Cardiovascular autonomic control during respiratory paced hypnosis

The capability of hypnosis to act on the Autonomic Nervous System under a controlled breath condition (12 breaths/min) was assessed in 11 healthy volunteers. Subjects were split into high and low susceptibility to hypnosis groups, using the Stanford hypnotic susceptibility scale form {C} (SHSS). Autoregressive power spectrum analysis of RR interval and SAP variabilities provided the markers of cardiac sympatho-vagal interaction (LF/HF) and vascular sympathetic vasomotor control ({LF}-{SAP}). Under controlled respiration, no significant changes in LF/HF ratio were observed between the two groups. Hypnosis induced a significant increase of {LF}-{SAP} in high susceptible subjects. These preliminary results highlight how the state of hypnotic trance acts directly on the cardiovascular autonomic profile by increasing the sympathetic vascular activity only in high susceptible subjects. These effects become evident when the role of potential changes in respiration rate are excluded by the controlled breathing condition.