Aging of the Respiratory System
This chapter addresses the following Geriatric Fellowship Curriculum Milestone: #9
Key Clinical Points
Age-related changes within alveoli account for “senile emphysema” characterized by alveolar dilatation without destructive changes to the alveolar walls. This causes reduced lung recoil, and increases dead space impairing gas exchange.
The mean maximal inspiratory pressure (MIP) is associated with decreased handgrip strength, lower body mass index, and current smoking status; for healthy 85-year-old men, it is approximately 30% lower than that of 65-year-old men.
Though total lung capacity (TLC), made up of the two components of vital capacity (VC) and residual volume (RV), does not change with age, age-related changes in lung physiology, bone, and muscle result in decreased VC with a corresponding increase in RV as measured by standard spirometry.
Aging results in a loss in forced expiratory volume in 1 second (FEV1) of about one-third liter per decade, and the decline in FEV1 with aging is greater than the decline in total forced vital capacity (FVC). Since FEV1/FVC values below 0.65 are typically indicative of airway obstruction, this parameter may overestimate obstructive disease in extreme old age.
It is imperative to understand the changes that occur in the respiratory system with age because many disease processes have a direct correlation with age-related changes in respiratory physiology. Intrinsic aging alone produces changes, but there are also consequences of lifetime accumulation of insults by environmental factors and recovery from such insults. Cigarette smoke, accounting for the greatest population impact on the respiratory system, produces effects similar to aging and this is reflected in disease processes such as chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). The term “accelerated aging” is often encountered in studies of these chronic diseases in older adults so we try here to describe the changes in the respiratory system that occur in a healthy, nonsmoking individual as a result of age and compare them with the changes indicative of chronic diseases in older adults. This chapter deals with changes in (1) structure of the lung and chest wall, (2) lung volumes and lung capacities, and (3) respiratory mechanics. We further compare and contrast the features of normal aging, COPD, and IPF to better understand the similarities and dissimilarities. Lastly, we address one of the most commonly encountered clinical dilemmas: attempting to differentiate COPD and asthma at the bedside; thus the chapter ends with a discussion on interpretation of spirometry results at baseline and with pharmacologic intervention in order to differentiate these diseases.
Structural changes associated with age occur most notably in the alveoli rather than ...