Qp/Qs Pulmonary-to-Systemic Flow Ratio
Pulmonary-to-systemic flow ratio (Qp:Qs) for intracardiac shunts: (SaO₂ − MvO₂) ÷ (PvO₂ − PaO₂), from the four saturations of a shunt run.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- Systemic-arterial SaO₂
- 95 %
- Mixed-venous MvO₂
- 60 %
- Pulmonary-vein PvO₂
- 98 %
- Pulmonary-artery PaO₂
- 85 %
Result: Qp/Qs 2.69 — large left-to-right shunt.
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Interpretation
- ≈ 1 no net shunt; small 1.1–1.5, moderate 1.5–2.0, large > 2.0 (closure often considered); < 1 net right-to-left.
What you enter
- Systemic-arterial SaO₂
- Mixed-venous MvO₂
- Pulmonary-vein PvO₂ (default 98)
- Pulmonary-artery PaO₂
How this is calculated
- Formula
- Qp/Qs = (SaO₂ − MvO₂) / (PvO₂ − PaO₂).
Wilkinson JL. Haemodynamic calculations in the catheter laboratory. Heart. 2001;85(1):113-120. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.