1- asthma

• Asthma

  Chronic inflammatory condition of the lung, characterized by:

  • airway limitation/obstruction (reversible spontaneously or with bronchodilator)
  • airway hyperresponsiveness
  • airway/bronchi inflammation
• Types of asthma

  • Extrinsic (atopic, allergic)
  • Intrinsic (non-atopic, adult-onset)
• Extrinsic asthma

  • Atopic patients (IgE to environmental allergens)
  • Childhood onset persistent asthma
  • Persistent reactions to common triggers, ex: dust, animal dander, pollens, fungi (90% of children & 70% of adults have +ve skin prick test)
• Intrinsic asthma

  • Not related to atopy or environmental/external triggers. Usually triggered by respiratory infections and starts in middle age
  • Non-atopic with extrinsic causes: Occupational agents (chemicals/biologics), Medications (NSAIDs, BB)
• Pathogenesis of asthma

  Airway narrowing due to:

  • Smooth muscle contraction
  • Thickening of wall by inflammation & cellular infiltration
  • Secretions in the lumen

  Dendritic cells, Th2 lymphocytes, cytokines, mast cells, eosinophils

  Remodeling of airway smooth muscles (hypertrophy & hyperplasia)

  Repair allogens (metaplasia: increased number of mucus-secreting goblet cells)
• Clinical features of asthma

  • SOB, chest tightness, wheezing, cough
  • Intermittent, worse at night & early morning (5-7 AM)
  • provoked by triggers (pollen, house dust, vapor, drugs (BBs, aspirin), tobacco smoke, cold air, emotions, exercise, pets, viral infections, cockroaches, pollution)
  • Assess SOB by:
  • Ability to complete the sentence
  • Use of accessory muscles
  • Audile wheeze or silent chest
  • Cyanosis

  Bilateral scattered wheeze

  • severity= expiratory >> inspiratory-expiratory >> silent chest

  Reduced chest expansion, prolonged expiratory time
• Investigations for asthma

  • PFTs: obstructive pattern, low FEV, FVC, & FEV1/FVC ratio, Reversible by bronchodilator (B2-agonist) 12% AND 200 ml in FEV1 or FVC
  • Peak expiratory flow rate (PEF): used for follow-up & monitoring patients not for actual diagnosis, PEFR is good as bedside to see if patient is improving in an acute attack, Normally, diurnal variation: lowest value in the early morning (morning dip), PFER is >400 in normal people
  • Methacholine challenge test: If PFTs are normal and highly suspicious of asthma, Most accurate test in asymptomatic patients (PTFs are normal between attacks)
  • Skin prick: allergic causes
  • ABG: Mild: high PH, low PCO2, normal PO2 (hyperventilation), Moderate: normal PH, normal PCO2, normal/low PO2, Severe: low PH, high PCO2, low PO2 (respiratory failure)
• Treatment of asthma

  Step 1: Symptoms less than twice a month, Inhaled corticosteroid-formoterol as needed or SABA + low dose ICS

  Step 2: Symptoms twice or more a month, but not daily, Daily lower dose of ICS, As needed ICS-formoterol (reliever)

  Step 3: Symptoms most days or waking with asthma once a week or more, Daily ICS-LABA (or ICS-LTRA)

  Step 4: Medium dose ICS -LABA (± add-on tiotropium or LTRA)

  Step 5: High dose ICS-LABA (± add-on low dose oral steroids)

  Step 4 &5: symptoms most of the day or waking with asthma once a week or more or low lung function

  LTRAs (leukotriene receptor antagonists) are useful esp. in aspirin-intolerant asthma, virus-associated wheezing, asthma in young children, & asthma with rhinitis

  Uncontrolled asthma if:

  • >2 attacks per month
  • Night symptoms
  • Reliever used more than once a day
  • Limitation of activity