PHYSICAL ADAPTATION OF CHILDREN TO LIFE AT HIGH-ALTITUDE

Children permanently exposed to hypoxia at altitudes of > 3000 m above sea level show a phenotypical form of adaptation. Under these environ mental conditions, oxygen uptake in the lungs is enhanced by increases in ventilation, lung compliance, and pulmonary diffusion. Lung and th orax volumes in children growing up at high altitude are increased. Th e haemoglobin concentration in highlanders is elevated. With respect t o the decreased arterial oxygen tension at high altitude, this seems a useful adaptation. Blood viscosity also increases as a result of the increase in red blood cell concentrations however, and this has potent ially negative effects on the microcirculation in the tissues. The dec reased partial pressure of oxygen in the lungs of highland children is associated with a higher pulmonary artery pressure. Pulmonary hyperte nsion, high altitude pulmonary oedema, and chronic mountain sickness f orm part of the pathophysiology afflicting highland dwellers. Birth we ight at high altitude is decreased. Decreased postnatal growth has bee n widely reported in populations at high altitude, particularly in ear ly studies from the Andes. Recent studies taking into account the effe cts of socio-economic deprivation, suggest that long-term exposure to altitudes of 2500-3900 m is associated with a moderate reduction in li near growth in children.