Baillie lab, Roslin Institute, University of Edinburgh

Effective shunt (ES): an eGFR for the lungs?

Effective shunt (ES) is an estimate of the proportion of cardiac output that would have to bypass the lungs entirely to obtain these blood gas results, at steady state. Obviously this is a rare event in clinical practice, but the measure provides an intuitively-interpretable result. This is analogous to an estimated glomerular filtration rate for the oxygenation function of the lungs.

We have systematically compared the predictive validity of effective shunt with other measures of pulmonary oxygenation defect. ES has better predictive validity than P:F ratio, A-a difference and another method based on an integrated computer model of oxygen delivery.

Chang et al. Predictive validity of effective shunt fraction in critically ill patients. biorxiv 2018.

Effective shunt calculator

This online calculator provides calculation of effective shunt using standard assumed values. Effective shunt can be calculated on any ABG result.

Click here for a minimalist mobile version which can be saved to the home screen of a mobile device for easy access.

Blood gas interpretation: automatic ABG analysis
Effective Shunt Calculator

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Baillie & Bretherick, 2018. Presented as is with no guarantees.

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Code availability

We believe in open science. All of our code is available from github.

A single python script to calculate effective shunt:

Download the full physiological model of oxygen delivery:


We are very grateful to recieve funding from the following sources: Wellcome Trust, BBSRC, Sepsis Research (FEAT), Intensive Care Society, MRC.

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