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Bronchitis and Bronchiolitis

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Lower Respiratory Infections

Infections of the lower respiratory tract include bronchitis, bronchiolitis and pneumonia (Fig 93-1). These syndromes, especially pneumonia, can be severe or fatal. Although viruses, mycoplasma, rickettsiae and fungi can all cause lower respiratory tract infections, bacteria are the dominant pathogens; accounting for a much higher percentage of lower than of upper respiratory tract infections.

Bronchitis and Bronchiolitis


Bronchitis and bronchiolitis involve inflammation of the bronchial tree. Bronchitis is usually preceded by an upper respiratory tract infection or forms part of a clinical syndrome in diseases such as influenza, rubeola, rubella, pertussis, scarlet fever and typhoid fever. Chronic bronchitis with a persistent cough and sputum production appears to be caused by a combination of environmental factors, such as smoking, and bacterial infection with pathogens such as H influenzae and S pneumoniae. Bronchiolitis is a viral respiratory disease of infants and is caused primarily by respiratory syncytial virus. Other viruses, including parainfluenza viruses, influenza viruses and adenoviruses (as well as occasionally M pneumoniae) are also known to cause bronchiolitis.


When the bronchial tree is infected, the mucosa becomes hyperemic and edematous and produces copious bronchial secretions. The damage to the mucosa can range from simple loss of mucociliary function to actual destruction of the respiratory epithelium, depending on the organisms(s) involved. Patients with chronic bronchitis have an increase in the number of mucus-producing cells in their airways, as well as inflammation and loss of bronchial epithelium, Infants with bronchiolitis initially have inflammation and sometimes necrosis of the respiratory epithelium, with eventual sloughing. Bronchial and bronchiolar walls are thickened. Exudate made up of necrotic material and respiratory secretions and the narrowing of the bronchial lumen lead to airway obstruction. Areas of air trapping and atelectasis develop and may eventually contribute to respiratory failure.

Clinical Manifestations

Symptoms of an upper respiratory tract infection with a cough is the typical initial presentation in acute bronchitis. Mucopurulent sputum may be present, and moderate temperature elevations occur. Typical findings in chronic bronchitis are an incessant cough and production of large amounts of sputum, particularly in the morning. Development of respiratory infections can lead to acute exacerbations of symptoms with possibly severe respiratory distress.

Coryza and cough usually precede the onset of bronchiolitis. Fever is common. A deepening cough, increased respiratory rate, and restlessness follow. Retractions of the chest wall, nasal flaring, and grunting are prominent findings. Wheezing or an actual lack of breath sounds may be noted. Respiratory failure and death may result.

Microbiologic Diagnosis

Bacteriologic examination and culture of purulent respiratory secretions should always be performed for cases of acute bronchitis not associated with a common cold. Patients with chronic bronchitis should have their sputum cultured for bacteria initially and during exacerbations. Aspirations of nasopharyngeal secretions or swabs are sufficient to obtain specimens for viral culture in infants with bronchiolitis. Serologic tests demonstrating a rise in antibody titer to specific viruses can also be performed. Rapid diagnostic tests for antibody or viral antigens may be performed on nasopharyngeal secretions by using fluorescent-antibody staining, ELISA or DNA probe procedures.

Prevention and Treatment

With only a few exceptions, viral infections are treated with supportive measures. Respiratory syncytial virus infections in infants may be treated with ribavirin. Amantadine and rimantadine are available for chemoprophylaxis or treatment of influenza type A viruses. Selected groups of patients with chronic bronchitis may receive benefit from use of corticosteroids, bronchodilators, or prophylactic antibiotics.

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