S8.1 Asthma

Question 1

What is asthma?

Answer 1

A chronic inflammatory disorder of the airways resulting in reversible airway obstruction, inflammation, bronchoconstriction and mucus production.

Question 2

What are the symptoms of asthma?

Answer 2

Wheezing (expiratory), SoB, chest tightness, cough

Question 3

Give some triggers of asthma

Answer 3

Pollen, exercise, cold air, medication

Question 4

Outline the pathophysiology of asthma

Answer 4

TH2 cells release cytokines, these activate inflammatory cells including mast cells, eosinophils and B cells (produce IgE).
Causes a type 1 hypersensitivity reaction, leading to airway narrowing as smooth muscle contracts, mucus is produced and inflammatory cells infiltrate.

Question 5

Why does inflammation cause airway narrowing?

Answer 5

Thickening of bronchial walls due to inflammatory cell infiltrate
Excess production of abnormal mucus
Smooth muscle contraction

Question 6

Describe the immediate response after exposure to an antigen in asthma

Answer 6

Immediate response: Type I hypersensitivity, interaction of allergen with specific IgE antibodies causing mast cell degranulation and release of mediators (histamine, prostaglandin D2 and leukotriene).
Causes bronchial smooth muscle contraction

Question 7

Describe the late phase response after exposure to an antigen in asthma

Answer 7

Type IV hypersensitivity, involves many inflammatory cells releasing mediators and cytokines causing airway inflammation.

Question 8

What is the role of eosinophils in asthma?

Answer 8

Release leukotriene C4 and other mediators, some of which are toxic to epithelial cells causing their shedding.

Question 9

How is asthma diagnosed?

Answer 9

History
Symptoms - wheeze, dry cough, SoB
Assess resp rate and accessory muscle use
FEV1/FVC ratio <70%

Question 10

What is the effect of asthma on gas exchange?

Answer 10

V/Q mismatch in affected area of alveoli as decreased ventilation.
Mild-moderate asthma causes type 1 RF as O2 reduced and CO2 normal/reduced.

Question 11

How can we manage asthma through education?

Answer 11

Education about inhaler use, prevention e.g smoking cessation, monitoring drugs, lifestyle.

Question 12

How can we manage asthma via medications?

Answer 12

SABA to relax smooth muscle for quick relief of symptoms E.g salbutamol

Steroid preventer decreases inflammation by inhibiting inflammatory cells and mediators. E.g prednisolone

LABA, used alongside ICS, slower onset of action so not for acute attack. E.g salmeterol

Question 13

Give some features of acute-severe asthma

Answer 13

RR >25/min
HR >110bpm
Inability to complete sentences in one breath

Question 14

Give some features of life threatening asthma

Answer 14

Altered conscious level
Exhaustion
Hypotension
Silent chest