Developmental aspects of lung disease

Question 1

When does the embryonic phase take place ?

Answer 1

3-18 weeks

Question 2

What happens during the embryonic phase ?

Answer 2

Lung buds start to develop as a respiratory diverticulum from the foetal foregut
2 lung buds-> lobar buds derived from endoderm
Tissues- mesoderm

Question 3

When does the Pseudoglandular phase take place ?

Answer 3

5-17 weeks

Question 4

What happens in the Pseudoglandular phase ?

Answer 4

Rapid branching of the airways
16-25 primitive segmental bronchi
Cilia and mucous glands start to appear

Question 5

When does the canalicular phase take place ?

Answer 5

16-26 weeks

Question 6

What happens during the canalicular phase ?

Answer 6

Distal architecture
Terminal bronchioles and alveoli form gas exchange units
Type I and type II pneumocytes appear

Question 7

When does the saccular phase take place ?

Answer 7

24-38 weeks

Question 8

What happens during the saccular phase ?

Answer 8

Alveolar sacs grow
More surfactant produces
Bronchioles elongate

Question 9

When does the alveolar phase take place ?

Answer 9

36 weeks - 2/3 years

Question 10

What happens during the alveolar phase ?

Answer 10

Lungs can independent sustain breathing

Question 11

What happens during postnatal lung growth ?

Answer 11

Alveolar septation continue after birth

20-60 million at birth to 200-300 million at age 3-8

Question 12

What is laryngomalacia ?

Answer 12

Commonly seen in infants
Present with stridor, worse with feeding or when upset/excited
Will improve within 1st year of life
Concern if affects feeding, growth or cause apnoea’s

Question 13

What is tracheomalacia ?

Answer 13

Can be isolated in healthy infants
Associated with genetic conditions
May be caused by external compression

Question 14

What is the presentation of tracheomalacia ?

Answer 14

Barking cough
Recurrent croup
Breathless on exertion
Stridor/wheeze

Question 15

What is the management of tracheomalacia ?

Answer 15

Management includes physio and antibiotics when unwell

Natural history resolution with time

Question 16

What is Tracheo-oesphageal fistula ?

Answer 16

Abnormal connection between trachea and oesphagus
Majority have associated oesphageal atresia
Association with genetic conditions

Question 17

What is the presentation of Tracheo-oesphageal fistula ?

Answer 17

Choking
Colour change
Cough with feeding
Unable to pass NG

Question 18

What is the treatment of Tracheo-oesphageal fistula ?

Answer 18

Surgical repair

Question 19

What are the complications of Tracheo-oesphageal fistula ?

Answer 19

Tracheomalacia
Strictures
Leak and reflux

Question 20

What is congenital pulmonary airway malformation ?

Answer 20

Abnormal non-functioning lung tissue
80% detected antenatally
Occur spontaneously 
May resolve spontaneously in utero
Conservative management if asymptomatic
Surgical intervention may be required 
Possible risk of malignant chnage

Question 21

What is congenital diaphragmatic hernia ?

Answer 21

Diaphragm develops from multiple tissues around 7 weeks and closes by 18 weeks
CDH affects 1 in 2500 births
Different types, most common Bochdalek (90%)
Usually left side > right side
Most diagnosed antenatally
Some cases diagnosis late

Question 22

What is neonatal lung disease ?

Answer 22

Significant changes occur at birth after the 1st breath

Lungs inflate and fluid in lungs is absorbed

Question 23

What is IRDS caused by ?

Answer 23

Surfactant deficiency

Question 24

How can IRDS be treated ?

Answer 24

Antenatal steroids
Surfactant replacement
Appropriate ventilation and nutrition

Question 25

What is chronic lung disease associated with ?

Answer 25

prematurity where ongoing oxygen requirement at term

Question 26

What is remodelling ?

Answer 26

Alteration of airway structure following external influence:
- environmental exposures
- chronic diseases of childhood
- infection
Leads to abnormalities due to interference of inter- cellular signalling