Hypoxia, Altitude

Extreme heat events are becoming more frequent, intense, and prolonged, increasing the risk of heat-related illness among workers performing physically demanding work in hot environments. Current occupational heat-stress guidelines aim to limit excessive increases in core body temperature and physiological strain through the use of work-rest schedules. However, these guidelines do not provide clear direction on the safe, maximum duration of continuous work that can be performed before heat-mitigation controls should be implemented, known as the initial stay time. Recent work has generated initial stay time recommendations for young and older workers performing moderate-intensity work in the heat, but these estimates were developed under normoxic conditions. In many occupational settings, workers may be exposed to additional environmental stressors such as hypoxia, including work at altitude or in oxygen-reduced environments. Hypoxia can increase cardiovascular strain, reduce arterial oxygen saturation, and alter exercise tolerance, potentially compromising the effectiveness of heat-stress guidance developed under normal oxygen conditions. Older workers may be especially vulnerable due to age-related reductions in thermoregulatory and cardiovascular function. To date, it remains unclear whether hypoxia alters physiological strain during work in the heat or whether current initial stay time and recovery recommendations remain protective under combined heat and hypoxic stress. The primary objective of this study is to determine whether exposure to hypoxia increases physiological strain during moderate-intensity work in the heat in young and older males. Specifically, investigators will assess whether normoxia-derived initial stay times and recovery recommendations for work at 29°C wet-bulb globe (37.5°C, 35% RH) temperature remain effective when workers are exposed to hypoxia equivalent to 14% inspired oxygen (simulating \~3000 m in altitude). Healthy young and older males will complete simulated occupational heat exposure under two conditions: heat alone and combined heat plus hypoxia. Participants will perform moderate-intensity treadmill work based on age-specific initial stay times, followed by prescribed work-rest cycles and seated recovery. Measures of core temperature, cardiovascular strain, oxygen saturation, skin temperature, hydration status, perceptual responses, mood, symptoms of environmental stress, and cognitive function will be assessed to determine whether hypoxia modifies responses to work in the heat. This study will provide important evidence on whether occupational heat-stress guidance requires refinement when workers are exposed to combined heat and hypoxic stress.

More and more people are engaging in sports in the mountains, including individuals with heart or lung diseases. At the same time, such diseases are becoming more common in Switzerland. At high altitude, less oxygen is available, which places stress on the body-particularly on the heart, which has to pump blood through the lungs. How the heart, especially the right ventricle, in people with asthma responds to this stress is still not well understood. Therefore, this study investigates how the heart responds to simulated altitudes of 2,500 m and 4,000 m, both at rest and during light physical activity in patients with asthma. The primary objective is to assess how right ventricular function changes under conditions of reduced oxygen availability. In addition, vital signs, changes in blood gases, oxygen levels in blood and tissue and shortness of breath are assessed. The "altitude" is simulated using a special gas mixture that participants inhale. Participants undergo three altitude conditions (490, 2,500, and 4,000 m above sea level). The order of the altitude conditions is assigned at random. The aim is to better understand how the right ventricle and other parameters respond to low-oxygen conditions and how affected patients can be better supported in the future.

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.

* Cognitive assessment of the influence of a 4-week proprietary training program under normobaric hypoxia conditions on the levels of inflammatory markers, disturbances in prooxidant-antioxidant balance, degree of intestinal damage, and mitochondrial energy production rate in young sedentary males. * Applied objective: Development of practical training guidelines utilizing training in normobaric hypoxia conditions to enhance mechanisms related to oxygen transport, adaptive changes within the immune system, body's antioxidant capacity, gut permeability, substrate utilization efficiency, and mitochondrial function for coaches and athletes.