eMedicine Specialties > Pulmonology > Obstructive Airways Diseases

Bronchitis

Author: Jazeela Fayyaz, DO, Senior Fellow, Department of Pulmonology, Lenox Hill Hospital
Coauthor(s): Ali Hmidi, MD, Staff Physician, Department of Internal Medicine, Brooklyn Hospital Center, Cornell University; Jeffrey Nascimento, DO, MS, Fellow, Department of Pulmonary Medicine, Lenox Hill Hospital; Roger B Olade, MD, MPH, Medical Director, Providence Health Group; Klaus-Dieter Lessnau, MD, FCCP, Clinical Associate Professor of Medicine, New York University School of Medicine; Medical Director, Pulmonary Physiology Laboratory; Director of Research in Pulmonary Medicine, Department of Medicine, Section of Pulmonary Medicine, Lenox Hill Hospital
Contributor Information and Disclosures

Updated: Jun 17, 2009

Introduction

Background

Bronchitis is one of the top conditions for which patients seek medical care. Bronchitis is characterized by inflammation of the bronchial tubes (or bronchi), which are the air passages that extend from the trachea into the small airways and alveoli. Triggers may be infectious agents, such as viruses or bacteria, or noninfectious agents, such as smoking or inhalation of chemical pollutants or dust.

Acute bronchitis is manifested by cough and, occasionally, sputum production that last for no more than 3 weeks. Although bronchitis should not be treated with antimicrobials, it is frequently difficult to refrain from prescribing them. Accurate testing and decision-making protocols regarding who might benefit from antimicrobial therapy would be useful but are not currently available.

Chronic bronchitis is defined clinically as cough with sputum expectoration for at least 3 months during a period of 2 consecutive years. Chronic bronchitis is associated with hypertrophy of the mucus-producing glands found in the mucosa of large cartilaginous airways. As the disease advances, progressive airflow limitation occurs, usually in association with pathologic changes of emphysema. This condition is called chronic obstructive pulmonary disease (COPD). When a stable patient experiences sudden clinical deterioration with increased sputum volume, sputum purulence, and/or worsening of shortness of breath, this is referred to as an acute exacerbation of chronic bronchitis as long as conditions other than acute tracheobronchitis are ruled out.
 
Generally, bronchitis is a diagnosis made by exclusion of other conditions such as sinusitis, pharyngitis, tonsillitis, and pneumonia.

Pathophysiology

Respiratory viruses are the most common causes of acute bronchitis. The most common viruses include influenza A and B, parainfluenza, respiratory syncytial virus, and coronavirus, although an etiologic agent is identified only in a minority of cases.¹

During an episode of acute bronchitis, the cells of the bronchial-lining tissue are irritated and the mucous membrane becomes hyperemic and edematous, diminishing bronchial mucociliary function. Consequently, the air passages become clogged by debris and irritation increases. In response, copious secretion of mucus develops, which causes the characteristic cough of bronchitis. For instance, with mycoplasmal pneumonia, bronchial irritation results from the attachment of the organism (Mycoplasma pneumoniae) to the respiratory mucosa, with eventual sloughing of affected cells. Acute bronchitis usually lasts approximately 10 days. If the inflammation extends downward to the ends of the bronchial tree, into the small bronchi (bronchioles), and then into the air sacs, bronchopneumonia results.

Chronic bronchitis is a condition associated with excessive tracheobronchial mucus production sufficient to cause cough with expectoration for at least 3 months for more than 2 consecutive years. The alveolar epithelium is both the target and the initiator of inflammation in chronic bronchitis.

A predominance of neutrophils and the peribronchial distribution of fibrotic changes result from the action of interleukin 8, colony-stimulating factors, and other chemotactic and proinflammatory cytokines. Airway epithelial cells release these inflammatory mediators in response to toxic, infectious, and inflammatory stimuli, in addition to decreased release of regulatory products such as ACE or neutral endopeptidase.

Chronic bronchitis can be categorized as simple chronic bronchitis, chronic mucopurulent bronchitis, or chronic bronchitis with obstruction. Mucoid sputum production characterizes simple chronic bronchitis. Persistent or recurrent purulent sputum production in the absence of localized suppurative disease, such as bronchiectasis, characterizes chronic mucopurulent bronchitis. Chronic bronchitis with obstruction must be distinguished from chronic infective asthma. The differentiation is based mainly on the history of the clinical illness. Patients who have chronic bronchitis with obstruction present with a long history of productive cough and a late onset of wheezing, whereas patients who have asthma with chronic obstruction have a long history of wheezing with a late onset of productive cough.

Chronic bronchitis may result from a series of attacks of acute bronchitis, or it may evolve gradually because of heavy smoking or inhalation of air contaminated with other pollutants in the environment. When so-called smoker's cough is continual rather than occasional, the mucus-producing layer of the bronchial lining has probably thickened, narrowing the airways to the point where breathing becomes increasingly difficult. With immobilization of the cilia that sweep the air clean of foreign irritants, the bronchial passages become more vulnerable to further infection and the spread of tissue damage.

Frequency

United States

In one study, acute bronchitis affected 44 of 1000 adults annually, and 82% of episodes occurred in fall or winter.² By way of comparison, 91 million cases of influenza, 66 million cases of the common cold, and 31 million cases of other acute upper respiratory tract infections occurred during that same year.

