The volunteers spent the three days in one test session laying normally in bed. Microgravity can increase that pressure and degrade vision. He’s holding a device that measures the pressure of fluid in the skull. European Space Agency astronaut Tim Peake worked on the International Space Station in 2016. Earlier research had shown that was enough time to cause fluid shifts like those astronauts would experience. Except for short bathroom breaks, the volunteers stayed flat. At least two weeks separated each three-day test period. “We had 10 subjects who each completed two bouts of 72 hours of bed rest,” he explains. His team tested a prototype with a small group of volunteers on Earth. “Otherwise, it feels really normal once you get settled in.” “You feel like you’re getting sucked into the sleeping sack a little bit,” admits Hearon. (The snug fit keeps water out of a kayak.) And a platform like a tractor seat keeps an astronaut from being sucked in too far when the device’s low-power vacuum is on. The seal around the sleeper’s waist is adapted from a kayaker’s skirt. Its outer shell is heavy vinyl, like that used on inflatable kayaks. The sleeping bag’s cone gets its structure from rings and rods. He began working with Hearon’s crew while he was with REI, a sporting-goods company. He’s a mechanical and innovation engineer in Kent, Wash. “You really need to have a chamber,” says Steve Nagode. That would backfire, pushing more fluid into the head. At some point the bag would collapse and press against the legs. The team knew that tucking someone into a regular sleeping bag and sucking out air wouldn’t work. Long periods in microgravity can take a toll on astronauts’ vision.
NASA astronauts Terry Virts (bottom) and Scott Kelly (top) worked on eye exams on the International Space Station in 2015. So his team decided try an approach that would treat astronauts when they weren’t working. But they ran into challenges, Hearon notes. Some groups had tried to harness that concept to prevent SANS. Earlier studies on blood pressure used methods that sucked out air to create negative pressure around the lower body, Hearon says. “So a long-duration space flight - like 15 months - could be a problem.” (That period is how long it would take to get to Mars.) Lee and others described SANS in npj Microgravity in 2020.Īnd here’s where Hearon and his team enter the story. “ The more time people spend in space, the more fluid stays in the head,” Lee says. And the extent of the effects depends on how long people spend in microgravity. “Folds can form in the back of the eye as well. The pressure also causes a part of the eye’s optic nerve to swell. “You get more far-sighted,” Lee explains. He works at Houston Methodist Hospital and at a new Weill Cornell Medical College program. As a neuro-ophthalmologist (Op-thuh-MOL-uh-gist), he’s a medical doctor who deals with the nerves in the eye. This extra fluid “presses on the back of the eye” and changes its shape, explains Andrew Lee. But without the pull of Earth’s gravity, too much fluid stays in the head and upper body. On Earth, gravity pulls fluids in the body down into the legs. That stands for spaceflight-associated neuro-ocular syndrome. The sleeping bag’s design aims to avoid something known as SANS. He and others described their new invention in JAMA Ophthalmology on December 9, 2021. He’s a physiologist at the University of Texas Southwestern Medical Center in Dallas. The idea for it came from a technique scientists use to study blood pressure, notes Christopher Hearon. The high-tech sleep sack looks like a giant sugar cone and covers only the lower half of the body. Astronauts experience this microgravity in space. The invention aims to relieve pressure that builds up behind the eyes during long periods of low gravity. A new sleeping bag could prevent vision problems on long space missions.
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