Altitude

The goal of this study is to investigate whether prospective memory, i.e., memory for delayed intentions, is impaired at moderate altitude (4,000m). It will also allow to study the effect of air and oxygen administration during hypoxia exposure. The main questions it aims to answer are: * Does moderate acute hypoxia impair prospective memory ? * If so, does air or oxygen adminsitration induce a restoration of prospective memory? Researchers will compare cognitive performance during normobaric hypoxia exposure to cognitive performance during normoxia (control situation). Participants will: * Session S0. Perform a battery of neuropsychological tests and questionnaires). EEG will be recorded during tests. A cheek swab will be performed. * Sessions S1 and S2. Perform several cognitive tasks while exposed to hypoxia and to normoxia (2 different sessions, randomized order) in a normobaric chamber. These are standardized cognitive tests administered on a computer and cognitive tests embedded in a flight simulator scenario. Various questionnaires will be performed on a regular basis. Several physiological measurements will be performed continuously: EEG, ECG, SpO2 and breathing rate. Blood pressure will be measured at the beginning and at the end of hypoxia/normoxia exposure. A blood sample will also be performed. At last, participants will inhale air or oxygen through a mask while making a cognitive task in the chamber.

The goal of this observational study is to learn whether intravenous iloprost treatment for severe frostbite (grades 3-4) is feasible and safe when delivered in pre-hospital, remote high-altitude settings. The main questions it aims to answer are: * Is it feasible to initiate and deliver guideline-based intravenous iloprost for grade 3-4 frostbite at high altitude and what logistical barriers arise? * Does field-based initiation of iloprost increase tissue preservation and reduce amputations (compared to historical cases from similar settings)? Participants receiving Iloprost as part of a frostbite treatment will be followed up after discharge as well as 6, 12 and 18 months to assess tissue preservation and long-term sequelae from the initial frostbite injury.

Iron is an essential micronutrient responsible for a whealth of biological processes of the human body. Iron plays a fundamental role especially in oxygen transport, by binding to hemoglobin in the blood circulation. Iron intake from the diet needs to be in balance the unavoidable losses that occur daily via different pathways. The recommended daily requirement of iron is based on the balance between absorption and losses and is calculated to maintain a balance so that the absorption equals losses. At higher altitudes, the absorption of iron may be higher due to adaptation mechanisms in response to low oxygen concentration, and to maintain a larger erytroid compartement. However, the long-term effects of altitude on iron balance are unknown. Filling this knowledge gap is important to better understand iron deficiency in populations living at high and moderate altitudes. Therefore, the investigators plan to study people that live at two different altitudes and measure iron absorption and losses over the long term. This will be useful to formulate specific recommendations for this population groups, to expand the knowledge base to better prevent iron deficiency in Switzerland but also worldwide. Participants will be asked to consume a dose of stable iron isotopes. After one year from isotope administration, the isotopes will be equally distributed in all body compartments and any change in the isotope abundance with the normal occurring body iron can be detected. From this point onwards, the investigators can observe the iron turnover and calculate iron absorption and losses per unit of time. At 4 different visits blood samples will be taken from each participant.

The goal of this clinical trial is to investigate the effects of acute passive continuous hypoxemia (simulated high-altitude at rest) on appetite and energy intake in healthy young female adults. The main questions it aims to answer are: * Does six hours of simulated high-altitude (5000 meters) reduce scores of subjective appetite and energy intake? * Do changes in appetite and energy intake persist in the hours following the end of hypoxic exposure? Researchers will compare the effects of simulated high-altitude to a control normoxia (sea-level) condition to see if exposure to low oxygen levels independently affect appetite and energy intake. Participants will: * Visit the laboratory for a preliminary screening session to assess eligibility. * Undergo two randomized, single-blind, experimental sessions consisting of six hours of passive exposure to normoxia or hypoxia in a climate-controlled chamber. * Consume foods provided from a curated list, served in ad libitum quantities, after leaving the laboratory to assess post-exposure energy intake.

Aortic stenosis is a common disease with increasing prevalence due to an aging population. Aortic valve replacement is indicated for symptomatic severe aortic stenosis. Leisure activities and tourism at high altitude destinations are popular but may impose a higher risk to patients with aortic stenosis. Pathophysiological considerations led to an expert consensus to avoid high altitude exposure, though there is no robust scientific evidence. Hence, the objective of this study is to evaluate the safety of high altitude exposure in patients with asymptomatic moderate or severe aortic stenosis by the measurement of surrogate markers for cardiac adverse events such as the decrease in exercise capacity, the assessment of changes in cardiac filling pressures, cardiac dimensions and function, and the evaluation of the incidence of cardiac arrhythmia.