[Effect of lower body negative pressure and rotating-table simulated push-pull effect in flight on cardiovascular...

Area of Science:

• Cardiovascular Physiology
• Human Physiology
• Aerospace Medicine

Background:

• The push-pull effect (PPE) is a critical factor in cardiovascular regulation, particularly in aerospace environments.
• Understanding physiological responses to simulated PPE is essential for astronaut health and safety.
• Lower body negative pressure (LBNP) is a common tool for simulating altered G-force environments.

Purpose of the Study:

• To investigate the physiological effects of a simulated push-pull maneuver using a lower body negative pressure (LBNP) rotating-table.
• To observe and quantify cardiovascular responses during a simulated push-pull maneuver compared to a control condition.

Main Methods:

• A specialized LBNP rotating-table was employed to simulate the push-pull effect.
• Eight healthy adults underwent two experimental conditions: simulated PPE test and a control test.
• The simulated PPE test involved a sequence of head-up stand (HUT), head-down stand (HDT), and HUT with LBNP (-50 mmHg); the control involved only HUT with LBNP.

Main Results:

• Three participants in the simulated PPE test experienced presyncope, with an average standing time of 8.99 minutes, compared to 10 minutes for all in the control.
• During simulated PPE, heart rate (HR) and basic impedance (Z0) decreased, while stroke output (SO) and cardiac output (CO) increased during HDT.
• HUT with LBNP during the PPE test showed significantly higher HR, Z0, and total peripheral resistance (TPR), but lower SV and CO compared to control and HDT.

Conclusions:

• Head-up stand combined with LBNP after a head-down position causes a greater decline in cardiovascular function than simple head-up stand with LBNP.
• The LBNP rotating-table effectively simulates the push-pull effect.
• These findings highlight the significant cardiovascular stress induced by simulated push-pull maneuvers.