Asthma

Question 1

What part of the airways is affected and how?

Answer 1

Condition of the small airways

• Bronchioles: bronchoconstriction and bronchospasm
• Bronchi: mucus plugging and mucosal oedema

Question 2

What are the ways that asthma can be induced?

Answer 2

• Exercise: triggered by physical exertion, possibly related to changes in air temperature or humidity
• Nocturnal: attacks occuring at night or early morning
• Irritant induced: occupational asthma such as smoke, fumes or gas
• Allergens: a hypersensitivity reaction occurs first and then subsequent exposures cause a asthma reaction

Question 3

What causes bronchospasm/bronchoconstriction and mucosal oedema?

Answer 3

Contraction of bronchiolar smooth muscles caused by:
-inflammatory mediators such as histamine and leukotrienes
-controlled by cGMP, antagonised by cAMP - induced by Ach causing stimulation of parasymp. nerves
Mucosal oedema caused by vasodilation of airway vasculature and increased capillary permeability stimulated by inflammatory mediators

Question 4

What causes mucus plugs?

Answer 4

• increased mucus production by goblet cells and submucosal glands stimulated by inflam. mediators
• epithelial cells shed from bronchial lining combine with mucus to form a plug

Question 5

What chronic changes of asthma exacerbate airway obstruction?

Answer 5

Airway remodelling:

• thickening of bronchial basement membrane
• bronchial smooth muscle hypertrophy
• goblet cell hyperplasia

Question 6

What signs and symptoms would you expect in an acute asthmatic reaction?

Answer 6

• Resp: dyspnoea, wheeze, low Sp02, non-productive cough, reduced peak expiratory flow, respiratory compromise (decreasing gas exchange, V/Q mm)
• CV: chest tightness, tachycardia, pulm. HT, decreased venous return
• Appearance: anxious, peripheral or central cyanosis

Question 7

If an asthmatic patient deteriorates, what signs might follow and how are they caused?

Answer 7

• Dynamic hyperinflation: due to gas trapping
• Hypercapnia: gas trapping
• decreased resp effort: resp muscle fatigue
• Silent chest: reduced airflow
• Cardiac failure: reduced venous return (increased intrathoracic pressure from hyperinflation)

Question 8

How would an acute asthmatic reaction be treated?

Answer 8

• Oxygen: to increase Sp02 and reduce hypoxia
• Salbutamol: B2 agonist induces SMC relaxation and bronchodilation
• Anticholinergic: reduce parasympathetic mediated constriction
• Adrenaline: bronchodilation, mast cell stabilisation
• Assisted ventilation: if decreased resp. effort