Physiological Correlates of Applied Tension May Contribute to Reduced Fainting During Medical Procedures

Background Applied tension (AT) is a behavioral technique used to reduce symptoms such as dizziness and fainting in people with blood and injury phobias as well as medical patients undergoing invasive procedures. AT has been found to reduce dizziness and fainting in several studies of blood donors. Purpose The purpose of this study was to examine the psychophysiological effects of AT in the context of blood donation. Methods Ninety-eight young adult blood donors wore ambulatory physiological monitors and were randomly assigned to one of two groups that practiced AT or one that did not. Measures of blood pressure, heart rate, stroke volume, and other physiological parameters were obtained while participants gave blood. Results Donors who did not practice AT were more likely to report symptoms in the donation chair and generally displayed a pattern of physiological activity consistent with risk for a vasovagal reaction. For example, heart rate and total peripheral resistance decreased. The drop in heart rate was probably due at least in part to an increase in vagal parasympathetic nervous system activity, as suggested by an increase in high-frequency heart rate variability. In contrast, donors who practiced AT displayed stable heart rate and high-frequency heart rate variability. Conclusions The results suggest that the physiological effects of AT, particularly the inhibition of vagal activity, interfere with those promoting a vasovagal reaction. There may be a number of useful applications for AT in medical settings.