Acute Bronchitis – Causes, Symptoms, Diagnosis, Treatment

Pathophysiology

Acute bronchitis is the result of acute inflammation of the bronchi? secondary to various triggers, most commonly viral infection?, allergens, pollutants, etc. Inflammation of the bronchial wall leads to mucosal thickening, epithelial-cell desquamation, and denudation of the basement membrane. At times, a viral? upper respiratory infection? can progress to infection? of the lower respiratory tract resulting in acute bronchitis. [rx]

Causes of Acute Bronchitis

Acute bronchitis is caused by infection of the large airways commonly due to viruses and is usually self-limiting. Bacterial infection? is uncommon. Approximately 95% of acute bronchitis in healthy adults are secondary to viruses. It can sometimes be caused by allergens, irritants, and bacteria. Irritants include smoke inhalation, polluted air inhalation, dust, among others.[rx]

Symptoms of Acute Bronchitis

• Chronic? daily cough?
• Coughing up blood
• Abnormal sounds or wheezing? in the chest with breathing
• Shortness of breath?
• Chest pain?
• Coughing up large amounts of thick mucus every day
• Weight loss?
• Fatigue?
• Change in the structure of fingernails and toenails, known as clubbing
• Frequent respiratory infections

Diagnosis? of Acute Bronchitis

History and Physical

An acute bronchitis patient presents with a productive cough?, malaise, difficulty breathing, and wheezing. Usually, their cough is the predominant complaint and is clear or yellowish, although sometimes it can be purulent. Purulent sputum? does not correlate with bacterial? infection or antibiotic? use. [rx] Cough after acute bronchitis typically persists for 10 to 20 days but occasionally may last for 4 or more weeks. The median duration of cough after acute bronchitis is 18 days[rx] Paroxysms of cough accompanied by inspiratory whoop or post-tussive emesis? should raise concerns for pertussis. A prodrome of URI? symptoms like runny nose, sore throat?, fever?, and malaise are common. A low-grade fever may be present as well. High-grade fevers in the setting of acute bronchitis are unusual and further diagnostic workup is required.

On physical exam, lung auscultation may be significant for wheezing; pneumonia? should be suspected when rales, rhonchi or egophony are appreciated. Tachycardia can be present reflecting fever as well as dehydration secondary to the viral illness. Rest of the systems are typically within normal limits.

Evaluation

Acute bronchitis is a clinical diagnosis based on history, past medical history, lung exam, and other physical findings. Oxygen saturation plays an important role in judging the severity of the disease along with the pulse rate, temperature, and respiratory rate. No further workup is needed if vital signs are normal, no exam findings suggestive of pneumonia. An exception to this rule is elderly patients >75 years old.  Also, further workup is needed when pneumonia is suspected, clinical diagnosis is in question or in cases of high suspicion for influenza or pertussis.

Chest x-ray findings are not specific and are typically normal. Occasionally, chest x-ray demonstrates increased interstitial markings consistent with thickening of bronchial walls. A chest x-ray differentiates pneumonia from acute bronchitis when infiltrates are seen. Evidence-based guidelines from the American College of Chest Physicians(ACCP) recommends obtaining a CXR only when heart rate > 100/min, respiratory rate >24 breaths/min, oral body temperature > 38 degree C and chest examination findings of egophony or fremitus.[rx]

Complete blood count and chemistry may be ordered as a workup for fever. White blood count might be mildly elevated in some cases of acute bronchitis. Blood chemistry can reflect dehydration changes.

Routine use of rapid microbiological testing is not cost-effective and would not change management except during influenza season and in cases with high suspicion of pertussis or other bacterial infection. Gram stain and bacterial sputum cultures are specifically discouraged bacteria is rarely the causative agent.

Spirometry, when performed, demonstrates transient bronchial hyperresponsiveness in 40% of patients with acute bronchitis. Reversibility of FEV1 >15% is reported in 17% of patients. [rx] Airflow obstruction and bronchial hyperresponsiveness typically resolve in 6 weeks.

