[Pulmonary function in aging].

Aging generates four important changes in the structure and function of the respiratory system. There is a reduction in the elastic recoil of the lung causing "senile emphysema", a condition characterized by reduction in the alveolar surface area without alveolar destruction, which is associated with hyperinflation, increased lung compliance and reduction in alveolar-capillary diffusing capacity. There is a decrease in the compliance of the chest watt, due to calcification of its articulations, dorsal kyphosis and "barrel chest". There is a decrease in the strength of respiratory muscles which correlates with cardiac Index, nutritional status and hyperinflation, and there is a reduction in the ventilatory response to hypoxia and hypercapnia as well as in the perception of increased airway resistance. The increased static lung compliance combined with the decreased chest watt compliance leads to an increase in the functional residual capacity with aging. On the other hand, the loss of alveolar and airways elastic recoil combined with the reduction in the strength of the expiratory muscles, leads to an increase in residual volume and decreased maximal expiratory airflow rates and vital capacity. Despite these changes, the respiratory system maintains an adequate gas exchange at rest and during exercise during the whole life span, showing a normal PaCO2 and a slight decline in PaO2 (-0,3 mmHg per year) which is attenuated to become almost undetectable over the age of 70.