Bronchitis and Asthma — Clinical Documentation Guide (2026)

🔍 Definition

Bronchitis is inflammation of the bronchial mucosa resulting in cough, mucus hypersecretion, and variable airflow obstruction. It is classified by duration and etiology:

• Acute bronchitis (J20.x): An acute lower respiratory tract infection, typically viral (90%+ of cases), lasting 1–3 weeks, characterized by cough, sputum production, and occasionally low-grade fever. Coding specificity requires identifying the causative organism when documented (CMS/CDC ICD-10-CM).
• Acute bronchiolitis (J21.x): Inflammation of the smaller bronchioles, predominantly affecting infants and children under 2 years; most commonly caused by RSV (J21.0). The clinical presentation includes wheezing, tachypnea, and hypoxia.
• Chronic bronchitis (J41.x, J42): Defined clinically as productive cough for at least 3 months per year for 2 consecutive years, as established by the WHO criteria. Simple chronic bronchitis (J41.0) produces mucoid sputum; mucopurulent chronic bronchitis (J41.1) produces purulent sputum without airflow obstruction. When neither acute nor chronic is specified and no COPD criteria are met, assign J40.
• COPD overlap (J44.x): Chronic bronchitis with airflow obstruction (FEV1/FVC <0.70) meets COPD criteria and should be coded to J44.x — see separate COPD CDG for full detail.

Asthma is a heterogeneous chronic inflammatory airway disease characterized by variable, reversible airflow obstruction, airway hyperresponsiveness, and bronchial inflammation. Per the GINA 2025 Strategy Report, asthma is defined by a history of respiratory symptoms (wheeze, shortness of breath, chest tightness, cough) that vary over time and in intensity, together with variable expiratory airflow limitation.

The FY2026 ICD-10-CM classification of asthma under J45.xx captures severity (mild intermittent, mild persistent, moderate persistent, severe persistent) and clinical status (uncomplicated, with acute exacerbation, with status asthmaticus). Eosinophilic asthma is classified separately under J82.83 (new code effective FY2025, carried forward to FY2026).

🗂️ Alternative Terminology

🩺 Signs & Symptoms

Bronchitis

• Acute bronchitis: Cough (dominant symptom), may be productive with white, yellow, or green sputum; low-grade fever; malaise; chest tightness; dyspnea on exertion; wheeze in some patients. Duration typically 7–21 days. Fever >38.5°C or purulent sputum with systemic signs may suggest bacterial superinfection or pneumonia.
• Acute bronchiolitis (pediatric): Tachypnea, intercostal/subcostal retractions, nasal flaring, expiratory wheeze, crackles, hypoxia (SpO₂ <95% in moderate-severe), feeding difficulties. Onset typically follows 2–3 days of upper respiratory symptoms.
• Chronic bronchitis: Productive cough ≥3 months/year × 2 consecutive years, increased sputum volume, recurrent respiratory infections, exertional dyspnea if airflow obstruction develops. Morning "smoker's cough" is characteristic.

Asthma

• Classic triad: Episodic wheeze, cough (worse at night/early morning), and dyspnea or chest tightness. Symptoms are variable and often triggered by allergens, viral infections, exercise, cold air, smoke, or irritants.
• Acute exacerbation: Progressive worsening of wheeze, dyspnea, chest tightness, and cough. Accessory muscle use, pulsus paradoxus, reduced air entry, O₂ saturation <92% indicate severity.
• Status asthmaticus: Severe, prolonged asthma attack unresponsive to initial bronchodilator therapy; may progress to respiratory failure. ICU-level monitoring required. Risk factors include prior intubation, ≥2 hospitalizations/year, food allergy, and psychosocial factors (GINA 2025).
• Cough-variant asthma: Chronic cough as predominant or sole symptom; absence of typical wheeze. Diagnosis requires bronchoprovocation testing (94070) or therapeutic response to ICS.
• Exercise-induced bronchoconstriction: Cough, wheeze, dyspnea triggered by sustained aerobic exercise, typically 5–10 minutes post-exercise. May be the only asthma manifestation in athletes.

🧭 Differential Diagnosis

📋 Clinical Indicators for Coders/CDI

🦴 Anatomy & Pathophysiology

Bronchitis Pathophysiology

The bronchial tree consists of the trachea bifurcating into right and left main bronchi, which subdivide into lobar, segmental, and subsegmental bronchi, terminating in bronchioles. In acute bronchitis, viral or bacterial invasion triggers mucosal inflammation with goblet cell hyperplasia and increased mucus secretion. Ciliary dysfunction impairs mucociliary clearance, promoting cough. Submucosal edema contributes to mild airflow limitation. Most cases are caused by respiratory viruses (rhinovirus, coronavirus, influenza, parainfluenza, RSV, adenovirus) with secondary bacterial superinfection uncommon (AAPC Knowledge Center).

