The lungs have two primary functions: to acquire oxygen from the air, which is required for life, and to remove carbon dioxide from the body. Carbon dioxide is a byproduct of many of the chemical reactions that sustain life.

During breathing, air enters and exits the lungs. It flows in through increasingly smaller airways, finally filling tiny sacs called alveoli. Blood circulates around the alveoli through capillaries (tiny blood vessels). Where the capillaries and alveoli meet, oxygen crosses into the bloodstream. At the same time, carbon dioxide crosses from the bloodstream into the alveoli to be exhaled.

The lungs are continuously being exposed to particles in the air, including smoke, pollen, dust, and microorganisms. Some of these inhaled substances can cause lung disease if enough is inhaled or if the body is particularly sensitive to them.

AGING CHANGES

People normally make new alveoli until about age 20. After that, the lungs begin to lose some of their tissue. The number of alveoli decreases, and there is a corresponding decrease in lung capillaries. The lungs also become less elastic (able to expand and contract) due to various factors including the loss of a tissue protein called elastin.

Changes in the bones and muscles increase the front-to-back size of the chest. Loss of bone mass in the ribs and spine bones (vertabrae), and mineral deposits in the rib cartilage, change the curve of the spine. There may be front-to-back curvature (kyphosis or lordosis) or side-to-side curvature (scoliosis).

The maximal force you can generate when breathing in (inspiration) or when breathing out (expiration) decreases with age, as the diaphragm and muscles between the ribs (intercostals) become weaker. The chest is less able to stretch to breathe, and the pattern of breathing may change slightly to compensate for this decreased ability to expand the chest.

EFFECT OF CHANGES

Maximum lung function decreases with age. The amount of oxygen diffusing from the air sacs into the blood decreases. The rate of air flow through the airways slowly declines after age 30. And the maximal force you can generate on inspiration and expiration decreases. However, even elderly people should have adequate lung function to carry out daily activities, because we have "extra" lung function in our youth. This is why normal people can tolerate surgical removal of an entire lung and still breathe reasonably well.

An important change for many older people is that the airways close more readily. The airways tend to collapse when an older person breathes shallowly or when they're in bed for a prolonged time. Breathing shallowly because of pain, illness, or surgery causes an increased risk for pneumonia or other lung problems. As a result, it is important for older people to be out of bed as much as possible, even when ill or after surgery. When this is not possible, it is helpful to do "incentive spirometry." This involves blowing into a small device to help keep the airways open and clear of mucus.

Normally, breathing is controlled by the brain. It receives information from various parts of the body telling it how much oxygen and carbon dioxide are in the blood. Low oxygen levels or high carbon dioxide levels trigger an increased rate and depth of breathing. It is normal for even healthy older people to have a reduced response to both decreased oxygen and increased carbon dioxide levels.

The voice box (larynx) also changes with aging. This causes the pitch, loudness, and quality of the voice to change. The voice may become quieter and slightly hoarse. The pitch may be decreased (becoming lower) in women and increased (becoming higher) in men. The voice may sound "weaker," but most people remain quite capable of effective communication.

COMMON PROBLEMS

Elderly people are at increased risk for lung infections. The body has many ways to protect against lung infections. With aging, these defenses may weaken.

The cough reflex may not trigger as readily, and the cough may be less forceful. The hairlike projections that line the airway (cilia) are less able to move mucus up and out of the airway. In addition, the nose and breathing passages secrete less of a substance called IgA (an antibody that protects against viruses). Thus, the elderly are more susceptible to pneumonia and other types of lung infections.

Common lung problems in the elderly include chronically low oxygen levels (which reduces tolerance to illness), decreased ability to exercise, abnormal breathing patterns including sleep apnea (episodes of stopped breathing during sleep), increased risk of lung infections such as pneumonia or bronchitis, and diseases caused by tobacco damage (such as emphysema or lung cancer).

PREVENTION

Avoiding smoking is the most important way to minimize the effect of aging on the lungs. Exercise and good overall fitness improve breathing capacity. Exercise tolerance can be affected by changes in the heart, blood vessels, muscles, and skeleton, as well as in the lungs. However, studies have shown that exercise and training can improve the reserve capacity of the lungs, even in elderly people.

Second, more than any other group the elderly need to be aware of the need to be up and about and should consciously try to increase deep breathing during illness or after surgery.

Continued use of the voice helps maintain overall vocal performance.

RELATED TOPICS

• Aging changes in organs, tissues, and cells
• Aging changes in the bones, muscles, and joints
• Aging changes in the heart and blood vessels
• Aging changes in vital signs