Ventilation at the base of the lungs in older adults is

• A. More
• B. Unchanged
• C. Variable
• D. Less

Answer: (D)

As people age, changes in lung and chest wall mechanics shift how air is distributed during breathing. The closing capacity (the point at which small airways begin to close during expiration) increases with age, especially in the dependent bases of the lungs. This makes the airways in the bases more prone to collapse during normal breathing, leading to less air reaching the lower regions. At the same time, weaker inspiratory muscles and a stiffer chest wall reduce the effort and efficiency of ventilation in the bases. Gravity would normally favor basilar ventilation, but airway closure and reduced elastic recoil limit air reaching the bases, so ventilation there tends to be less in older adults.