Acute Bronchitis and Upper Respiratory Tract Infections

1. THE 2-MINUTE PHYSIOLOGY (Rapid Pathophysiology)

• The Viral Invasion: Upper respiratory infections (URIs) and acute bronchitis are predominantly acute, self-limited infections of the respiratory tract (nasopharynx, oropharynx, and bronchi) driven by viral pathogens. The most common viral isolates include influenza A and B, parainfluenza virus, respiratory syncytial virus (RSV), and coronaviruses.
• The Inflammatory Cascade: The viral infection triggers mucosal inflammation and edema within the respiratory epithelium. This leads to increased mucus production and impaired mucociliary clearance, driving the classic symptoms of nasal congestion, rhinorrhea, and cough.
• Reactive Airway Component: In acute bronchitis, this inflammation extends into the larger airways of the lower respiratory tract, often resulting in transient bronchial hyper-responsiveness, bronchospasm, and a persistent cough that can last for weeks, even after the initial infection has cleared.

2. THE BEDSIDE ACTION PLAN (Rapid ER Management)

• Immediate Stabilization: Assess the patient's Airway, Breathing, and Circulation (ABC). Place the patient on a continuous cardiorespiratory monitor and pulse oximetry.
• Oxygenation Parameters: Administer supplemental oxygen if the patient's ambient room air oxygen saturation is <94%, targeting an SpO2 of 94–98%. Crucial titration: In patients with underlying Chronic Obstructive Pulmonary Disease (COPD), strictly target an SpO2 of 88–92% to avoid suppressing their hypoxic respiratory drive.
• Pharmacotherapy (Symptom-Directed):
• Bronchospasm: For patients exhibiting wheezing or a reactive airway component, administer nebulized or metered-dose inhaler (MDI) (\beta)2-agonists (e.g., albuterol) and/or anticholinergics (e.g., ipratropium).
• Inflammation: Consider adding oral or intravenous systemic corticosteroids for patients with significant bronchospasm.
• Supportive Care: Utilize antihistamines, antipyretics, and intravenous fluids for rehydration if the patient exhibits signs of volume depletion or severe systemic symptoms.
• Pediatric Caveat: Over-the-counter (OTC) cough and cold remedies are strongly not recommended for children <6 years of age.

3. THE DIAGNOSTIC GRID (Differential Diagnosis & Workup)

• Top "Can't-Miss" Mimics:
• Pneumonia: Frequently coexists with or mimics bronchitis; differentiated by focal rales, higher fevers, and pulmonary infiltrates on imaging.
• Epiglottitis / Deep Space Neck Infections: Beware of the patient presenting with a "sore throat" who actually has impending airway compromise. Look for the classic signs: drooling, inspiratory stridor, a muffled voice, and tripod positioning.
• Acute Coronary Syndrome (ACS) / Pulmonary Embolism (PE): Dyspnea or an "anginal equivalent" may be the primary complaint in older adults or those with multiple risk factors.
• Foreign Body Aspiration: Must be ruled out in young children presenting with sudden-onset cough, wheeze, or stridor.
• Prioritized Diagnostic Workup:
• Tier 1: For classic, uncomplicated URIs and acute bronchitis in well-appearing patients, no routine laboratory testing is indicated.
• Tier 2: In patients presenting with hemoptysis, obtain a CBC, basic metabolic panel, coagulation profile (PT/INR), and type and screen.
• Tier 3: Consider a sputum Gram stain/culture and rapid viral PCR panels (e.g., Influenza, COVID-19, RSV) if the patient is highly toxic, immunocompromised, or if the results will directly change disposition or isolation requirements.

4. THE VISUAL BOARD (ECG / POCUS / Imaging)

• Chest Radiograph (CXR): In acute bronchitis, the CXR is typically negative. A CXR is explicitly indicated to rule out pneumonia, pneumothorax, or foreign body aspiration if "red flags" are present: hemoptysis, abnormal vital signs (fever >39°C with WBC >20,000/mcL in children <5), or uncertainty regarding the diagnosis.
• Electrocardiogram (ECG): An ECG is a mandatory diagnostic tool in older adults presenting with dyspnea, shortness of breath, or chest pain to rule out silent ischemia (ACS) or signs of right heart strain (S1Q3T3) indicative of a pulmonary embolism.
• Lateral Soft Tissue Neck Radiograph: If there is clinical concern for epiglottitis without impending airway collapse, a portable lateral neck radiograph may reveal the classic "thumb sign" (an enlarged, swollen epiglottis).

