Patricia Polgar-Bailey Acute bronchitis is an acute and self-limited inflammation of the trachea and major bronchi, generally characterized by cough lasting 1 to 3 weeks and without evidence of bronchial consolidation (as seen in pneumonia) or underlying cardiopulmonary disease.1 Clinically, it is diagnosed on the basis of acute cough, with or without phlegm, and occasionally dyspnea and wheezing. It is typically viral in origin2 and is considered part of the spectrum of upper respiratory infections (URIs), which also include acute otitis, pharyngitis, tonsillitis, and acute sinusitis; but by definition bronchitis is an inflammation of the lower respiratory tract.3 Cough is the most frequent reason for visits to primary care physicians, accounting for approximately 8% of all visits.4 The most common causes of acute cough are URIs and acute bronchitis, which together account for approximately 60% of diagnosed cases.3 In the United States, acute bronchitis affects approximately 5% of the population annually and is the most common cause of acute cough.5 Symptom relief is the primary reason for seeking medical attention, and of those who seek care, most do so within the first week of illness.6 Each episode of acute bronchitis results in approximately 2 to 3 missed work days.7 A higher incidence of acute bronchitis has been noted during the autumn and winter months, when other URIs occur with frequency.4 Environmental factors such as living in substandard housing also predispose individuals, particularly children, to higher rates of acute bronchitis.8 Viruses account for an estimated 85% to 95% of cases of acute bronchitis and include most commonly influenza A and B viruses, parainfluenza virus, and respiratory syncytial virus (RSV), and less commonly coronavirus, adenovirus, rhinovirus, and metapneumovirus.4,6 Influenza occurs in distinct outbreaks and can result in significant morbidity because of its rapid spread.6 The incidence of RSV is high in households with small children and in areas where the elderly predominate, such as geriatric wards, senior day care settings, and nursing homes, and it can be a significant cause of morbidity in older adults.6 Severe acute respiratory syndrome (SARS), first defined by the World Health Organization in 2003, is caused by a novel coronavirus.6 Less than 10% of cases of acute bronchitis are bacterial in origin, and these are more common in patients with chronic health problems.5 These less common nonviral causes of acute bronchitis include atypical bacteria that also cause community-acquired pneumonia (CAP), such as Bordetella pertussis, Mycoplasma pneumoniae, Moraxella catarrhalis, and Chlamydia pneumoniae (as distinguished from Chlamydia trachomatis, which causes pneumonia in neonates). Common upper respiratory flora such as Haemophilus influenzae and Streptococcus pneumoniae are often found in sputum samples of patients with acute bronchitis, but it is unclear if their presence contributes to disease development.3 The causative pathogen for acute bronchitis is rarely identified; however, the cause of cough in uncomplicated acute bronchitis is multifactorial.9 It is the result of edematous changes in the mucous membrane of the tracheobronchial tree, epithelial cell damage, the release of proinflammatory mediators, and an increase in secretions.4 Destruction of the bronchial epithelium and loss of ciliary function are usually minimal with the common cold viruses but may be more extensive with M. pneumoniae and influenza viruses. Transient airflow obstruction and bronchial hyperresponsiveness occur in approximately 40% of previously healthy adults without concomitant conditions and usually resolve within 6 weeks.6 Acute bronchitis may be associated with a variety of symptoms, depending on anatomic distribution of the pathogen involved. For example, rhinovirus, a pathogen generally presumed to cause URI, has been found in a significant percentage of bronchoalveolar lavage specimens. Viral infection of lower airways may help explain the association between viral infection, such as that caused by rhinovirus, and asthma exacerbations.4 Cigarette smoking and chemical irritants may increase the severity of the infection. Undiagnosed asthma may be a factor, but this can be difficult to establish because of the transient bronchial hyperresponsiveness and abnormal spirometry results that often accompany acute bronchitis. A cough with or without sputum production is the most common symptom reported with acute bronchitis. Characteristics of the cough may vary. It is often described as dry and nonproductive, but it commonly progresses to a productive cough as the illness evolves. The sputum may be clear at the onset of the infection and become mucoid. Approximately 50% of patients with acute bronchitis report a cough productive of purulent sputum.3 A common but inaccurate belief is that a productive cough or purulent sputum is indicative of a bacterial infection and requires antibiotic therapy. In fact, in otherwise healthy individuals, the production of purulent sputum is the often the result of sloughing of the tracheal bronchial epithelium and inflammatory cells.3 The cough may also produce a burning substernal pain with inspiration. Nasal and pharyngeal symptoms subside after 3 or 4 days, but the cough usually