Development aspects of lung disease Flashcards
What are the 5 stages of lung development and at what gestational age do they occur?
Embryonic = 3-8 weeks
Pseudoglandular = 5-17 weeks
Canalicular = 16-26 weeks
Saccular = 24-38 weeks
Alveolar = 36 weeks - 2/3 years
What happens during embryonic stage?
Lung bud develops off of foregut
- Respiratory diverticulum from foregut
- Lung bus then divides into lobar buds
- Cells derived from endoderm
What happens during pseudoglandular phase?
Rapid branching of airways
- Eventually 16-25 primitive segmental bronchi
Development of specialised cells such as cilia and mucous glands.
What happens during canalicular stage?
Lung develop distal architecture
- Terminal bronchioles, alveolar sacs, capillaries, blood vessels all from gas exchange units
- Type 1 and 2 pneumocytes appear
When is the limit of viability of life?
24 weeks
At canicular stage
What do type 1 pneumocytes do?
Allow for gas exchange
What do type 2 pneumocytes do?
Produce and store surfactant which stops alveolar from collapsing
What happens during the saccular stage? (6)
Alveolar sacs grow and become well formed
More surfactant is produced
Bronchioles elongate
Interstitial tissue between sacs reduces
Alveolar walls become thinner, improving gas exchange
What happens in alveolar stage?
Lungs can independently sustain breathing without support
Cells well differentiated
Pulmonary vasculature is well developed and forming the final alveolar structure.
What happens with lung development post-natal?
Alveolar development continues
Prior to birth in healthy foetus 20-60 million alveolar air sacs growing to 200-300 million sacs at 3-8 years old.
What are congenital abnormalities?
Those present at birth
Give some examples of upper congenital abnormalities
Laryngomalacia
Tracheomalacia
Tracheooesophageal fistula
What are some lower congenital abnormalities?
Congenital pulmonary airway malformation (CPAM)
Congenital diaphragmatic hernia
When are congenital abnormalities picked up?
Antenatal screening
New-born
Childhood
Incidental
How is antenatal screening done?
Ultrasound
MRI
What are the signs of congenital abnormality in newborns?
Tachypnoea
Resp distress
Feeding issues
What are the signs of congenital abnormality in childhood?
Stridor/wheeze
Recurrent pneumonia
Cough
Feeding issue
What is laryngomalcia?
Dynamic abnormal collapse of the larynx due to floppiness
When is laryngomalacia picked up?
Seen in infants from 6 weeks onwards
How does laryngomalacia present?
Stridor
- Worse with feeding or when upset/excited
How does laryngomalacia progress?
Will improve within the first year as airways become bigger
When does laryngomalacia become a concern?
If affecting feeding or growth (weight gain)
OR causes apnoea
What is tracheomalacia?
A floppiness of the trachea
What can cause tracheomalacia?
Genetic conditions
External compression (e.g. vessels or tumour)
How does tracheomalacia present?
Barking cough
Recurrent croup
Breathless on exertion
Stridor/wheeze
What is the management of tracheomalacia?
Usually no management, child will grow out of it as airways grow and firm up
Physio and antibiotics
Natural history resolution with time
What is a tracheooesophageal fistula?
Abnormal connection between trachea and oesophagus
What are tracheooesophageal fistulas associated with?
Oesophageal atresia
Genetic conditions
When are tracheooesophageal fistulas diagnosed?
Antenatally or post-natal
What does tracheooesophageal fistula present as?
Chocking
Colour change
Cough with feeding
Unable to pass NG into stomach
How is tracheooesophageal fistulas treated?
Surgical repair
What are some complications of tracheooesophageal fistulas?
Tracheomalacia
Strictures
Leak
Reflux
What is congenital pulmonary airway malformation?
Abnormal non-functioning lung tissue
When can congenital pulmonary airway malformation be detected?
80% detected antenatally
How can congenital pulmonary airway malformation occur?
