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Functional changes cardiovascular: normobaric activity and microgravity in young healthy human subjects
N Alessandri1, M Petrassi, F Tufano
1Department of Heart and Great Vessels "A. Reale", School of Medicine, Sapienza University of Rome, Italy. nicola.alessandri@uniroma1.it
European Review for Medical and Pharmacological Sciences
|April 26, 2012
Summary
This study shows that the cardiovascular system adapts to simulate spaceflight conditions using tilt-tests and Lower Body Negative Pressure (LBNP). These adaptive responses help maintain cardiac output during postural changes.
Area of Science:
- Cardiovascular Physiology
- Space Medicine
- Autonomic Nervous System Function
Background:
- The cardiovascular system maintains homeostasis through adaptive responses to physiological demands.
- Gravity significantly impacts cardiovascular function, particularly during postural changes, leading to blood flow redistribution.
- Simulating microgravity effects is crucial for understanding astronaut health during long-duration spaceflights.
Purpose of the Study:
- To evaluate cardiovascular adaptive responses to simulated postural changes, with and without Lower Body Negative Pressure (LBNP).
- To investigate the efficacy of LBNP in mitigating cardiovascular shifts experienced during simulated microgravity.
- To provide insights into the physiological challenges faced by astronauts on extended missions.
Main Methods:
- Thirty healthy volunteers (20 males, 10 females) underwent tilt-tests simulating gravitational stress (+Gz and -Gz) and Lower Body Negative Pressure (LBNP) at -20 mmHg.
- Physiological parameters including blood pressure, heart rate, and cardiac output were monitored using Transthoracic Echocardiogram (TTE).
- Experimental conditions included head-up (+60°), head-down (-30°, -8°, -15°) tilts, with and without LBNP application.
Main Results:
- Orthostatic (+60°) tilt without LBNP caused reduced ventricular volumes and increased heart rate, while cardiac output remained stable.
- Head-down (-15°) tilt without LBNP significantly altered cardiac output and systolic blood pressure compared to baseline.
- LBNP during head-down tilts (-8°, -15°) prevented significant changes in arterial pressure, ventricular volumes, and cardiac output, maintaining stability compared to higher head-down tilts without LBNP.
Conclusions:
- The cardiovascular and autonomic nervous systems effectively adapt to postural changes and simulated volemia alterations.
- Physiological cardiac output is maintained to meet metabolic demands during simulated microgravity conditions.
- LBNP demonstrates potential as a countermeasure to preserve cardiovascular function during spaceflight.
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