Chronic Bronchitis

Chronic bronchitis is defined as a cough that occurs every day with sputum production that lasts for at least 3 months, 2 years in a row.

Bronchitisis a term that describes inflammation of the bronchial tubes (bronchi and the smaller branches termedbronchioles) that results in excessive secretions ofmucusinto the tubes, leading to tissue swelling that can narrow or close off bronchial tubes. Bronchial tubes extend from the trachea and terminate at the alveoli in thelungs．The bronchial system resembles an inverted tree and is sometimes termed the "bronchial tree." A few authors include the trachea and upperairwayin the definition ofbronchitis．

There are two major types ofbronchitis:

• Acute bronchitis
• Chronic bronchitis

Chronic bronchitis differs fromacute bronchitisin several ways, for example, pathology, progression of disease, major causes, treatments, and prognosis. Recurrent incidences of acute bronchitis are the first steps that can lead to developing chronic bronchitis, according to some doctors and researchers.

Picture of the structures of the lungs

Chronic bronchitis is defined as acoughthat occurs every day with sputum production that lasts for at least 3 months, two years in a row. This definition was developed to help select uniform patient populations for research purposes, for example, to study medication therapies for the treatment of chronic bronchitis.

米any of the bronchi develop chronic inflammation with swelling and excess mucus production. The inflammation causes a change in the lining cells of the airways to varying degrees. Many cells that line theairwaylose the function of their cilia (hair-like appendages that are capable of beating rapidly), and eventually, the ciliated cells are lost. Cilia perform the function of moving particles and fluid (usually mucus) over the lining surface in such structures as the trachea, bronchial tubes, and nasalcavitiesto keep these hollow structures clear of particles and fluids. These ciliated cells that help in the clearance of secretions are often replaced by so-called goblet cells. This group of cells secretes mucus into the airway. The warm moist environment of the airway along with the nutrients in the mucus is an excellent medium for growing bacteria. The mucus often becomes infected and discolored from the bacterial overgrowth and the body's inflammatory response to it. The inflammation, swelling, and mucus frequently and significantly inhibit the airflow to and from the lung alveoli by narrowing and partially obstructing the bronchi and bronchioles.

The muscles that surround some of the airways can be stimulated by this airway irritation. This muscular spasm also known as bronchospasm can result in further airway narrowing. With long-standing inflammation, as can be seen in chronic bronchitis, this muscular spasm and inflammation result in a fixed, nonreversible narrowing of the airway, and the condition is termedchronic obstructive pulmonary disease(COPD). Chroniccoughing发展身体试图开放和清晰的the bronchial airways of particles and mucus or as an overreaction to ongoing inflammation. Chronic bronchitis can be a progressive disease; symptoms (listed below) increase over time. Some NIH investigators consider chronic bronchitis a type ofCOPD．

COPDalso includes the entities ofemphysema, chronic bronchitis, and chronicasthma．These conditions are not always separable and patients often have components of each. In the case of chronic bronchitis, fixed airway obstruction, airway inflammation, and retained secretions can result in a mismatch of blood flow and airflow in thelungs．This can impair the oxygenation of the blood as well as the removal of the waste product, carbon dioxide.

Although people of any age can develop chronic bronchitis, the majority of people diagnosed with the disease are 45 years of age or older.

There are many causes of chronic bronchitis, but the main cause iscigarettesmoke. Statistics from the US Centers for Disease Control andPrevention(CDC) suggest that about 49% ofsmokers患慢性支气管炎和24%的开发emphysema/COPD．

• 米any other inhaled irritants (for example, smog, industrial pollutants, and solvents) can also result in chronic bronchitis.
• Viral andbacterial infectionsthat result in acute bronchitis may lead to chronic bronchitis if people have repeated bouts with infectious agents.
• Also, underlying disease processes (for example,asthma,cystic fibrosis, immunodeficiency,congestive heart failure, familial genetic predisposition to bronchitis, and congenital or acquired dilation of the bronchioles, known asbronchiectasis) may cause chronic bronchitis to develop, but these are infrequent causes compared tocigarette smoking．

The major risk factor for individuals to develop chronic bronchitis istobacco smokingand second-hand tobacco smoke exposure. However, there are others, such as:

• Repeated exposure to pollutants (especially airborne materials such as ammonia, sulfur dioxide, chlorine, bromine, and hydrogen sulfide)
• Dust
• Repeated bouts of acute bronchitis orpneumonia
• Gastric reflux (byinhalationof gastric contents)

The major signs and symptoms of chronic bronchitis include:

• Cough and sputum productionare the most common symptoms. They usually last for at least 3 months and occur daily. The intensity ofcoughingand the amount and frequency of sputum production vary from patient to patient. Sputum may be clear, yellowish, greenish, or occasionally, blood-tinged. Sincecigarettesmoke is the most common cause of chronic bronchitis, it should not be surprising that the most common presentation is the so-called smoker's cough. This is characterized by a cough that tends to be worse upon arising and is often productive of discolored mucus in the early part of the day. As the day progresses, less mucus is produced.
• Shortness of breath(呼吸困难)逐渐增加的程度the disease. Usually, people with chronic bronchitis get short of breath with activity and begin coughing; dyspnea at rest usually signals thatCOPDor emphysema has developed.
• Wheezing(a coarse whistling sound produced when airways are partially obstructed) often occurs.

