Cardiovascular, Lymphatic, and Ocular Health in Space

Victoria Ly,Suhas Rao Velichala,Alan R Hargens

doi:10.3390/life12020268

Victoria Ly, Suhas Rao Velichala + Show 1 more

Open Access

https://doi.org/10.3390/life12020268

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Journal: Life	Publication Date: Feb 11, 2022
Citations: 6	License type: CC BY 4.0

Affiliation: University of California San Diego Medical Center

Abstract

Life on Earth has evolved continuously under Earth’s 1 G force and the protection of the magnetosphere. Thus, astronauts exhibit maladaptive physiological responses during space travel. Exposure to harmful cosmic radiation and weightlessness are unique conditions to the deep-space environment responsible for several spaceflight-associated risks: visual impairment, immune dysfunction, and cancer due to cosmic radiation in astronauts. The evidence thus reviewed indicates that microgravity and cosmic radiation have deleterious effects on the cardiovascular, lymphatic, and vision systems of astronauts on long-duration space missions. The mechanisms responsible for the decline in these systems are potentially due to cytoskeletal filament rearrangement, endothelial dysfunction, and muscular atrophy. These factors may alter fluid hemodynamics within cardiovascular and lymphatic vasculatures such that greater fluid filtration causes facial and intracranial edema. Thus, microgravity induces cephalad fluid shifts contributing to spaceflight-associated neuro-ocular syndrome (SANS). Moreover, visual impairment via retinal ischemia and altered nitric oxide production may alter endothelial function. Based on rodent studies, cosmic radiation may exacerbate the effects of microgravity as observed in impaired endothelium and altered immunity. Relevant findings help understand the extent of these risks associated with spaceflight and suggest relevant countermeasures to protect astronaut health during deep-space missions.

Highlights

Long-duration spaceflight subjects astronauts to unique conditions not present onEarth, generating altered physiological responses to environmental stress
The purpose of this review is to summarize the current understanding of physiological changes induced by space travel and to explore potential countermeasures against maladaptive responses to spaceflight
The loss of hydrostatic pressures due to weightlessness causes fluid shifts resulting in facial edema and mild but chronically increased intracranial pressure (ICP)

Summary

Introduction

Long-duration spaceflight subjects astronauts to unique conditions not present on. Earth, generating altered physiological responses to environmental stress. Microgravity and exposure to cosmic radiation contribute to a decline in cardiovascular, lymphatic, and ocular health systems, which may pose significant risks to astronauts both acutely and chronically. On Earth, gravity-dependent hydrostatic forces maintain body fluid equilibrium, and the magnetosphere protects organisms from harmful cosmic radiation. Weightlessness in space eliminates the typical hydrostatic pressure gradients resulting in facial edema and headward fluid shift, a possible contributor to spaceflightassociated neuro-ocular syndrome (SANS). The purpose of this review is to summarize the current understanding of physiological changes induced by space travel and to explore potential countermeasures against maladaptive responses to spaceflight

Fluid Shifts and Venous Changes Due to Space Travel

Microgravity Analogs on the Lymphatic System

Ocular Health in Space

Spaceflight-Associated Neuro-Ocular Syndrome

Lower Body Negative Pressure to Prevent SANS

Findings

Conclusions