Fetal and Newborn Pulm Physiology

Question 1

What order are all the structures in the lungs developed?

Answer 1

Bronchi
Bronchioles
Terminal Bronchioles
Resp Bronchioles
Alveolar Ducts
Alveolar sacs (birth)

Question 2

When does surfactant start to be produced?

Answer 2

25-26 weeks

Question 3

What is meant by the Pardoxical movement of chest wall in development?

Answer 3

As the diaphragm goes down, the chest wall caves in.

Question 4

What are the functions of the T1 and T2 Pneumocytes?

Answer 4

T1 Structural

T2 Surfactant production

Question 5

What happens during the Saccular Phase of lung devt?

Answer 5

Clusters of sacs form on terminal Bronchioli
Fibroblasts begin to produce ECM
SURFACTANT SYNTHESIS
appearance of lamellar bodies in Alveolar Type 2 cells

Question 6

What is the composition of Surfactant?

Answer 6

90% lipid 
75% of that lipid is Lecithin
Lecithin/Sphingomyeln ratio will tell you how mature the fetal lung is.
10% Protein
9% serum proteins 
1% Surfactant specific proteins

Question 7

What are the different Surfactant Proteins?

Answer 7

SP-A Water soluable
SP-D
-Immune defense function (macrophage)

SP-B
SP-C
-Critical for surface area

Question 8

What stimulates Surfatant Synthesis?

Answer 8

GLucocorticoids
Thyroid Hormones
cAMP
Epidermal Growth Factor
B-Adr Agonists (terbutaline)
Purinoceptor agonist(adenosine)

Question 9

What inhibits Surfactant production?

Answer 9

Maternal Diabetes

Question 10

What happens during the Alveolar Phase of lung development? 36wks to 2 wk PP

Answer 10

Alveoli form from terminal Endings and they grow and get thinner as lungs mature

Question 11

What are the caricteristics of the lung right before birth?

Answer 11

Filled with pulmonary fluid
Shallow breathing movements
Vessels constricted, low BF
Low lung compliance
High Chest compliance

Question 12

What happens upon onset of air breating?

Answer 12

Chem Stimuli: increased pCO2 decreased pO2
Envt Stimuli: Cooling, light, sound, pressure, J receptors
First Breath:
-forceful inspiration
-active expiration
-generates transpulm pressure to open air passages
-estabilish funct residual capacity
New lung-air interface

Question 13

How is Fetal lung fluid Absorbed?

Answer 13

Perinatal Epi Surge activates transepi Na+ transport
Abs enhanced by
-thyroid and steroid hormones
-alveolar capillary pressure gradient

Question 14

What are the respiratory mechanics of infants?

Answer 14

Low static and dynamic lung compliance

Low nasal resistance

Higher airway resistance

Paradoxical inward movement of upper chest during inspiration

Low efficiency

• Loss of energy
• respiratory muscles

Question 15

What is the ventilation-perfusion relationship in infants?

Answer 15

Inhomogeneous air distribution

• pliant airway
• chest wall distortion
• immature respiratory muscles

Decrease in pulmonary arteries: decreases resistance

Question 16

How is respiration controlled in the neonate?

Answer 16

Less episodic and more continuous
AROUSAL is mechanism 
Chemical
-increased response to CO2
-biphasic response to hypoxia