L5 - Neonatal lung disease Flashcards
What is respiratory distress syndrome?
- Usually caused by a deficiency in surfactant
- and often occurs in premature infants.
Effect of decreased surfactant
Lung compliance decreases.
Work of inflating stiff lung increases.
Administration of what may cause an increase in surfactant production?
Corticosteroids.
- stimulates lung development and surfactant production
Effect of decreased surfactant in a new born infant
Lung collapses with each successive breath.
So infant must work as hard with each successive breath.
What might progressive atelectasis and reduced lung compliance lead to…
Uneven perfusion and hypoventilation.
- results in protein rich fibrin rich exudation
- into the alveolar spaces
- with the formation of hyaline membrane.
Problems associated with formation of hyaline membrane
- Becomes barrier to gas exchange
- leading to CO2 retention and hypoxemia.
- Hypoxemia itself further impairs surfactant synthesis.
Babies with RDS may present with (3)
- Tachypnoea
- Laboured breathing with chest wall recession
- Cyanosis (severe cases)
How might a pneumothorax be demonstrated on examination?
Transillumination into bright fibre optic light source applied to chest wall.
How might tension pneumothorax be treated
Treated urgently with decompression by inserting chest drain
Summarise the different stages in lung development of a neonate?
- Embryonic
- Psuedoglandular
- Canalicular
- Saccular
- Alveolar
- Post-natal
Embryonic stage of lung development
(4-7 weeks)
- lung bud differentiation
- trachea and bronchi forming
- pulmonary vein and artery forming
Psuedoglandular stage of development
(7-17 weeks)
- further division
- conducting airways formed
- terminal bronchioles
- immature neural network
- pre-acinar blood vessels
Canalicular stage of development
(17-26 weeks)
- primitive alveoli
- type I, type II cells
- surfactant synthesis
Describe surfactant
- lipoprotein
- produced by type II cells
- keeps surface tension low
- prevents formation of water-air interface which has a high surface tension
- maintains similar pressure in alveoli despite changes in diameter
Describe respiratory distress syndrome?
- impaired surfactant and secretion leads to atelectasis
- ventilation perfusion v/q inequality
- hypoventilation with resultant hypoxemia and hypercarbia
What is the result of respiratory and metabolic acidosis?
- causes pulmonary vasoconstriction
- impaired endothelial and epithelial integrity
- leakage of proteinaceous exudate
- formation of hyaline membranes
Deficiency lung surfactant?
- decrease in lung compliance
- decrease in functional residual capacity
- increase in deadspace
- large v/q mismatch
Voltrauma
- ultrastructural lung injury
- due to overdistention
- occurring during mechanical ventilation.
Barotrauma
Injuries caused by increased air and water pressure
What sequence of events may lead to bronchopulmonary dysplasia?
- oxygen toxicity with barotrauma,
- voltrauma in the structurally immature lungs
- causes an influx of inflammatory cells.
- exacerbates the vascular injury.
- leads to broncho pulmonary dysplasia
Signs and symptoms of bronchopulmonary dysplasia in newborns
- low birth weight
- significant weight loss during first 10 days of life.
Management of Bronchopulmonary Dysplasia (3)
- surfactant replacement with oxygen supplementation
- continuous positive airway pressure
- mechanical ventilation
Bronchopulmonary dysplasia pathophysiology
- overall reduction in SA for gas exchange
- by alveolar septatum interferance
- damage to developing pulmonary microvasculature
Pulmonary interstitial emphysema (4)
- Rupture of small airway, alveoli.
- Air leaks out
- due to high intra-alveolar pressure.
- More frequently due to mechanically applied pressure
How may changes in transpulmonary pressure cause damage to the respiratory epithelium?
- if transpulmonary pressure exceeds the tensile strength of the non-cartillaginous terminal airway and alveolar saccules
Summarise the different surfactant proteins
Hydrophillic
Immunity
- SP-A
- SP-D
Hydrophobic
Spread of surfactant
- SP-B
- SP-C
Role of SP-A
‘immune system’
- protects surfactant transport
Role of SP-B
- essential for lung function
- absorption and spreading
Role of SP-D
‘immune system’
- regulates surfactant balance
Role of SP-C
Absorption
What occurs during the saccular phase?
27-36 weeks
- Formation of alveolar saccules, ECM.
- Neural network maturation
- More nerves and BV
What occurs during the alveolar phase?
36 months - 2 years
- expansion of gas exchange area, nerves and capillaries
What occurs during the post natal phase
2-18 years
- continued cellular proliferation
- lung growth and expansion
What is required in order for lungs to develop properlly
- fetal breathing
- fetal lungs secrete lung fluid
- pressure generated by amniotic fluid around fetus
How do fetuses adapt at birth
Cut cord, baby will cry.
- babies filling lungs with oxygen and pushing out lung fluid
How is the clearance of lung fluid controlled during labour?
Hormonally mediated :
- catecholamines
- ADH
- thyroid hormones
Slow secretion and increase absorption.
How is clearance of lung fluid controlled during delivery
‘thoracic squeeze’
- expels fluid and reduces lung volume
Describe haemodynamic adaptation at birth?
- fall in pulmonary vascular resistance
- rise in systemic vascular resistance
- increase in pulmonary blood flow
Pulmonary hypoplasia
Small lungs that never develop properlly
Congenital diaphragmatic hernia
Where bowel goes up into chest through hole in diaphragm and gets in way of lung.
Congenital lobar emphysema
Hyperinflated lung on one side
Compression of adjacent lung
Cystic adenomatoid malformation
Benign lung lesion that appears before birth as a cyst or mass in chest.
What is given to mums at risk of pre-term labour?
Steroids
- increase surfactant production in baby, thus preventing possible RDS
Hypoxic ischaemic encephalopathy
- oxygen deprivation at birth
- septic
RDS on CXR
- granular appearnce of lungs
- umbilical lines, place canulla to provide antibiotics and nutrition
