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Asthma

Basics

  • Chronic airway inflammation with variable airflow obstruction.
  • Common triggers: exercise, allergens, irritants, viral infections, weather changes, laughter.
  • Phenotypes:
  • Allergic asthma: childhood onset, family history of allergies.
  • Nonallergic asthma
  • Late-onset asthma (more common in females)
  • Fixed airflow limitation (due to airway remodeling)
  • Asthma with obesity
  • Severity assessed retrospectively based on treatment required for symptom control.

Epidemiology

  • Global prevalence: 262 million cases.
  • 455,000 deaths worldwide in 2019.
  • Higher asthma mortality in African Americans (3× higher).
  • US prevalence: ~10% children aged 5-18 years.
  • Boys more affected in childhood; women more in adulthood.
  • Obesity increases asthma risk.
  • Highest asthma death rates in ≥65 years age group.

Etiology and Pathophysiology

  • Airway hyperreactivity due to inflammation, epithelial injury, smooth muscle hypertrophy, mucus hypersecretion, angiogenesis.
  • Genetics: linked to IL and IgE production, airway hyperresponsiveness.
  • Risk factors: genetic predisposition, sex, obesity, prematurity/SGA.
  • Environmental: viral infections, allergens, tobacco/e-cigarette use, pollution, stress.
  • NSAID/aspirin hypersensitivity increases risk.
  • Food allergies with asthma increase risk of fatal anaphylaxis.

Associated Conditions

  • Atopy: eczema, allergic conjunctivitis, allergic rhinitis.
  • Obesity.
  • GERD.
  • Obstructive sleep apnea.

Diagnosis

History

  • Variable respiratory symptoms: wheezing, dyspnea, cough, chest tightness.
  • Symptoms worse at night and with triggers.

Physical Exam

  • May be normal.
  • Accessory muscle use.
  • Nasal findings: rhinitis, polyps, turbinate swelling.
  • Expiratory wheezing, prolonged expiration.
  • Eczema on skin.

Differential Diagnosis

  • Children: allergic rhinitis, sinusitis, foreign body, vocal cord dysfunction, bronchiolitis, cystic fibrosis, heart disease.
  • Adults: COPD, bronchiectasis, heart failure, PE, Churg-Strauss, ACE inhibitor cough, vocal cord dysfunction.

Diagnostic Tests

  • Spirometry: reduced FEV1/FVC ratio, reversibility after SABA (≥12% and 200 mL increase in FEV1).
  • Methacholine challenge: positive if FEV1 decreases >20%.
  • Exercise challenge: fall in FEV1 >10% and 200 mL.
  • Peak expiratory flow variability >10% over 2 weeks.
  • Chest X-ray: rule out alternate diagnoses.
  • FeNO: indicates eosinophilic airway inflammation.
  • Allergy skin testing for trigger identification.
  • Blood eosinophilia or elevated IgE (allergic asthma).

Treatment

General Measures

  • Control symptoms and prevent exacerbations.
  • Use spacers with inhalers.
  • Written asthma action plan.
  • Encourage physical activity, weight loss, smoking cessation, stress management.
  • Avoid occupational irritants.
  • Annual influenza vaccination; pneumococcal vaccine for high-risk.
  • Carry epinephrine if at risk of anaphylaxis.

Pharmacotherapy (Stepwise)

  • Step 1: As-needed low-dose ICS-formoterol or low-dose ICS + SABA.
  • Step 2: Daily low-dose ICS + as-needed SABA; alternatives: LTRA or dust mite immunotherapy.
  • Step 3: Low-dose ICS-LABA; alternatives: medium-dose ICS or ICS + LTRA.
  • Step 4: Medium-dose ICS-LABA; alternatives: high-dose ICS, add tiotropium or LTRA.
  • Step 5: High-dose ICS-LABA; refer for phenotype assessment and consider add-on therapies (LAMA, anti-IgE, anti-IL5/IL4).

Reliever Medication

  • SABA (albuterol/levalbuterol) as rescue for breakthrough symptoms.
  • Avoid SABA-only treatment per GINA guidelines.

Pediatric Considerations

  • Tiotropium not indicated <12 years.
  • SABA reliever for children 6-11 years.
  • School-based self-management programs reduce morbidity.

Pregnancy Considerations

  • Avoid bronchial challenge and step-down controller treatment until after delivery.
  • 1/3 worsen, 1/3 improve, 1/3 stable during pregnancy.
  • ICS cessation risks exacerbations.
  • Leukotriene receptor antagonists category B but limited data.

Management of Acute Exacerbations

  • Mild: speak full sentences, HR <120, O2 sat 90-95%, PEF >50% predicted.
  • SABA + ICS/formoterol, consider oral steroids.
  • Severe: inability to speak full sentences, HR >120, O2 <90%, PEF <50%, confusion, silent chest.
  • Admit for oxygen, frequent SABA, systemic steroids.
  • Epinephrine only if associated with angioedema or anaphylaxis.
  • Avoid sedatives.

Ongoing Care

  • Continue ICS therapy during admission.
  • Smoking cessation.
  • Regular follow-up; step down treatment after 3 months of control.
  • Identify and control triggers.

Patient Education

  • AAAAI and AAFA resources for patients.
  • Teach self-management and trigger avoidance.

Prognosis

  • Good prognosis in males, nonsmokers, and mild disease in children.
  • Death and respiratory failure higher in elderly.

Complications

  • Atelectasis, pneumonia.
  • Medication side effects and interactions.
  • Respiratory failure and death predominantly in older adults.

ICD10 Codes

  • J45.20 Mild intermittent asthma, uncomplicated
  • J45.51 Severe persistent asthma with exacerbation
  • J45.52 Severe persistent asthma with status asthmaticus

Clinical Pearls

  • SABA + ICS or formoterol/ICS is most effective rescue.
  • Spacers improve drug delivery.
  • ICS remain cornerstone for long-term control across ages.