research activities in 2007 - CSEM

Clinical Validation Results of the Long-Term Medical Survey System
O. Chételat, A. O'Hare, P. Pilloud, J-M. Koller, S. Droz, A. Ridolfi, P. Theurillat, P. Renevey, J. Solà I Caros, O. Grossenbacher
The paper describes the clinical validation of a physiological multi-parameter monitoring system made by CSEM for ESA. Results of the validation
showed that the system fulfils its purpose. The real conditions of the validation also hinted at further potential enhancements.
The European Space Agency (ESA) commissioned CSEM to
design, build, validate and deliver one fully operational ground
prototype of a system (LTMS2) measuring physiological
parameters. The system was shipped and will be used during
2008 at Concordia station (www.concordiastation.com) in
Antarctica to study the physiological adaptation of manned
crews to remote, isolated and extreme environments. The
underlying long-term objective for ESA is to obtain experience
in the field which will be used in preparing a possible manned
mission to Mars around the year 2030. This paper describes
the clinical validation of the system performed in December
2007 on volunteers at the Emergency Care Unit of the
University Hospital of Bern (Inselspital).
LTMS2 is composed of an ‘ambulatory unit’, a ‘stationary unit’
and some accessories, as well as acquisition, processing,
archiving, and visualization software. The ambulatory unit (see
Figure 1) simultaneously measures − in an unobtrusive,
comfortable and modular way − ECG (Electrocardiograph),
respiration, pulse oximetry (at the earlobe or fingertip),
activity/posture, core body temperature (at the armpit or ear
canal) and blood pressure (with a cuff at the arm). The data is
recorded for 24 hours while the subject performs his or her
usual daily tasks. During setup or modification of the
configuration, the signals can also be visualized online.
Figure 1: The ‘ambulatory unit’ of the LTMS2 system
The ambulatory unit integrates commercial sensors with
CSEM technology. In particular, the ‘electrode’ shown in
Figure 2 is actually made of two active dry stainless steel
electrodes measuring ECG and impedance, as well as an
acceleration sensor (used for activity and noise removal). The
data is digitalized in the electrode and transmitted to a
centralized data logger.
Figure 2: The ambulatory unit ‘electrode’ comprising analogue and
digital electronics to measure ECG, impedance and activity
The stationary unit measures the body weight and
composition (fat mass, water and muscle mass). All data is
transferred to a laptop where it is processed further to
obtained secondary signals such as ECG parameters (heart
rate, heart rate variability, ST-segment amplitude and
duration, QT-index − see Figure 3) or activity classification
(resting, walking, running, lying or standing). All signals are
then transferred to a database for storage where they can be
remotely accessed by a medical doctor (MD). Special
mechanisms ensure that no data can be lost, accidentally
erased or viewed by unauthorized people. The visualization of
the signals is multi-scale and several sessions can be
displayed on the same time axis. Out-of-boundary sections for
any signal are marked and can be quickly accessed.
Figure 3: The different parameters of a typical ECG wave
The LTMS2 system was designed, built and tested according
to the European directive #93/42/ECC and follows the relevant
medical standards, especially EN60601-1 and EN60601-2-47
for CSEM ECG electronics. However, the system is not CE
marked (even though many of its components are), because
the intended use is for clinical trials in Concordia.
Nevertheless, after having obtained the ethical committee and
Swissmedic authorizations, and fulfilled other requirements of
the norm ISO14155, the system was clinically validated by
Prof. Dr. MD S. Jakob at Bern hospital.
The principle of the validation was to test the system on a few
healthy volunteers in a controlled environment and to compare
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