There is a large variation in different physiologic measures among older adults, making it difficult to construct “normal” limits to differentiate a disease from a normal state. Respiratory system undergoes various structural, physiological, and immunological changes with age. Differentiating a disease state from “normal” aging is vital when encountering this population in the clinical setting. The number of persons aged 65 and over is projected to increase from 35 million in 2000 to an estimated 71 million in 2030, with the largest increase in individuals age 80 and above ( US Census 2005). Increased life expectancy reflects, in part, a better understanding of the disease states, newer interventions, and the success of public health programs. Since the 1950s the median age of the US population increased by 20 years. Older adults have decreased sensation of dyspnea and diminished ventilatory response to hypoxia and hypercapnia, making them more vulnerable to ventilatory failure during high demand states (ie, heart failure, pneumonia, etc) and possible poor outcomes.

The airways receptors undergo functional changes with age and are less likely to respond to drugs used in younger counterparts to treat the same disorders. The alveolar dead space increases with age, affecting arterial oxygen without impairing the carbon dioxide elimination.

The lung matures by age 20–25 years, and thereafter aging is associated with progressive decline in lung function.

Respiratory muscle strength decreases with age and can impair effective cough, which is important for airway clearance. The lung parenchyma loses its supporting structure causing dilation of air spaces: “senile emphysema”. The structural changes include chest wall and thoracic spine deformities which impairs the total respiratory system compliance leading to increase work of breathing. The respiratory system undergoes various anatomical, physiological and immunological changes with age. With the looming expansion of the elderly population of the US, a thorough understanding of “normal” aging-related changes on the respiratory system is paramount.

Dead space in the lungs