Neonatal Physiology

Question 1

What is Surfactant?

Answer 1

• Surfactant is a fluid which is produced by type 2 alveolar cells
• It contains proteins and fats
• It reduces the surface tension of the fluid in the lungs

Question 2

How does Surfactant work?

Answer 2

• Surfactant keeps the alveoli inflated and maximises the surface area
• Surfactant increases lung compliance - which is the force needed to expand the alveoli and the lungs during inspiration
• As the alveoli become more expanded the surfactant becomes more thinly spread and the surface tension increases making it more difficult for the alveolus to expand

Question 3

When is surfactant produced?

Answer 3

• Surfactant is produced between 24-34 weeks gestation

Question 4

How does the baby start breathing after birth?

Answer 4

• During birth the thorax is squeezed as the body pass through the vagina
• This helps to clear fluid from the lungs
• A strong first breathe is required to expand the collapsed alveoli for the first time
• Adrenalin and cortisol are released in response to the stress of labour, stimulating the respiratory effort