21. Why do Infants wheeze?

Question 1

Why is life of a preterm baby not viable if they are born prior to 24 weeks?

Answer 1

Do not have sufficient development of the lungs - lack of air/tissue interface

Lack of surfactant production

Question 2

Why does the pulmonary artery have thin walls?

Answer 2

Carrying low pressure blood to the lungs

Question 3

What is normal size relation of the broncus?

Answer 3

Normally roughly the same size as the pulmonary artery

Question 4

Define ‘wheeze’

Answer 4

Breathe with a whistling or rattling sound in the chest, as a result of airway obstruction

Question 5

Describe what is meant by a wheeze (lecture definition)

Answer 5

Musical lung sound
From oscillations in narrowed airways
Can be inspiratory or expiratory (virtually all wheezes will have some component of an expiratory wheeze - unusual to have just inspiratory wheeze)
High or low pitched

Question 6

What does the frequency of a wheeze depend on?

Answer 6

Degree of narrowing
Elasticity of airway wall
Local airflow

Question 7

Where does the sound appear to come from in wheezes?

Answer 7

The breathing sound comes from the ‘chest’ - not the throat

Wheezing comes from the intrathoracic airways?

Question 8

What is the effect of expiration on the intrathoracic airways?

Answer 8

When expiring, this causes the intrathoracic airways to narrow

Question 9

What is the relation of the intrathoracic airways to a wheeze?

Answer 9

If there is an over-narrowing of the intrathoracic airways on expiration, this will present as a wheeze

Question 10

Does a narrowing of the extrathoracic airways result in a wheeze?

Answer 10

No - will hear a squeaking/barking noise depending on size of the individual

Question 11

a

Answer 11

a

Question 12

How does a preschool wheeze present?

Answer 12

Attacks that are usually triggered by colds
There are few or no symptoms between the attacks
Most of these are triggered by viral colds with a cough and then resolves as the viral infection ends
The attacks are short (tend to trail off after about four days)

Question 13

What age is the preschool range?

Answer 13

From 10 months up to 6 years of age

Question 14

How common is a preschool wheeze?

Answer 14

This is very common - about a third of children will wheeze at least once before three years of age

Question 15

What are the risk factors for a preschool wheeze?

Answer 15

Smoking during pregnancy

Air pollution

Question 16

Why does smoking during pregnancy lead to wheezing in the infant/

Answer 16

Change to the structure of the membranous airway

The airways of the airways are not as rigid and have a lower threshold to narrow in response to e.g. the cold

Question 17

What are the different types of wheeze causes during childhood?

Describe these

Answer 17

Transient early wheeze - during the first three years of life - born with low lung function and develop hyper-reactive airways with colds - have normal lung function by 11 years

Non-atopic wheezes - symptomatic lower respiratory tract viral infections e.g. bronchiolitis in early life - continue to wheeze beyond third year - tend to resolve but some (less than a third) will develop asthma later on

IgE associated wheeze i.e. asthma - persistent inflammation throughout central and peripheral airways - infiltration of lymphocytes and eosinophils

Question 18

What is the difference to the histology of children with atopic asthma?

Answer 18

Goblet cell hyperplasia
Thick sub basement membrane
Cellular infiltration

Question 19

What is the treatment for a preschool wheeze?

Answer 19

(Surprisingly very similar to treatment of atopic asthma)
Dependent on severity:
Inhaled short acting beta 2 agonist e.g. salbutamol
Add in inhaled steroids or leukotriene receptor antagonists
Refer to respiratory paediatrician

Question 20

What are the differential diagnoses for a wheeze?

Answer 20

NB. These are incredibly world

Structural causes e.g. cystic abnormality
Bronchogenic cysts
Congenital lobar emphysema