Impedance threshold device as a countermeasure for spaceflight associated neuro-ocular syndrome (SANS): Mitigating mechanisms in proposed pathophysiology

Long-duration spaceflight (LDSF) is associated with unique hazards and linked with numerous human health risks including Spaceflight Associated Neuro-ocular Syndrome (SANS). The proposed mechanisms for SANS include microgravity induced cephalad fluid shift and increased Intracranial Pressure (ICP). SANS is a disorder seen only after LDSF and has no direct terrestrial pathologic counterpart as the zero G environment cannot be completely replicated on Earth. Head-down tilt, bed rest studies however have been used as a terrestrial analog and produce the cephalad fluid shift. Some proposed countermeasures for SANS include vasoconstrictive thigh cuffs and lower body negative pressure. Another potential researched countermeasure is the impedance threshold device (ITD) which can reduce ICP. We review the mechanisms of the ITD and its potential use as a countermeasure for SANS.