Measurements of jugular, portal, femoral, and calf vein cross-sectional area for the assessment of venous blood redistribution with long duration spaceflight (Vessel Imaging Experiment)

To determine if 6 months in microgravity resulted in significant changes in the major central and peripheral veins indicating a redistribution of venous blood flow. Ten astronauts participated in the study. Jugular vein (JV), portal vein (PV), femoral vein (FV), tibial vein (TibV), and gastrocnemius vein (Gast V) were assessed by echography for the measurement of vessel cross-sectional area. Inflight exams were conducted by astronauts using a volume capture method in which images collected were processed to produce a 3D reconstruction of the vessel which was later analyzed by a trained sonographer. Measurements were conducted pre-flight, at the beginning of the flight (day 15), near the end of the flight (4-5.5 months), and post-flight. During the flight, JV, PV, JV/PV ratio, and FV were found significantly increased from pre-flight at 15 days and 4-5.5 months (JV: 178 and 225 %, p < 0.05; PV: 36 and 45 %, p < 0.05; JV/PV ratio: 102 and 120 %, p < 0.05; FV: 124 and 169 %, p < 0.05). Conversely, calf veins decreased at day 15 and at 4-5.5 months (TibV: -45 % and-52 %, p < 0.05; Gast V: -68 and -55 %, p < 0.05). All veins returned to base line conditions 4 days after returning to Earth. The increase in JV, PV, and FV cross-sectional area during spaceflight confirmed that there was venous blood pooling in the cephalic, splanchnic, and pelvic regions. Further investigation is needed to determine the consequences of this fluid stagnation on the brain, eye, splanchnic, and pelvic organ morphology and or function.