Cardiovascular response to altered gravity in healthy adults: Insight from graded tilt testing

Area of Science:

• Cardiovascular Physiology
• Space Medicine
• Human Physiology

Background:

• Spaceflight induces fluid shifts affecting the cardiovascular system.
• Understanding sex-based cardiovascular responses is crucial as female astronaut numbers rise.

Purpose of the Study:

• To investigate sex differences in cardiovascular hemodynamics and vascular morphology during altered gravity.
• To establish comprehensive sex-specific data for spaceflight and clinical applications.

Main Methods:

• Examined central hemodynamics, carotid artery and internal jugular vein (IJV) morphology, and IJV pressure.
• Utilized graded head-up to head-down tilt (-45° to +45°) in healthy males and females.
• Measured variables including cardiac output, vascular resistance, and sympathovagal balance.

Main Results:

• Most cardiovascular variables showed strong gravitational dependence.
• Few significant sex differences were observed in hemodynamics, vascular morphology, or IJV pressure.
• Cardiac output, total peripheral resistance, and sympathovagal balance (LF/HF ratio) differed between sexes.

Conclusions:

• Cardiovascular responses to tilt are largely similar between sexes, with minor differences in specific parameters.
• This study expands the cardiovascular response database to include females, crucial for spaceflight countermeasures.
• Findings support applications in terrestrial medicine, such as managing patients in Trendelenburg position.