77. Congenital anomalies of the lungs, atelectasis, acute lung injury

Bronchogenic cyst?

Abnormal budding of the lung primordium.

- Located in anterior mediastinum, contains respiratory epithelium & cartilage

Congenital lobar emphysema?

Hyperinflation of one or multiple lobes.

- Surgical removal of the affected region cures the disease

Pulmonary sequestration?

Piece of lung is not connected to the airways.

1. Extralobar type: has its own pleural surface & blood supply

2. Intralobar type: occurs inside another, healthy lobe.

= Both are associated with mucus accumulation & pneumonia

Congenital pulmonary airway malformation?

When the lung parenchyma of an entire lobe is replaced with abnormal lung tissue.

- May lead to carcinoma

Pulmonary hypoplasia?

Number & size of alveoli is decreased.

Can be caused by:

- Abdominal herniation into the thorax, not allowing lung to grow

- Lack of respiratory movement

- Loss of lung liquid

Pulmonary agnesis?

When one lobe, one lung or both lungs are absent.

Atelectasis?

Term to describe inadequate expansion of air spaces in the lung.

3 types exists:

1. Resorption atelectasis

2. Compression atelectasis

3. Contraction atelectasis

Resorption atelectasis?

Obstruction in the airways which prevents air from reaching the distal airways.

- Lung can collapse

Compression atelectasis?

When fluid or air inside the pleural space compresses the lung

Contraction atelectasis?

When fibrotic tissue in the lung/pleura hampers the expansion & decrease compliance of lung.

- Restricts the lung

Acute lung injury?

A spectrum of bilateral lung damage, which can occur in many conditions:

- Pneumonia

- Aspiration of gastric content

- Sepsis

- Circulatory shock

Symptoms of acute lung injury?

- Dyspnoea

- Hypoxaemia

- Bilateral pulmonary edema

Can progress into acute respiratory distress syndrome (ARDS)

Acute respiratory distress syndrome (ARDS)?

There is alveolar capillary & epithelial damage.

- Life-threatening respiratory failure occurs, with resulting cyanosis & hypoxemia.

Histological manifestation of ARDS?

Diffuse alveolar damage (DAD)

- Vascular permeability increases, allowing exudate to enter the alveoli & prevent gas exchange

- Alveolar macrophages recruits neutrophils, causing further damage to endothelium.

Repair process of ARDS?

1. exudative phase: fibrin rich exudate and remnants of necrotic epithelial cells organize and form hyaline membranes which cover gas exchange membrane and blocks it

2. regenerative phase: occurs 1-2 weeks later, type 2 pneumocytes prolif and differentiate into type 1 to rebuild epithelium

3. repair phase: new CT formation will cause distortion of lung architecture and shrinkage of the lungs. A new BM is formed, which incorporates the CT into the interstitium

Neonatal respiratory distress syndrome (NRDS)?

Occurs in premature new-borns.

- Not enough production of surfactant

= Lungs collapse

Bronchopulmonary dysplasia?

Infants staying too long on respiratory support with NRDS.

- Can cause injury to the alveolar septa, decreasing the number of alveoli.