Acute Bronchitis: Etiology

• Acute bronchitis involves inflammation of the bronchioles, bronchi, and trachea, typically following an upper respiratory infection or exposure to chemical irritants.
• It presents with an acute onset of persistent cough, with or without sputum production, resulting from acute inflammation of the trachea and large airways.
• Acute bronchitis occurs without evidence of pneumonia or COPD and is self-limiting, diagnosed clinically.

Etiology

• Viral infections are the most common cause (Rhinovirus, enterovirus, influenza A/B, parainfluenza, coronavirus, RSV, human metapneumovirus, Coxsackie virus, Metapneumovirus).
• Bacterial causes are rare, detected in about 6% of cases.
• Common bacterial causes include Bordetella Pertussis (rising outbreaks, 10% of cases with cough >2 weeks), Mycoplasma Pneumoniae, and C. Pneumoniae.
• Secondary bacterial infections can occur from Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Chlamydia pneumoniae, Bordetella pertussis, or other bacteria.
• Inhaled chemical irritants and, possibly, fungal infections can also cause acute bronchitis.

Incidence

• Acute bronchitis is a common condition in clinical practice, prompting patients to seek treatment for bothersome, slow-to-resolve coughs.
• It accounts for 10% of ambulatory care cases in the US, resulting in 2.7 million outpatient and 4 million emergency room visits annually.
• Occurs at a higher rate in the fall and winter, affecting up to 5% of adults annually.

Risk Factors

• Risk factors include upper respiratory infections, air pollutants, smoking, or secondary smoke exposure.
• Reflux esophagitis, allergies, COPD, acute and chronic sinusitis, being an infant/older adult, immunosuppression, and environmental changes also increase risk.

Assessment Findings

• Initial dry, nonproductive cough progresses to productive, possibly purulent cough, lasting 1-3 weeks (average 18 days).
• Often follows URI symptoms like nasal congestion, headache, and sore throat.
• Cough becomes the dominant symptom, possibly with wheezing and mild dyspnea.
• Fever occurs about 30% of the time, typically not after the first few days.
• Patients may report fatigue and mild illness.
• Musculoskeletal pain from coughing or a burning sensation in the chest may occur.
• Wheezing or rhonchi usually improve with coughing.
• Fever suggests bacterial infection, more common in smokers and COPD patients.
• Detailed review of preexisting conditions and exposure history is important.

Differential Diagnoses

• Common cold needs to be ruled out
• Acute rhinosinusitis, pneumonia, influenza, tuberculosis, asthma, COPD, heart failure, pulmonary embolism (PE), pertussis, URI, GERD, bronchiectasis, and chronic cough should be considered.

Diagnostic Studies

• Diagnosis is based on history and physical examination, ruling out other causes.
• Suspect acute bronchitis with acute onset of persistent cough (1-3 weeks), no COPD history, and no pneumonia findings.
• Pneumonia is suggested by fever, tachypnea, dyspnea, rales, dull percussion, and mental status changes.
• Pertussis is indicated by cough >2 weeks with paroxysmal cough, "whoop", and post-cough emesis, especially during outbreaks.
• Rule out influenza, pneumonia, and TB with influenza tests, chest X-rays, and PPD tests if indicated.
• Biomarkers like procalcitonin and C-reactive protein can determine if the cause if bacterial, but are not routinely used.
• Chest X-rays are unnecessary unless cough persists or worsens; decision criteria include tachypnea, hypoxia, fever, and abnormal lung exam.
• Sputum cultures are usually not diagnostic, often containing mixed flora.
• CBC, viral panel, and influenza titer can be considered.
• Test for pertussis if there is a local outbreak or known exposure.

Prevention

• Smoking cessation and avoidance of secondary smoke are recommended.
• Avoid known respiratory irritants.
• Treat underlying conditions that contribute to risk (asthma, gastroesophageal reflux disease, etc.).
• Influenza and pneumococcal immunization are recommended for high-risk populations.

Nonpharmacological Management

• Rest, increased fluid intake, throat lozenges, hot tea, honey, humidifiers, and saline nasal sprays are recommended.
• Honey can be given to children older than 1 year.
• Patient education about the disease, treatment, expected course of cough, and emergency actions is important.

Pharmacologic Management

• If there is underlying sinusitis or allergy, 1st generation antihistamines like diphenhydramine 25-50 mg PO every 4-6 hours, can be administered.
• Avoid unnecessary antibiotics as 90% of acute bronchitis diagnoses are viral.
• Delayed prescribing tactics are recommended.
• Educate patients on realistic duration of illness, which may persist for 3-4 weeks.
• Hand hygiene and up to date vaccines are crucial.
• 2020 guidance suggests NO routine prescription of antibiotics, antivirals, antitussives, inhaled beta agonists, inhaled anticholinergics, inhaled or oral corticosteroids, or NSAIDs.
• Avoid antihistamines unless sinusitis or allergy is underlying.
• Antibiotics are appropriate if the causative organism is bacterial.
• Antivirals if influenza is diagnosed.
• Decongestants and antihistamines are ineffective unless there is underlying sinusitis or allergy.
• Bronchodilators if wheezing or prior history of asthma are present.
• If cough worsens due to suspected acute bronchitis: reassess and consider antibiotic treatment if a bacterial infection is suspected, or treat for alternative conditions deemed likely.

Consultation/Referral

• Referral to a pulmonologist is recommended if symptoms do not improve after 4 weeks.

Follow Up

• Follow up if symptoms worsen, progressive dyspnea, chest pain, fever, or cough persists for more than 3 weeks.
• Follow up in 7 days if not improved or if condition worsens.
• High-risk groups (e.g., patients with coexisting disease) warrant quicker follow-up.

Expected Course

• Shorter symptom duration if the causative agent is rhinovirus or coronavirus.
• Symptoms may persist 3-4 weeks.

Complications

• Complications include pneumonia, chronic cough, chronic bronchitis, secondary bacterial infection, and bronchiectasis.

Geriatric Considerations

• Geriatric patients will present with similar clinical manifestations.
• It’s Important to rule out pneumonia because treatment approach will change.
• Treatment is symptom management unless co-morbidities presents (COPD, asthma, immunocompromised).
• Flu & pneumonia vaccine recommended.