Aging of the respiratory system

Abstract

Changes in the respiratory system caused by aging generally include structural changes in the thoracic cage and lung parenchyma, abnormal findings on lung function tests, ventilation and gas exchange abnormalities, decreased exercise capacity, and reduced respiratory muscle strength. Decreased respiratory system compliance caused by reduced elastic recoil of the lung parenchymaand thoracic cage is related to decreased energy expenditure by the respiratory system. Lung function, as measured by 1-second forced expiratory volume and forced vital capacity (FVC), decreases with age, whereas total lung capacity remains unchanged. FVC decreases because of increased residual volume and diffusion capacity also decreases. Increased physiological dead space and ventilation/perfusion imbalance may reduce blood oxygen levels and increase the alveolar-arterial oxygen difference. More than 20% decrease in diaphragmstrength is thought to beassociated withaging-related muscle atrophy. Ventilation per minute remains unchanged, and blood carbon dioxide concentration does not increase with aging. However, responses to hypoxia and hypercapnia are decreased. Exercise capacity also decreases, and maximum oxygen consumption decreases by > 1%/year. Consequence of these changes, many respiratory diseases occur with aging. Thus, it is important to recognize these aging-related respiratory system changes.