Qp/Qs Ratio Calculator
Calculate the pulmonary-to-systemic blood flow ratio (Qp/Qs). Used to assess left-to-right shunts in congenital heart disease.
Formula
Qp/Qs = Pulmonary Flow (Qp) / Systemic Flow (Qs)
- Qp = pulmonary blood flow (left pulmonary artery flow)
- Qs = systemic blood flow (ascending aorta flow)
- Used to quantify left-to-right shunts in ASD, VSD, PDA
- Ratio > 1 indicates shunted blood from systemic to pulmonary circulation
Example
Inputs
- Pulmonary Blood Flow (L/min): 5
- Systemic Blood Flow (L/min): 5
Qp 5 L/min, Qs 5 L/min: Ratio = 1.0 (normal, no shunt).
Frequently asked questions
What does Qp/Qs ratio mean?
It compares blood flow to lungs versus body. Normal is ~1:1. Ratios > 1 indicate extra blood recirculating to the lungs.
When is it measured?
During cardiac catheterization or echocardiography. Key diagnostic tool for congenital heart defects.