2.1.1 Acute Lung Injury

Question 1

What are some of the complications/factors that contribute to the respiratory issues associated with bronchopulmonary dysplasia?

Answer 1

1. Abnormality in alveolar septation (reduced surface area)
2. Dysregulation of pulmonary vasculature development
3. Superimposed effects of hyperoxemia, hyperventilation, prematurity, inflammatory mediators

Question 2

What is the most common cause of respiratory distress in premature infants?

Answer 2

Neonatal respiratory distress syndrome

Question 3

What are 2 factors that increase surfactant production? Decrease surfactant production?

Answer 3

Increase: Glucocorticoids, Labor

Decrease: Insulin (infants of diabetic mothers), congenital surfactant deficiency (SFTBC genes)

Question 4

A majority of infants gradually improve from bronchopulmonary dysplasia. What is the typical timeline for this gradual improvement?

Answer 4

2-4 months

Question 5

What length of survival indicates an excellent chance of recovery in NRDS?

Answer 5

3-4 days

Question 6

What are the two phases of retrolental fibroplasia?

Answer 6

Phase I: hyperoxic phase of therapy

• Reduced VEGF
• Endothelial apoptosis

Phase II: w/ hypoxic room air ventilation

• VEGF levels recover
• Retinal vessel proliferation

Question 7

Describe the pathophysiological progression of neonatal RDS starting with prematurity and finishing with hyaline membrane.

Answer 7

Question 8

What are some of the causes of ARDS?

Answer 8

Infections, Gastric aspiration, Sepsis, Trauma, inhalants, chemicals/drugs, shock, metabolic, hypersensitivity reactions

Question 9

What are two possible complications of oxygen therapy?

Answer 9

Bronchopulmonary dysplasia

Retrolental fibroplasia (retinopathy of prematurity)

Question 10

A congested, atelectatic lung (prior to first breath) has the gross appearance of what organ? Does it sink or float?

Answer 10

Liver; sink

Question 11

What is a histological characteristic of neonatal RDS?

Answer 11

hyaline membrane in peripheral airspaces

Question 12

What are some of the ways to manage neonates at risk of and/or experiencing neonatal RDS?

Answer 12

Assess maturity using amniotic fluid phospholipids

Delay labor

Induce lung maturity w/ corticosteriods

Surfactant replacement therapy

Oxygenation/ventilation

Question 13

What is the composition of surfactant?

Answer 13

Lecithin, phosphatidyl glyceral, hydrophobic glycoproteins (SP-B, SP-C)

Question 14

What are some potential sources of microvascular injury that results in pulmonary edema?

Answer 14

Infection: pneumonia, septicemia

Inhaled gases

Liquid aspiration

Drugs and chemicals

Shock, trauma

Radiation

Transfusion related

Question 15

What are the brown-tinged cells?

Answer 15

Hemosiderin-laden macrophages - “heart failure cells”

Question 16

What changes occur b/t 22 and 32 wks of gestation that allow for better respiratory outcomes for a neonate?

Answer 16

Lungs continue to develop and divide. The epithelium transitions from cuboidal to squamous. The alveoli become more closely apposed to surrounding capillaries.

Question 17

What are the three stages of difuse alveolar damage?

Answer 17

Edema, Destruction stage (hyaline membranes), Organizing Stage (pneumocyte hyperplasia, fibrosis)

Question 18

Widespread pulmonary edema as a result of alveolar injury can lead to what condition?

Answer 18

Acute Respiratory Distress Syndrome (ARDS)

Question 19

What is the pathogenesis of ARDS?

Answer 19

Question 20

What are the three most common causes of hemodynamic pulmonary edema (in order of most common to least common) and some examples?

Answer 20

1. Increased hydrostatic pressure (L-sided HF, volume overload, pulmonary vein obstruction)
2. Decreased oncotic pressure (low protein states, renal disease, liver disease, protein-losing enteropathies)
3. Lymphatic obstruction

Question 21

What are two hemodynamic changes that would lead to pulmonary edema?

Answer 21

Increased hydrostatic pressure, decreased plasma colloid pressure

(both result in an increase in filtration force)

Question 22

What does this patient have, doc?

Answer 22

Pulmonary edema

Question 23

Describe how sufficient surfactant in a newborn aids with respiration.

Answer 23

The first breath of life needs high inspiratory pressures to expand lungs; lungs retain 40% of the residual air volume after 1st breath; subsequent breaths require less inspiratory pressure (reduced surface tension)

Question 24

What are some of the processes involved in resolution of ARDS/DAD?

Answer 24

resorption of the exudate and dead cell removal, fibrogenic cytokines, epithelial cell repopulation, endothelial repopulation

Question 25

What is this an image of?

Answer 25

Congestion of alveolar capillaries and fluid-filled alveoli

Question 26

What is pulmonary edema?

Answer 26

Increase in interstitial fluid which then accumulates within alveolar spaces

Question 27

What are the arrows pointing at?

Answer 27

Hyaline membranes that come as a result of neonatal RDS

Question 28

What is another name for neonatal respiratory distress syndrome?

Answer 28

Hyaline membrane dz

Question 29

What two factors attribute to neonatal respiratory distress syndrome?

Answer 29

Immature lung tissue and lack of surfactant

Question 30

How does surfactant affect the surface tension and pressure required to maintain alveoli patency?

Answer 30

Surfactant reduces surface tension at the air-liquid barrier; less pressure to keep alveoli patent and aerated

Question 31

What are the clinical manifestations of ARDS?

Answer 31

rapid onset (days to wks) of severe life-threatening respiratory insufficiency, cyanosis, severe arterial hypoxemia refactory to oxygen therapy, diffuse alveolar infiltrates

Question 32

What type of cells produce surfactant?

Answer 32

Type II pneumocytes

Question 33

What do these histo slides illustrate?

Answer 33

Fibrosis - honeycomb lung

Question 34

What are the three causes of pulmonary edema?

Answer 34

1. Hemodynamic disturbances (cardiogenic)
2. Alveolar wall injury (microvascular or epithelial injury)
3. Undetermined origin (head injury, high altitude)

Question 35

What are some other causes of respiratory disress in the neonate?

Answer 35

excessive maternal sedation

fetal head injury

blood or amniotic fluid aspiration

nuchal cord

transient tachypnea of the newborn

meconium aspiration syndrome

infection

persisten fetal circulation (persistent pulmonary HTN)

pulmonary hypoplasia

Question 36

What is the histological manifestation of acute lung injury?

Answer 36

diffuse alveolar damage (DAD)

Question 37

What is acute interstitial pneumonia?

Answer 37

ALI/DAD of unknown etiology, rare, mean age of 59, acute respiratory failure following upper respiratory tract infection-like illness

Question 38

What are the three types of complications associated with neonatal RDS?

Answer 38

Air leaks

Complications of oxygen therapy

Complications of prematurity

Question 39

What is name for noncardiogenic pulmonary edema?

Answer 39

Acute Lung Injury, abrupt onset of significant hypoxemia and diffuse pulmonary infiltrates in the absence of cardiac failure

Question 40

What are the different gestation ages and their corresponding rate of neonatal RDS?

Answer 40

<28 wks: 60% of infants born

28-34 wks: 30% of infants born

34 wks and beyond: under 5%

Question 41

Describe how a deficiency in surfactant leads to neonatal respiratory distress.

Answer 41

The first breath of life needs high inspiratory pressures to expand lungs; Lungs collapse with each additional breath, so each successive breath requires as much effort as the first. Stiff atelectatic lungs are further impeded by the soft thoracic wall that is pulled in as the diaphragm descends