Answer
The respiratory system matures at about 25 years of age. From that time onward the amount of O2 that active people can use decreases by about 9% per decade. Several degenerative changes take place in respiratory structures that account for this and other functional changes in the respiratory system as one ages.
The following are some changes in respiratory parameters that signal decline in respiratory effectiveness and efficiency:
--Vital capacity declines with age; by the 70s it is reduced to about 1/3rd of what it was at age 25.
--Peak air flow declines
--Efficiency of gas exchange decreases
--Alveolar dead space increases
--Residual volume increases
--Functional residual capacity rises
--Respiratory system reserve falls
Work Step by Step
The following are some structural changes that cause decrease in respiratory performance as one ages:
--The chest wall, and the spine become deformed; as a consequence, the thorax loses elasticity.
This decreases total compliance, and increases the energy requirement for ordinary
breathing.
--The loss of elasticity by lung tissue also contributes to the loss in compliance.
--The muscles of respiration get weaker, and they become less able to ventilate the lungs. This
results in older people being less able to participate in vigorous activities--running, swimming
and biking.
--In the lungs , dilation of air sacs, enlargement of air spaces, and loss of supporting tissues (in the
air ways) serve to increase residual volume and functional residual capacity.
The loss of sensitivity of airway receptors makes a person less able to respond to hypoxia and hypercapnia and therefore more susceptible to harm from heart failure, infections and airway obstructions.
Several of the respiratory protective mechanisms become less effective with advancing age. Some of these are respiratory tract mucus, mucosal villi, and lung macrophages: lung macrophages become less active ; the number of nasal mucosal glands decreases; mucosal villi are less active, and blood flow to the nasal mucosa decreases. Because of the loss in effectiveness of thees mechanisms, older persons become more susceptible to respiratory infections--pneumonia, bronchitis, and influenza.
