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Asthma: Pathophysiology, Diagnosis, and Management

Excerpt

Asthma is a chronic inflammatory airway disease characterised by episodic bronchoconstriction, airway hyperresponsiveness, and mucus production. It affects millions worldwide, leading to significant morbidity. This article discusses its pathophysiology, clinical features, diagnostic approach, and management strategies, including pharmacological and non-pharmacological interventions.

ICD Codes and HCC Classification

ICD-10 Codes:
- J45.9 (Asthma, unspecified)
- J45.2 (Mild intermittent asthma)
- J45.3 (Mild persistent asthma)
- J45.4 (Moderate persistent asthma)
- J45.5 (Severe persistent asthma)
- J45.990 (Exercise-induced bronchospasm)
- J45.991 (Cough-variant asthma)
HCC Code: HCC 110 (Asthma and Chronic Obstructive Pulmonary Disease)
Related Codes:
- J44.9 (Chronic obstructive pulmonary disease, unspecified)
- J46 (Status asthmaticus)

Definition

Asthma is a chronic inflammatory disease of the airways marked by episodic wheezing, dyspnea, chest tightness, and coughing, often triggered by allergens, exercise, or infections. It is characterized by reversible airway obstruction and bronchial hyperresponsiveness.

Pathology

Inflammatory cells: Increased eosinophils, mast cells, and T-helper 2 cells.
Airway remodelling: Goblet cell hyperplasia, subepithelial fibrosis, and hypertrophy of bronchial smooth muscle.
Mediators: Increased levels of histamine, leukotrienes, and cytokines (IL-4, IL-5, IL-13) leading to bronchoconstriction and airway inflammation.

Types of Asthma

Allergic (Extrinsic) Asthma: Triggered by allergens (e.g., pollen, dust mites, pet dander)
Non-allergic (Intrinsic) Asthma: Triggered by infections, cold air, exercise, or stress
Exercise-induced asthma (EIA): Occurs during or after physical exertion
Occupational Asthma: Triggered by workplace irritants (e.g., chemicals, fumes)
Aspirin-Exacerbated Respiratory Disease (AERD): Associated with NSAID sensitivity
Cough-Variant Asthma: Persistent cough as the main symptom without classic wheezing
Nocturnal Asthma: Symptoms worsen at night due to circadian variations in lung function
Severe/Refractory Asthma: Persistent symptoms despite maximum treatment

Symptoms and Signs

Episodic wheezing, dyspnoea, and chest tightness
Cough, often worse at night or early morning
Increased mucus production
Symptoms triggered by allergens, cold air, exercise, or infections

Diagnosis

Pulmonary Function Tests (PFTS)

Spirometry: FEV1/FVC <70% with >12% reversibility after bronchodilator use.
Methacholine challenge test: Confirms hyperresponsiveness in borderline cases.

Other Diagnostic Tests

Peak Expiratory Flow Rate (PEFR): Measures airway obstruction.
Fractional Exhaled Nitric Oxide (Feno): Indicates eosinophilic inflammation.
Allergy Testing: Identifies allergic triggers.
Chest X-ray: Rules out differential diagnoses.

Differential Diagnosis

COPD: Irreversible airflow obstruction, older age, smoking history
Heart Failure: Basal crepitations, pulmonary oedema on imaging
Vocal Cord Dysfunction: Stridor, normal spirometry
Bronchiectasis: Chronic productive cough, abnormal CT findings
Pulmonary Embolism: Sudden onset of dyspnoea, pleuritic chest pain, D-dimer elevation

Treatment

Acute Exacerbation Management

Bronchodilators:
- Salbutamol 2.5 mg nebulised every 20 minutes or MDI 4–8 puffs every 20 minutes
Corticosteroids:
- Prednisolone 40–60 mg PO once daily for 5 days
- IV Hydrocortisone 100 mg every 6 hours (if severe)
Oxygen Therapy: Maintain Spo2>92%
Magnesium Sulfate: IV 2 g over 20 minutes (for severe cases)
Antibiotics: If ba acterial infection is suspected

Long-Term Management (Stepwise Approach)

Step 1: Intermittent Asthma (Mild, <2 episodes per week)
- SABA (Salbutamol) PRN
Step 2: Mild Persistent Asthma
- Low-dose ICS (Budesonide 200 mcg BID) + SABA PRN
Step 3: Moderate Persistent Asthma
- Low-dose ICS + LABA (Budesonide/Formoterol 200/6 mcg BID)
Step 4: Severe Persistent Asthma
- Medium/High-dose ICS + LABA ± LAMA (Tiotropium 5 mcg QD)
Step 5: Refractory Asthma: Biologic Therapy (Omalizumab for allergic asthma, Mepolizumab for eosinophilic asthma)

Surgical Interventions

Bronchial Thermoplasty: Reduces airway smooth muscle mass in severe asthma

Statistical Data

Global prevalence: ~300 million people worldwide
Asthma mortality: ~455,000 deaths annually (WHO)
Risk factors: Genetic predisposition, environmental allergens, air pollution

Clinical Case

Patient Profile:

A 32-year-old female with seasonal allergies presents with episodic wheezing and nighttime cough

Findings:

Spirometry: FEV1 improved by 15% post-bronchodilator
Feno: Elevated, suggestive of eosinophilic asthma

Treatment & Outcome:

Started on Budesonide/Formoterol 200/6 mcg BID + Salbutamol PRN
Symptom control was achieved within 4 weeks with improved lung function

Mnemonic for for Asthma

ASTHMA (Symptoms)
- A: Accessory muscle use
- S: SOB (Shortness of breath)
- T: Tight chest
- H: High-pitched wheezing
- M: Mucus production
- A: Audible wheeze
A-B-C-D for Asthma Management
- A: Albuterol (Salbutamol)
- B: Budesonide (ICS)
- C: Corticosteroids
- D: Diagnosis with Spirometry