According to estimates from national interviews taken by the National Center for Health Statistics in 2006, approximately 9.5 million people, or 4% of the population, were diagnosed with chronic bronchitis. These statistics may underestimate the prevalence of COPD by as much as 50% because many patients underreport their symptoms and their conditions remain undiagnosed. However, an overdiagnosis of chronic bronchitis by patients and clinicians has also been suggested. The term bronchitis is often used as a common descriptor for a nonspecific and self-limited cough, thereby falsely increasing its incidence even though the patient does not meet the criteria for diagnosis.

International

Acute bronchitis is common throughout the world and is one of the top 5 reasons for seeking medical care in countries that collect such data.

Mortality/Morbidity

Bronchitis is almost always self-limited in individuals who are otherwise healthy, although it may result in absenteeism from work and school. Severe cases occasionally produce deterioration in patients with significant underlying cardiopulmonary disease or other comorbidities.

Race

No difference in racial distribution is reported; however, bronchitis occurs more frequently in populations with a low socioeconomic status and in people who live in urban and highly industrialized areas.

Sex

Bronchitis affects males more than females.

Age

Although found in all age groups, acute bronchitis is most frequently diagnosed in children younger than 5 years, whereas chronic bronchitis is more prevalent in people older than 50 years. In the United States, up to two thirds of men and one fourth of women have emphysema at death.

Clinical

History

Obtain a complete history, including information on exposure to toxic substances and smoking. Patients with chronic bronchitis are often overweight and cyanotic. Initially, cough is present in the winter months. Over the years, the cough progresses from hibernal to perennial, and mucopurulent relapses increase in frequency, the duration and severity of which increase to the point of exertional dyspnea.

Symptoms of acute bronchitis include the following:

• Cough and sputum production
  • Cough is the most commonly observed symptom. It begins early in the course of many acute respiratory infections and becomes more prominent as the disease progresses.
  • Cough begins within 2 days of infection in the majority of patients. In patients with acute bronchitis, cough generally lasts from 10-20 days.
  • Sputum production is reported in approximately half the patients in whom cough occurred. Sputum may be clear, yellow, green, or even blood-tinged.
  • Purulent sputum is reported in 50% of persons with acute bronchitis. Changes in sputum color are due to peroxidase released by leukocytes in sputum; therefore, color alone cannot be considered indicative of bacterial infection.
• Sore throat
• Runny or stuffy nose
• Headache
• Muscle aches
• Extreme fatigue
• Fever: This is a relatively unusual sign and, when accompanied by cough, suggests either influenza or pneumonia.
• Nausea, vomiting, and diarrhea: These are rare. Severe cases may cause general malaise and chest pain. With severe tracheal involvement, burning, substernal chest pain associated with respiration, and coughing may occur.
• Dyspnea and cyanosis: These are not observed in adults unless the patient has underlying COPD or another condition that impairs lung function.

Physical

The physical examination findings in acute bronchitis can vary from normal-to-pharyngeal erythema, localized lymphadenopathy, and rhinorrhea to coarse rhonchi and wheezes that change in location and intensity after a deep and productive cough. Diffuse wheezes, high-pitched continuous sounds, and the use of accessory muscles can be observed in severe cases. Occasionally, diffuse diminution of air intake or inspiratory stridor occurs; these findings indicate obstruction of a major bronchi or the trachea, which requires sequentially vigorous coughing, suctioning, and, possibly, intubation or even tracheostomy.

• Sustained heave along the left sternal border indicates right ventricular hypertrophy secondary to chronic bronchitis.
• Clubbing on the digits and peripheral cyanosis indicate cystic fibrosis.
• Bullous myringitis may suggest mycoplasmal pneumonia.
• Conjunctivitis, adenopathy, and rhinorrhea suggest adenovirus infection.

Causes

Acute bronchitis is usually caused by infections, such as those caused by Mycoplasma species, Chlamydia pneumoniae, Streptococcus pneumoniae, Moraxella catarrhalis, and Haemophilus influenzae, and by viruses, such as influenza, parainfluenza, adenovirus, rhinovirus, and respiratory syncytial virus. Exposure to irritants, such as pollution, chemicals, and tobacco smoke, may also cause acute bronchial irritation.

• Cigarette smoking is indisputably the predominant cause of chronic bronchitis. Estimates suggest that cigarette smoking accounts for 85-90% of chronic bronchitis and COPD. Studies indicate that smoking pipes, cigars, and marijuana causes similar damage.
  • Smoking impairs ciliary movement, inhibits the function of alveolar macrophages, and leads to hypertrophy and hyperplasia of mucus-secreting glands.
  • Smoking can also increase airway resistance via vagally mediated smooth muscle constriction.
  • Unless some other factor can be isolated as the irritant that produces the symptoms, the first step in dealing with chronic bronchitis is for the patient to stop smoking.
• Air pollution levels have been associated with increased respiratory health problems among people living in affected areas. The Air Pollution and Respiratory Health Branch of the National Center for Environmental Health directs the fight of the US Centers for Disease Control and Prevention (CDC) against respiratory illness associated with air pollution.
  • According to the Healthy People 2000 report, each year in the United States, the following occur:
    • "The health costs of human exposure to outdoor air pollutants range from $40 to $50 billion."
    • "An estimated 50,000 to 120,000 premature deaths are associated with exposure to air pollutants."
    • "People with asthma experience more than 100 million days of restricted activity, costs for asthma exceed $4 billion, and about 4,000 people die of asthma."
• A growing body of literature has demonstrated that specific occupational exposures are associated with the symptoms of chronic bronchitis. The list of agents includes coal, manufactured vitreous fibers, oil mist, cement, silica, silicates, osmium, vanadium, welding fumes, organic dusts, engine exhausts, fire smoke, and secondhand cigarette smoke.

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