Vrije Universiteit Ambulatory Monitoring System: Quo vadis?
E.J.C. de Geus1, J. den Hartog2 and P.F.C. Groot2
1Department of Biological
Psychology, Vrije Universiteit, Amsterdam, The Netherlands
2Department of Instrumentation (ITM), Vrije Universiteit, Amsterdam, The
Netherlands
The Vrije Universiteit Ambulatory Monitoring System (VU-AMS) plays a
key role in the cardiovascular research of the department of Biological
Psychology and The Netherlands Twin Registry on the (interactive) influence
of genetic and environmental factors (e.g. chronic stress) on cardiovascular
disease risk. This ongoing scientific demand from within has maintained
the VU-AMS in a continuous state of innovation since its first prototypes
in the early 1990s. This demand for continuous innovation is reinforced
by the over 40 external research groups that use the VU-AMS world-wide.
To meet this demand, we will release the first VU-AMS of the new 5fs-series
in the fall of 2005. The new full storage VU-AMS (version 5fs.1) will
continuously record the ECG, thorax impedance and (optionally) skin conductance
and store these to flash memory. The new version will not lead to a change
in the main VU-AMS philosophy of rapid data-reduction based on ensemble
averaging over labeled periods. Ensemble averaged values over the relevant
labeled periods will still be extracted in as short a time frame as possible
without compromising full visual interactive control over signal scoring.
Put otherwise, the device will be downward compatible to existing software
and data analysis strategies. The new device tops the old one, however,
on three major accounts. A number of new variables can be extracted including
the T-wave amplitude and QT interval variability (both indices of sympathetic
drive that are less dependent on pre- and afterload), convergence of skin
conductance and thorax impedance changes (can now jointly measured by
a single device), and fourier- or wavelet-based frequency decomposition
of the variance in heart period and respiration signals. Secondly, because
memory is .ash-card based, repeated 24-hour measurements on the same subject
can be scheduled by minimal contact of the researcher with the participant/patient.
Finally, availability of continuous data sampled at a much higher frequency
(1000 Hz) than before will allows us to reduce measurement error and increase
automaticity of scoring of the impedance cardiogram (ICG) and the respiration
signal.
Paper presented
at Measuring Behavior 2005
, 5th International Conference on Methods and Techniques
in Behavioral Research, 30 August - 2 September 2005, Wageningen, The
Netherlands.
© 2005 Noldus
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