Micro-g environment

Cardiovascular effects

Many studies on the physiological effects of weightlessness on the cardiovascular system are done in parabolic flights. It is one of the only feasible options to combine with human experiments, making parabolic flights the only way to investigate the true effects of the micro-g environment on a body without traveling into space. Parabolic flight studies have provided a broad range of results regarding changes in the cardiovascular system in a micro-g environment. Parabolic flight studies have increased the understanding of orthostatic intolerance and decreased peripheral blood flow suffered by astronauts returning to Earth. Due to the loss of blood to pump, the heart can atrophy in a micro-g environment. A weakened heart can result in low blood volume, low blood pressure and affect the body's ability to send oxygen to the brain without the individual becoming dizzy. Heart rhythm disturbances have also been seen among astronauts, but it is unclear whether this was a result of pre-existing conditions or an effect of the micro-g environment. One current countermeasure includes drinking a salt solution, which increases the viscosity of blood and subsequently increases blood pressure, which mitigates post-micro-g-environment orthostatic intolerance. Another countermeasure includes administration of midodrine, which is a selective alpha-1 adrenergic agonist. Midodrine produces arterial and venous constriction resulting in an increase in blood pressure by baroreceptor reflexes.