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INTRODUCTION

Acute bronchitis is a self-limited respiratory infection causing inflammation of the large airways characterized by cough without evidence of pneumonia. The common cold is a viral infection of the upper respiratory tract, primarily affecting the nasal mucosa causing congestion, rhinorrhea, and sneezing. Influenza, or the flu, is a respiratory illness with fever, myalgias, cough, and fatigue. The clinical syndromes associated with these conditions overlap, and their causative pathogens are often similar. Infections of the upper respiratory tract also cause specific clinical conditions such as otitis media (see Chapter 242, “Ear Disorders”), pharyngitis and epiglottitis (see Chapter 246, “Neck and Upper Airway”), bronchiolitis (see Chapter 116, “Neonatal Emergencies and Common Neonatal Problems”), tracheitis (see Chapter 126, “Stridor and Drooling in Infants and Children”), and sinusitis (see Chapter 244, “Nose and Sinuses”).

ACUTE BRONCHITIS

Bronchitis is the ninth most common diagnosis for adult patients presenting to the ED in the United States1 and ranks as one of the 10 most common outpatient diagnoses worldwide.2

PATHOPHYSIOLOGY

Respiratory viruses are the most common documented causative agent in acute bronchitis2-4; however, epidemiologic studies are hampered by inadequate specimen sampling.3 The most common viral isolates are influenza A and B viruses, parainfluenza virus, respiratory syncytial virus, coronavirus, adenovirus, and rhinovirus.1,3 Bacteria have been detected by polymerase chain reaction in 6% to 15.5% of acute bronchitis cases,3,4 excluding patients with chronic bronchitis, for whom bacterial detection rates are higher (see Chapter 70, “Chronic Obstructive Pulmonary Disease,” for management). Haemophilus influenzae and Streptococcus pneumoniae were the most common bacterial isolates.3 Atypical bacterial species such as Mycoplasma pneumoniae, Bordetella pertussis, and Chlamydia pneumoniae have also been isolated.3,4

Epithelial infection of the bronchi leads to inflammation and thickening of the bronchial and tracheal mucosa. This inflammatory condition results in airflow obstruction and bronchial hyperresponsiveness, which can cause decreased forced expiratory volume in 1 second. These physiologic changes can manifest as cough, wheezing, and dyspnea. Sputum production may or may not be prominent. Expectorated sputum is composed of lower respiratory tract secretions along with nasopharyngeal and oropharyngeal secretions, cellular debris, and microorganisms.5 Discoloration of sputum from clear or white to a yellow or green color may be due to cellular debris or a combination of microorganisms and cellular debris.5,6

CLINICAL FEATURES

The clinical manifestations of acute bronchitis include fever, mild dyspnea, and cough (with or without sputum production) persisting for more than 5 days and lasting up to 3 or 4 weeks.2 During the first few days of infection, the symptoms of an acute upper respiratory infection and acute bronchitis may be indistinguishable. However, the cough will persist for more than 5 days, and abnormal pulmonary function testing (e.g., reversible decrease ...

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