Other signs and symptoms that may accompany chronic bronchitis include:

• Fatigue
• Sore throat
• 米uscle aches
• Nasal congestion
• Headaches

Exacerbation of chronic bronchitis occurs when symptoms worsen or become more frequent. These exacerbations often require antibiotics and may need steroid medication and an increase in respiratory inhaled medications.

Signs and symptoms of exacerbation of chronic bronchitis include:

• Severe coughing that causes chest discomfort orchest pain．
• Cyanosis (bluish/grayish skin coloration) may develop in people with advanced COPD.
• Fevermay indicate a secondary viral or bacterial lung infection.

Ideally, a person should seek medical care before chronic bronchitis develops. It is reasonable for people to seek care for tobaccoaddictionand the occasional chronic cough (occurring less than daily for 3 months) and to get medical help to potentially avoid developing chronic bronchitis. However, any daily cough that lasts for at least 3 months in a person should be investigated by a physician.

If a person develops chronic (3 months or longer) cough, difficultybreathing, sputum production, and other symptoms, it may represent the first bout of chronic bronchitis. Thus, seeking medical care may help slow or prevent the usual progression of the disease.

If a person with diagnosed chronic bronchitis (or COPD or emphysema) develops severe problems withbreathing, cyanosis, or fever, they should seek emergency medical care immediately.

Healthcare professionals diagnose chronic bronchitis based on a person's medical history, physical exam, and diagnostic tests. A history of a daily productive (sputum production) cough that lasts at least 3 months, especially if has occurred two years in a row, fits the criteria for a clinical diagnosis of chronic bronchitis. The physical examination often allows healthcare professionals to hear wheezes and a prolongation of theexhalationof breathing, which are signs of airflow obstruction.

Achest X-rayis often performed to help rule out other lung problems (for example,pneumonia, bronchial obstructions). Additional tests such as acomplete blood count(CBC), arterial bloodgasmeasurements,CT scanof the chest, and pulmonary function tests are often done to characterize the structure and function of the lungs and to help exclude other conditions (for example,lung cancer,tuberculosis, lung infections). Often apulmonologist(a physician with specialized training in the management of lung diseases) can help diagnose and treat chronic bronchitis.

For the majority of cases, the initial treatment is simple to prescribe but frequently ignored or rejected by the patient – stopsmokingcigarettes and avoid second-hand tobacco smoke. People should be encouraged in every way to ceasesmoking, as continuation will only cause further lung damage. Similarly, blocking or removing other underlying causes of repeated bronchial irritation (for example, exposure to chemical fumes) is a treatment goal. Half of the patients with chronic bronchitis who smoke will no longer cough after 1 month ofsmoking cessation．

Two major classes of medications are used to treat chronic bronchitis,bronchodilators, and steroids.

1. Bronchodilators(for example,albuterol[Vent Olin, Proventil,AccuNeb,Vospire, ProAir], metaproterenol [Alupent], formoterol [Foradil],salmeterol[Serevent]) work by relaxing the smooth muscles that encircle the bronchi, which allows the inner airways to expand. Anticholinergicdrugsalso can act as bronchodilators, including tiotropium (Spiriva) and ipratropium (Atrovent).
2. Steroids(for example,prednisone, andmethylprednisolone[米edrol,Depo-Medrol]) reduce the inflammatory reaction and thus decrease the bronchial swelling and secretions that in turn allows better airflow because of reduced airway obstruction. Often inhaled steroids are administered since they have fewer side effects than systemic (oral) steroids. Examples includebudesonide(Pulmicort), fluticasone (Flovent), beclomethasone (Qvar), andmometasone(Asmanex). Combination therapy with both steroids and bronchodilators is often utilized. These include fluticasone/salmeterol (Advair),budesonide/formoterol (Symbicort), andmometasone/formoterol (Dulera).

PDE4 Inhibitors

PDE4 inhibitors are a class of anti-inflammatory agents for certain exacerbations of COPD. They are primarily for exacerbations that involve excessive bronchitis and mucus production. There is currently only one agent available called roflumilast (Daliresp), a pill taken once per day.

