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5.9: Diseases of the Respiratory System

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    While age changes in the respiratory system have only a small impact on the ordinary activities of daily living, changes caused by disease can have a substantial effect. Respiratory diseases reduce a person's speed and endurance in physical activities and cause significant disability. Treatment can extend for long periods and is often expensive. Furthermore, respiratory system diseases (not including cancer of the lungs) are the third leading cause of death for those over age 65. If lung cancer is added, respiratory disease ranks as the second leading cause of death among the elderly. (Suggestion: Chap 05 - 109-1-3)

    The reasons for the high incidence of respiratory diseases among older people are similar to those for other diseases. They include reductions in defense mechanisms; more time for the development of slowly progressing diseases; and increases in the number of exposures and the total time of exposure to disease‑promoting factors.

    There is one factor that contributes to the development of virtually all these diseases: air pollution. One of the most common forms is smoking and inhaling smoke from tobacco products. Though the proportion of smokers in the population has declined, the effects of smoking among older people will be evident for many years because many older people have smoked for long periods. The rate of decline of the respiratory system slows when a person stops smoking, and there may even be a period of improvement in gas exchange. However, most effects from long‑term smoking are not reversible. (Suggestion 109.01.03)

    Other forms of air pollution include particulate matter such as dust from coal mining, woodworking, farming, and the manufacture of fabrics. Fumes and vapors such as those from painting, chemical plants, and scientific laboratories can harm the lungs. Smog, automobile fumes, and other types of air pollution associated with urban environments are also significant risk factors for lung damage.

    Reducing the inspiration of air pollutants can significantly reduce both the incidence and severity of respiratory disease. Doing this will preserve much of the capacity for gas exchange by the respiratory system.

    Respiratory diseases that are most common among people of advancing age include lung cancer, chronic bronchitis, emphysema, pneumonia, and pulmonary embolism. These diseases and two other abnormal conditions (sleep apnea and snoring) will be considered here. In examining these respiratory diseases and abnormal conditions, keep in mind that the ability of hemoglobin to bind oxygen is affected by CO2, pH, and temperature. Respiratory diseases and conditions can reduce ventilation, leaving more CO2 in the blood and more warm air in the lungs. These changes reduce the ability to oxygenate blood not only because the O2 supply to the lungs is reduced. The elevated CO2 reduces the pH in blood in the lungs, and the blood remains somewhat warmer. Under these conditions, the hemoglobin in blood passing through the lungs cannot pick up and hold as much oxygen. Therefore, the hemoglobin in the blood passing through the lungs cannot transport as much O2 to body cells.

    Lung Cancer

    Normally, cells reproduce when the body needs more of them; once the need is met, they stop reproducing. An example is the temporary rapid reproduction of skin cells that occurs until a cut in the skin heals. Cancer consists of cells that continue to divide and spread out in an uncontrolled fashion even when they are not needed. A clump of these cells is called a tumor.

    Some forms of cancer develop from lung cells and are called primary lung cancer. These are the types caused primarily by smoking. Many other cancers of the lungs develop when the circulatory system moves cancer cells from another place in the body to the lungs. Cancer that moves to another part of the body is called metastatic cancer. Metastatic lung cancer often comes from the breasts or the reproductive system. (Suggestion 109.02.03)

    A person with lung cancer may have from one tumor to very many tumors. Whether the cancer is primary or metastatic, the effects on the lungs are similar. Ventilation becomes more difficult because airways get blocked when tumors grow inside them or squeeze them closed. Air volumes are reduced as alveoli become filled with cancer cells. Occasionally the cancer becomes so large or stiffens the lungs so much that they cannot inflate or deflate adequately for ventilation. Cancer cells in the alveoli may reduce diffusion by thickening or replacing the respiratory membrane between the air and the blood. Sometimes cancer will distort, squeeze, or replace the pulmonary vessels so that perfusion is reduced. Some blood vessels are weakened, causing bleeding.

