Comparison of Different Methods for the Calculation of the Microvascular Flow Index

Abstract EN

The microvascular flow index (MFI) is commonly used to semiquantitatively characterize the velocity of microcirculatory perfusion as absent (0), intermittent (1), sluggish (2), or normal (3).

There are three approaches to compute MFI: (1) the average of the predominant flow in each of the four quadrants (MFIby quadrants), (2) the direct assessment during the bedside video acquisition (MFIpoint of care), and (3) the mean value of the MFIs determined in each individual vessel (MFIvessel by vessel).

We hypothesized that the agreement between the MFIs is poor and that the MFIvessel by vessel better reflects the microvascular perfusion.

For this purpose, we analyzed 100 videos from septic patients.

In 25 of them, red blood cell (RBC) velocity was also measured.

There were wide 95% limits of agreement between MFIby quadrants and MFIpoint of care (1.46), between MFIby quadrants and MFIvessel by vessel (2.85), and between MFIby point of care and MFIvessel by vessel (2.56).

The MFIs significantly correlated with the RBC velocity and with the fraction of perfused small vessels, but MFIvessel by vessel showed the best R2.

Although the different methods for the calculation of MFI reflect microvascular perfusion, they are not interchangeable and MFIvessel by vessel might be better.