Acute bronchiolitis affects the terminal and respiratory bronchioles (<2 mm diameter), predominantly in infants. RSV (and human metapneumovirus) cause necrosis of the bronchiolar epithelium, luminal obstruction with mucus and cellular debris, peribronchiolar infiltration, and air trapping. The small airway diameter makes infants uniquely susceptible to hemodynamically significant obstruction.

In chronic bronchitis, prolonged noxious stimuli (primarily tobacco smoke) cause squamous metaplasia of the respiratory epithelium, goblet cell hyperplasia, hypertrophy of submucosal mucous glands (Reid index >0.4), and chronic inflammation. Unlike COPD, spirometry may remain normal in pure chronic bronchitis without emphysema.

Asthma Pathophysiology

Asthma is fundamentally a chronic inflammatory airway disease. The dominant inflammatory phenotype in allergic (atopic) asthma is Type 2 (T2)-high, driven by Th2 lymphocytes, ILC2 cells, and key cytokines IL-4, IL-5, IL-13, and TSLP. This drives IgE production, mast cell activation, eosinophil recruitment, and airway remodeling. Key pathological features include:

• Bronchoconstriction: Smooth muscle contraction in response to allergens, irritants, cold air, exercise; partially reversed by bronchodilators
• Airway edema and mucus hypersecretion: Contributes to airflow obstruction and mucus plugging
• Airway hyperresponsiveness (AHR): Exaggerated bronchoconstriction response to methacholine, histamine, exercise, or cold air; measured by bronchoprovocation testing (CPT 94070)
• Structural remodeling: Subepithelial fibrosis, smooth muscle hypertrophy/hyperplasia, increased mucous glands — occurs with chronic untreated disease and is only partially reversible
• Eosinophilic airway inflammation: In eosinophilic asthma (J82.83), blood and tissue eosinophilia (≥300 cells/µL) drives inflammatory damage; targeted by anti-IL5/IL5R biologics (AAAAI Biologics for Asthma)

Non-T2 (T2-low) asthma phenotypes include neutrophilic asthma (associated with obesity, smoking, occupational exposure) and paucigranulocytic asthma, which are less responsive to ICS and have limited biologic options. Tezepelumab (anti-TSLP) targets a broad upstream signal and has efficacy across T2-high and T2-low phenotypes.

💊 Medication Impact / Treatment

Acute Bronchitis

Treatment is primarily supportive. Antibiotics are generally NOT indicated for acute bronchitis (viral etiology in >90% of cases) per CDC antimicrobial stewardship guidance. Symptomatic management includes:

• Antitussives (dextromethorphan) or expectorants (guaifenesin) for symptom relief
• Short-acting bronchodilator (albuterol) via nebulizer (CPT 94640) if wheeze or bronchospasm present
• Inhaled corticosteroid (ICS) — short course may reduce cough duration in selected patients
• Antivirals (oseltamivir) for influenza-confirmed cases within 48 hours of onset

Acute Bronchiolitis (Pediatric)

Supportive care is the mainstay per AAP Clinical Practice Guideline: supplemental O₂ (target SpO₂ ≥90%), hydration, nasal suctioning. Bronchodilators and systemic corticosteroids are NOT routinely recommended. High-flow nasal cannula (HFNC) may be used for moderate-severe cases. Palivizumab prophylaxis for high-risk infants (premature, congenital heart disease) during RSV season.

Chronic Bronchitis

Smoking cessation (most critical intervention; use F17.2xx codes for current tobacco use), mucolytics (N-acetylcysteine), pulmonary rehabilitation, and influenza/pneumococcal vaccination. If spirometry confirms COPD, refer to COPD CDG for full treatment algorithm.

Asthma — GINA 2025 Stepwise Therapy

Per GINA 2025, all adults and adolescents should receive ICS-containing therapy. SABA-only treatment is no longer recommended at any step.

Biologic Therapy for Severe Asthma (Step 5)

Per CHEST 2026 Biologic Guidelines and ACCP 2026, biologic selection is based on phenotype:

• Allergic (T2-high, high IgE): Omalizumab (anti-IgE, Xolair) — approved ≥6 years; preferred or dupilumab for moderate-severe allergic asthma with ≥1 OCS exacerbation/year
• Eosinophilic (eos ≥300 cells/µL): Mepolizumab (Nucala, anti-IL5), benralizumab (Fasenra, anti-IL5Rα), reslizumab (Cinqair IV, anti-IL5), or dupilumab (anti-IL4Rα/IL-13)
• Mixed/Broad T2: Dupilumab (atopic dermatitis or EoE comorbidity preferred) or tezepelumab (Tezspire, anti-TSLP — efficacy across all phenotypes including T2-low)
• Aspirin-exacerbated respiratory disease (AERD): Dupilumab preferred; code J45.990 + external cause code for aspirin sensitivity

Preview ends here. The full guide continues with FY2026 ICD-10-CM code sets, CPT surgical coding, MS-DRG mapping, reimbursement guidance, CDI query templates, and an audit checklist — all available to CCO Members.

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