Pulmonary System

Question 1

Pulmonary system develops rapidly during

Answer 1

3rd or last trimester

Question 2

Age of gestation when there will be ADEQUATE GAS EXCHANGE

Answer 2

24 - 26 weeks AOG

Question 3

Number of alveoli continues to increase in number until

Answer 3

8 years old

Question 4

First 5-10 mins of life

Answer 4

1. Alveoli transition from fluid-filled to air-filled state
2. Normal ventilatory pattern
3. Normal volumes

Question 5

Negative intrathoracic pressure in the range of ___ to ___ cmH20 is generated to expand the collpased and fluid-filled alveoli

Answer 5

40-60 cmH20

Question 6

By 10-20 mins of life

Answer 6

1. Achieved near-normal FRC

2. Blood gas stabilize with the establishment of increased pulmonary blood flow

Question 7

Normal blood gas values in the neonate

Answer 7

1. Highest PCO2 55 mmHg - term fetus at end of labor
2. Highest PO2 mmHg 75 mmHg - term newborn at 1 week
3. Lowest pH 7.2 - term newborn at 10 mins of life
4. Normal pH 7.35 - term newborn at 1 hour of life

Question 8

Tidal volume (neonate vs child/adult)

Answer 8

Same

Question 9

Respiratory rate (neonate vs child/adult)

Answer 9

INCREASED

Question 10

Closing volumes

Answer 10

HIGH (within the range of normal tidal volume)

Question 11

Minute ventilation

Answer 11

INCREASED due to higher oxygen consumption, about double seen in adult

Question 12

MV:FRC ratio

Clinical significance?

Answer 12

2-3 times higher in the newbord

Clinical significane:
1. Volatile anesthetic agent should be FASTER, as should emergence

2. Less oxygen reserve in the FRC - MORE RAPID DROP IN ARTERIAL OXYGEN LEVELS

Question 13

HIGH or LOW

1. Lung compliance
2. Chest wall compliance

Answer 13

1. Lung compliance: LOW

2. Chest wall compliance: HIGH

Question 14

Providing most of the gas exchange?

Intercostal muscle or diaphragm

Answer 14

DIAPHRAGM

Intercostal muscles are poorly developed at birth

Question 15

Diaphragm fibers:

Slow twitch, high oxidative fibers for sustained contraction with very little fatigue

Answer 15

TYPE 1

Question 16

Diaphragm fibers:

Fast teitch, low oxidative fibers, quick contractions, fatigue easily

Answer 16

TYPE 2

Question 17

Distribution of diphragm fibers:

Type 1

Preterm __
Newborn __
2 years __

Answer 17

Preterm 10%
Newborn 25%
2 years 55%

Question 18

Continued presence of ________ is necessary to maintain both distensibility of the alveoli and the maintenance of an FRC at exhalation

Answer 18

SURFACTANT

Question 19

Decreased surfactant production can cause RDS (respiratory distress syndrome), causes are

Answer 19

1. Prematurity

2. Maternal diabetes

Question 20

Consequences of decreased surfactant production (5)

Answer 20

1. Alveolar collpase
2. Decrease in lung compliance
3. Hypoxia
4. Increased work of breathing
5. Respiratory failure

Question 21

Breathing pattern common in neonates especially in pretermand can persist up to 1 year of age

Answer 21

PERIODIC BREATHING

Neonates respond less to hypercapnia and respond to hypoxia with a brief period of hyperventilation followed by hypoventilation

*The initial hyperventilatory response is prevented by hypothermia — hypothermic neontes increased risk of hypoventilatory response to hypoxia

Question 22

Term used when there is high level of pulmonary artery pressure due to hypoxia, acidosis and inflammatory mediators

Answer 22

PPHN (persistent pulmonary hypertension of the newborn)

Persistent fetal circulation

Question 23

Causes of PPHN (8)

Answer 23

1. Severe birth asphyxia
2. Meconium aspiration
3. Sepsis
4. Congenital diaphragmatic hernia (CDH)
5. Maternal use of NSAIDS - constriction of ductus arteriosus
6. Maternal diabetes
7. Maternal asthma
8. CS delivery

Question 24

Patent ductus arteriosus and foramen ovale cause which shunt?

Answer 24

RIGHT to LEFT shunt - bypassing the pulmonary circulation

• Due to elevated pulmonary vascular resistance
• Results in profound hypoxia and normal or elevated paCo2

Question 25

Treatment of profound hypoxia due to right to left shunt (PDA or PFO)

Answer 25

1. Correct predisposing disease (hypoglycemja, polycythemia)
2. Improve poor tissue oxygenation
3. Goal: maintain normocapnia and PaO2 of 60-100 mmHg

Question 26

Only FDA approved medication treatment of PPHN

Answer 26

INHALED NITROUS OXIDE

• indicated when newborn expresses oxygen index of 15 or more
• has not been shown to reduce the need for ECMO

Other treatments:

1. Standard mechanical ventilation
2. High-frequency ventilation
3. Exogenous surfactant
4. Alkalinization
5. ECMO

Question 27

Vasodilator therapy for PPHN

Answer 27

1. Prostacyclin (epoprostenol)
2. Phosphodiesterase inhibitors (sildenafil)
3. Endothelin receptor antagonists (bosentan)

Question 28

Vasopressor used to maintain right ventricular function which is paramount to survival in PPHN

Answer 28

DOBUTAMINE

• used in normotensive patient
• provide inotropy and decreased systemic vascular resistance

Question 29

One of the most important pulmonary challenges in the newbord period; marker of chronic fetal hypoxia in the 3rd trimester

Answer 29

MECONIUM ASPIRATION

• fetal hypoxia can result in an increase in the amount of muscle in the blood vessels of the distal respiratory units
• CHRONIC FETAL HYPOXIA leads to passage of meconium in utero

Question 30

Current recommendations for newborns at delivery with frank meconium aspiration or staining (conservative approach)

Answer 30

INTUBATION & SUCTIONING

Routine oropharyngeal suctioning immediately at the time of delivery

If the newborn is vigorous and crying — NO further suctioning needed

If the newbord is depressed — Intubate and suction from beneath the glottis

Meconium retrieved with NO bradycardia — reintubate and suction

(+) bradycardia — positive pressure ventilation and suction