RESPIRATORY FUNCTION

As lung function changes with age, it often is difficult to differentiate the effects of age from those of environmen­tal and disease factors. Maximal oxygen consumption (VO₂ max), a measure used to determine overall cardiopulmo-nary function, declines with age. Numerous studies have indicated that VO₂ max can improve significantly with ex­ercise and that the VO₂ max of older adult master athletes can meet and exceed that of their younger counterparts.

A progressive loss of elastic recoil in the lung is caused by changes in the amount of elastin and composition of collagen fibers. Calcification of the soft tissues of the chest wall causes increased stiffness and thus increases the work­load of the respiratory muscles. There is a loss of alveolar structure that decreases the surface area of gas exchange. Although the total lung capacity remains constant, the consequences of these changes result in an increased resid­ual lung volume, increased functional reserve capacity, and a decline in vital capacity. There is a linear decrease in arterial oxygen tension (PO₂) of approximately 20 mm Hg from 20 to 70 years of age. This is thought to result pri­marily from the ventilation-perfusion mismatching of the aging lung.²¹