Compliance of the chest wall changes with age, which gets stiffer and less compliant. The muscular force of the diaphragm is reduced with advancing years. The combination of these two factors reduces the maximal amount of air that can be moved into and out of the lungs. This diminution in the so-called forced vital capacity (FVC) of the lungs occurs as one gets older. There is less compliance, less recoil, and greater dead space. The original lung capacity, however, is sufficient to allow for sufficient gas exchange throughout life in the absence of underlying pulmonary disease. Nonetheless, the longitudinal Framingham Heart Study found an association between decrease in lung capacity and all-cause mortality.
The hygiene of the respiratory airways is somewhat compromised by a decreasing function of the microcilia of the bronchial epithelial cells. Since this mechanism is used to clear microbial pathogens, it has a direct influence on host defenses. Finally, since the basis of the respiratory system is an exchange of gases (oxygen, carbon dioxide, trace gases) with the bloodstream, any cardiovascular changes involving the right-side chambers of the heart will influence the overall gas-exchange efficiency for the body.
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