Allergy in the Lung

Question 1

What is the clinical definition of asthma?

Answer 1

• Dry cough
• Yellow/clear sputum
• Breathlessness
• Reduced exercise intolerance
• Episodic (diurnal)
• Triggered
• Variable (paroxysmal)
• Respond to asthma therapies
• Bilateral widespread polyphonic wheeze

Question 2

What is the physiological definition of asthma?

Answer 2

• Reversible airflow obstruction and airway hyper-responsiveness
• Should show reduced FEV1/FVC ratio

Question 3

What does the airway lumen look like in asthmatics?

Answer 3

• Full of mucus
• Epithelium are friable and destroyed
• Thickened basement membrane
• Smooth muscle is hypertrophied

Question 4

What cytokines drive asthmatic airway remodelling?

Answer 4

• IL-5
• IL-13
• TNF alpha
• TGF beta
• VEGF
• TSLP

Question 5

What is the pathophysiology of EAA/HP?

Answer 5

• Met trigger before and formed antibodies
• Trigger lodges in periphery of the lung
• Antibody combats trigger
• Leads to acute inflammatory response with neutrophils and other immune cells which fill up the lung
• T cell mediated response

Question 6

What are the clinical consequences of EAA?

Answer 6

• Thickening of the septae
• Filling of the alveolus with fluid

Question 7

What type of hypersensitivity reaction is EAA and what effect does it have on spirometry?

Answer 7

• Type III
• No effect on flow/volume

Question 8

What are the histological features of chronic EAA/HSP?

Answer 8

• Bronchiocentric pattern
• Non-necrotising granulomatous inflammation
• Foamy macrophages in alveolar spaces
• Chronic interstitial inflammation
• Organising pneumonia

Question 9

Diagnosis of asthma

Answer 9

• BTS guidelines
  
  • If high clinical suspicion no further testing required - try treatment
  • If intermediate probability perform spirometry with reversibility testing
  • If low probability consider referral and investigating for other causes
• NICE guidelines
  
  • Fractional exhaled nitric oxide - gaseous molecule produced in response to inflammatory process
  • Spirometry with bronchodilator reversibility
  • Peak flow variability (over 2-4 weeks)
  • Direct bronchial chalenge test with histamine or methacholine

Question 10

Long term management of asthma in adults

Answer 10

Question 11

Long term management of asthma in children

Answer 11

Question 12

Defining acute asthma in adults (NB for life threatening remember 33 92 CHEST)

Answer 12

• Moderate acute asthma
  
  • Increasing symptoms;
  • Peak flow > 50-75% best or predicted;
  • No features of acute severe asthma.
• Severe acute asthma
  
  • Any one of the following:
    
    • Peak flow 33-50% best or predicted;
    • Respiratory rate ≥ 25/min;
    • Heart rate ≥ 110/min;
    • Inability to complete sentences in one breath.
• Life-threatening acute asthma
  
  • Any one of the following, in a patient with severe asthma:
    
    • 33 - Peak flow < 33% best or predicted;
    • 92 - Arterial oxygen saturation (SpO2) < 92%;
    • Cyanosis
    • Hypotension
    • Exhaustion
    • Silent chest
    • Tachycardia/arrhythmia
    • Partial arterial pressure of oxygen (PaO2) < 8 kPa;
    • Normal partial arterial pressure of carbon dioxide (PaCO2) (4.6–6.0 kPa);
    • Poor respiratory effort;
    • Altered conscious level;
• Near-fatal acute asthma
  
  • Raised PaCO2 and/or the need for mechanical ventilation with raised inflation pressures.

Question 13

Defining acute asthma in children

Answer 13

• Moderate acute asthma
  
  • Able to talk in sentences;
  • Arterial oxygen saturation (SpO2) ≥ 92%;
  • Peak flow ≥ 50% best or predicted;
  • Heart rate ≤ 140/minute in children aged 1–5 years; heart rate ≤ 125/minute in children aged over 5 years;
  • Respiratory rate ≤ 40/minute in children aged 1–5 years; respiratory rate ≤ 30/minute in children aged over 5 years.
• Severe acute asthma
  
  • Can’t complete sentences in one breath or too breathless to talk or feed;
  • SpO2 < 92%;
  • Peak flow 33–50% best or predicted;
  • Heart rate > 140/minute in children aged 1–5 years; heart rate > 125/minute in children aged over 5 years;
  • Respiratory rate > 40/minute in children aged 1–5 years; respiratory rate > 30/minute in children aged over 5 years.
• Life-threatening acute asthma
  
  • Any one of the following in a child with severe asthma:
    
    • SpO2 < 92%;
    • Peak flow < 33% best or predicted;
    • Silent chest;
    • Cyanosis;
    • Poor respiratory effort;
    • Hypotension;
    • Exhaustion;
    • Confusion.

Question 14

Management of an acute asthma attack (remember O SHIT ME - bold given all together and others if needed with senior input)

Answer 14

• Oxygen (use oxygen driven nebs)
• Salbutamol NEB (back to back nebs)
• Hydrocortisone IV or prednisolone PO
• Ipratropium NEB (if poor response/severe/life threatening)
• Theophylline - aminophylline infusion in 0.9% NaCl (usually in ICU)
• Magnesium sulphate IV (one off dose if life threatening)
• Escalate care (intubation and ventilation)