Respiratory Health and Disorders

before you start

A variety of diseases can affect the respiratory system. These conditions affect the gas exchange process and result in labored breathing and other difficulties. In this lesson, you will learn about some common disorders associated with the respiratory system. However, it is important to keep in mind that this list is not exhaustive, as there are many disorders associated with the respiratory system.

1. Disorders Caused by Irritants

Airborne irritants can cause damage to a part of the respiratory system, and this may lead to difficulty breathing. Some common disorders caused by irritants are described here.

1a. COPD, Emphysema, and Bronchitis

One widely prevalent obstructive respiratory disease is chronic obstructive pulmonary disease (COPD). COPD is a chronic condition characterized by inflammation of the airways, blood vessels, and lung tissues that obstruct gas exchange. Most commonly, an irritant (e.g., smoking) causes dangerous levels of inflammation. This results in changes to the airways, including narrowing, smooth muscle hypertrophy, and increased mucus production.

Over time, scar tissue can form and cause further narrowing of the airways. If the lungs are inelastic, they can't exchange gases as efficiently as they usually would. This results in problems with exhalation and trapping CO₂, and emphysema occurs.

Bronchitis occurs when an irritant increases mucus secretions, causing mucus to accumulate in the airways. There's usually a lot of coughing and difficulty breathing associated with bronchitis. Chronic bronchitis is a type of COPD and is the result of continuous inflammation of the airway linings, causing increasing mucus with clinical manifestations that include a productive cough of at least 2 months occurring within a 2-year time frame (NIH, 2022b; Widysanto & Mathew, 2023). As with emphysema, cigarette smoking, active or passively, or inhaling toxic chemicals and industrial pollutants is the leading causative factor in developing chronic bronchitis.

terms to know

Chronic Obstructive Pulmonary Disease (COPD)

A widely prevalent obstructive pulmonary disease characterized by inflammation of the airways, blood vessels, and lung tissues that obstruct gas exchange.

Emphysema

Frequent inflammation of the lungs causing airways to become stiffened and alveoli breakdown; this leads to insufficient gas exchange.

Bronchitis

Inflammation of the mucous membranes within the bronchial tubes caused by irritants.

1b. Asthma

As you previously learned, asthma is a chronic disease characterized by inflammation and edema of the airway, and bronchospasms (that is, bronchoconstriction), which can inhibit air from entering the lungs. Bronchospasms occur periodically and lead to an “asthma attack.” An attack may be triggered by environmental factors such as dust, pollen, pet hair, or dander, changes in the weather, mold, tobacco smoke, and respiratory infections, or by exercise and stress.

Symptoms of an asthma attack involve coughing, shortness of breath, wheezing, and tightness of the chest. Symptoms of a severe asthma attack that require immediate medical attention would include difficulty breathing that results in blue (cyanotic) lips or face, confusion, drowsiness, a rapid pulse, sweating, and severe anxiety.

In many cases, the underlying cause of the condition is unknown. However, recent research has demonstrated that certain viruses, such as human rhinovirus C (HRVC), and the bacteria Mycoplasma pneumoniae and Chlamydia pneumoniae that are contracted in infancy or early childhood, may contribute to the development of many cases of asthma.

IN CONTEXT

Everyday Connection

The Effects of Secondhand Tobacco Smoke

The burning of a tobacco cigarette creates multiple chemical compounds that are released through mainstream smoke, which is inhaled by the smoker, and through sidestream smoke, which is the smoke that is given off by the burning cigarette. Secondhand smoke, which is a combination of sidestream smoke and the mainstream smoke that is exhaled by the smoker, has been demonstrated by numerous scientific studies to cause disease.

At least 40 chemicals in sidestream smoke have been identified that negatively impact human health, leading to the development of cancer or other conditions, such as immune system dysfunction, liver toxicity, cardiac arrhythmias, pulmonary edema, and neurological dysfunction. Furthermore, secondhand smoke has been found to harbor at least 250 compounds that are known to be toxic, carcinogenic (cancer-causing), or both. Some major classes of carcinogens in secondhand smoke are polyaromatic hydrocarbons (PAHs), N-nitrosamines, aromatic amines, formaldehyde, and acetaldehyde.

