Fig. 1.

Variations of indexed right ventricular end-diastolic volume and cardiac index during and after prone positioning in the study group (n = 8) with stable hemodynamics and in the single patient who deteriorated his hemodynamic status. Variations of indexed right ventricular end-diastolic volume (blue symbols) during and after prone ventilation are plotted with those of cardiac index (green symbols), when using baseline as reference. Box plots indicate median (thick horizontal bar), 25th and 75th percentiles (bottom/top of the boxes), as well as 5th and 95th percentiles (thin horizontal bars). Closed circles indicate individual values of indexed right ventricular end-diastolic volume and cardiac index in the patient who deteriorated during and after prone positioning. Dotted lines connect median and dashed lines connect individual values. The grey area indicates the normal range of indexed right ventricular end-diastolic volume measured with RT3D TEE. In the single patient who deteriorated, preload-dependence was identified by significant superior vena cava (SVC) collapsibility index at baseline and 1 h after prone positioning (upper left panel). A 1.5L fluid challenge reduced SVC collapsibility index (lower right panel) but failed to avoid further deterioration of cardiac index. The transgastric short-axis view of the heart depicted a moderate cor pulmonale at baseline, with an end-systolic eccentricity index of 1.5 (lower left panel) which transiently normalized close to unity during prone positioning (lower middle panel). Moderate cor pulmonale resumed after return to supine position with an end-systolic eccentricity index of 1.4 (upper right panel)