Automated quantification of the effects of low body negative pressure on left ventricular function during parabolic flight

To study modifications in left ventricular (LV) dimensions induced by gravitational stresses, and evaluate the effects due to lower body negative pressure (LBNP) countermeasure, we performed 2D echocardiographic imaging during parabolic flights on a group of eleven subjects (mean age ± SD, 46 ± 5 years) in upright position with and without LBNP applied. To detect LV endocardial contours, a semi-automatic procedure based on level set methods was applied. The analysis was performed both averaging four consecutive end diastolic (ED) and end systolic (ES) frames, and frame by frame in a cardiac cycle, allowing the computation of ED (EDA) and ES (ESA) areas and LV area over time. Modifications in LV dimensions according to different gravity conditions were found: a LV dilation was observed during 0 Gz, preceded by its contraction during 2 Gz. When LBNP was applied, it appeared effective in reducing venous return and minimizing LV dilation.