Antibiotics

Occasionally, antibiotics are used to treat chronic bronchitis exacerbations caused bybacterial infections．Broad-spectrum antibiotics are often the choice. Examples include:

• Fluoroquinolones (levofloxacin[Levaquin])
• 米acrolides (clarithromycin[Biaxin],azithromycin[Zithromax,Zmax])
• Sulfonamides(sulfamethoxazole and trimethoprim[Bactrim])
• Tetracyclines (doxycycline[Vibramycin])

Of course, if a culture is obtained, directed therapy at the specific offending organism is always best.

Over-the-Counter (OTC) Cough Suppressants

Over-the-counter(OTC) cough suppressants such as dextromethorphan (for example, Pertussin, Vicks 44, orBenylin) may help reduce cough symptoms. OTC preparations withguaifenesin(for example,Robitussinor米ucinex) may make patients feel more comfortable but there is no scientific evidence that it helps mucus to become less viscous.

What are other treatments for chronic bronchitis?

• Pulmonary rehabilitationis another treatment method that combines education and graded physicalexercise．The education portion often includessmoking cessationtechniques and the relationship of tobacco use to symptoms. Breathing techniques can be very helpful in overcoming theanxietyand discomfort of exacerbations. When chronic bronchitis is severe, airflow and blood flow may not move appropriately through the lungs. It is crucial for lung function that airflow and blood flow to the lung are precisely matched. When they are not, drops in oxygen and increases in carbon dioxide can result in profound negative consequences.
• Supplemental oxygen therapymay be an integral part of treatment. Often it is required with activity andsleep．Patients with severe disease may benefit from purchasing a small finger oximeter for monitoring blood oxygen levels at rest and with activity.

Certain "home remedies" may ease the symptoms of chronic bronchitis, such as:

• One of the lessons of pulmonary rehabilitation is to instruct patients on the proper path for air to follow. This involves breathing in through the nose so that the air is moistened, cleansed, and warmed by the function of the upper airways (sinuses). Air is then expelled through the mouth and in some cases with pursed lips to help optimize the lung's function.
• Coldair often aggravates coughing and difficulty breathing, so avoiding cold air or wearing a cold-air mask (such as a ski mask or face scarf) may help when in cold environments.
• Dry air also aggravates coughing so warm, humidified air may help by reducing coughing and also may allow mucus to flow more freely, which may result in better clearing of the bronchial airways and less blockage by viscous mucus.
• Alternative treatments have been suggested by some researchers with little or no evidence of any benefit, and some may even be harmful (for example, herbal teas, high doses ofvitamin C, South African geranium herb, eucalyptus oil inhalation therapy, and many others). Check with your doctor or other healthcare professional before using any of these remedies or products.

Although the disease is chronic and progressive, affected individuals that are diagnosed early before much bronchial damage occurs stopsmoking(or avoid airborne dust, chemicals, or other situations that lead to bronchial irritation), they often have a good prognosis for many years.

Approximately half ofsmokerswith chronic bronchitis will stop coughing after 1 month of smoking cessation. Most patients will no longer cough with continued abstinence from smoking. If airflow obstruction has occurred, this can improve but the improvement level depends on the duration of injury and the compliance with therapy. The more impaired patients will have a lesser recovery of lung function.

Conversely, those individuals that have continued bronchial irritation have only a fair to poor prognosis, since repeated bouts with the disease usually get worse, with affected individuals having more frequent incidents of coughing and dyspnea over time and further progression of lung function abnormalities.

The major complications of chronic bronchitis include:

• Difficulty breathing, sometimes severe
• Respiratory failure
• Pneumonia
• Enlargement andweaknessof the rightheart ventricleof theheartcaused by lung disease
• Pneumothorax(collection of air or gas in the lung causinglung collapse)
• Polycythemia(abnormally high concentration ofred blood cellsneeded to carry oxygen)
• Chronic obstructive pulmonary disease(some NIH researchers consider chronic bronchitis a type of COPD)
• Emphysema
• Chronic advancement of the disease
• High mortality (death) rate (COPD is the fourth leading cause of death in the United States)

The majority of instances of chronic bronchitis can be prevented by not smoking and avoidingsecond-hand smoke．Fluand pneumococcalvaccinescan help prevent repeated infections that may lead to the disease.

Certain industries (for example, chemical, textile, and farm workers) are often associated with air-borne chemicals and dust; avoiding air-borne chemicals and dust with appropriate masks may prevent or reduce the individual's chance of developing chronic bronchitis.

Good control ofasthmamay prevent chronic bronchitis from developing. The genetic predisposition to chronic bronchitis is not currently preventable.