Reliability of infrared plethysmography in BVP biofeedback therapy and the relevance for clinical application.

Biofeedback methods are well established as behavioral techniques for the therapy of various psychophysiological diseases. The forms of feedback generally employed are muscle activity (electromyogram), skin temperature, brain activity (electroencephalogram), and vasomotoricity. The latter technique, which employs plethysmographic feedback, has been studied most extensively in the therapy of migraine (vasoconstriction training, blood volume pulse training). Although the clinical efficacy has been demonstrated in several studies, little is known about the psychometric properties of this technique. This study examined the intrasession and intersession reliability of the pulse volume amplitude (PVA). The results showed that the PVA measurements within a single biofeedback session were highly reliable. Repositioning of the probe within the session resulted in a lower correlation coefficient, but one that was still sizable and significant. The PVA values from different sessions were not reliable (or comparable).