Asthma

• What is asthma?


  Chronic respiratory condition characterised by bronchial hyperresponsiveness and variable airway obstruction
• Pathophys - asthma

  Initial trigger exposure → activates immune cells (mast cells, DCs, macrophages, Th2) → release histamine, leukotrienes & cytokines (IL-4, IL-5, IL-9, IL-13) → inflam → bronchoconstriction (smooth muscle contraction) → narrows airway → SOB

  Stimulate goblet cells → excess mucous production → more airflow obstruction → cough & wheeze

  Chronic inflammation → structural changes → persistent airflow limitation & reduces treatment effectiveness

  Combined effects of inflam, airway hyperresponsiveness, mucus overproduction, & remodelling = episodic symptoms (SOB, wheeze, cough)
• What can trigger asthma?


  Allergens

  Resp infections

  Cold air

  Exercise

  Irritants
• What are the structural changes in asthma due to chronic inflammation?

  Smooth muscle hypertrophy

  Thickening of basement membrane

  Increased mucous secretion

  Angiogenesis
• How can asthma severity be classified?

  Intermittent

  Mild persistent

  Moderate persistent

  Severe persistent
• What is intermittent asthma?


  Symptoms < 2 times a week

  Nighttime awakenings < 2 times a month

  Spirometry results -> FEV1 or PEFR greater than 80% of the predicted value.

  Short-acting beta2-agonists (SABA) are used less than two days per week.
• What is mild persistent asthma?


  Symptoms > 2 times a week (not daily)

  Nighttime awakenings = 3-4 times a month

  Spirometry results show FEV1 or PEFR greater than 80% of predicted value

  SABA use > 2 days per week (not daily)
• What is moderate persistent asthma?


  Daily symptoms with exacerbations affecting daily activities

  Nighttime awakenings more than once a week (not nightly)

  Spirometry results show FEV1 or PEFR between 60-80% of predicted value

  Daily SABA use
• What is severe persistent asthma?


  Symptoms throughout day, affecting daily activities

  Nightly awakenings frequent

  Spirometry results show FEV1 or PEFR less than 60% of predicted value

  Continuous SABA use along high dose ICS & LABA or oral corticosteroids
• Other than severity, how else can asthma be classified?


  Based on aetiology

  • Allergic (extrinsic) -> triggered by exposure to allergens
  • Non-allergic (intrinsic) -> induced by factors (exercise, cold air, stress or certain medications)
• What are the Inx for asthma?

  Obs

  Full Hx & examination

  PEFR

  ECG

  Sputum culture

  Bloods (FBC, U&Es, LFTs, CRP, ABG, IgE)

  CXR

  Spirometry

  FeNO
• What does spirometry look like in asthma?


  Obstructive pattern w/bronchodilator reversibility

  Post bronchodilator improve in FEV1 or PEF of > 12% and > 200ml → suggestive of asthma
• How can FeNO be used in asthma?


  High levels of exhaled NO typically correlate with inflammation

  Results

  • Adults > 40 ppb is positive
  • Children > 35 ppb is positive
• What is the methacholine challenge test? Why might it be used in asthma?


  Aerosol (methacholine) is inhaled → bronchoconstriction → decreased in FEV1 of 20% or more indicates hyperreactive airways (consistent with asthma)
• Why might a CXR be done in asthma?


  Exclude other diagnoses

  Typically normal in asthma (may be hyperexpanded)
• What are the DDx of asthma?


  COPD

  Bronchiectasis

  GORD

  Ciliary dyskinesia

  Cystic fibrosis

  Dysfunctional breathing

  Foreign body aspiration

  HF

  Interstitial lung disease

  Lung cancer

  Pertussis

  PE

  TB

  Upper airway cough syndrome

  Vocal cord dysfunction
• What are the RFs of asthma?

  FHx of atopy

  Male (pre-pubertal asthma)

  Female (persistence of asthma from childhood to adulthood)

  Premature birth & associated low birth weight

  Smoking/exposure to tobacco smoke

  Obesity

  Social deprivation

  Resp infections in infancy

  Exposure to inhaled particulates

  Workplace exposures
• What are the symptoms of asthma?

  SOB

  Chest tightness

  Dry cough

  Fatigue

  Symptoms should improve with bronchodilators

  Symptoms commonly episodic, diurnal, and/or triggered or exacerbated by exercise, viral infection, and exposure to cold air or allergens
• Poorly controlled asthma may lead to frequent exacerbations, hospital admissions & impaired QoL
• What are the possible complications of asthma?

  Death

  Pneumonia (due to impaired mucociliary clearance)

  Lung collapse (full or partial)

  Resp failure

  Pneumothorax

  Status asthmaticus

  COPD

  Impaired QoL
• What is status asthmaticus?


  Severe & potentially life-threatening form of asthma attack that doesn’t respond to standard treatments w/bronchodilators & corticosteroids

  Requires immediate medical intervention & often hospitalisation
• What should be worrying on an asthma ABG?


  Hypercapnia/normocapnia

  Gas exchange is becoming impaired -> resp drive will plummet -> possible resp arrest
• How can be classify severity in an acute asthma attack?


  Mild/moderate

  Severe

  Life-threatening
• What is the criteria for a mild/moderate acute asthma attack?

  PEFR > 50% predicted or personal best

  Dyspnoea limiting activity

  Talking in phrases & sentences

  Prefers sitting to lying

  Possible accessory muscle use

  SpO2 > 90% on room air

  HR < 100
• What is the criteria for a severe acute asthma attack?

  PEFR ≤ 50% predicted or personal best

  Dyspnoea at rest

  Talks in words

  Sits hunched forward (tripod position)

  Accessory muscle use

  Agitated, diaphoresis

  SpO2 < 90% on room air

  RR > 30

  HR > 120
• What is the criteria of a life-threatening acute asthma attack?

  PEFR < 25% predicted or personal best

  Too dyspneic to speak

  Depressed mental status

  Cyanosis

  Inability to maintain respiratory effort

  Absent breath sounds

  Minimal or no relief from frequently inhaled SABA

  Bradycardia/hypotension
• What are the signs of asthma on examination?


  Wheeze

  Use of accessory muscles/tripod position

  Hypoxia

  Tachypnoea

  Tachycardia

  Pallor

  Silent chest (signs of worsening asthma)

  Fine tremor (due to salbutamol use)

  Oral candidiasis (due to ICS use)

  Obstructive pattern on spirometry with reversibility
• What is the management of acute asthma exacerbations?


  OSHITME

  O2

  SABA

  Hydrocortisone (IV)

  Ipratropium (SAMA) -> back to back with salbutamol

  Theophylline (later)

  Magnesium sulphate

  Escalate -> may need ITU input
• What is the long-term management of acute asthma exacerbations?

  Patient education

  Keep PEFR diary

  Avoidance of triggers

  Medication

  • SABA
  • ICS
  • LABA
  • LTRA, theophylline or anti-IgE therapy

  Regular follow-up

  Annual flu jab

  Prevention of acute exacerbations