Computational modeling of orthostatic intolerance for travel to Mars

Fig. 1. Pressure-volume loop: effect of stand test on the left ventricle before and after a short duration spaceflight. Pressure-volume loop of the left ventricle pre-flight (black) and on landing day after a short duration space flight (orange), with solid lines representing the supine position and the dashed lines after standing up.

Fig. 2. Hemodynamic responses to stand test pre-flight and on landing day under different conditions. a Is pre-flight, b Landing day after short-duration space flight (<10 days), c Long-duration spaceflight, no fluid loading, and Earth’s gravity, d Long-duration space flight, fluid loading prior to return to Earth, and Earth’s gravity, and e Long-duration space flight, no fluid loading, and Mars’ gravity. Line colours: dashed line = start stand test, red = mean arterial pressure, dashed green = heart rate, black = cardiac output, and blue = central venous pressure.

Fig. 3. Diagram and conceptual model of the 21-compartment cardiovascular model. 0: Ascending aorta. 1: Brachiocephalic arteries. 2: Upperbody arteries. 3: Upper body veins. 4: Superior vena cava. 5: Thoracic aorta. 6: Abdominal aorta. 7: Renal arteries. 8: Renal veins. 9: Splanchnic arteries. 10: Splanchnic veins. 11: Lower body arteries. 12: Lower body veins. 13: Abdominalveins. 14: Thoracic inferior vena cava. 15: Right atrium. 16: Right ventricle. 17: Pulmonary arteries. 18: Pulmonary veins. 19: Left atrium. 20: Left ventricle. a Anatomic model. Dashed square indicated the intrathoracic pressure. b Hydraulic circuit model. The orange circles with numbers are elastic elements with a pre and post resistance in blue and annotated with Roman numbers. The cardiac compartments are illustrated with red circles and represent time-variant elastances, together with their valves (green single triangles). The dashed rectangle outlines the intrathoracic compartments, and the brown wide-dashed line with round arrowheads indicates the lymphatic flow from the lower and upper body to the super vena cava. The green and red apple indicate gravity and its direction (green = added, red = subtracted)18,39.

Fig. 4. Time-varying heart elastances. Red lines indicate the left heart, and blue lines the right heart. Dashed lines indicate the atria, and solid lines the ventricles.

Fig. 5. Schematic overview of the baro- and cardiopulmonary reflex control model. Step I; create a mean blood pressure, Step II; create an error signal, Step III convolute the error signal with 6 different impulse responses, and step IV; influence hemodynamic effector sides. See text section 2.3.2, ref. 60, and model code for more information.

Fig. 6. Ventilation. Simulated intra-thoracic pressure curve with a respiratory rate of 12/min.