    Several warning signs indicate that lung cancer may be present. They include a persistent cough, coughing or spitting up blood, pain in the chest, difficulty swallowing, hoarseness, easy fatigability and the feeling of breathlessness, and a swelling of the fingertips. Any of these indicators warrant evaluation by a physician.

    Though some forms of lung cancer can be cured if discovered early enough, most cases are not identified until the cancer has grown so much that it cannot be eliminated. The vast majority of cases of lung cancer result in death within a few years. The only effective "cure" is prevention: avoiding tobacco smoke and other forms of air pollution.

    Chronic Bronchitis

    To understand chronic bronchitis, recall that the trachea and bronchi are lined with a thin layer of mucus and that as the mucus is made, cilia sweep it up and out of the airways.


    If a person inspires air with an excess amount of harmful particles or noxious chemicals, the cells lining the trachea and bronchi become injured. The resulting inflammation causes those cells to make mucus much faster, and the lining of the airways becomes swollen. In addition, the beating of cilia slows. The person now has bronchitis and will begin to cough to remove the extra mucus and pollutants.

    If this person breathes the pollutants frequently and continuously, the airways remain inflamed for a longer time, and the person then has chronic bronchitis. This condition is accompanied by extra mucus production and coughing. After a while the cilia will be damaged and may completely disappear.


    The major effect of chronic bronchitis is to reduce ventilation by making the airways narrow in two ways. First, mucus accumulates because it is being produced more quickly and removed more slowly. Second, the lining of the airways swells inwardly. The effect on airflow through the trachea and bronchi is similar to the stuffed‑up feeling that occurs when a head cold causes swelling and the accumulation of mucus in nasal passages.

    Expiration becomes especially difficult because the lower airways normally narrow during expiration. The additional narrowing from the mucus and swelling makes them so narrow that expiration can occur only very slowly. This decreases the minute volume, and so having enough gas exchange to meet the bodys needs is quite difficult. The problem is compounded because the person will begin to rely more on forced expiration, increasing the work of breathing. The effort used in coughing raises the work of breathing to levels that may leave the victim dizzy, breathless, and temporarily incapacitated.

    The problem becomes very serious when the person tries to do something physically active. Fatigue and the sense of being out of breath develop quickly and are rather severe. Some individuals are disabled by this disease.

    Fortunately, many cases of chronic bronchitis that have not been allowed to progress too long can be cured. The person need only eliminate breathing polluted air. Eventually, mucus production will slow and the cilia will grow back and begin to function as before.

    Curing chronic bronchitis can be difficult if smoking is the source of the air pollution, however, because tobacco smoke contains addictive chemicals such as nicotine. Also, as the respiratory system begins to clear itself, coughing increases temporarily. Smokers often experience extra coughing in the morning because the clearing action began during the night, when they were not smoking. After a period of abstention, smoking seems to help because it relieves the withdrawal symptoms and stops the clearing action, and thus stops the coughing. Of course, continuing to smoke only relieves certain symptoms while the disease continues to destroy the person's respiratory system.

    Besides reducing directly the performance of the respiratory system, chronic bronchitis increases the risk of infection of the respiratory system because the accumulation and slow removal of mucus allow microbes to flourish in the airways. It can also lead to emphysema, and the chronic coughing contributes to hemorrhoids. Long‑term smoking is also a major risk factor for nonrespiratory diseases such as heart attack, atherosclerosis, and stroke.


    Emphysema is a disease that involves actual destruction of some parts of the lungs.

    There are two main forms: centrilobar emphysema (CLE) and panlobar emphysema (PLE). Both types will be present in most people with emphysema, though one type will predominate.

    Centrilobar Emphysema

    Centrilobar emphysema most often develops along with or after chronic bronchitis. It involves a thinning and weakening of the smallest bronchioles and the production of much mucus. Many results are similar to those of chronic bronchitis. Additionally, the damage to the bronchioles usually results in a decrease in the number of small blood vessels in the lungs, decreasing perfusion. The reduction in blood vessels also makes it harder for the heart to pump blood through the lungs, and the overworked heart eventually becomes weaker. If CLE continues to progress, the victim eventually dies of respiratory failure, respiratory infection, or heart failure.

