For over 20 years, more people have been spending extended periods of time on the International Space Station (ISS) in space. There are plans for space to be used commercially by humans in the future. The number of people in space will increase accordingly. This is where space medicine comes into play, which deals with the effects of a stay in space on the human body. There are various medical challenges for the human organ system as soon as it leaves Earth and enters space.
Reduced gravity leads to a loss of muscle and bone tissue. Fluid shifts occur within the body and circulation deteriorates. Radiation results in cell damage and the development of tumours. Isolation can lead to behavioural abnormalities and sleep disorders. This also has an impact on team performance. In addition, the closed environment on a space station is accompanied by special conditions in terms of atmosphere and temperature.
Scarce resources such as water and food, as well as the occurrence of pathogens, can also put space travel to the test. However, medical care must be provided autonomously. The great distance from Earth also adds to communication delays.1
Volume shifts and bone loss in space can cause problems for the nephrological system. In space, there is a volume shift towards the head. Interestingly, however, central venous pressure in space has been lower in test subjects than on Earth, according to Prof. Jordan. Another way to study changes in blood volume in the human body in space is through impedance measurements of the thorax. This method has yielded insightful data: During a stay in space, the fluid volume in the thorax is lower than on Earth in a standing position.
Prof Jordan explained this observation as follows: First, there is a shift of fluid towards the cranium. Increased excretion of sodium and water results in central hypovolaemia. Viewed from the outside, however, the neck veins of astronauts are congested despite hypovolaemia. A look at the natriuretic peptides of people in space shows that these are reduced.1
Maintaining fluid volume in the bodies of astronauts is the goal of various space research studies. Prof Jordan presented the most important methods and measures that have been investigated in studies on Earth. The test subjects spent their bed rest in a head-down position and tested various interventions for the prevention of central hypovolaemia. Lower body negative pressure (LBNP) was one of them. It is a unique tool for investigating the physiology of integrated systemic compensatory responses to altered haemodynamic patterns under conditions of central hypovolaemia in humans.
This tool generated negative pressure for 6 hours a day in the study setting. Another measure was regular endurance training. The study results showed that only regular endurance training had a beneficial effect on maintaining plasma volume.1
Prof Jordan presented the audience with a kidney disease that is out of this world: ‘cosmic kidney disease’ has very special characteristics. According to scientific study results from 2024, space flights have the following effects on the kidneys:
In addition to these changes in kidney tissue associated with ‘cosmic kidney disease’, radiation exposure of the kidneys on the ISS, the Moon and Mars is also a cause for concern. The study currently underway on this topic (ARTEMIS 1 Mission Mare Experiment) will provide important data on this, according to Prof Jordan.1