Lecture 18: Airway Hyperresponsiveness

Question 1

What is the bronchial tree?

Answer 1

A piping system that conducts air to the functional units of the lung (alveoli)

Question 2

What is asthma?

Answer 2

A prevalent (~10%) obstructive airway disease characterised by airflow limitation with variable symptoms of wheeze, chest tightness and cough

Question 3

How is asthma treated?

Answer 3

Broncho dilators like salbutamol in ventilin

Question 4

What is FEV1?

Answer 4

Forced expired volume after a maximal breath. Low FEV1 suggests reduced air flow, high resistance, constricted airway

Question 5

What is the main feature of hyperresponsiveness?

Answer 5

They have an increase in the maximal response to stimuli (Increased reactivity) and an increase in the sensitivity to stimuli

Question 6

What is a bronchial challenge?

Answer 6

Exposure to a stimulus via the airway

Question 7

What is a direct bronchial challenge?

Answer 7

Makes use of receptors on the smooth muscle, agent directly stimulates these (histamine [binds H1 receptors] usually use methacholine [binds M3 receptors)

Question 8

What is an indirect bronchial challenge

Answer 8

provoke bronchoconstriction through inflammatory pathways (trigger endogenous mediator release like histamine and leukotrienes)

Question 9

Everyone will respond to an/a _________ bronchial challenge but only asthmatics will respond to a _________ bronchial challenge

Answer 9

Direct

Indirect

Question 10

What is PC20?

Answer 10

The provocative dose or concentration of agonist that produces a 20% fall in FEV1

Lower the PC20 the more likely to be hyperresponsive

Question 11

What causes normal airway narrowing?

Answer 11

1. Trigger crosses the epithelial barrier and bind to receptors
2. ASM gets activated
3. Narrowing can be opposed by cartilage and mucosa stiffness and alveolar load

Question 12

What happens in airway remodelling?

Answer 12

Wall Thickening
More Mucous
Epithelial abnormalities
Basement membrane thickens
Smooth muscle thickens

Question 13

Why is the perimeter of the basement membrane used as a control in studies looking at airway size?

Answer 13

It is constant even if the airway is inflated, deflated or constricted

Question 14

How does the airway remodel in asthma?

Answer 14

Hyperplasia
Hypertrophy
Increase in ECM
No change in the proportions between layers

Question 15

Deep inspiration causes _____________ in healthy humans. This is lost in asthma.

Answer 15

Bronchodilation