Asthma

Chronic inflammatory airway disease characterized by variable, reversible airflow obstruction, airway hyperresponsiveness, and chronic inflammation involving eosinophils, mast cells, T-helper 2 (Th2) lymphocytes, and in some phenotypes neutrophils.

Bronchial smooth muscle hyperreactivity leads to episodic wheeze, breathlessness, chest tightness, and cough, typically worse at night/early morning and triggered by identifiable stimuli.

Classified by:

• Phenotype: allergic/atopic (childhood-onset, IgE-mediated, eosinophilic), non-allergic (adult-onset, often neutrophilic), exercise-induced, occupational, aspirin exacerbated respiratory disease (AERD; asthma + nasal polyps + NSAID sensitivity), obesity-associated

• Severity (based on treatment step needed for control, per GINA): mild, moderate, severe

• Control status: well-controlled, partly controlled, uncontrolled (based on symptom frequency, reliever use, exacerbations, lung function)

• Episodic symptoms: wheeze (expiratory, polyphonic), dyspnea, chest tightness, dry cough (may be sole symptom: cough-variant asthma)

• Diurnal variability: worse at night/early morning

• Triggers: allergens (dust mites, pollen, pet dander), viral URTIs, exercise, cold air, irritants (smoke, strong odors), NSAIDs/aspirin, beta-blockers, emotional stress, occupational exposures

• Examination: expiratory wheeze on auscultation (may be absent between exacerbations, "silent chest" in severe attack is an ominous sign of minimal air movement), prolonged expiratory phase, hyperinflated chest in poorly controlled disease

• Personal/family history of atopy: eczema, allergic rhinitis, food allergy

Acute exacerbation severity grading (critical for triage):

• Mild–moderate: PEFR ≥50% predicted/best, talks in sentences, RR normal-increased, no accessory muscle use

• Severe: PEFR 33–50%, unable to complete sentences in one breath, RR ≥25/min, HR ≥110/min, accessory muscle use

• Life-threatening: PEFR <33%, silent chest, cyanosis, feeble respiratory effort, exhaustion, bradycardia/hypotension, arrhythmia, confusion/reduced consciousness, SpO2 <92%

• Near-fatal: raised PaCO2 (normal or rising CO2 in an asthmatic tachypneic patient is a red flag;suggests fatigue and impending respiratory failure) and/or requiring mechanical ventilation.

Clinical suspicion + objective demonstration of variable airflow obstruction.

• Spirometry: obstructive pattern; FEV1/FVC <0.7 (or below lower limit of normal); bronchodilator reversibility test: FEV1 improvement ≥12% AND ≥200mL post-salbutamol confirms diagnosis

• Peak expiratory flow rate (PEFR): diurnal variability >10% (amplitude % mean) over 2 weeks supports diagnosis; useful for home monitoring and exacerbation severity

• FeNO (fractional exhaled nitric oxide): >40ppb supports eosinophilic airway inflammation (adults); helpful when spirometry equivocal

• Bronchial challenge testing (methacholine/histamine): used when diagnosis uncertain and spirometry normal; positive if PC20 <8mg/mL (specialist setting)

• Allergy testing (skin prick or specific IgE) to identify triggers in atopic phenotype

• CXR: usually normal; used to exclude alternative diagnoses or complications (pneumothorax, consolidation) during severe exacerbation

Differentials: COPD (fixed obstruction, smoking history, older age ;overlap syndrome ACO possible), vocal cord dysfunction/paradoxical vocal fold motion, heart failure ("cardiac asthma"), bronchiectasis, foreign body aspiration (esp. children), pulmonary embolism, GERD-related cough, ABPA (allergic bronchopulmonary aspergillosis ;consider if poorly controlled with high IgE, eosinophilia, central bronchiectasis).

Chronic/maintenance therapy : GINA stepwise approach (current guidelines favor ICS-containing reliever over SABA-only, given SABA-monotherapy mortality risk):

• Step 1 (mild, infrequent symptoms): as needed low dose ICS - formoterol (e.g., budesonide-formoterol) preferred over SABA alone

• Step 2: low dose maintenance ICS (e.g., budesonide 200–400mcg/day or equivalent) + as needed ICS-formoterol or SABA

• Step 3: low-dose ICS-LABA maintenance (e.g., budesonide-formoterol 200/6mcg one puff bd) + as-needed reliever

• Step 4: medium-dose ICS-LABA

• Step 5: high-dose ICS-LABA + add-on: LAMA (tiotropium), or biologic therapy if severe eosinophilic/allergic phenotype : omalizumab (anti-IgE), mepolizumab/benralizumab (anti-IL5/5R, eosinophilic), dupilumab (anti-IL4/13); oral corticosteroids as last resort, lowest effective dose, given long-term toxicity

• Leukotriene receptor antagonists (montelukast 10mg od adults): add-on option, especially in aspirin-sensitive or exercise-induced asthma; counsel on neuropsychiatric side effects (mood changes, nightmares)

• Inhaler technique and adherence review at every visit: major cause of "poor control" is technique failure, not undertreatment

• Trigger avoidance, smoking cessation, weight management if obese, treat comorbid allergic rhinitis/GERD

Acute exacerbation management:

• Oxygen: titrate to SpO2 94–98%

• Salbutamol (SABA): nebulized 5mg (or 2.5mg in children) repeated/continuous in severe cases, or via spacer 4–10 puffs every 20 min for 1 hour in mild-moderate

• Ipratropium bromide: nebulized 500mcg 4-6 hourly, added in moderate-severe/life-threatening exacerbations

• Systemic corticosteroids: prednisolone 40–50mg PO od for 5–7 days (adults), or IV hydrocortisone 100mg 6-hourly if unable to tolerate oral/severe: start early, within 1 hour of presentation

• Magnesium sulfate: IV 1.2–2g over 20 minutes for severe/life-threatening exacerbations not responding to initial bronchodilators

• IV salbutamol or aminophylline: considered in life-threatening cases unresponsive to above (specialist/ICU setting, aminophylline loading 5mg/kg over 20 min if not on theophylline, then infusion, with levels monitored)

• Escalate to ICU/anesthetics for intubation if: exhaustion, rising PaCO2, deteriorating consciousness, or failure to improve despite maximal therapy

Discharge criteria: PEFR >75% predicted/best, stable on reliever ≥4 hourly, inhaler technique checked, written asthma action plan provided, steroid course completed/prescribed, follow-up arranged within 2–7 days.

Monitoring: step down treatment after 3 months of good control; step up if uncontrolled (assess adherence/technique/triggers before escalating). Annual review including spirometry, exacerbation history, and comorbidity screening.