Three-dimensional ballistocardiography and seismocardiography in parabolic flight: Preliminary results from the esa b3d project

Ballistocardiography (BCG) is a technique that had a large interest in cardiology between the fifties and eighties. Typically BCG consisted in the recording of mechanical acceleration (Acc), caused by cardiac activity, on a subject lying on a table. As Acc was recorded only in the 2-dimensions (2D) of the horizontal plane, the antero-posterior (Z-axis) component was often neglected. From past experiments conducted in space [1,2] it was suggested that this component was comparable in magnitude to the other two and that Ballistocardiography should be recorded in threedimensions (3D). These observations and the recent modest regain of interest in the BCG technique were the starting point of the B3D project selected by ESA for the definition phase after the AO-2009. We recorded 3D Acc at various positions on the surface of the body (close to the centre of mass (CM), at the apex of the heart and on the sternum) of 8 healthy volunteers during free floating periods of parabolic flight (PF) manoeuvre (ESA 55th and DLR 19th PF campaigns conducted on-board the A300-zéroG airplane of NOVESPACE). Out of the many recordings collected, only a very limited number provided body Acc free from artefacts. Nevertheless, our results show that Seismocardiograms (SCG) and Ballistocardiograms (BCG) waves were qualitatively and quantitatively comparable in the frontal plane while larger differences were present along the antero-posterior component. Our limited number of artefact free episodes demonstrates the intrinsic difficulties of 3D recordings of SCG and BCG in PF and thus the need for a study in sustained microgravity. Moreover, our results confirm that the ventro-dorsal component of BCG is of similar amplitude as the other two which further demonstrates that the three components are essential to provide a physiological interpretation of BCG and SCG signals.