3-D ballistocardiography, a tool revisited for following astronaut cardiovascular function?

A recording on a crew member of the D2-Spacelab mission constitutes, to our knowledge, the only 3-D acceleration data that includes respiratory movements. In a previous paper [1], the description of the Balistocardiogram (BCG) on three axes revealed that the information along the antero-posterior axis (which is inaccessible on earth) was of the same magnitude as the 2 other projections, and thus of crucial importance for the physiological interpretation. The present study analyses in details the 3-D displacement vector (DV).