Tobacco and secondhand smoke are considered carcinogenic (cancer-causing). Exposure to secondhand smoke can cause lung cancer in individuals who are not tobacco users themselves. It is estimated that the risk of developing lung cancer is increased by up to 30% in nonsmokers who live with an individual who smokes in the house compared with nonsmokers who are not regularly exposed to secondhand smoke.

Children are especially affected by secondhand smoke. Children who live with an individual who smokes inside the home have a larger number of lower respiratory infections, which are associated with hospitalizations, and a higher risk of sudden infant death syndrome (SIDS). Secondhand smoke in the home has also been linked to a greater number of ear infections in children as well as worsening symptoms of asthma.

2. Disorders Caused by Viruses and Bacteria

Some disorders of the respiratory system are caused by viruses or bacteria that produce infection. This includes disorders such as pneumonia, tuberculosis, and pertussis.

2a. Pneumonia

Pneumonia is an umbrella term for a variety of infections that affect the lungs and cause inflammation. Infection can be caused by a virus, bacteria, or fungi. When a virus, bacteria, or fungi enters the lungs, macrophages try to eradicate the pathogen by surrounding it. This triggers inflammatory cells to travel to the infected area. Once lung tissues become inflamed, the capillaries become damaged. The affected alveoli can fill with fluid or pus, limiting the body’s ability to oxygenate and ventilate. In aspiration pneumonia, food, fluid, upper airway secretions, or emesis (vomit) enter the trachea and respiratory tract, causing an inflammatory response.

term to know

Pneumonia

An infection of the lungs in which fluid buildup makes it difficult to breathe.

2b. Tuberculosis

Tuberculosis, or TB, is a disease caused by the airborne bacterium Mycobacterium tuberculosis (M. tuberculosis) that causes patches of lung tissue to be destroyed. Tiny particles called droplet nuclei are expelled from an infected person during talking, coughing, or singing, and these droplets remain airborne for several hours. While airborne, the infectious particles can be inhaled by others, eventually reaching the alveoli.

Once inhaled, the droplet nuclei bring the tubercle bacilli to the lungs, where they eventually reach the alveoli. Macrophages ingest the tubercle bacilli, damaging and destroying many of them. In some cases, the body will clear the initial infection. In other cases, the initial infection persists but becomes latent. The tubercle bacilli become walled off into a capsule called a granuloma, which prevents spread.

Often, the initial infection will become reactivated, causing the tubercle bacilli to spread to other locations within the lung. Again, the body attempts to control the infection by encasing the tubercle bacilli in a granuloma. During widespread infection, however, this becomes problematic. Granulomas can develop cavities. They are filled with a lipid-rich substance, which can accelerate the spread throughout the lungs and body via the lymphatic or circulatory systems.

term to know

Tuberculosis

A lung infection caused by a type of bacteria which destroys lung tissue.

2c. Pertussis

The causative agent of pertussis, commonly called whooping cough, is Bordetella pertussis, a Gram-negative coccobacillus. The disease is characterized by mucus accumulation in the lungs that leads to a long period of severe coughing. Sometimes, following a bout of coughing, a sound resembling a “whoop” is produced as air is inhaled through the inflamed and restricted airway—hence the name whooping cough. Although adults can be infected, the symptoms of this disease are most pronounced in infants and children. Pertussis is highly communicable through droplet transmission, so the uncontrollable coughing produced is an efficient means of transmitting the disease in a susceptible population.

Following inhalation, B. pertussis specifically attaches to epithelial cells using an adhesin, filamentous hemagglutinin. The bacteria then grow at the site of infection and cause disease symptoms through the production of exotoxins. One of the main virulence factors of this organism is an exotoxin called the pertussis toxin (PT). When PT enters the host cells, it increases the cyclic adenosine monophosphate (cAMP) levels and disrupts cellular signaling. PT is known to enhance inflammatory responses involving histamine and serotonin.

In addition to PT, B. pertussis produces a tracheal cytotoxin that damages ciliated epithelial cells and results in accumulation of mucus in the lungs. The mucus can support the colonization and growth of other microbes and, as a consequence, secondary infections are common. Together, the effects of these factors produce the cough that characterizes this infection.

term to know

Pertussis

A contagious illness caused by Bordetella pertussis that causes severe coughing fits followed by a whooping sound during inhalation; commonly known as whooping cough.

