Asthma Pathophysiology

Question 1

What is asthma?

Answer 1

Recurrent bronchial spasms causing airway swelling, narrowing & DIB

Question 2

Common triggers for asthma

Answer 2

Allergens (pollen, dust mites, pet dander)
Irritants (cold air, smoke)
Exercise
Stress
Infection

Question 3

Symptoms

Answer 3

Wheezing
Coughing
SOB
Chest tightness

Question 4

Mechanism of an asthma attack

Answer 4

bronchial inflammation = muscle tightening = excessive mucous = airway narrowing = wheezing, coughing, SOB

Question 5

Management of asthma attacks

Answer 5

Avoiding triggers
bronchodilators (relieve spasm)
corticosteroids (reduce inflammation)
patients often have quick relief medication

Question 6

Pathophysiology: Immune Response

Answer 6

Antigen & IgE = mast cell activation = chemical mediators (histamine, kinins and prostaglandins) = bronchoconstriction, mucous and oedema

Question 7

What do kinins cause?

Answer 7

vasodilation in vessels and bronchoconstriction in lungs

Question 8

What do prostaglandins cause?

Answer 8

vasoconstriction and inflammation

Question 9

Pathophysiology: Air Trapping

Answer 9

vagal stimulation = excess mucous & bronchoconstriction = forced expiration = bronchial collapse = increased residual volume = poor mucous clearance = hypoxia, arrythmias and depression of the CNS

Question 10

What triggers vagal stimulation in asthma?

Answer 10

excessive coughing

Question 11

Pathophysiology: Severe obstruction

Answer 11

Mucous plugging = atelectasis = hypoxia = increased muscle activity

Question 12

What is atelectasis?

Answer 12

collapse of the airway beyond blockage

Question 13

Pathophysiology: Acid Base Balance

Answer 13

Respiratory acidosis = carbon dioxide retention = carbonic acid formation = lower blood pH

Metabolic acidosis = anaerobic metabolism = lactic acid build up = further reduced blood pH

Result: Hypoxaemia = pulmonary vasoconstriction = higher right side of the heart workload = pulmonary hypertension = right heart failure

Question 14

Pathophysiology: Chronic Inflammation

Answer 14

Cellular involvement: increased leukocytes and eosinophils = release of leukotrienes = ongoing airway narrowing and damage

Amplified Immune Response: mast cells release chemotactic factors and cytokines = attraction of more WBC = sustained inflammation = worsening obstruction = hypoxia

Question 15

What are chemotactic factors?

Answer 15

released by mast cells and act as a signal to attract other immune cells

Question 16

What are cytokines?

Answer 16

involved in cell communication: activate, attract and increase production of other WBC

Question 17

How does inflammation affect airway diameter in asthma?

Answer 17

Narrows

immune cells swell airway

inflammatory mediators cause goblet cells to increase in number and produce excessive amounts of mucous = blocks airways

Smooth muscle contracts causing bronchoconstriction due to overactive inflammation