Developmental responses to high altitude hypoxia.

From a review of published literature on developmental responses to high altitude, three major conclusions are derived. First, the small birth weight of high altitude native populations are adaptive responses to reduce the oxygen requirements, while the relative increase in the placental weight is a compromise mechanism to increase the volume and surface area €or a better oxygenation. Second, the small stature of the high altitude native is due to slow prenatal and postnatal growth. Third, the enlarged chest size, increased lung volumes and predominance of the right ventricle of the heart are due to accelerated development during childhood and adolescence. However, there is not adequate information to determine whether or not the developmental responses of the high altitude native are population-specific, based on a genetic structure different from that of sea level populations. Hence, the need for further study of developmental factors is emphasized. In recent years there has been increasing interest in the study of responses by man to high altitude hypoxia. The interest of human biologists in studying human populations at high altitudes lies not only in the investigation of how man reacts to environmental extremes, but also in finding out the mechanisms whereby a population adapts to such an environment. The mechanisms may be genetic, developmental or short-term adjustments. Considering that the period of growth and development consists of more than a quarter of the average person's lifetime, and the major selective forces operate prior to reproductive age, the developmental responses of a population must be viewed as one of the most important sources of inter-population variations in physiological and morphological adaptation to environmental stress. The purpose of this paper, therefore, is to evaluate the major morphological and physiological responses to the stress of high altitude hypoxia during the prenatal and postnatal development of man.