High Altitude Effects

To study the effect of a re-ascent to high altitude (Quito Ecuador: 2850m) after a one-week stay at sea level (after prior descent from 2850m) on lung function and pulmonary resistance/reactance in patients with pulmonary arterial disease PAH, who live permanently \> 2600m.

To study the effect of relocation from high altitude (Quito: 2850m) to sea level on six-minute walking distance and scores in patients with pulmonary arterial hypertension PAH, who live permanently \>2600m.

To study the effect of a re-ascent after a one-week stay at sea level (after prior descent from 2850m) to high altitude (Quito Ecuador: 2850m) on pulmonary resistance (sPAP/CO) and other hemodynamic outcomes in healthy individuals, who live permanently \>2600m.

To study the effect of a re-ascent to high altitude (Quito Ecuador: 2850m) after a one-week stay at sea level (after prior descent from 2850m) on lung function and pulmonary resistance/reactance in healthy individuals, who live permanently \> 2600m.

To study the effect of relocation from high altitude (Quito Ecuador: 2850m) to sea level and re-ascent from sea level to 2850m on heart rate variability and other hemodynamic parameters in healthy individuals, who live permanently \>2600m.

To study the effect of relocation from high altitude (Quito Ecuador: 2850m) to sea level and re-ascent from sea level to 2850m on heart rate variability and other hemodynamic parameters in patients with pulmonary arterial hypertension PAH, who live permanently \>2600m.

To study the effect of relocation from high altitude (Quito Ecuador: 2850m) to sea level on sleeping parameters by polygraphy in patients with pulmonary arterial hypertension PAH, who live permanently \>2600m.

To study the effect of relocation from high altitude (Quito Ecuador: 2850m) to sea level on sleeping parameters by polygraphy in healthy individuals, who live permanently \>2600m.

To study the effect of descent from high altitude (Quito Ecuador: 2850m) to sea level on six-minute walking distance and scores in healthy individuals, who live permanently \>2600m.

To study the effect of a re-ascent after a one-week stay at sea level (after prior descent from 2850m) to high altitude (Quito Ecuador: 2850m) on six-minute walking distance and other scores in healthy individuals, who live permanently \>2600m.

To study the effect of a re-ascent after a one-week stay at sea level (after prior descent from 2850m) to high altitude (Quito Ecuador: 2850m) on six-minute walking distance and other scores in patients with pulmonary arterial hypertension PAH, who live permanently \>2600m.

This multicenter observational study will evaluate the association between geographic altitude, availability of critical care resources, and clinical outcomes in children with pediatric acute respiratory distress syndrome (PARDS). Data on demographics, physiology, and hospital structure will be collected from PICUs located at different altitudes worldwide. The study aims to identify gaps in PARDS management and provide recommendations adapted to diverse resource settings.

Each year, millions of people living at low altitude (\< 1,000 m) travel to high altitude (≥ 2,500 m) for work, tourism, or sports activities. These individuals are exposed to hypobaric hypoxia, which can trigger acute mountain sickness (AMS)-the most common form of altitude-related illness. Therefore, understanding the physiological responses to hypoxia that allow acclimatization, as well as the pathophysiology of acute mountain sickness, is of primary importance. The hematological response to high-altitude exposure initially includes a reduction in plasma volume (PV), leading to an early increase in hemoglobin concentration within the first 24 hours. In contrast, an increase in hemoglobin mass requires several weeks at high altitude. Recent well-controlled physiological studies conducted in hypobaric chambers have demonstrated that this hypoxia-induced PV contraction results from fluid redistribution from the intravascular to the extravascular compartment, rather than from water loss due to increased diuresis. Prophylaxis of AMS is primarily based on the administration of 250 mg/day of acetazolamide (ACZ), a carbonic anhydrase inhibitor with a mild diuretic effect. Acetazolamide induces metabolic acidosis, which stimulates ventilation and thereby improves oxygenation. The effect of prophylactic ACZ use during high-altitude exposure on PV in lowlanders remains unknown: it is unclear whether ACZ leads to a greater reduction in PV due to its diuretic effect, or to a smaller hypoxia-induced PV contraction as a result of improved oxygenation induced by increased ventilation.

As altitude increases, the availability of oxygen in the air decreases, and just to compensate for this lack, the body increases cardiac and respiratory work and changes blood pressure. But that is not all: at altitude the body's ability to use oxygen is also limited. Thus, there is on one hand less oxygen available, and on the other a lower capacity to use it. All this generates significant alterations at the cardiovascular level, to the point of running possible risks of heart attack, stroke and acute pulmonary edema, particularly for individuals already suffering from cardiovascular disease. The availability of modern cable cars allows an increasingly large number of individuals, including sedentary people, elderly subjects, and cardiorespiratory patients, to easily and rapidly reach high-altitude locations. Data on what happens on the cardiovascular system at high altitude are relatively scarce, and most experiments in the literature are limited by low sample sizes. The primary purpose of this study is to assess the characteristics of a large population that acutely reached high altitude at Punta Helbronner (3,466 m above sea level), a location on Mont Blanc that is readily accessible by a 20-minute cableway ride from Courmayeur (Entreves station, 1,300 m, Skyway Monte Bianco). We aim to create a unique database and study correlations between altitude and cardiorespiratory parameters (heart rate, blood pressure, and Hb saturation) by collecting medical history data and biometric measurements in a very large population and to identify subjects most at risk of developing hypoxia at altitude. In a subset of subjects, differences in biometric variables after acute exposure at high altitude (in the transition between the downstream and the upstream measuring station) will be evaluated. Two biometric multiparametric recording systems (Keito K9; Keito, Barcelona, Spain) were installed at Entreves station as well as at Punta Helbronner. Keito K9 is an automatic multiparametric recoding system for measuring peripheral oxygen saturation SpO2, heart rate HR (pulse oximeter), blood pressure (BP; wrist pressure cuff, automatic), height (laser height meter), weight (scale platform), and body mass index (BMI). Once initiated by the subject with the completion of a cardiology history questionnaire (self-reported), the automated Keito K9 system provides a sequence of vocal and animated directions to guide subjects through the measurements (the subject may elect to abstain from some of the measurements). Upon completion, the system prints a summary receipt for the subject, and the measurements are transmitted through a Wi-Fi network and collected in an Excel sheet. It should be noted that all data collected will be anonymized or not traceable to the subject, through the use of a disposable identification card (for subjects who will perform both downstream and upstream measurement).