Comprehensive Analysis of Macrocirculation and Microcirculation in Microgravity During Parabolic Flights

Area of Science:

• Cardiovascular Physiology
• Space Medicine
• Human Physiology

Background:

• Understanding cardiovascular adaptations to microgravity is crucial for human space missions.
• Previous research highlighted venous fluid shifts, but macrocirculatory and microcirculatory mechanisms remain unclear.

Purpose of the Study:

• To investigate the effects of microgravity on macrocirculation and microcirculation.
• To assess hemodynamic responses and sublingual microcirculation during parabolic flights.

Main Methods:

• Twelve healthy volunteers underwent parabolic flights with alternating microgravity and hypergravity.
• Sublingual microcirculation was assessed using intravital sidestream dark field microscopy.
• Beat-to-beat analysis recorded heart rate, blood pressure, and cardiac output in seated and supine postures.

Main Results:

• Seated systolic and diastolic blood pressure decreased, while cardiac output increased in microgravity compared to normal gravity.
• These macrocirculatory changes were not observed in the supine posture.
• Microcirculation, including perfused vessel proportion and total vessel density, remained unaffected by acute weightlessness.

Conclusions:

• Significant macrocirculatory alterations occur in seated postures during microgravity exposure.
• Microcirculation demonstrates stability across different postures and gravitational conditions.
• Findings provide insights into cardiovascular adaptations relevant to spaceflight.