Altitude sickness for missions to Mars
Headaches, nausea or even swollen hands and feet: the test subjects currently ascending at a rapid pace to Europe’s highest building to voluntarily experience altitude sickness have all of these things coming their way. Ten test subjects will gather at the Margherita Hut in the Valais Alps in Italy, where their bodies will be closely monitored to see how they respond to an altitude of 4554 metres above sea level, oxygen depletion and low air pressure. “If astronauts are stationed in a Mars habitat some time in the future, it is extremely probable that they will live and work in an atmosphere with similar pressure conditions,” explains Ulrich Limper, the mission’s medical director from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). “As things stand, though, we are unable to predict which persons will experience altitude sickness and what the causes may be.” A possible explanation: “The oxygen depletion encountered at high altitudes damages the vascular barrier, allowing fluid and proteins to seep into the connective tissue. In some instances, this will produce dangerous oedema in the body, especially in the lungs and the brain."
This is why the participants in the study ‘The formation of oedema during a stay in the High Alps’ – five men and five women – will be medically examined on a daily basis in order to acquire data, as well as to avoid any risk to their health. They will submit samples of blood, urine and saliva every day, and their blood pressure and heart rate will be accurately logged. They will also keep a ‘journal’ to record what symptoms of altitude sickness are noticeable, and to what extent. Do they feel slight, moderate or even severe dizziness? Do they have a normal appetite, mild nausea, are they vomiting or experiencing severe nausea? To a large extent, altitude sickness affects one’s mental state, and each test subject will be asked to record their mood as precisely as possible.
Searching for the trigger
Daily ultrasounds of the lungs, forehead, hands and feet provide entirely objective information on whether fluid is accumulating in the participants’ tissue. This manifests easily because the vessels become more permeable. Fragments of the vascular wall or protein molecules in the blood would confirm the hypothesis that a stay at higher altitudes damages the vascular barriers for a short time, and hence may trigger a dangerous retention of fluid in the lungs, brain and elsewhere. “Our analyses have only just begun,” says Limper, “but the results of the study will tell us which mechanisms we need to address to find effective remedies.” Given that the test subjects will be exposed to altitude conditions over a period of six days, it will also be possible to research whether the destroyed capillary walls regenerate again after a few days, and whether the body adapts to altitude conditions.
Changing atmospheres on the Red Planet
This knowledge would be important for astronauts and their work on site during a mission to Mars: in order to make the frequent exits from the habitat as smooth as possible, the astronauts would live in an atmosphere with low pressure and low oxygen partial pressure compared with Earth. This would ensure that the body is better prepared for the change in atmosphere in the spacesuit during exits. “Currently, however, we are unable to predict the risk that the astronauts will suffer from symptoms of altitude sickness.” In contrast, astronauts encounter quasi-Earth-like conditions in the International Space Station (ISS), where the pressure and oxygen content barely differ from the conditions back home. Accordingly, there is no risk that the body will experience symptoms of altitude sickness.
Stress for the body
While the astronauts on future Mars missions will experience physical stress due to isolation and radiation – not to mention psychological challenges – the test subjects in this study are also exposed to stress factors such as physical exhaustion caused by the ascent, freezing temperatures and psychological tension. “We are working in an unfamiliar and complex environment that, for the test subjects, is as unfamiliar as Mars would be for astronauts,” says Limper from the DLR Institute of Aerospace Medicine.
The first physical limitations can occur as low as 1500 metres. The test subjects will therefore ascend with two overnight stays at 2500 and 3647 metres. Any test subject experiencing severe problems such as acute shortness of breath, a loss of faculties or rattling sounds in the lungs on the way to the international centre for high-altitude physiological research in the Margherita Hut will return to the valley, escorted by a mountain guide.
Benefits for astronauts and earthly patients
Patients at normal altitudes may also benefit from the study. In many cases, oedema formation can take place in response to blood poisoning or severe trauma, hence impeding recovery. “Discovering how to avoid this dangerous accumulation of fluid would enable us to use this insight to help patients in hospitals,” emphasises Limper.
DLR will publish a Blog 1 about High Alps study 2016: When bad news is good news to track the progress of the study.