Asthma and Exercise-Induced Bronchoconstriction Review

Asthma and Bronchoconstriction
Prevalence and Statistics

  • 26 Million individuals diagnosed with asthma in the U.S. (BRFSS 2021).

  • Lifetime Prevalence of Asthma: Varies by U.S. region, with states like DC at 18.1%. Globally, there's a 5% annual increase.

Demographics of Asthma Prevalence

  • Racial/Ethnic: Multirace NH (22.6%) and Black NH (16.5%) have higher rates than White NH (13.9%) and Hispanic (12.4%).

  • Age: Children (9.3%) have higher prevalence than adults (8.0%).

  • Sex: Females (9.5%) have higher prevalence than males (7.0%).

Protective Factors for Asthma

  • Household/Birth: Younger sibling, natural birth, breastfeeding.

  • Environmental/Dietary: Farm living (agriculture, animal farming, unpasteurized milk, constant stay in animal sheds, silage), healthy diet, low pollution, regular exercise.

  • Microbiological: Diverse microbiota, some foodborne pathogens (e.g., HAV, H. pylori), high burden helminth infections.

  • Socioeconomic: Higher socioeconomic status (better healthcare access, increased education, lower stress).

Risk Factors for Asthma

  • Household/Birth: Family history of asthma, Caesarian section, formula feeding.

  • Environmental/Dietary: Urban living, sheep farming, exposure to pressed/loose hay, smoking, obesity, antibiotic use.

  • Microbiological: Dysbiotic microbiota, respiratory viral infections (e.g., RV, RSV), bacterial pathogens, lower burden of helminth infections.

  • Socioeconomic: Increased smoking rates in lower statuses, higher stress levels.

Early-Life Microbial Exposure and Asthma Development

  • Hygiene Hypothesis: Increased early-life exposures (siblings, pets, soil) reduce asthma risk due to diverse microbial exposure. Decreased exposure from overuse of antimicrobials and limited outdoor interactions increases risk.

  • Infectious-Asthma Hypothesis: Diverse airway microbiome (e.g., Staphylococcus, Corynebacterium) can reduce risk; specific infections influence risk based on host immune response.

Pathology of Asthma

  • Asthmatic airways have inflamed and thickened walls, tightened smooth muscles, and trapped air in alveoli, unlike normal open airways.

Pathophysiology of Asthma and Exercise-Induced Bronchoconstriction (EIB)

  • Involves: Airway Inflammation >> Airway Remodeling >> Airway Hyper-reactivity >> Airflow Limitation >> Symptoms.

  • Can be acute, sub-acute, or chronic; often spontaneous at night/early morning due to hypersensitivity.

  • 50-90% of asthmatics are sensitive to exercise.

Factors Influencing Asthma Development and Expression

  • Inflammatory factors, respiratory infections, irritants (cold air, pollutants), exercise, temperature changes, allergens, strong odors, work-related factors, medication interactions, food additives, psychological stress, tobacco use, and gastric reflux issues.

Symptoms of Asthma and EIB

  • Clinical: Coughing, wheezing, chest tightness, dyspnea/SOB, excess mucus.

  • Performance-related (during exercise): Feelings of being out of shape or heavy legs, especially post-activity; fluctuating symptoms with environmental/seasonal changes.

Assessment of Airflow Limitations and Obstruction

  • Measurements: FEV1, FEV1/FVC, FEF25-75, Peak Flow (PEF/PEFR).

  • Provocation Challenge Tests: Confirm asthma by assessing lung function variability after exercise or bronchodilator challenges. Contraindicated in acute bronchitis, chest pain, or increased SOB.

Bronchial Provocation Challenge Testing

  • Inhaling increasing doses of Methacholine.

  • Positive diagnosis: FEV1 decrease of > 20% post-exposure.

Contraindications to Methacholine Challenge Testing

  • Absolute: Severe airflow limitation (FEV1 < 50% predicted or < 1.0L), MI/stroke within 3 months, uncontrolled hypertension (SBP > 200, DBP > 100 mmHg), known aortic aneurysm.

  • Relative: Moderate airflow limitation (FEV1 < 60% predicted or < 1.5L), inability to perform tests, pregnancy/nursing, recent respiratory infections, failure to withhold medications.

Asthma Assessment Approach

  • Spirometry tests: Low FEV1/FVC ratios indicate obstruction. Responses to bronchodilator administration differentiate asthma from other chronic lung diseases.

Components of Asthma Severity Before Treatment

  • Severity based on control, not just initial treatment.

  • PEF variability: < 20% (optimal), 20-30% (average), > 30% (poor).

  • Exacerbation frequency/intensity provides further insight.

Exercise Testing for EIB

  • Key Factors: Sustained high-level ventilation with low moisture inhaled air.

  • Protocol: Closely mirrors VO2max setups; spirometry before and at intervals post-exercise (5, 10, 15, 30 min).

  • Indicators: FEV1 drop of > 15% confirms EIB.

  • Severity Classifications: Mild (10-15% drop), Moderate (25-50% drop), Severe (>50% drop).

Important Considerations for Medication Withdrawal

  • Scheduled withholding of medications (SABA, LABA, ICS, etc.) before challenge testing for accurate results.

Goals of Asthma Treatment

  • No cure. Aim to control symptoms, enable participation in physical activity, promote sleep, prevent absences, minimize rescue inhaler use/hospitalizations, limit side-effects, and enable a normal, active life.

Managing Asthma

  • Daily Control Tools: Peak Flow Meters (Green, Yellow, Red zones), Controller, and Fast-Acting Medications.

Exercising With Asthma

  • Carry rescue inhaler, adjust environment (avoid cold/dry air, allergens), warm-up/cool-down, continuous assessment of respiratory status.

Exercise Training Recommendations for Asthma Patients

  • Regular activity is encouraged; improves fitness without increasing EIB. (Asthma control via medication is essential).

Role Models with Asthma

  • Individuals like Bill Koch demonstrate successful athletic careers with effective asthma management.