A capnometer measures carbon dioxide in the breath and thus can detect (degree of) over-breathing - arguably the most significant stress related physiological indicator of all, since it strongly influences oxygen delivery to brain cells.

The capnometry biofeedback module offers three applications:
A capnometer is also known as a capnograph.
Basic Capnometry Application User Guide
Capnometry with EMG Application User Guide
Capnometry with HRV Application User Guide
Capnometry with BVA Application User Guide