The gravity-free environment in outer space can have strange and frightening effects on the human body. One of them is the backflow of blood.
According to a new study published in the JAMA Network Open, scientists have discovered two astronauts, one male and one female with retrograde blood flow in the carotid vein. Backflow has allowed small blood clots to form – a condition that can lead to death.
Fortunately, both of our astronauts are safe and healthy. They were given blood thinners to dissolve the blood clot.
The study also kicked off a health screening program for many astronauts who have been on space missions and returned to Earth. If blood clots are found to be caused by backflow, they will also need to be monitored and treated.
The zero gravity environment causes the astronauts' blood to flow backwards, a phenomenon that is very dangerous
The carotid vein is one of the two veins found in the neck region of many animals, including humans. It is responsible for receiving blood from the head and neck, merging with the inferior vena cava and then pouring into the anterior vena cava to the heart.
In their study, scientists have found blood flowing backwards in the carotid vein in the left of some astronauts. It is one of the two routes of movement of blood out of the head when we lie down.
When we stand upright, the carotid vein is almost closed to prevent excessive blood from flowing out of the head under the influence of gravity. The blood must then circulate through a different path, with more resistance.
On Earth, doctors sometimes detect someone with blood flowing backwards in the left vein. This will happen if a patient has congestion points below the neck, such as a growing tumor in the chest.
The zero gravity environment has been known to alter the blood flow in the astronaut's circulatory system. So, Dr. Karina Marshall-Goebel, a researcher from the KBR company in Houston and colleagues wondered: Does the zero gravity environment affect the circulation of blood in the carotid vein?
They performed blood vessel measurements and ultrasound on 11 astronauts, including nine men and two women, before they set out to carry out their missions. The same measurements were repeated the moment they got to the International Space Station, after the 50th and the 150th day of the trip.
The results showed that the two astronauts had retrograde blood flow in the carotid veins – an effect of the zero gravity environment causing the organs in the chest to float and putting pressure on the lower veins, Dr. Marshall said. -Goebel said.
She further noted that the carotid vein is very sensitive to pressure and that it is often blocked by its special position in the body.
The carotid vein is very sensitive to pressure and it is often blocked by its special position in the body.
In addition to the two astronauts with backflow blood, the researchers also found five other members of the crew had blood stagnant in the carotid vein. An astronaut even developed a blood clot.
"That is an alarming situation"Marshall-Goebel said. Blood clots can be fatal if they continue to move to the lungs, so the astronaut was immediately given blood thinners to disrupt it.
After this unexpected discovery, Dr. Marshall-Goebel's team also requested a general screening of ultrasound results from another group of astronauts who returned to Earth.
As a result, an astronaut was also discovered with a blood clot in his body. Dr. Marshall-Goebel said the two astronauts had a male and a female. She noted that female astronauts can use a method to limit blood clots, which is to stop taking oral contraceptives to curb menstruation.
For male astronauts, they are allowed to test a device on the International Space Station. The device requires the astronaut to cycle inside, bringing the lower body into a chamber with lower air pressure for an hour. The low pressure draws more blood to your feet to simulate the gravity effect like being on the ground.
However, this method is not currently effective. While 10 astronauts have shown improved blood flow, two of the 17 astronauts testing the device have poorer blood circulation.
The zero gravity environment can cause blood to flow back in the astronaut's vein.
"Humans have been in space for more than 50 years, but this is the first report of blood clots in astronauts' veins on space flights.", the study authors wrote.
This finding requires scientists to perform many follow-up studies on backflow and clots in space flight. Those are necessary safety measures to help us advance to long-term flights in the future, such as the mission to land Mars.