Asthma

Aka: Asthma

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II. Definitions

  1. Asthma
    1. Reversible airway obstruction
    2. Airway inflammation (Cytokine and IgE mediated)
    3. Increased Bronchial hyperresponsiveness (bronchospasm)
  2. Status Asthmaticus
    1. Severe airway obstruction developing over days-weeks

III. Epidemiology: Worldwide

  1. Prevalence: 300 Million people
    1. Variable from country to country (may affect as many as 18% of population in some countries)
  2. Mortality: 250,000 deaths/year worldwide

IV. Epidemiology: United States

  1. Adults and Children
    1. Prevalence: 25.7 million people in United States diagnosed with Asthma (2011)
      1. Asthma-related deaths per year: 3345 (in 2011)
      2. At least 4.1 million Asthma Exacerbations in children in 2011
      3. http://www.cdc.gov/nchs/data/series/sr_03/sr03_035.pdf
    2. Emergency department Asthma visits: 1.8 Million/year (2004-2005)
      1. Children: 168 per 10,000
      2. Adults: 50 per 10,000
      3. Hospitalization rate: 10-25% (resulted in 497,000 Asthma hospitalizations)
    3. From National Health Interview Survey
      1. http://www.cdc.gov/nchs/data/series/sr_10/sr10_228.pdf
  2. Children: Annual statistics for children under age 15 years in U.S.
    1. Asthma Prevalence: 5% or 5 million children
    2. Asthma clinic visits: 3 million per year
    3. Asthma emergency department visits: 570,000
    4. Asthma hospitalizations: 164,000 per year
    5. Asthma Missed school days: 10 million per year
    6. Asthma Prescriptions: 8.7 million
  3. Ethnicity: Outcomes much worse in black children
    1. Prevalence 26% higher in black children
    2. More severe Disability
    3. More frequent hospitalizations
    4. Black children 4-6 times more likely to die of Asthma

V. Pathophysiology

  1. Hallmark of Asthma: Bronchial wall Hyperresponsiveness
    1. Develops as a final step in "allergic march"
    2. Base: Allergic predisposition by Family History
    3. Step 1: Onset of allergic disease in infants
      1. Food Allergy GI disorders (serum IgE increased)
      2. Atopic Dermatitis
    4. Step 2: Progression of allergy in young children
      1. Allergic Rhinitis and Allergic Conjunctivitis
      2. Consider early Antihistamines and Immunotherapy
        1. May prevent progression to Asthma
        2. Warner (2001) J Allergy Clin Immunol 108:929-37 [PubMed]
    5. Step 3: Asthma develops
  2. Early Phase Asthma Reaction: Bronchoconstriction
    1. Antigenic Stimulation of Bronchial wall
      1. Extrinsic Asthma (allergic triggers)
      2. See Intrinsic Asthma for non-allergic triggers
        1. Associated with irritants as seen in adults
    2. Mast Cell Degranulation releases
      1. Histamine
      2. Chemotactics
      3. Proteolytics
      4. Heparin
    3. Findings
      1. Smooth Muscle Bronchoconstriction
  3. Late Phase Asthma Reaction: Bronchial Inflammation
    1. Cytokine and IgE mediated airway inflammation
    2. Inflammatory Cells Recruited
      1. Neutrophils
      2. Monocytes
      3. Eosinophils
    3. Release Cytokines, Vasoactives, Arachidonic Acid
    4. Epithelial and Endothelial Cell inflammation
    5. Release of Interleukin 3-6, TNF, Interferon-gamma
    6. Findings
      1. Bronchial edema and mucous plugging
      2. Ultimately may progress to airway remodelling
      3. Inspissated thick mucous may completely obstruct the airway resulting in death

VI. Risk Factors

  1. Family History
    1. One parent with Asthma: up to 25% risk for child
    2. Two parents with Asthma: up to 50% risk for child
  2. Parental Tobacco Abuse
  3. Associated Aspirin or NSAID allergy
    1. Classic Triad: Asthma, Nasal Polyps, Aspirin Allergy
  4. RSV Bronchiolitis history
    1. Strongly associated with later development of Asthma
  5. Strenuous Exercise in areas of high ozone (pollution)
    1. McConnell (2002) Lancet 359:386-91 [PubMed]

VII. Types

  1. Extrinsic Asthma (Allergic triggers)
  2. Intrinsic Asthma (Irritant triggers)
  3. Mixed Asthma (Extrinsic and Intrinsic Asthma)
  4. Occupational Asthma
    1. Toluene diisocyanate
    2. Polyvinyl chloride
    3. Phthalic anhydride
    4. Trimellitic anhydride
    5. Plicatic acid (Western Red Cedar trees)
    6. Metal salts
      1. Platinum
      2. Nickel
  5. Aspirin or NSAID induced Asthma
    1. Jenkins (2004) BMJ 328:434-40 [PubMed]
  6. Exercise Induced Asthma
  7. Cough Variant Asthma
    1. Very common! (Especially in children)

VIII. Symptoms

  1. See Asthma Evaluation

IX. Management

  1. See Asthma Management
  2. See Asthma Exacerbation

X. References

  1. (1997) Practical Guide for Asthma, NIH 97-4053
  2. Serrano (2014) Crit Dec Emerg Med 28(6):2-10
  3. Wojtczak (1999) Guidelines for Pediatric Asthma Lecture
  4. Evans (1992) Chest 101(6 suppl):368S-71S [PubMed]
  5. Falk (2016) Am Fam Physician 94(6): 454-62 [PubMed]
  6. Kemp (2001) Am Fam Physician 63(7):1341-54 [PubMed]
  7. Moffitt (1994) Am Fam Physician 50(5): 1039-50 [PubMed]
  8. Shutari (1995) Am Fam Physician 52(8): 2225-35 [PubMed]
  9. (1996) MMWR Morb Mortal Wkly Rep 45:350-3 [PubMed]

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