Sporadically and many resolve in utero
What are the management options for congenital pulmonary airway malformation?
Watchful waiting - conservative management if asymptomatic
Surgical intervention - if severe or symptomatic
What is a possible risk of congenital pulmonary airway malformation?
Malignant changes but is uncommon
What is a congenital diaphragmatic hernia (CDH)?
Where diaphragm doesn’t close properly during development
When does the diaphragm develop?
Week 7 to Week 18
How common is CDH?
1 in 2500 births
What is the most common type of CDH?
Bochdalek (90%)
What side of the diaphragm is most likely impacted?
Usually the left side more than the right
(if the right side then usually worse outcomes)
When is CDH diagnosed?
Antenatally
Some later
What are the complications of CDH?
Underdevelopment of the lungs leading to significant morbidity and mortality.
What is the management options and prognosis of CDH?
Surgical repair
Prognosis depends on degree of lung hypoplasia
What changes occur after birth (neonatal)?
Lungs inflate and fluid is absorbed
What is transient tachypnoea?
When there is a delay in clearing foetal lung fluid after birth
- Usually child has vigorous first breath and this forces the fluid out
What is the prognosis of transient tachypnoea?
Improves/self resolves within 1-2 days
What is infant respiratory distress syndrome and who does it occur in?
Due to a surfactant deficiency - alveolar collapse when no air is in them so makes inspiration much harder work
What is the treatment for IRDS?
Antenatal steroids
- Promote lung development prior to delivery if child is expected to be preterm
Surfactant replacement
- Given directly into the lungs via a tube
Appropriate ventilation and nutrition
- important for lung development
What is Chronic lung disease?
Inflammation and infection due to the significant resp insult that occurs from being born premature.
What is chronic lung disease associated with?
Being born preterm
Or when ongoing oxygen is required at term
What are the complications of chronic lung disease?
Increased childhood respiratory morbidity
- Tendency to infection
- Increased O2 requirements
- Hospital admissions
Leads to chronic obstructive disorders in later life
What are the 4 main contributing factors to lung function later in life?
Individual factors
Early life events
Environment and lifestyle
Allergic diseases
What early life events can effect lung function later in life? (10)
Parental atopy
Parental education
Maternal age at delivery
Maternal smoking during pregnancy
Second-hand smoke exposure at home
Season of birth
Birth weight
Breastfeeding
Peak weight/height velocity
Lung infection
What environmental and lifestyle factors can effect lung function? (5)
Short/long term air pollution
Indoor second hand smoke exposure
Active smoking
Serum vitamin D concentration
BMI
What are some allergic diseases that could affect lung function in later life? (4)
Asthma
Rhinitis
Aero/food allergen
Sensitization
What individual factors affect lung function in later life? (3)
Age
Sex
Height
What can a low lung function growth trajectory be attributed to? (5)
Genetics
Preterm birth
Early life environment exposures
LRTI
Childhood persistent asthma
What can a potential lung function catch up be attributed to? (6)
Genetics and host factors
Exposure avoidance
Diet
Physical activity
Supplementation of beneficial factors
Prevention and/or treatment via precision medicine
What can poor lung function lead to in later life?
Adult obstructive diseases (e.g. COPD)
What can improve lung function? (4)
Diet
Exercise
Exposure to irritants
Medication
What is remodelling of the airways?
Alteration of airway structure following external influence
What external influence leads to remodelling?
Environmental exposures
Chronic disease of childhood
Infection
What is the effect of airway remodelling on the airways? (7)
Narrowing of lumen
Increased mucous plugging
Changes to cell of the airway with tendency to increase mucous production
Changes to the interstitial
Hypertrophy of muscles
Increase in number of inflammatory cells
Changes to vasculature of the airway
What are the signs of chronic inflammation?
Increased bronchial responsiveness
Increased mucus secretion
Airway oedema
Airway narrowing
