Most of the pulmonary diseases present in the elderly also exist in younger patients; however, the incidence and presentation of these diseases can differ greatly between these two age groups. Elderly patients tend to have other comorbidities that can increase the difficulty with which diagnoses are made and interfere with recovery. This is particularly true when disease processes advance to cause respiratory failure.

PHYSIOLOGICAL CHANGE WITH AGING

Changes to the respiratory system occur with aging that have an impact on pulmonary reserve and decrease the respiratory system's ability to respond to physiological stress and disease. These “normal aging” changes are mild and usually not clinically relevant in the healthy state. The changes discussed later should never limit a patient's usual activity or cause significant dyspnea at rest in the absence of lung disease.

As a patient ages, elastic tissue in the lung is replaced by collagen. This change results in smaller airway size. Airway diameter decreases significantly after the fourth decade, resulting in increased air trapping as small airways collapse at end expiration. The alveolar–arterial oxygen gradient increases with advancing age because of a number of factors including increased collagen deposition in the walls of alveoli, changes in alveolar structure, and decreased alveolar surface area. The thoracic cage and respiratory muscles also change with age. Arthritis of the costovertebral joints, kyphoscoliosis, and calcification of intercostal cartilage result in decreased chest wall compliance and increased stiffness.