Which parameter remains unchanged with age?

Functional Residual Capacity (FRC) remains largely unchanged with age. FRC is the volume of air remaining in the lungs after a normal expiration, and it is influenced by the balance between elastic recoil of the lungs and the tendency of the chest wall to expand. As people age, various pulmonary functions may decline due to factors such as decreased elasticity of the lungs, increased stiffness of the chest wall, and changes in respiratory muscles. However, FRC tends to remain stable throughout adulthood because the same balance keeps it relatively constant, even as other lung volumes may decrease.

In contrast, vital capacity can decrease with age due to reduced lung elastic recoil and increased airway resistance. Inspiratory capacity, which is the maximum amount of air one can inhale after a normal expiration, can also diminish as lung function declines with age. Dynamic lung compliance, which reflects the lung's ability to stretch during breathing, may decrease as the lung tissues and chest wall become stiffer with age. All these factors point to FRC's unique position in remaining stable despite the natural physiological changes associated with aging.