With age-related structural changes, the number of alveoli (air sacs) diminishes. Chronic alveolar hypoxia (low oxygen) from such diseases as emphysema or chronic bronchitis may lead to pulmonary hypertension (high blood pressure in the arteries of the lungs), which, in turn, overworks the right ventricle of the heart.
Systemic hypertension often weakens the left ventricle, leading to congestive heart failure (CHF) and pulmonary edema in which excess tissue fluid collects in the alveoli decreases gas exchange.
Many of the protective mechanisms of the respiratory system decline with age. The ciliary activity of the mucosa decreases and the phagocytes in the lungs become less effective. As a result, the elderly are more prone to respiratory infections, especially pneumonia.