Acute tracheobronchitis is an acute inflammation of the tracheobronchial mucosa in the large airway or lobar and/or segmental bronchi, caused by biological, physical, and chemical stimulation or allergy, mostly sporadic and spontaneous healing in 1 - 3 weeks, without epidemic tendency, and occurs in 5% of population every year. The older and infirm individuals are susceptible. The main symptoms are cough and expectoration. The disease often occurs in cold seasons or when the climate changes suddenly, and can also be caused by the protracted course of acute upper respiratory tract infection.
Etiology and pathogenesis
Pathogens are analogous to those of upper respiratory tract infections. Viruses are mostly adenovirus, influenza virus (type A and B), coronavirus, rhinovirus, herpes simplex virus, respiratory syncytial virus, and parainfluenza virus, while bacteria are mainly Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis. In recent years, chlamydia and mycoplasma infections have increased significantly, and secondary bacterial infection on the basis of viral infection is also common. These pathogens can cause not only inflammation of the large airways but also inflammation of the small airways and even the alveoli. Therefore, patients have cough, wheezing, and tachypnea.
Physical and chemical factors such as inhalation of cold air, dust, and irritating gases or fumes including sulfur dioxide, nitrogen dioxide, ammonia, and chlorine can stimulate the tracheobronchial mucosa and cause acute damage and inflammatory reaction.
Human body may be allergic to inhaled allergens such as pollen, organic dust, fungal spores, animal fur and excrement, and bacterial proteins. The migration of the larvae of hookworm and roundworm in the lungs can also cause acute tracheobronchial inflammatory reaction.
Pathology
The tracheobronchial mucosa is congested and edematous, with infiltration of lymphocytes and neutrophils, and may be accompanied by damage and shedding of ciliated epithelial cells and hypertrophy and hyperplasia of mucous glands. In case of concurrent bacterial infection, the secretions are purulent.
Clinical manifestations
Rapid onset, mild systemic symptoms, and fever are usually present. Initial dry cough or little phlegm is followed by increased phlegm and aggravated cough, occasionally accompanied by bloody sputum. Cough and expectoration can last for 2 - 3 weeks, and may progress into chronic bronchitis if with protracted course. Patients with recurrent cough and expectoration for three months each year for two consecutive years can be diagnosed with chronic bronchitis. When acute bronchitis is accompanied by bronchospasm, chest tightness and tachypnea may occur.
Evident positive signs may be absent. The scattered dry and moist crackles in various parts of the lungs may be heard, and may decrease or subside after cough.
Laboratory and auxiliary examinations
Peripheral white blood cell count may be normal, but an increase in the total white blood cell count, elevation of neutrophil percentage, and increased erythrocyte sedimentation rate can be seen in patients with bacterial infection, Pathogens can be seen in sputum culture. Increased lung markings can be found in chest x-ray in most patients, but abnormal findings may be absent in few patients.
Diagnosis
A clinical diagnosis can be established on the basis of medical history, cough, expectoration, and scattered dry and moist crackles, in combination with routine blood tests and chest x-ray. Basically, a diagnosis can be readily established if there are clinical symptoms such as cough and pneumonia is excluded. Viral and bacterial examinations are helpful for etiological diagnosis.
Differential diagnosis
Influenza
Influenza is characterized by acute onset, high fever, generalized myalgia, headache, malaise, and mild respiratory symptoms. Epidemiology, viral isolation from secretions, and serological examination are helpful for differentiation.
Acute upper respiratory tract infection
Acute upper respiratory tract infection is manifested by apparent nasopharyngeal symptoms, mild cough, absence of sputum, course less than a week, no abnormal signs in the lungs, and normal chest x-ray.
Other lung diseases
Other lung diseases, such as bronchopneumonia, tuberculosis, lung cancer, pulmonary abscess, measles, and pertussis, present with cough and expectoration. Careful and complete examinations are required for differentiation.
Treatment
Symptomatic treatment
Patients with cough but with no or little sputum can be treated using compound methoxyphenamine and pentoxyverine. Patients with cough and expectoration can be treated using ambroxol hydrochloride or eucalyptol, limonene and pinene, and nebulization can be applied. Bronchospasm can be treated using antiasthmatics such as theophylline, β2 receptor agonists, and cholinergic blockers. Fever can be treated symptomatically with antipyretics and anti-inflammatory agents.
Antibiotic treatment
In principle, antibiotic treatment is only used when there is evidence of bacterial infection. Generally, if cough lasts for more than 10 days, the probability of infection with bacteria, mycoplasma, Chlamydia pneumoniae, or Bordetella is high. New macrolides and penicillin are preferred, and cephalosporins and fluoroquinolones can also be administered. The recommended treatment regimen is oral azithromycin for 5 days, clarithromycin for 7 days, or erythromycin for 14 days. Most patients can be treated using oral antibiotics, while intramuscular or intravenous administration is common in severe patients. In few patients, medications need to be guided by the results of pathogen culture.
General measures
Good rest may be required. Overexertion, cigarette smoking, and exposure to fumes should be avoided.
Prognosis
Good prognosis is present in most patients, and few infirm patients may present with protracted course. Symptoms last for over one month in 20% of patients.