‘Suction’ Sleeping Bag Could Solve Astronaut Eyesight Problems

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When Scott Kelly returned to Earth following his year in space, the shape and structure of his eyeball was different than when he left. The integrity of his retina had worsened in the zero-gravity environment he called home for 350 days.

This development wasn’t surprising to NASA as the space agency has documented spaceflight-associated neuro-ocular syndrome, or SANS, in more than half of its astronauts who served 6 months or more on the ISS. Even though eyesight appears to return to normal with time back on Earth, the occurrence of the condition in Kelly highlights one of the biggest health questions about long-term space travel.

Benjamin Levine, M.D., a cardiologist at UT Southwestern and space travel research expert of more than 30 years, has been studying SANS for years. In 2017, he demonstrated pivotal findings about the underlying mechanisms of the disease, which causes flattening of the eyeball, swelling of the optic nerve and vision impairment.

Now, Levine’s most recent study offers a possible solution to astronauts’ vision woes—a sealed, vacuum-equipped sleeping bag.

Four years ago, Levine and colleagues were the first to provide compelling evidence that SANS is caused by the constant pressure body fluids apply to the brain. To test this theory, Levine recruited cancer survivors who still had ports on their heads from where they had received chemotherapy, offering researchers rare access to measure pressure directly in the brain. For the study, each volunteer agreed to go on a zero-gravity airplane flight into the upper atmosphere.

The results showed that brain pressure in a person who lies down on Earth is actually higher than in space. However, on Earth the pressure is unloaded when the individual stands and gravity pulls the fluids down. Space provides no such relief for astronauts. Rather, the lack of gravity allows more than half a gallon of body fluids to gather in their head—applying undue pressure to the eyeball.

Building on this insight, Levine’s team worked with REI, an outdoors equipment retailer, to develop a high-tech sleeping bag that could be used by astronauts every night to solve the problem. The resulting bag fits over an astronaut from the waist down and employs suction to pull body fluids down to the lower body, unloading pressure in the brain.  

To test the bag, 10 volunteers spent three days on bed rest in a zero-gravity environment, with the sleeping bag applied to the lower body for 8 hours each night. The volunteers also completed three days of “regular” bed rest, with gravity and without the sleeping bag.

The study results, published last week in JAMA Ophthalmology, show that while just three days of lying flat induced enough pressure to slightly alter the eyeball’s shape, no such change occurred when the sleeping bag technology was used.

While several questions still need to be answered before NASA employs the technology on a mission, Levine said the findings indicate SANS may not be the health risk it currently is by time the space agency is ready to man Mars in a little over 10 years.

“This is perhaps one of the most mission-critical medical issues that has been discovered in the last decade for the space program,” said Levine. “I’m thankful for the volunteers who are helping us understand, and hopefully, fix the problem.”

In the early 1990s, Levine implanted the first catheter to monitor the heart pressure of an astronaut in space. Since then, the cardiologist has worked with NASA on various projects and advises its flight surgeons on cardiovascular medical issues. NASA recently awarded him $3.8 million over 13 years to study the effects of space travel on the heart.

Photo: James Leidner spent three nights in a high-tech sleeping bag that unloads pressure in the brain by suctioning fluids into the lower body. NASA hopes the sack can be used by astronauts in space to alleviate the vision problems they commonly endure during longer missions. Credit: UT Southwestern Medical Center

 

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