The most prominent effects of aging on the pulmonary system are stiffening of the chest wall and a decrease in elasticity of the lung parenchyma.
The need for greater lung inflation to prevent small airway collapse is reflected by the increase in closing capacity with age. Closing capacity typically exceeds functional residual capacity in the mid 60s and eventually exceeds the tidal volume at some later age.
These changes, plus a modest reduction in alveolar surface area with age, contribute to a modest decline in resting PaO2.
Changes within the nervous system further influence the respiratory system. Aging leads to an approximate 50% decrease in the ventilatory response to hypercapnia and an even greater decrease in the response to hypoxia, especially at night.
Generalized loss of muscle tone with age applies to the hypopharyngeal and genioglossal muscles and predisposes elderly individuals to upper airway obstruction.
A high percentage, perhaps even 75%, of people older than age 65 years have sleep-disordered breathing, a phenomenon that may or may not be the same as sleep apnea but certainly places elderly individuals at increased risk for postoperative hypoxia.
Aging also results in less effective coughing and impaired swallowing. Aspiration is a significant cause of community-acquired pneumonia and may well play a role in the development of postoperative pneumonia.