FUNCIÓN RESPIRATORIA EN LA SENECTUD

Resumen

Aging generates four important changes in the structure and function of the respiratory system: a) 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; b) a decrease in compliance of the chest wall, due to calcification of its articulations, dorsal kyphosis and ”barrel chest”; c) a decrease in the strength of respiratory muscles which correlates to cardiac index, nutritional status and hyperinflation, and d) 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 wall 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.

Notwithstanding these changes, the respiratory system remains able of maintaining 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 be almost undetectable over 70 years-old.

* Este artículo está basado en la conferencia del mismo nombre pronunciada en el Simposio “Tópicos de Fisiología del Envejecimiento”, 22ª Reunión anual Sociedad Chilena de Ciencias Fisiológicas y 50ª Reunión anual Sociedad de Biología de Chile, Pucón, 21 de noviembre, 2007.