Comparison of Internal Jugular Vein Cross-Section Area During a Russian Tilt-Table Protocol and Microgravity.

To date, we lack U.S. data on the effects of the long-used Russian tilt-table training protocol known as the Russian pre-launch tilt-table training protocol on internal jugular vein cross sectional area (IJV-CSA) in microgravity. A case study of a single healthy male astronaut volunteer was used for this study. The right IJV-CSA was measured using real time ultrasound at set times throughout the Russian pre-launch tilt-table training protocol, a method of physiological preparation for microgravity using tilt-table training. In microgravity, the subjects right IJV-CSA was measured again for comparison. The mean difference from in-flight right IJV-CSA for pre-tilt (0) was 0.438 cm², for 15 was 0.887 cm², for 30 was 0.864 cm², for 50 was 1.15 cm², and for post-tilt (0) the difference was 0.305 cm². The cross-sectional areas of the subjects right IJV-CSA were significantly different between in-flight values and several angles of the Russian tilt-table protocol, except for the 0 measurement. In summary, this case-study represents the first time IJV-CSA has been compared between various angles of a tilt-table training protocol and microgravity in the same astronaut subject. The findings support prior cohort studies studying the same principles. Further investigation is merited; both to better describe the relationship between the cardiovascular effects of tilt-table simulations of microgravity and their correlating in-flight values, and to evaluate and study the Russian tilt-table protocol effects on cardiovascular physiology from a training and preparation perspective.