EFFECTS OF AGING ON THE RESPIRATORY SYSTEM
Aging affects most aspects of the respiratory system. But even though vital capacity, maximum ventilation rates, and gas exchange decrease with age, the elderly can engage in light to moderate exercise because the respiratory system has a large reserve capacity.
With age, mucus accumulates within the respiratory pas-sageways. The mucus-cilia escalator is less efficient because the mucus becomes more viscous and the number of cilia and their rate of movement decrease. As a consequence, the elderly are more susceptible to respiratory infections and bronchitis.
Vital capacity decreases with age because of reduced ability to fill the lungs (decreased inspiratory reserve volume) and to empty the lungs (decreased expiratory reserve volume). As a result, maximum minute ventilation rates decrease, which in turn decreases the ability to perform intense exercise. These changes are related to the weakening of respiratory muscles and the stiffening of cartilage and ribs.
Residual volume increases with age as the alveolar ducts and many of the larger bronchioles increase in diameter. This increases the dead space, which decreases the amount of air available for gas exchange. In addition, gas exchange across the respiratory membrane declines because parts of the alveolar walls are lost, which decreases the surface area available for gas exchange, and the remaining walls thicken, which decreases the diffusion of gases. A gradual increase in resting tidal volume with age compensates for these changes.