    Panlobar Emphysema

    Panlobar emphysema is less common than CLE. Though the major cause is air pollution, some people inherit a tendency to develop this type of emphysema.

    PLE causes destruction of the walls of the alveoli and alveolar sacs. The results are like a highly exaggerated version of age changes in the alveoli. Many walls between the alveoli shrink and disappear. Neighboring alveoli blend to form large air‑filled spaces. The lungs change from having microscopic spaces like those found in Styrofoam to having large spaces like those in a sponge. The wall material that remains is weaker and less elastic. All these changes reduce ventilation.

    With PLE, expiration becomes more difficult and more residual air is left in the lungs. As passive expiration decreases, forced expiration increases, increasing the work of breathing. Perfusion also decreases because the number of capillaries declines as the alveolar walls are destroyed. Besides reducing gas exchange, this overworks the heart, occasionally leading to heart failure. Finally, diffusion is reduced because there is a decrease in the amount of surface area.

    A complication of PLE is the partial or complete collapse of a lung. This occurs when a hollow space developing close to the lung surface bursts like a bubble. As escaping air separates the lung from the thoracic wall, the lung collapses like a balloon with a small leak. This condition is called pneumothorax. Proper inspiration is impossible unless the leak heals and the body absorbs the air from the thoracic cavity.

    Overall Effects of Emphysema

    People in the early stages of emphysema may hardly notice the decline in their ability to perform physical activities. As the disease progresses and devastates more of the lungs, gas exchange plummets. Eventually, even walking at an ordinary pace becomes a challenge. Individuals with advanced cases are so disabled that they may be unable to get up, sit up, or even roll over in bed without extreme fatigue. Mild exertion or a slight respiratory infection can cause death. Among people over age 55, emphysema is the fifth leading cause of death for men and the seventh leading cause for women.


    Pneumonia is actually a group of related diseases involving inflammation in the lungs. Several types reduce a person's ability to inspire. Older people are especially affected by pneumonia caused by microbes (bacteria, viruses, and fungi) and by dust and chemical vapors. Pneumonia can also result from aspirating stomach contents that have moved up into the throat.

    Microbial Pneumonia

    Reasons for the age‑related increased susceptibility to microbial pneumonia include age changes in the functioning of the mucociliary escalator, white blood cells, and the immune system; the rising prevalence of chronic bronchitis and emphysema; and other diseases that weaken the body and make it less able to ward off infections.

    Pneumonia caused by bacteria results in filling of the airways and alveoli with fluids and cells from their walls. This material blocks the airways. It usually becomes somewhat solid after 1 to 2 days. If a person is otherwise healthy and receives proper treatment, such as antibiotics, the infection can be overcome and the material will be cleared away after about a week.

    Many types of bacteria that cause pneumonia leave the lungs with no residual damage. However, some forms cause serious and permanent damage that results in a reduction in respiratory functioning and can cause death. These forms are the ones most likely to occur in weakened or hospitalized individuals.

    Viral pneumonia affects the walls of the alveoli, causing them to accumulate fluids and become thicker, reducing gas exchange. If a person is healthy and has a good immune system, the immune response will eliminate the virus in a few days and the lungs will return to normal functioning.

    Because fungal pneumonia, Coronavirus COVID-19 and tuberculosis cause death of the portions of the lungs they infect, they can be more serious than bacterial or viral pneumonia. Thus, after fungal, COVID-19 and tubercular infections are stopped, the lungs are left with regions that no longer function. Areas affected by tuberculosis are filled in with solid scar tissue which, if calcified, can be detected on x‑ray. If enough areas of the lungs are destroyed, gas exchange and activity levels are permanently reduced. More extensive damage results in death.

