Jugular venous flow dynamics during acute weightlessness and partial gravity in parabolic flight

Area of Science:

• Space Medicine
• Cardiovascular Physiology
• Fluid Dynamics

Background:

• Spaceflight, including weightlessness and partial gravity, may cause internal jugular vein (IJV) distension and alter cerebral blood flow.
• These changes could potentially elevate the risk of venous thrombosis, a significant concern for astronaut health.

Purpose of the Study:

• To investigate the effects of varying reduced gravity levels on internal jugular vein (IJV) dimensions, pressure, and blood flow.
• To assess the potential risk of venous stasis and thrombosis in astronauts during space missions.

Main Methods:

• Nine participants underwent assessments during parabolic flights simulating 0.00-G to 0.75-G.
• Bilateral IJV cross-sectional area (CSA), pressure, and flow were measured using 2D and Doppler ultrasound in seated and supine positions.

Main Results:

• IJV cross-sectional area and pressure increased significantly with reduced gravity compared to preflight seated conditions.
• Left IJV CSA increased at 0.00-, 0.25-, and 0.50-G; right IJV CSA increased at 0.00- and 0.25-G.
• While most participants maintained normal IJV flow, venous stasis was observed in the left IJV in two participants during 0.00-G.

Conclusions:

• Reduced gravity exposures demonstrate a graded effect on IJV size and pressure.
• The development of venous stasis in some individuals highlights the need for monitoring IJV flow abnormalities in astronauts.
• Early monitoring is recommended during space missions, including lunar and Martian exploration.