2d. The Common Cold, Flu, and COVID-19

The common cold is a generic term for a variety of mild viral infections of the nasal cavity. More than 200 different viruses are known to cause the common cold. The most common groups of cold viruses include rhinoviruses, coronaviruses, and adenoviruses. These infections are prevalent in the human population and are transmitted through direct contact and droplet transmission. Coughing and sneezing efficiently produce infectious aerosols, and rhinoviruses are known to persist on environmental surfaces for up to a week.

Commonly known as the flu, influenza is a common viral disease caused by an orthomyxovirus that primarily affects the upper respiratory tract but can also extend into the lower respiratory tract. Influenza is pervasive worldwide and causes 3,000–50,000 deaths each year in the United States. The annual mortality rate can vary greatly depending on the virulence of the strain(s) responsible for seasonal epidemics.

Influenza infections are most typically characterized by fever, chills, and body aches. This is followed by symptoms similar to the common cold that may last a week or more. The table below compares the signs and symptoms of influenza and the common cold.

A disease you are likely familiar with is coronavirus disease 2019 (COVID-19). COVID-19 is caused by the virus SARS-CoV-2, which resulted in a global pandemic in 2020. This virus produces some symptoms that are similar to those of influenza but has some important differences. In particular, it can cause some systemic and long-term symptoms that are not yet fully understood. In children, it can also potentially cause multisystem inflammatory syndrome (CDC, 2022). COVID-19 is closely related to two other respiratory system infections caused by coronaviruses: severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS).

terms to know

Common Cold

The most common cause of rhinitis in humans; associated with a variety of adenoviruses, coronaviruses, and rhinoviruses.

Influenza

A highly contagious and acute viral disease of the respiratory tract caused by the influenza virus.

COVID-19

A highly contagious respiratory infection caused by the virus SARS-CoV-2.

3. Other Respiratory Disorders

In addition to disorders caused by irritants, bacteria, and viruses, there are other factors that can also cause respiratory disease.

EXAMPLE

Some are caused by an underlying genetic mutation (e.g., cystic fibrosis), whereas others may be caused by physiological conditions (e.g., sleep apnea), trauma (e.g., pneumothorax and pleural effusion), and even organ failure (e.g., pulmonary edema).

3a. Cystic Fibrosis

Cystic fibrosis (CF) is an inherited disease caused by a gene mutation. This mutation impacts how sodium and chloride ions travel across cell membranes. As a result, thick mucus accumulates in the lungs and throughout the body. Serious breathing problems and other physical issues occur.

did you know

In the United States, more than 30,000 people are affected by CF. It is most common in white persons and especially persons of Northern European descent. In those populations, about one in 3,500 births is affected.

CF is caused by a mutation affecting the CF transmembrane conductance regulator (CFTR) gene. Some people carry the gene but do not develop CF. Because of treatment advances, life expectancy has climbed for patients with CF. Currently, the median survival age for patients with CF is 40. While the pulmonary implications of CF are the primary cause of illness and death, it does affect other organ systems. There is a major treatment burden associated with CF, and recurrent hospitalizations are common (Brown et al., 2017; Karakashian et al., 2021).

terms to know

Cystic Fibrosis

A disorder caused by a genetic mutation that causes production of thick mucus that damages organs and leads to breathing difficulties.

3b. Sleep Apnea

Sleep apnea is a chronic disorder that can occur in children or adults, and it is characterized by the cessation of breathing during sleep. These episodes may last for several seconds or several minutes and may differ in the frequency with which they are experienced. Sleep apnea leads to poor sleep, which is reflected in the symptoms of fatigue, evening napping, irritability, memory problems, and morning headaches. In addition, many individuals with sleep apnea experience a dry throat in the morning after waking from sleep, which may be due to excessive snoring.

There are two types of sleep apnea: obstructive sleep apnea and central sleep apnea. Obstructive sleep apnea is caused by an obstruction of the airway during sleep, which can occur at different points in the airway, depending on the underlying cause of the obstruction.

