Mal chronique des montagnes

Chronic mountain sickness (CMS) is a disease in which the proportion of blood volume that is occupied by red blood cells increases (polycythaemia) and there is an abnormally low level of oxygen in the blood (hypoxemia). CMS typically develops after extended time living at high altitude (over ). It is most common amongst native populations of high altitude nations. The most frequent symptoms of CMS are headache, dizziness, tinnitus, breathlessness, palpitations, sleep disturbance, fatigue, loss of appetite, confusion, cyanosis, and dilation of veins. CMS was first described in 1925 by Carlos Monge Medrano, a Peruvian doctor who specialised in diseases of high altitude. While acute mountain sickness is experienced shortly after ascent to high altitude, chronic mountain sickness may develop only after many years of living at high altitude. In medicine, high altitude is defined as over , but most cases of CMS occur at over . It has recently been correlated with increased expression of the genes ANP32D and SENP1. CMS is characterised by polycythaemia (with subsequent increased haematocrit) and hypoxaemia; raised blood pressure in the lungs (pulmonary hypertension) can develop over time and in some cases progress to heart failure (cor pulmonale). CMS is believed to arise because of an excessive production of red blood cells (erythrocytes) due to the low oxygen levels at altitude, which increases the oxygen carrying capacity of the blood. The increased levels of erythrocytes causes increased blood viscosity and uneven blood flow through the lungs (V/Q mismatch). However, CMS is also considered an adaptation of pulmonary and heart disease to life under chronic hypoxia at altitude. Consensus for clinical diagnosis of CMS use laboratory values: haemoglobin in Males ≥ 21 g/dL; Females ≥ 19 g/dL, haematocrit > 65%, and arterial oxygen saturation (SaO2) < 85% in both sexes. Migration to low altitude is curative, though not immediate, as the body adapts to the normal oxygen level near sea-level and the haematocrit normalises.

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Effects of high altitude on humans

The effects of high altitude on humans are mostly the consequences of reduced partial pressure of oxygen in the atmosphere. The oxygen saturation of hemoglobin determines the content of oxygen in blood. After the human body reaches around above sea level, the saturation of oxyhemoglobin begins to decrease rapidly. However, the human body has both short-term and long-term adaptations to altitude that allow it to partially compensate for the lack of oxygen.

Background: Testing the hypoxic ventilatory response (HVR) at low-altitude helps to detect those who do not hyperventilate appropriately in hypoxia but might not necessarily predict the HVR and the risk to develop acute mountain sickness (AMS) at high alti ...

ELSEVIER2020

Physiological Responses in Humans Acutely Exposed to High Altitude (3480 m): Minute Ventilation and Oxygenation Are Predictive for the Development of Acute Mountain Sickness

Johannes Burtscher

Burtscher, Martin, Michael Philadelphy, Hannes Gatterer, Johannes Burtscher, Martin Faulhaber, Werner Nachbauer, and Rudolf Likar. Physiological responses in humans acutely exposed to high altitude (3480 m): Minute ventilation and oxygenation are predictiv ...

MARY ANN LIEBERT, INC2019

Are Pre-ascent Low-Altitude Saliva Cortisol Levels Related to the Subsequent Acute Mountain Sickness Score? Observations from a Field Study

Johannes Burtscher

Background: The associations among cortisol levels, body water status, and acute mountain sickness (AMS) remain unclear. We investigated associations between AMS prevalence and severity with resting saliva cortisol levels at low altitude (LA) and high alti ...

MARY ANN LIEBERT, INC2019