2.1.1 Acute Lung Injury

Question 1

What is another name for neonatal respiratory distress syndrome?

Answer 1

Hyaline membrane dz

Question 2

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

Answer 2

Neonatal respiratory distress syndrome

Question 3

What two factors attribute to neonatal respiratory distress syndrome?

Answer 3

Immature lung tissue and lack of surfactant

Question 4

What is a histological characteristic of neonatal RDS?

Answer 4

hyaline membrane in peripheral airspaces

Question 5

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

Answer 5

<28 wks: 60% of infants born

28-34 wks: 30% of infants born

34 wks and beyond: under 5%

Question 6

What type of cells produce surfactant?

Answer 6

Type II pneumocytes

Question 7

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

Answer 7

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

Question 8

What is the composition of surfactant?

Answer 8

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

Question 9

Describe how sufficient surfactant in a newborn aids with respiration.

Answer 9

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 10

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

Answer 10

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

Question 11

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

Answer 11

Question 12

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

Answer 12

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

Question 13

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

Answer 13

Liver; sink

Question 14

What are the arrows pointing at?

Answer 14

Hyaline membranes that come as a result of neonatal RDS

Question 15

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

Answer 15

Increase: Glucocorticoids, Labor

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

Question 16

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

Answer 16

Assess maturity using amniotic fluid phospholipids

Delay labor

Induce lung maturity w/ corticosteriods

Surfactant replacement therapy

Oxygenation/ventilation

Question 17

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

Answer 17

3-4 days

Question 18

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

Answer 18

Air leaks

Complications of oxygen therapy

Complications of prematurity

Question 19

What are two possible complications of oxygen therapy?

Answer 19

Bronchopulmonary dysplasia

Retrolental fibroplasia (retinopathy of prematurity)

Question 20

What are the two phases of retrolental fibroplasia?

Answer 20

Phase I: hyperoxic phase of therapy

• Reduced VEGF
• Endothelial apoptosis

Phase II: w/ hypoxic room air ventilation

• VEGF levels recover
• Retinal vessel proliferation

Question 21

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

Answer 21

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

Question 22

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

Answer 22

2-4 months

Question 23

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

Answer 23

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 24

What is pulmonary edema?

Answer 24

Increase in interstitial fluid which then accumulates within alveolar spaces

Question 25

What are the three causes of pulmonary edema?

Answer 25

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

Question 26

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

Answer 26

Increased hydrostatic pressure, decreased plasma colloid pressure

(both result in an increase in filtration force)

Question 27

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

Answer 27

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 28

What is this an image of?

Answer 28

Congestion of alveolar capillaries and fluid-filled alveoli

Question 29

What are the brown-tinged cells?

Answer 29

Hemosiderin-laden macrophages - “heart failure cells”

Question 30

What does this patient have, doc?

Answer 30

Pulmonary edema

Question 31

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

Answer 31

Infection: pneumonia, septicemia

Inhaled gases

Liquid aspiration

Drugs and chemicals

Shock, trauma

Radiation

Transfusion related

Question 32

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

Answer 32

Acute Respiratory Distress Syndrome (ARDS)

Question 33

What is the histological manifestation of acute lung injury?

Answer 33

diffuse alveolar damage (DAD)

Question 34

What is name for noncardiogenic pulmonary edema?

Answer 34

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

Question 35

What are the clinical manifestations of ARDS?

Answer 35

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

Question 36

What are some of the causes of ARDS?

Answer 36

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

Question 37

What is the pathogenesis of ARDS?

Answer 37

Question 38

What are the three stages of difuse alveolar damage?

Answer 38

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

Question 39

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

Answer 39

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

Question 40

What do these histo slides illustrate?

Answer 40

Fibrosis - honeycomb lung

Question 41

What is acute interstitial pneumonia?

Answer 41

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