Artificial gravity: an effective countermeasure for microgravity-induced headward fluid shift?

Area of Science:

• Space physiology
• Neuroscience
• Biomedical engineering

Background:

• Long-duration spaceflight causes intracranial volume changes, linked to microgravity-induced headward fluid shifts.
• These changes may contribute to spaceflight-associated neuro-ocular syndrome.
• Artificial gravity (AG) is explored as a potential countermeasure.

Purpose of the Study:

• To investigate if daily artificial gravity (AG) sessions can mitigate intracranial pathophysiological effects during simulated headward fluid shift.
• To assess the efficacy of intermittent and continuous AG as countermeasures.

Main Methods:

• Twenty-four healthy volunteers underwent 60 days of 6° head-down tilt bed rest (HDTBR).
• Subjects were randomized into three groups: no AG (control), daily 30-min intermittent AG (iAG), or daily 30-min continuous AG (cAG).
• Intracranial volumetrics, internal carotid artery hemodynamics, and cerebrospinal fluid flow were measured using 3T MRI.

Main Results:

• HDTBR induced significant increases in intracranial volumes and cerebrospinal fluid flow velocity, alongside decreased internal carotid artery stroke volume and flow rate by day 52.
• Internal carotid artery resistive index increased at day 14 but normalized later.
• Neither iAG nor cAG interventions significantly altered these HDTBR-induced changes, indicating insufficient mitigation.

Conclusions:

• Thirty minutes of daily AG exposure was insufficient to counteract the intracranial fluid shifts simulated by HDTBR.
• Future research should explore longer AG session durations or higher gravitational forces.
• Optimized AG protocols may be necessary to prevent spaceflight-associated neuro-ocular syndrome.