remains prominent and progressive, typically lasting for 10 to 20 days, but it may occasionally persist for up to 5 to 6 weeks.4 A low-grade fever, wheezes, rhonchi, and coarse rales may be present. However, substantial abnormalities in vital signs are infrequent, especially in older adults, even when symptoms have been present for a week or more.4 Approximately 40% to 60% of patients may have significant reductions (a value below 80% of predicted) in forced expiratory volume in 1 second (FEV1), with gradual improvement during the ensuing 5 to 6 weeks.4,7 Individuals with M. pneumoniae or C. pneumoniae infections often have lower FEV1 values and demonstrate a greater degree of reversibility than do those with viral causes.6 Diagnostic tests are generally not necessary in the diagnosis of acute bronchitis. Cough and normal vital signs, in the absence of tachypnea, tachycardia, rales, and egophony, are strongly suggestive of acute bronchitis and minimize the likelihood of pneumonia. Routine sputum cultures are not helpful because they are often contaminated by bacterial flora that normally colonize the nasopharyngeal area. Viral cultures and serologic assays should not be routinely performed because they are rarely helpful in identifying the causative agent and as a result are not useful in guiding treatment.3,6 Rapid diagnostic tests exist for several of the pathogens that cause acute bronchitis. However, not all of these tests are widely available, and routine use in outpatient settings is not cost-effective. Their use is indicated when there is suspicion of a treatable organism, an infectious outbreak in the community, and a patient with specific signs and symptoms that are identifiable—for example, testing of patients with cough and fever for influenza during influenza season.4 Multiplex polymerase chain reaction testing of nasopharyngeal swabs or aspirates is being developed for diagnosis of infections resulting from B. pertussis, M. pneumoniae, or C. pneumoniae.4 A chest radiograph may be useful if the history and physical examination suggest the possibility of CAP. A heightened suspicion of CAP is reasonable in elders because they may be seen initially with more subtle symptoms of lower respiratory tract infections or cough without any other distinctive signs and symptoms. Data suggest that only one third of individuals 75 years of age and older who had CAP had temperatures higher than 38° C and heart rates above 100 beats per minute.4 According to the American College of Chest Physicians (ACCP) 2006 clinical practice guidelines, the absence of the following findings reduces the likelihood of pneumonia sufficiently to eliminate the need for a chest radiograph: heart rate above 100 beats per minute; respiratory rate above 24 breaths per minute; oral body temperature higher than 38° C; and chest examination findings of focal consolidation, egophony, or fremitus.6 Distinguishing between acute bronchitis and a simple URI within the first several days of illness is difficult, but a cough that persists for longer than 7 days is suggestive of acute bronchitis.5 Because acute bronchitis is a clinical diagnosis, how providers assign the diagnosis varies. For example, some providers diagnose acute bronchitis only if a productive cough is present, whereas others make the determination based on the presence of purulent sputum. Discolored sputum is commonly but mistakenly interpreted by both patients and health care providers as clinical evidence of bacterial infection. There has been no evidence to indicate correlation between discolored sputum and a bacterial cause of acute bronchitis.10 A cough that lasts for longer than 3 weeks should prompt consideration of another diagnosis. Other causes of cough, with or without phlegm production, include the common cold, reflux esophagitis, acute asthma, chronic obstructive pulmonary disease (COPD), and pneumonia. The symptoms of the common cold or URI, such as nasal stuffiness, discharge, sneezing, sore throat, and cough, can also be present in acute and chronic bronchitis.5 Acute sinusitis in the context of a cold may stimulate cough receptors.5 Because pneumonia is the third most common cause of cough (following asthma), usually not self-limited, often bacterial in origin, and associated with considerable morbidity and mortality when it is not treated with antimicrobial therapy, distinguishing between acute bronchitis and pneumonia is of primary importance. This is particularly true in elders, because older adults are less likely to have respiratory or nonrespiratory symptoms.6 CAP should be suspected if the patient’s history includes dyspnea, high fever, tachycardia, evidence of consolidation on examination, or presence of symptoms for 2 weeks or more.11 Acute bronchitis is an inflammation of the trachea and bronchi and should be differentiated from asthma and bronchiolitis, which are acute inflammations of the small airway and generally characterized by wheezing, tachypnea, respiratory distress, and hypoxemia. Acute bronchitis should also be distinguished from bronchiectasis, which is associated with bronchial dilation and chronic cough.4
Acute Bronchitis
Definition and Epidemiology
Pathophysiology
Clinical Presentation and Physical Examination
Diagnostics
Differential Diagnosis
Acute Bronchitis
Chapter 102
