How to measure emotional reactions in forensic psychiatric patients with schizophrenia - focusing on Galvanic Skin Response og Heart Rate Variability ?

As a part of a phd project I am in the process of investigating how or if I can supply qualitative data from music therapy sessions with quantitative data by measuring activity in the autonome nervoussystem during music therapy sessions. Participants in the pdh project is forensic psychiatric patients with schizophrenia and a low functional level. In the litteratur search in this field I have found the below mentioned article informative  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2756702/ The article describes different variables in the autonomic nervous system and how they show different reactions in the autonome nervous system. Reactions in the Galvanic Skin Response (GSR) primarily shows arousal reactions in the sympathetic  nervous system. Whereas Heart Rate Variability (HRV) is important when you want to measure reactions in the parasympathetic nervous system. Because the patients I want to include in the phd project is very vulnerable it is important to find a measurement tool which impact on the patient is as little as possible and creates as few bias as possible. GSR is possible to measure by an armband from Sensewear : http://sensewear.bodymedia.com/ Some patients in  forensic psychiatry has tried them out, and some patients forgets they are wearing this armband, others react with bodily sensations and paranoia. It helps to use very simple explanations as “This armband measure bodily reactions to music either of becoming exalted or relaxed when you listen to music” But is GSR a suitable measurement for reactions in the autonome nervous system in forensic psychiatric patients with schizophrenia ? GSR measures arousal and shows reactions in the sympathetic nervous system . In my phd project I want to find out how the patients are capable of calming down an regulate arousal. This regulation happens through activity in the parasympathetic nervous system. Activity in the parasympathetic nervous system can be derived by data from Sensewear measurements, but is not a direct measure of activity in the parasympathetic nervous system. I have been in contact with different persons interested in the Polyvagale theory of Porges (Porges 2001) and through that found measurement tools to measure Heart Rate Variability (HRV) The analysis of HRV data reflects the balance between parasympathetic and sympathetic nervoussystem. Flemming Kærby who is a psychotherapist and cand.scient in fysiological biochemistry has been teaching doctors in how stresshormons  affects the human body. He is very interested in the polyvagal theory, and has used measurement of HRV directly in Trauma therapy. In the article mentioned below he describes how he used measurement of HRV in Trauma Therapy: http://www.seforeningen.dk/files/articlefiles/Bibliotek/Offentligeartikler/FYSIOLOGISK-TEORI/kaereby_psykofysiologisk_traumeterapi_%203_2010.pdf Flemming Kæreby used the Emwave measurement tools http://www.heartmathstore.com/category/emwave-desktop/emwave-desktop-anxiety-relief&source=heartmath-emwavetech&kw=desktopnav Flemming Kæreby comment on the use of Em-wave that it cannot measure frequencies higher than 0.26 Hz. The ventrale nervus vagus is essential accordingly to measure parasympathetic reactions, and activity in the ventrale nervus vagus might show frequencies as high as 0,4 Hz. The company called MindWare uses Porge´s matematic analyse program in their measurement tools, but it is very expensive. By using Emwave you place a sensor at the earflip or on a fingertip, and is also not very invasive, and therefore might be usefull in my phd project, with very vulnerable forensic psychiatric patients with schizophrenia.  The company called MindWare uses Porge´s matematic analyse program in their measurement tools, but it is very expensive. Britta Frederiksen, Music therapist, Ph.D student at the Music therapy Phd Programme, Department of Communication and Psychology, Aalborg University Litt: Porges , S.W. (2001) The polyvagale theory: Phylogenetic substrates of a social nervosus system International journal of Psychophysiology, 42:123-146