Education

What can mNIRS measure?

Muscle near infrared spectroscopy (mNIRS) can provide information about a number of different physiological variables. However, what an mNIRS instrument actually measures, and how those measurements should be interpreted, is not always straightforward.

This educational section provides short introductions to some of the measurements that can be made using mNIRS and the methods used to make them. For each method, I will also provide a link to an early paper describing its development — remembering the giants whose shoulders we are standing on — together with a more recent open-access example of the method in use.

The aim is not to provide comprehensive reviews, but to explain the principles behind the measurements, their strengths and limitations, and some of the issues that need to be considered when interpreting them.

Unless otherwise specified, I use the “Barstow” nomenclature for the globin chromophores, because myoglobin and haemoglobin cannot generally be distinguished by mNIRS:
total[heme] — total haemoglobin + myoglobin
oxy[heme] — oxygenated haemoglobin + myoglobin
deoxy[heme] — deoxygenated haemoglobin + myoglobin

I use StO₂ for tissue oxygen saturation.

Educational topics

1. The first ever mNIRS measurement
2. Measuring changes in heme concentration
3. How to measure absolute heme concentrations
4. Measuring oxygen saturation by a physiological calibration
5. Measuring oxygen saturation using Spatially Resolved Spectroscopy (SRS)
6. Measuring oxygen saturation – other multi-distance methods