Developmental Abnormalities of the Respiratory System ✅ Flashcards
What can congenital anomalies in the lungs be classified into?
Malformations in;
- Tracheobronchial tree
- Distal lung parenchyma
- Pulmonary arterial and venous trees and the lymphatics
At what stage of development do most pulmonary malformations arise?
During the embryonic and pseudo glandular stages
Can insults during the neonatal period lead to pulmonary malformations?
Yes
How can insults during the neonatal period cause pulmonary malformations?
Acute lung injury may alter subsequent alveolar and airway growth and development
What are the most common pulmonary and extra-pulmonary malformations?
- Congenital diaphragmatic hernia
- Congenital pulmonary airway malformations
- Tracheo-oesophageal fistula
- Bronchopulmonary sequestaration
- Congenital hydrothorax
What is the incidence of congenital diaphragmatic hernia (CDH)?
1 in 2000-3000 births
In what proportion of cases is CDH an isolated lesion?
2/3
When might CDH not be an isolated lesion?
Can be part of a syndrome including chromosomal anomalies
What does CDH result from?
Failure of normal development of the diaphragm during the first trimester
What are the types of CDH?
- Posterior lateral defect
- Anterior or central portion defect
- Complete absence of diaphragm
- Eventration
Are posterior lateral CDHs more common on left or right?
Left
Which of the types of CDH is not a true hernia?
Eventration
What does eventration result from?
Failure of muscle development in the primitive diaphragm
How severe is CDH?
Produces spectrum of severity, from very mild pulmonary hypoplasia causing minimal clinical compromise, to severe cases that are incompatible with life
How does CDH lead to respiratory compromise?
The compression of fetal lungs results in lung hypoplasia
On which side is the lung hypoplasia more severe in CDH?
Lung ipsilateral to the defect
What can be compromised in severe cases of CDH?
Cardiac function
What happens to infants with CDH following delivery?
Can be further cardiorespiratory compromise
What causes further cardiorespiratory compromise following delivery in infants with CDH?
Gaseous distention of the intrathoracic gut
When is gaseous distention causing further compromise in CDH a particular hazard?
In babies given bag-valve-mask ventilation
What commonly develops as a result of CDH?
Pulmonary hypertension of the newborn (PPHN)
Why does PPHN commonly develop in CDH?
Due to pulmonary hypoplasia (including abnormalities of the pulmonary vasculature) and poor oxygenation following delivery
When might the presentation of CDH be delayed?
In mild cases
What treatment option is used for severe CDH?
Fetal surgery
What fetal surgical option is used in severe CDH?
Fetal endoscopic tracheal occlusion (FETO)
What is the purpose of FETO in severe CDH?
Promote lung growth and limit pulmonary hypoplasia
How is FETO performed?
Using fetal tracheoscopy, a balloon is inserted
When is FETO ideally performed for CDH?
26-28 weeks
When is the occlusion reversed in FETO surgery for CDH?
34 weeks
What is the limitation of FETO for CDH?
It offers little benefit, and its use should be limited to clinical trial
How is CDH managed at delivery if diagnosed antenatally?
- Avoid face mask ventilation
- Intubation and artificial ventilation as soon as possible
- Continuous drainage (decompression) of gas from abdomen is started
Why is face mask ventilation avoided at birth in CDH?
It distends the GI tract
What should be minimised in CDH?
Factors that could precipitate PPHN and lung injury
How is PPHN managed if present in CDH?
Pulmonary vasodilators
Is surfactant useful in CDH?
No evidence to support its use, except in premature infants with co-existing surfactant deficiency
What is the definitive management for CDH?
Surgical repair
When should surgical repair of CDH be done?
When the baby is stable
Is ECMO useful in CDH?
Able to provide stability and control PPHN, but benefit in CDH is unclear
What is the incidence of tracheo-oesophageal fistula?
1 in 3000-4500 live births
What does a tracheo-oesophageal fistula result from?
Failure of the process of separation of the primitive foregut into the respiratory and gastrointestinal tract at 3-6 weeks gestation
What is tracheo-oesopahgeal fistula usually found in combination with?
