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Data Acquisition for physiology research and education

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TREV = Trans-radial Electrical Bioimpedance Velocimetry

In psychophysiological research, variability in heart contractility is a good index of the sympathetic tone, but it's not trivial to measure! The most common non-invasive method to estimate contractility is PEP (Pre Ejection Period) which is obtained by measuring the thoracic ICG. The thorax is complex and the method is very sensitive to movements. The PEP analysis from ICG requires that you determine the B point on the noisy ICG signal and it is therefore very difficult to identify. The method often requires averaging and therefore in practice does not provide a beat-2-beat index.

Trans-radial Electrical Bioimpedance Velocimetry, is a bioimpedance method named by Donald Bernstein. It is based on measuring impedance variations in a similar way to ICG, but in the forearm instead of the thorax. The advantages are several but as the forearm is not as complex as the thorax it is less affected by posture and breathing and therefore it is easier to get a beat-2-beat index of the sympathetic tone.

One of the keys to the new method is that, unlike old models, it makes use of the fact that the electrical conductivity of the blood changes dynamically when the blood changes speed, which is due to that the orientation of the red blood cells inside the vessels is partially synchronized perpendicular to the direction of flow.
The measurement method behind TREV is based on associating the contractility of the heart with the maximum acceleration of the blood after the aortic valve is opened, which is therefore in turn indexed by the peak value of the second derivative of the impedance. This is more robust than identifying a b-point in an artifact-sensitive ICG.

- faster and easier to apply electrodes
- less invasive and more comfortable for the subject
- less artifacts - less affected by sitting position and venous return
- simpler and more robust analysis
- beat-2-beat index for event-related analysis after corrections

To read more about the TREV method
and further information links, see:

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