EXAMPLE

The tongue and throat muscles of some individuals with obstructive sleep apnea may relax excessively, causing the muscles to push into the airway.

EXAMPLE

Obesity is also a known risk factor for sleep apnea. Excess adipose tissue in the neck region can push the soft tissues toward the lumen of the airway, causing the trachea to narrow.

In central sleep apnea, the respiratory centers of the brain do not respond properly to rising carbon dioxide levels and therefore do not stimulate the contraction of the diaphragm and intercostal muscles regularly. As a result, inhalation does not occur, and breathing stops for a short period. In some cases, the cause of central sleep apnea is unknown. However, some medical conditions, such as stroke and congestive heart failure, may cause damage to the pons or medulla oblongata. In addition, some pharmacologic agents, such as morphine, can affect the respiratory centers, causing a decrease in the respiratory rate. The symptoms of central sleep apnea are similar to those of obstructive sleep apnea.

IN CONTEXT

Sleep Apnea Treatment

Treatment of sleep apnea commonly includes the use of a device called a continuous positive airway pressure (CPAP) machine during sleep. The CPAP machine has a mask that covers the nose or the nose and mouth, and forces air into the airway at regular intervals. This pressurized air can help to gently force the airway to remain open, allowing more normal ventilation to occur.

Other treatments include lifestyle changes to decrease weight, eliminate alcohol and other sleep apnea-promoting drugs, and changes in sleep position. In addition to these treatments, patients with central sleep apnea may need supplemental oxygen during sleep.

term to know

Sleep Apnea

A chronic disorder that is characterized by the cessation of breathing during sleep.

3c. Pneumothorax and Pleural Effusion

The pleural space is the area between the inner (visceral) pleural layer and the outer (parietal) pleural layer. Under normal circumstances, the two pleural layers are separated by only a small volume of pleural fluid. Pneumothorax, also known as a collapsed lung, occurs when air enters the pleural space. Air can enter the pleural space when there is trauma through the chest wall, or if there is a rupture of the inner (visceral) pleural layer. The accumulation of air increases pressure, causing the lung to collapse and deflate. As a result of collapse and deflation, the lung area available for oxygenation and ventilation is dramatically decreased.

Although pneumothorax is caused by trauma in many cases (traumatic pneumothorax), there are also nontraumatic forms that may be spontaneous (primary spontaneous pneumothorax), caused by underlying lung disease (primary spontaneous pneumothorax), or as a complication from surgery or an invasive medical procedure (e.g., iatrogenic pneumothorax).

In contrast, pleural effusion occurs when there is abnormal fluid buildup in the pleural space between the chest wall and the lungs. Pleural effusion can result in cough, shortness of breath (dyspnea), fever, and sharp chest pain that is worse when inhaling.

terms to know

Pneumothorax

An abnormal accumulation of air in the pleural space.

Pleural Effusion

An abnormal accumulation of fluid in the pleural cavity.

3d. Pulmonary Edema

Recall from a previous lesson that edema is the accumulation of excess water in the tissues. The physiological causes of edema include water leakage from blood capillaries. Pulmonary edema is excess fluid in the air sacs of the lungs, a common symptom of heart and/or kidney failure. People with pulmonary edema likely will experience difficulty breathing, and they may experience chest pain. Pulmonary edema can be life-threatening, because it compromises gas exchange in the lungs, and anyone having symptoms should immediately seek medical care.

In pulmonary edema resulting from heart failure, excessive leakage of water occurs because fluids get “backed up” in the pulmonary capillaries of the lungs, when the left ventricle of the heart is unable to pump sufficient blood into the systemic circulation. Because the left side of the heart is unable to pump out its normal volume of blood, the blood in the pulmonary circulation gets “backed up,” starting with the left atrium, then into the pulmonary veins, and then into pulmonary capillaries. The resulting increased hydrostatic pressure within pulmonary capillaries, as blood is still coming in from the pulmonary arteries, causes fluid to be pushed out of them and into lung tissues.

term to know

Pulmonary Edema

A buildup of fluid in the veins and alveoli of the lungs caused by the inability of the heart to adequately circulate blood.