Various forms of oesophageal atresia
What is the most commonly found combination of tracheo-oesophageal fistula and oesophageal atresia?
Oesophageal atresia with distal tracheo-oesophageal fistula
What % of cases are of TOF are a combination of oesophageal atresia with distal trachea-oesophageal fistula?
91%
What is it called when trachea-oesophageal fistula occurs without oesophageal atresia?
H-type fistula
Are H-type fistulas common?
No, extremely rare
When do H-type TOF present?
Usually after the neonatal period
What is the problem in tracheomalacia?
Absence or softening in the cartilaginous rings causes the trachea to collapse on expiration
What causes the softening of cartilaginous rings in tracheomalacia?
A reduction in the cartilage to soft tissue ratio
Is the anomaly in tracheomalacia/bronchomalacia segmental or diffuse?
Can be either
What is bronchopulmonary seqeusteriation?
Development of a mass of non-functioning lung tissues, not connected to the tracheo-bronchial tree
How does the mass in bronchopulmonary sequestration receive its blood supply?
From one or more anomalous systemic arteries arising from the aorta
Does bronchopulmonary sequestration occur inside or outside of the visceral pleural lining?
Can be either
What is it called when bronchopulmonary sequestration occurs on the inside of the visceral pleural lining?
Intralobar
What is it called when bronchopulmonary sequestration occurs on the outside of the visceral pleural lining?
Extralobar
How does bronchopulmonary sequestration appear on CXR?
As triangular or oval-shaped lung tissue on one side of the chest
On what side is bronchopulmonary sequestration more common?
Left
How is a diagnosis of bronchopulmonary sequestration made?
CT or MRI scan of chest
What does congenital lobar emphysema result from?
Malformation in the bronchial cartilage with absent or incomplete rings
How does malformation in the bronchial cartilage result in congenital lobar emphysema?
It results in lobar or segmental over-inflation and therefore compression of the remaining ipsilateral lung or lobes
What other fetal abnormalities can pulmonary hypoplasia occur secondary to?
- Renal agenesis
- Oligohydraminos
- Diaphragmatic hernia
- Large pleural effusion
- Congenital anomalies of the neuromuscular system
By what mechanisms can other fetal anomalies cause pulmonary hypoplasia?
They either restrict physical growth or expansion of the peripheral lung
What was congenital pulmonary airway malformation formerly known as?
Congenital cystic adenomatoid malformation (CCAM)
What is a congenital pulmonary airway malformation (CPAM)?
A pulmonary maldevelopment with cystic replacement of smaller airways and distal lung parenchyma
What are CPAMs classified on the basis of?
Gross appearance and histological features
What are CPAMs broadly divided into?
- Macrocystic
- Microcystic
What are the features of macrocystic CPAM?
Cysts more than 5mm in diameter and visible on fetal ultrasonography
What are the features of microcystic CPAM?
Cysts smaller and mass has solid appearance
What has a better prognosis, microcystic or macrocystic CPAM?
Macrocystic
What features worsen the prognosis of microcystic CPAM?
- Large mass
- Mediastinal shift
- Polyhydraminos
- Pulmonary hypoplasia
- Hydrops fetalis
What are the cysts connected to in CPAM?
The airways
What is the result of the cysts being connected to the airways in CPAM?
They fill with air
What happens when the cysts fill with air in CPAM?
They cause compression of the adjacent lungs
How can CPAM be treated?
Fetal surgery
When is fetal surgery used in CPAM?
Severe cases associated with hydros
What is the main concern with fetal surgery in CPAM?
Onset of preterm labour
What is congenital pulmonary lymphangiectasis (CPL) characterised by?
Marked distention of pulmonary lymphatics
Is the distention of pulmonary lymphatics generalised or localised in congenital pulmonary lymphangiectasis?
Can be either
How does congenital pulmonary lymphangiectasis present?
Pleural effusion which is typically chylous
How can congenital pulmonary lymphangiectasis be managed if identified antenatally?
A catheter shunt inserted between the chest and amniotic cavity
What is congenital pulmonary lympheangiectasis associated with?
A number of syndromes, including Noonan’s and Down’s syndrome
