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When Space Makes You Dizzy
Imagine trying to land the Space Shuttle after you just got off a spin-and-whirl ride -- cross your fingers and hope you don't throw-up! During landing, some astronauts get that same dizzy feeling, but not from spinning around. As astronauts come down from space, the blood rushes down toward their legs and away from their heads. This shift in blood makes some feel lightheaded and dizzy.

Richard Cohen of the Harvard-MIT Division of Health Sciences and Technology says that on Earth gravity pulls blood toward the lower body. But in space, the blood that is normally in the legs moves to the upper body instead. That's why astronauts have puffy-looking faces and spindly "chicken legs."

Diagram showing the changes in blood flow for astronauts prior to, during and after space flight
Image to right: Microgravity causes an astronaut's body to change while in space. Credit: NASA

Veins in our legs contain tiny muscles that contract when the veins fill with blood. The muscles help send the blood back up to the heart, keeping our blood pressure balanced. But in space there is no "up," so those tiny muscles don't have to work as hard to keep the blood pressure balanced. The longer astronauts stay in space, the weaker their muscles get.

When astronauts come home and gravity takes hold again, their tiny vein muscles aren't ready to start working as hard. That means not enough blood is pushed back to equal out the pressure. The longer an astronaut stays in space, the more unbalanced the pressure can be when they come home.

Astronaut in G-suit
Image to left: Astronauts wear G-suits to help prevent dizziness.
Credit: NASA

Astronauts have tried to prevent the dizziness by drinking lots of salt water. That increases the amount of fluids in the body. They also wear rubberized full-body suits, called "G-Suits," that can be inflated with air. The suit squeezes arms and legs to push the blood back and balance the pressure.

However, those methods haven't worked well. So, NASA is trying a drug called Midodrine. It constricts blood vessels and increases blood pressure. It was designed to help people on Earth with blood pressure problems. Richard thinks it might help astronauts too.

Richard is working with Janice Meck, at NASA's Johnson Space Center, and Gordon Williams, a doctor at the Brigham and Women's hospital. They are studying this drug to help astronauts.

Research is continuing and every mission teaches us more how the body reacts to the environment of space. Hopefully, astronauts soon will be returning home from space without getting dizzy.
Adapted from When Space Makes You Dizzy