Adaptation and acclimatisation in humans and animals at high altitude.

Rapid ascent into high altitude or permanent residence there leads to a wide range of disturbances of function or alterations in histological appearances in most organs of the body. The influences which lead to these changes are those inherent in the environment of high altitude, especially hypobaric hypoxia resulting from the diminished barometric pressure. One of the major aspects of research carried out at the Department of Pathology at Liverpool over the last 25 years has been the study of the effects of hypobaric hypoxia on the histological structure of the pulmonary circulation of lowlanders and lowland animals exposed to high altitude, of native highlanders, and of indigenous mountain mammals. In some mammals, including man, the hypobaric hypoxia of high altitude induces a mild degree of pulmonary arterial hypertension with associated alterations in the structure of the peripheral portions of the pulmonary arterial tree. In other species it does not. This paper gives an account of the histological structure of the pulmonary circulation in the two groups namely, the reactors and the non-reactors and seeks to establish the difference in the biological status of the two groups. The biological variety at high altitude can best be illustrated by taking a mental stroll around the streets and surrounding countryside of any small settlement in the Andes. One such is the mining town of Cerro de Pasco (4330 m) in central Peru where much of the work at Liverpool began. Most of the people in the streets of Cerro de Pasco are native Quechua Indians born and bred in the Andes. These people have very characteristic physical features and deeply polycythaemic and suffused conjunctivae and lips. Some will have a capacious chest which looks prominent and out of proportion to their short stocky physique. These highlanders lead normal busy lives; they shop, go to school, visit the cinema, and play football at altitudes exceeding the summit of the Matterhorn. Living on the pastures surrounding Cerro de Pasco are examples of indigenous mountain animals such as the llama (Lama glama), the alpaca (L pacos), the vicunia (L vicugna), and the guanaco (L guanacoe). These species have been living on the Andean altiplano for many thousands of years, preceding the appearance of the Quechuas. One cannot help but be impressed by the vigour and activity of the animals in an atmosphere characterised by severe hypobaric hypoxia. Other indigenous mountain species such as the mountain vish.