5. THE SCORING MATRIX (Risk Stratification & Guidelines)

• Centor Criteria: A validated clinical decision rule used to estimate the probability that pharyngitis is caused by Group A (\beta)-hemolytic streptococci (GABHS), guiding the need for rapid testing or empiric antibiotics. The criteria include the presence of fever, absence of cough, tender anterior cervical lymphadenopathy, and tonsillar exudates.
• Disposition Criteria: Patients with acute exacerbations of reactive airway disease or bronchitis can be safely discharged home if they demonstrate an intermediate or complete response to therapy, maintain an SpO2 >92% on room air, and have acceptable vital signs post-ambulation (HR <100, RR <20).

6. THE DANGER ZONE (Pitfalls & Critical Actions)

• Pitfall - The Antibiotic Reflex: Reflexively prescribing antibiotics for acute bronchitis and pharyngitis. Critical Action: Viral etiologies account for 90% of pharyngitis cases and the vast majority of acute bronchitis presentations; symptomatic treatment is the standard of care, and inappropriate antibiotics contribute to resistance and adverse effects.
• Pitfall - Missing the Airway Threat: Treating a patient with a "sore throat" or "URI" who has subtle signs of a deeper space infection (e.g., Ludwig angina or epiglottitis). Critical Action: Drooling, stridor, and a muffled voice indicate an advanced airway process. Do not agitate the patient (especially children); immediately maintain them in an upright position and obtain emergent consultation from anesthesiology and otolaryngology (ENT) for definitive airway management.
• Pitfall - Anchoring on "Just a Cold": Dismissing dyspnea or cough in an elderly patient as a simple URI. Critical Action: Maintain a low threshold to order a CXR and ECG in older adults to rule out subtle presentations of CHF, ACS, or pneumonia.

7. MCQ MASTERCLASS (Written Exam Tips)

• High-Yield Fact: If a board question asks for the most common cause of trace (small-volume) hemoptysis or blood-tinged sputum in an otherwise healthy patient, the correct answer is acute bronchitis.
• Common Distractor: A question describes a 6-year-old child with a 3-day history of clear rhinorrhea, congestion, non-productive cough, and bilateral expiratory wheezes without crackles. An option will suggest "Admit to the hospital for intravenous antibiotic therapy." Differentiate: This represents a viral illness with a reactive airway component; antibiotics are incorrect. The correct next step is administering a short-acting (\beta)-agonist (and potentially oral corticosteroids).
• Common Distractor: A patient presents with a sore throat, drooling, and inspiratory stridor. An option suggests "Group A streptococcal pharyngitis." Differentiate: Simple pharyngitis does not cause stridor and drooling. These are hallmark signs of impending airway compromise caused by epiglottitis.

8. THE BOARDROOM SCRIPT (OSCE & Oral Board Tips)

• The Opening Salvo: "This patient is presenting with symptoms consistent with an upper respiratory tract infection and acute bronchitis. My immediate priorities are to assess the airway for patency, evaluate the work of breathing, and check the vital signs. I will place the patient on a continuous cardiac monitor and pulse oximetry, providing supplemental oxygen to target an SpO2 of 94 to 98 percent."
• Articulating the Workup: "Because acute bronchitis is primarily a clinical diagnosis driven by viral pathogens, routine laboratory testing is not required for a well-appearing patient. However, given the patient's age and associated symptom of dyspnea, I will order a chest radiograph to explicitly rule out a coexisting pneumonia, and a 12-lead ECG to rule out an atypical presentation of acute coronary syndrome."
• Formulating the Disposition: "The patient’s chest radiograph is clear, their vital signs have normalized, and their wheezing has resolved following a nebulized albuterol treatment in the ED. I will discharge the patient home with a short course of bronchodilators for symptom relief. I will explicitly counsel them that antibiotics are not indicated for this viral infection, and I will provide strict return precautions should they develop a high fever, worsening shortness of breath, or an inability to tolerate oral fluids."