CONGRESS ABSTRACT

Background : Individuals who reach high altitudes engage in strenuous physical activity that increases their oxygen demand in an environment where atmospheric oxygen availability is reduced and the body's ability to use it is compromised. These effects are influenced by hypoxia but also by adverse environmental conditions, such as cold and low humidity, which imply greater energy consumption compared to exercise performed at sea level. Aim of this analysis is to evaluate in detail the cardiovascular, respiratory, and muscular adaptations to high altitude, in order to improve understanding of the underlying physiological mechanisms. Methods : 12 healthy subjects (46±12 y/o, 75% males) performed maximal cardiopulmonary exercise testing (CPET) at sea level and at Capanna Gnifetti (Monte Rosa, 3647 m.), after at least 1 day of acclimatization. The same ramp protocol, on an electronically braked cycle ergometer, was applied for each individual. Before and after each test, a blood sample was collected for the assessment of haemoglobin, haematocrit, lactates and BNP. This is a preliminary analysis of data from a larger research project that includes the simultaneous measurement of peripheral muscle extraction (NIRS – Near Infra-Red Spectroscopy) and non-invasive cardiac output (Physioflow) during maximal physical exertion. Results : Effects of high altitude are already evident at rest with higher systolic blood pressure and ventilation, and lower SpO 2 , PetCO 2 , PetO 2 compared to sea level (p<0.05). High altitude also affects peak exercise performance, with a lower workload achieved, heart rate, and oxygen consumption (peakVO 2 ), regardless the increase in Hb induced by altitude. There is no statistically significant effect on ventilation, but ventilatory efficiency (VE/VCO 2 slope) is increased by being at high elevation. BNP increases during exercise in both environments but never exceeding the threshold of clinical significance. The increase in lactate levels induced by physical exertion is reduced at high altitudes. Conclusions : Although ventilation peak values are very similar, our data confirm a significant reduction in performance after exposure to high altitude in a non-hyperacute manner. Further analyses considering peripheral muscle extraction and cardiac output are underway.