EXAM #1: FETAL AND NEWBORN PULMONARY PHYSIOLOGY

Question 1

When do the alveoli begin to develop?

Answer 1

Week 28

Question 2

When does the majority of lung development occur?

Answer 2

Post-natal

Question 3

What are the phases of lung development?

Answer 3

1) Embryonic
2) Pseudoglandular
3) Canalicular
4) Saccular
5) Alveolar

Question 4

In what stage of lung development does surfactant get produced?

Answer 4

Saccular

Question 5

What week does surfactant development start?

Answer 5

~25-26

Question 6

What is the embryonic phase of lung development?

Answer 6

0-8 weeks

• 1st segments of the 5 lobes appear
• Pulmonary vessels form

Question 7

How are the breathing movements described in the embryonic phase?

Answer 7

Paradoxical

Question 8

What is paradoxical breathing?

Answer 8

Diaphragm contract and the chest wall moves INWARD (not the normal outward)

Question 9

What is the pseudogranular phase of lung development?

Answer 9

8-17 weeks

• Lungs resemble a gland
• Type II pneumocytes precursors form (surfactant producing)

Question 10

What is the canalicular phase of lung development?

Answer 10

16-26 weeks

• Type I pneumocytes differentiate from Type II
• Respiratory epithelium produces amniotic fluid

*Note that the maturity of the lung is dependent on the Type II pneumocytes

Question 11

What is the saccular phase of lung development?

Answer 11

24-38 weeks

• Sacs form on terminal bronchioli
• Primary septa contain 2x networks of capillaries

Question 12

What marks the onset of functional lung maturity?

Answer 12

Apperance of LAMELLAR BODIES in Type II pneumocytes

*These contain the lipids that compose surfactant

Question 13

What are the two phospholipids that contribute to surfactant?

Answer 13

Lecithin and sphingomyelin

Question 14

What is the clinical utility of the Lecithin/Sphingomyelin ratio?

Answer 14

• This is a marker of fetal lung maturity (Greater than 2.0)
• Lecithin is produced in high quantities as the lung matures

Question 15

What are the surfactant specific proteins?

Answer 15

SP-A, B, C, and D

Question 16

What surfactant proteins play a role in immune defense?

Answer 16

SP-A*
SP-D

*Note that this is water soluble and it NOT a part of the synthetic surfactant given to premature babies.

Question 17

What surfactant proteins are critical for relieving surface tension?

Answer 17

SP-B
SP-C

*Both are present synthetically

Question 18

What stimulates surfactant synthesis?

Answer 18

1) Glucocorticoids
2) Thyroid hormone
3) cAMP
4) Epidermal growth factor
5) B-adrenergic agonist
6) Purinoceptor agonist

Question 19

What is the clinical significance of the surfactant stimulators?

Answer 19

IF baby has low Lecithin/Sphingomyelin ratio, THEN prescribe a stimulator

Question 20

What can inhibit surfactant synthesis?

Answer 20

Maternal DM

Question 21

What is the alveolar phase of lung maturation?

Answer 21

36 weeks to 2 week post-partum

• Alveoli increase in diameter
• Connective tissue septa decreases
• Increased number and size of alveoli

Question 22

Describe the full-term lung while it is “intrauterine.”

Answer 22

1) Filled with fluid
2) 30% shallow breathing
3) Vessels constricted
4) Low lung compliance
5) High chest compliance

Question 23

What are the stimuli for the first breath?

Answer 23

1) Chemical
- Increased pCO2 and decreased pO2
2) Environmental

*The pressure of the birthing process in the vaginal canal, temperature change, and light/ sound stimulate the first breath

Question 24

Physiologically, what happens with the first breath? What pivotal events occur at this point?

Answer 24

Forced inspiration and active expiration generates the pressure gradient needed to open the air passages

*The FRC is established at this point and the new air interface opens pulmonary capillaries b/c the hypoxic vasoconstriction is counteracted.

Question 25

What stimuli promote the absorption of fetal lung fluid?

Answer 25

1) Perinatal epi surge
- Beta receptors activated
- Na+/K+ ATPase is activated
- Na+ excreted and water follows
2) Thyroid and steroid hormones promote absorption
3) Alveolar-capillary pressure gradient

Question 26

How is the neonatal breathing apparatus described?

Answer 26

“Low efficiency”

*Note that there is also an “inhomogenous” air distribution that alters the V/Q relationship

Question 27

What happens to the pulmonary circulation with birth?

Answer 27

• Decreased pulmonary arteries
• Increased alveoli

*Thus, there is a decrease in pulmonary vascular resistance

Question 28

Periodic episodic breathing is normal in the neonate. What can you do to facilitate the transition to normal breathing pattern?

Answer 28

Arousal

Question 29

What is the biphasic response to oxygen in the neonate?

Answer 29

N/A