Physiological Responses to Four Different Baseline Accelerations on a Human Centrifuge

Area of Science:

• Aerospace Medicine
• Human Physiology
• Cardiovascular Research

Background:

• Human centrifuges utilize baseline acceleration between high-G exposures.
• These baselines aim to optimize performance and minimize motion sickness.
• Understanding cardiovascular changes is crucial for effective human centrifuge trials and training.

Purpose of the Study:

• To assess cardiovascular changes associated with different human centrifuge baseline accelerations.
• To evaluate the impact of these baselines on physiological responses during G-force exposure.

Main Methods:

• Ten subjects were exposed to varying Gz levels (+1.2, +1.4, +1.6, +1.8 Gz) on a human centrifuge.
• Cardiovascular variables were measured using the volume-clamp method and ECG.
• Blood volume changes in the abdomen and lower limbs were assessed via impedance plethysmography.

Main Results:

• Significant interactions were observed between Gz baselines and cardiac output, stroke volume, heart rate, and total peripheral resistance.
• Higher Gz baselines (+1.8 Gz) led to increased heart rate and peripheral resistance, with decreased cardiac output and stroke volume.
• Blood pressure responses varied, with notable changes in mean arterial pressure at head level.

Conclusions:

• Cardiovascular responses to transitions from +1 Gz to higher levels (+1.6, +1.8 Gz) resemble those seen when transitioning from supine to standing.
• These findings necessitate careful consideration of baseline acceleration levels in cardiovascular research conducted on human centrifuges.