P.-F. Migeotte is with the Department of Cardiology, Universite Libre de Bruxelles 1050, Brussels, Belgium (e-mail: Pierre-Francois.Migeotte@ulb.ac.be).K.-S. Park is with the Department of Biomedical Engineering, Seoul National University, Seoul 110-799, Korea (e-mail: kspark@bmsil.snu.ac.kr).M. Etemadi is with the Department of Bioengineering and Therapeutic Sciences, University of California at San Francisco, San Francisco, CA 94143 USA (e-mail: mozziyar.etemadi@ucsf.edu).K. Tavakolian is with the Department of Electrical Engineering, University of North Dakota, Grand Forks, ND 58202 USA (e-mail: kouhyart@gmail.com).R. Casanella is with the Instrumentation, Sensors, and Interfaces Group, Universitat Politecnica de Catalunya, 08034 Barcelona, Spain (e-mail: ramon. casanella@upc.edu).J. Zanetti is with Acceleron Medical Systems, Arkansaw, WI 54721 USA (e-mail: jmzsenior@gmail.com).J. Tank is with the Klinsche Pharmakologie, Medizinische Hochschule Hannover, 30625 Hannover, Germany (e-mail: Tank.Jens@mh-hannover.de).I. Funtova is with the

Impaired autonomic control represents a cardiovascular risk factor during long-term spaceflight. Little has been reported on blood pressure (BP), heart rate (HR), and heart rate variability (HRV) during and after prolonged spaceflight. We tested the hypothesis that cardiovascular control remains stable during prolonged spaceflight. Electrocardiography, photoplethysmography, and respiratory frequency (RF) were assessed in eight male cosmonauts (age 41-50 yr, body-mass index of 22-28 kg/m2) during long-term missions (flight lengths of 162-196 days). Recordings were made 60 and 30 days before the flight, every 4 wk during flight, and on days 3 and 6 postflight during spontaneous and controlled respiration. Orthostatic testing was performed pre- and postflight. RF and BP decreased during spaceflight (P < 0.05). Mean HR and HRV in the low- and high-frequency bands did not change during spaceflight. However, the individual responses were different and correlated with preflight values. Pulse-wave transit time decreased during spaceflight (P < 0.05). HRV reached during controlled respiration (6 breaths/min) decreased in six and increased in one cosmonaut during flight. The most pronounced changes in HR, BP, and HRV occurred after landing. The decreases in BP and RF combined with stable HR and HRV during flight suggest functional adaptation rather than pathological changes. Pulse-wave transit time shortening in our study is surprising and may reflect cardiac output redistribution in space. The decrease in HRV during controlled respiration (6 breaths/min) indicates reduced parasympathetic reserve, which may contribute to postflight disturbances.

Balistocardiography was recorded in 3-D on a free floating astronaut in space as well as on healthy volunteers participating to a dry immersion study in a terrestrial laboratory. We demonstrate a new technique suitable for the analysis of 3-D BCG. The spatial curve of the displacement vector is analyzed instead of the three components of acceleration. The technique presented is invariant from the axis of representation and provides important novel physiological information.

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Ballistocardiography was recorded in 3-D on a free floating astronaut in space as well as on healthy volunteers participating to the ESA 55(th) and DLR 19(th) parabolic flights campaigns. In this paper we demonstrate further the usefulness of recording and analyzing ballistocardiograms (BCG) in three dimensions. The spatial curves of the displacement, velocity and acceleration vectors are analyzed instead of their individual 2-D components. The maximum magnitude of the force vector is shown to be poorly correlated to the HI and IJ wave amplitude traditionally computed on the longitudinal (feet-to-head) component of acceleration (uni-dimensional BCG). We also suggest that kinetic energy and work are useful parameters to consider for a physiological interpretation of the 3D-BCG. The technique presented is invariant from the axis of representation and provides important novel physiological information. We stress further the need of 3D recordings and analysis techniques for Ballisto- and Seismo-cardiography.

Orthostatic tachycardia (POTS) can occur after space flights. We determined orthostatic heart rate responses in 18 cosmonauts before and 3-5 days after long-term space missions. Cosmonauts undergoing a cardiovascular training program in space experienced only moderate POTS after their return to earth. Cardiovascular countermeasures may have attenuated POTS. Another possible interpretation is that cardiovascular deconditioning is not sufficient to elicit full blown POTS in the absence of additional genetic or environmental factors.

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