Introduction
The VU-AMS is an Ambulatory Monitoring System developed at the Vrije Universiteit (see also www.psy.vu.nl/vu-ams). It can be used to assess autonomic reactivity during stress and conditioned emotional responses. Main parameters assessed are the Pre-Ejection Period (PEP), the Inter Beat Interval (IBI), Respiratory Sinus Arrhythmia (RSA) and Skin Conductance Level (SCL). At the heart of the VU-AMS is a battery-powered ambulatory monitoring device (VU-AMD) capable of recording a three lead ElectroCardioGram (ECG) and a four lead Impedance CardioGram (ICG) or a two lead Skin Conductance Level (SCL). The VU-AMD is used in several psychophysiological laboratories, but its full potential is realized in ambulatory research - i.e. research not bound to an artificial laboratory situation. For this reason, the VU-AMD is kept small (dimensions 32 x 65 x 120 mm), weighing only 225 g. At the Vrije Universiteit alone, 1405 24-hour measurements have been performed on 980 subjects, amounting to 33720 hours of ambulatory data. Experience so far learns that subjects experience very little inconvenience from the device and can easily follow their normal routines. Reliability and validity of the ECG and ICG signals is high. Unrelated to the performance of the VU-AMD, a number of pitfalls remain in the interpretation of ambulatory data from any ambulatory device. These pitfalls, as well as current strategies to deal with them, other practical information and recent reseach findings will be exchanged during the VU-AMS User Meeting.

Aim of the meeting
The VU-AMS User Meeting gave participants an update on the theoretical background and an overview of the practical use of the VU-AMS (version 4.6). The focus was on the acquisition and analysis of ambulatory cardiovascular data.

Program

• 9:30. Welcome and introduction of the VU-AMS. Eco de Geus.
• 10:00. Using an electronic diary with the VU-AMS. Suzanne Pieper and Jos Brosschot.
• 10:45. Coffee break.
• 11:00. Neurobiological factors in aggressive and antisocial juveniles. Arne Popma, Theo Doreleijers, Herman van Engeland and Stephanie van Goozen.
• 11:45. Impedance derived variables measured with the VU-AMS in a laboratory setting. Gonneke Willemsen, Harriëtte Riese and Eco de Geus.
• 12:30. Lunch break.
• 13:30. VU-AMS derived differential contribution of cardiac vagal tone, central respiratory drive, and respiratory parameters to RSA during mental stress and physical exercise. Jan Houtveen, Simon Rietveld and Eco de Geus.
• 14:15. Circadian rhythmicity in cardiac stress reactivity; using the VU-AMS in a constant routine protocol. Sander van Eekelen and Jan Houtveen.
• 15:00. Tea break.
• 15:15. VU-AMS derived cardiac function measures - validity and field studies. Harriëtte Riese, Mireille van den Berg, Tanja Vrijkotte, Gonneke Willemsen and Eco de Geus.
• 16:00. A technician’s view on the future of the VU-AMS. Paul Groot.
• 16:30. Closing.