 mL/dL, CvO₂: 14.00 mL/dL） Inputs: Input mode Hb + sats/gases (compute contents), CcO₂ (end-pulmonary ideal) 20.5 mL/dL, CaO₂ (arterial) 18.5 mL/dL, CvO₂ (mixed venous) 14.0 mL/dL, Haemoglobin (gas mode) 12 g/dL, FiO₂ (gas mode) 0.50 fraction or %, PaCO₂ (gas mode) 40 mmHg, PaO₂ (gas mode) 80 mmHg… → Result: Qs/Qt 35.2 %（CcO₂: 17.03 mL/dL, CaO₂: 15.04 mL/dL, CvO₂: 11.38 mL/dL）