ABSTRACT
The study of healthy subjects at altitude has given valuable insights into the effects of hypoxia on human physiology and pathology. In this chapter we consider the similarities and differences between humans at high altitude and patients at sea level with various medical conditions. Altitude-acclimatized humans are a very good model for the hypoxia suffered by patients with lung diffusion limitation due to conditions such as fibrosing alveolitis where there is little or no airway obstruction. Chronic obstructive lung diseases (chronic bronchitis, emphysema and chronic asthma) have many similarities to acclimatized humans but differ in that such patients have normal or raised PCO2 whereas acclimatized humans have a low PCO2. Healthy subjects at altitude have some similarities to patients with cardiac conditions which limit the heart in its response to exercise. The sensation of fatigue in the working muscles is similar and is experienced by both. It is probably due to insufficient oxygen supply in both cases. Anemia gives rise to the same sensation due to oxygen lack though through different mechanisms. The problems of patients with cyanotic heart disease are also
At a more fundamental level, altitude physiology has influenced clinical medicine through concepts such as the importance of partial pressure of gases, especially of oxygen and carbon dioxide and, by extension, of anesthetic gases, and of acid-base balance and oxygen dissociation curves. Much early work in these areas was stimulated by interest in humans and animals at altitude. In hematology the very early work on polycythemia of altitude provided a stimulus to work on erythropoiesis. In cardiology the raised pulmonary artery pressure found at altitude has stimulated work on the control of pressure in the lesser circulation. Individual or population differences in response to hypoxia are often genetically determined. This fact has stimulated research in both the altitude and genetics communities.