    Unfortunately, many older individuals are not healthy and do not have strong immune systems when they get pneumonia. Weakened persons may have great difficulty combating the infection. Then the disease lasts longer and has a greater impact on the respiratory system. The proportion of individuals who survive microbial pneumonia decreases rapidly with age. Those who survive are often left weakened for long periods.

    Dust and Vapors

    Some individuals breathe large amounts of certain types of air pollution repeatedly for long periods, usually because of their occupations. Examples include farmers, miners, textile mill workers, sandblasters, and woodworkers. The heavy exposure and the size and chemical natures of such air pollutants cause the lungs to form large quantities of fibers and develop the condition called pulmonary fibrosis.

    With pulmonary fibrosis, the normal amount and rate of age changes in the lungs increase dramatically, leading to a rapid decline in gas exchange. Very severely affected people will become quite disabled. Since the fibrosis is permanent, affected individuals can recover little if any of the lost respiratory functioning even if they avoid future exposure to air pollution. The only solution is to prevent pulmonary fibrosis by avoiding its causes.

    Pulmonary Embolism

    Pulmonary embolism (Chapter 4) is a disease condition in which blood clots have moved to the lungs from the systemic veins or the heart. Conditions commonly promoting the formation of such emboli in the elderly include varicose veins, congestive heart failure, and immobility. The elderly are especially prone to having conditions that cause immobility. These include heart attack, stroke, hospitalization, recovery from surgery, and fractures. The effects of pulmonary embolism depend on the size and number of pulmonary emboli.

    Control Errors

    Two age changes involving the control of ventilation that have not yet been discussed are sleep apnea and snoring.

    Sleep Apnea

    A person has sleep apnea (SA) if he or she exhibits at least five temporary cessations of ventilation per hour or exhibiting at least 10 occasions of depressed ventilation and cessation of ventilation per hour when asleep. The incidence of sleep apnea increases with age up to age 65, after which the incidence plateaus. It is present in 4 percent of younger adults but in 25 percent to 30 percent of people over age 64. The male:female ratio for SA is approximately 3:1.

    Sleep apnea may be caused by narrowing and collapsing of the pharynx, especially when in a supine position (i.e., sleeping on one's back); because the respiratory center becomes less sensitive; or because the center simply stops initiating inspiration. Then blood levels of O2 and CO2 change. These alterations in the blood may provide the necessary stimulation to begin inspiration again. People with sleep apnea tend to snore and to have frequent sudden awakenings with feelings of respiratory distress.

    Mild sleep apnea seems to have no deleterious affect on the body. However, frequent awakenings can lead to fatigue, indications of sleep deprivation, and adverse alterations in mood and personality. Because sleep apnea causes significant fluctuations in O2, CO2, and blood pressure, serious cases increase the risk of heart attack and stroke. Treatments for SA include avoiding sleeping in a supine position; using masks with pumps that provide positive pressure into the respiratory system; reversal of obesity; medications; and surgical correction of the pharyngeal region.


    Snoring, or making loud breathing sounds when asleep, is due to partially obstructed upper airways. Approximately half of all women and well over half of all men above age 65 snore. Some individuals who snore also have sleep apnea.

    Snoring causes a variety of problems. Biologically, it causes from mild to severe adverse effects on blood O2 and CO2 levels and on circulation. It can also contribute to high blood pressure and heart disease. Since snoring disrupts normal sleep patterns even if the person who is snoring does not awaken, it can result in fatigue and other indications of sleep deprivation.

    Anyone who sleeps near a person who snores can attest to some of the social implications. Their responses to the person who snores, together with the multitude of jokes about snoring, can add to the psychological impact produced by sleep deprivation. The fatigue felt by many snorers also affects their social interactions and can impinge on their ability to carry out their jobs.

    Though the causes of snoring and the role of the nervous system in snoring are not clear, research has provided methods of treatment for this condition.

    This page titled 5.9: Diseases of the Respiratory System is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Augustine G. DiGiovanna via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.