Treatment of Acute Bronchitis

Acute bronchitis is self-limiting and treatment is typically symptomatic and supportive therapy. For cough relief, nonpharmacological and pharmacological therapy should be offered. Nonpharmacological therapy includes hot tea, honey, ginger, throat lozenges, etc. No clinical trials evaluated the efficacy of these interventions. Antitussive agents like dextromethorphan, codeine or guaifenesin are frequently used in clinical practice to suppress cough based on their effectiveness in chronic bronchitis and studies on cough in common cold. No randomized trials exist to evaluate their effectiveness in acute bronchitis. Codeine should be avoided for the addictive potential. Data on the use of a mucolytic agent is conflicting.

Beta-agonists are routinely used in acute bronchitis patients with wheezing. Small Randomized control trials on beta agonists for cough in acute bronchitis had mixed results. A Cochrane review of five trials demonstrated no significant benefit of beta-agonists on daily cough except for a small benefit in a subgroup of patients with wheezing and airflow obstruction at baseline.[rx] A more recent Cochrane review demonstrated similar results [rx]

Analgesic and antipyretic agents may be used to treat associated malaise, myalgia, and fever. Prednisone or other steroids can be given to help with the inflammation as well. Although there is not enough evidence showing their benefit, it is useful in patients with underlying chronic obstructive pulmonary disease (COPD) or asthma. Typically steroid is used as short-term burst therapy. Sometimes longer tapering dose of steroid might be warranted, especially in patients with underlying asthma or COPD. [rx][rx]

ACCP guidelines recommend against antibiotic use in simple acute bronchitis in otherwise healthy adults. A Cochrane review of nine randomized, controlled trials of antibiotic agents showed a minor reduction in the total duration of cough (0.6 days). The decrease in the number of days of illness was not significant per this review.[rx] Hence antibiotic use should be avoided in simple cases considering the cost of antibiotic, the growing global problem of antibiotic resistance and the possible side effects of antibiotic usage. Multiple other international medical societies recommend against antibiotic use in viral acute bronchitis. Despite these recommendations, a large proportion of patients with acute bronchitis are prescribed antibiotics. No data exist to justify the prospect of cough being less severe or less prolonged with antibiotic therapy. Antimicrobial therapy is recommended when a treatable pathogen is identified as with influenza or pertussis. In patients with influenza infection, oseltamivir or Zanamivir should be promptly started. Macrolides are the treatment of choice for Pertussis along with 5 days of isolation. It is interesting to note that whooping cough is only present in a minority of patients with pertussis.

Procalcitonin might be useful in deciding on antibiotic use when the diagnosis of acute bronchitis is uncertain. A meta-analysis demonstrated procalcitonin-guided antibiotic therapy reduced antibiotic exposure and improved survival. [rx]

Lifestyle modification like smoking cessation and the avoidance of allergens and pollutants play an important role in the avoidance of recurrence and complications. Flu vaccine and pneumonia vaccine are especially recommended in special groups including adults older than 65, children younger than two years (older than six months), pregnant women, and residents of nursing homes and long-term care facilities. People with asthma, COPD, and other immunocompromised adults are also at higher risk of developing complications. Recurrence is seen in up to a third of the cases of acute bronchitis.

In summary, the data for the use of beta-agonists, steroids, and mucolytic agent, especially in patients with no underlying COPD and asthma, is lacking. Treatment should be guided by the individual response to them and reported benefit, as well as, weighing risk and benefit in each case.

Differential Diagnosis

Other causes of acute cough should be considered especially when a cough persists for longer than 3 weeks.

• Asthma: Acute asthma is misdiagnosed as acute bronchitis in approximately one-third of the patients who present with acute cough.
• Acute/chronic sinusitis
• Bronchiolitis
• COPD
• GERD
• Viral pharyngitis
• Heart Failure
• Pulmonary Embolism