A new study featuring astronauts' activities in space offers better insights on what causes people to suffer low blood pressure even while standing.
Researchers at UT Southwestern Medical Center examined a condition known as orthostatic intolerance to understand how it affects people and how it can be prevented. They believe they may have found the answer in the day-to-day activities of astronauts after they returned home from a spaceflight.
What Is Orthostatic intolerance?
Orthostatic intolerance is a condition where certain individuals have difficulty staying in an upright position such as when standing, according to the Baker Heart and Diabetes Institute.
OI sufferers often feel like fainting, but they may also experience weakness, lightheadedness, palpitations or abnormal sweating, and nausea. Some also have problems concentrating while undergoing an OI episode.
In most cases, OI occurs when people go from lying to standing. This movement causes the blood throughout the body to be dragged to the legs and pelvis due to gravity. The flow of blood activates the pressure receptors located in the neck and chest, which, in turn, signals the brain to let it know that the blood has "gone south".
Normally, the body would react to this by activating the "fight or flight" instinct in the nervous system. The nerves would then release a nerve transmitter called noradrenaline, causing the blood vessels in the legs, abdomen, and pelvis to tighten and forcing the blood to go against gravity and move back to the heart.
This entire sequence often occurs in less than a second to keep the body's blood flow and blood pressure stable. This is to make sure that the brain continues to receive a good blood supply even when people go from lying to standing.
How To Prevent Orthostatic intolerance
For their study, the UT Southwestern researchers looked at how astronauts deal with the rigors of spaceflight. They noted how some crewmen cannot help but faint during their journey back to Earth.
The team monitored the health of eight male and four female astronauts as they undergo their tour of duty into space. Each participant was given a small blood pressure cuff placed on their finger. The device helped keep track of the astronaut's blood pressure and heartbeat during several 24-hour periods before, during, and after their spaceflight.
Once they return from space, the astronauts were given an exercise regimen, as well as saline shots to help them deal with the effects of orthostatic intolerance. The researchers discovered that the combination prevented the onset of the condition.
"Doing an hour or more of daily exercise was sufficient to prevent loss of heart muscle, and when it was combined with receiving hydration on their return, the condition was prevented entirely," said Dr. Benjamin Levine, a professor of Internal Medicine at UT Southwestern and lead investigator of the study.
"We expected to see up to two-thirds of the space crew faint. Instead, no one fainted."
The researchers are exploring ways on how to use the treatment to address other similar conditions. One such illness is Postural Orthostatic Tachycardia Syndrome or POTS, which often causes women to suffer debilitating dizziness.
The findings of the UT Southwestern study are featured in the journal Circulation.