2.1.1 Acute Lung Injury Flashcards
What are some of the complications/factors that contribute to the respiratory issues associated with bronchopulmonary dysplasia?
- Abnormality in alveolar septation (reduced surface area)
- Dysregulation of pulmonary vasculature development
- Superimposed effects of hyperoxemia, hyperventilation, prematurity, inflammatory mediators
What is the most common cause of respiratory distress in premature infants?
Neonatal respiratory distress syndrome
What are 2 factors that increase surfactant production? Decrease surfactant production?
Increase: Glucocorticoids, Labor
Decrease: Insulin (infants of diabetic mothers), congenital surfactant deficiency (SFTBC genes)
A majority of infants gradually improve from bronchopulmonary dysplasia. What is the typical timeline for this gradual improvement?
2-4 months
What length of survival indicates an excellent chance of recovery in NRDS?
3-4 days
What are the two phases of retrolental fibroplasia?
Phase I: hyperoxic phase of therapy
- Reduced VEGF
- Endothelial apoptosis
Phase II: w/ hypoxic room air ventilation
- VEGF levels recover
- Retinal vessel proliferation
Describe the pathophysiological progression of neonatal RDS starting with prematurity and finishing with hyaline membrane.
What are some of the causes of ARDS?
Infections, Gastric aspiration, Sepsis, Trauma, inhalants, chemicals/drugs, shock, metabolic, hypersensitivity reactions
What are two possible complications of oxygen therapy?
Bronchopulmonary dysplasia
Retrolental fibroplasia (retinopathy of prematurity)
A congested, atelectatic lung (prior to first breath) has the gross appearance of what organ? Does it sink or float?
Liver; sink
What is a histological characteristic of neonatal RDS?
hyaline membrane in peripheral airspaces
What are some of the ways to manage neonates at risk of and/or experiencing neonatal RDS?
Assess maturity using amniotic fluid phospholipids
Delay labor
Induce lung maturity w/ corticosteriods
Surfactant replacement therapy
Oxygenation/ventilation
What is the composition of surfactant?
Lecithin, phosphatidyl glyceral, hydrophobic glycoproteins (SP-B, SP-C)
What are some potential sources of microvascular injury that results in pulmonary edema?
Infection: pneumonia, septicemia
Inhaled gases
Liquid aspiration
Drugs and chemicals
Shock, trauma
Radiation
Transfusion related
What are the brown-tinged cells?
Hemosiderin-laden macrophages - “heart failure cells”
What changes occur b/t 22 and 32 wks of gestation that allow for better respiratory outcomes for a neonate?
Lungs continue to develop and divide. The epithelium transitions from cuboidal to squamous. The alveoli become more closely apposed to surrounding capillaries.
What are the three stages of difuse alveolar damage?
Edema, Destruction stage (hyaline membranes), Organizing Stage (pneumocyte hyperplasia, fibrosis)
Widespread pulmonary edema as a result of alveolar injury can lead to what condition?
Acute Respiratory Distress Syndrome (ARDS)
What is the pathogenesis of ARDS?
What are the three most common causes of hemodynamic pulmonary edema (in order of most common to least common) and some examples?
- Increased hydrostatic pressure (L-sided HF, volume overload, pulmonary vein obstruction)
- Decreased oncotic pressure (low protein states, renal disease, liver disease, protein-losing enteropathies)
- Lymphatic obstruction
What are two hemodynamic changes that would lead to pulmonary edema?
Increased hydrostatic pressure, decreased plasma colloid pressure
(both result in an increase in filtration force)
What does this patient have, doc?
Pulmonary edema
Describe how sufficient surfactant in a newborn aids with respiration.
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)
What are some of the processes involved in resolution of ARDS/DAD?
resorption of the exudate and dead cell removal, fibrogenic cytokines, epithelial cell repopulation, endothelial repopulation
What is this an image of?
Congestion of alveolar capillaries and fluid-filled alveoli
What is pulmonary edema?
Increase in interstitial fluid which then accumulates within alveolar spaces
What are the arrows pointing at?
Hyaline membranes that come as a result of neonatal RDS
What is another name for neonatal respiratory distress syndrome?
Hyaline membrane dz
What two factors attribute to neonatal respiratory distress syndrome?
Immature lung tissue and lack of surfactant
How does surfactant affect the surface tension and pressure required to maintain alveoli patency?
Surfactant reduces surface tension at the air-liquid barrier; less pressure to keep alveoli patent and aerated
What are the clinical manifestations of ARDS?
rapid onset (days to wks) of severe life-threatening respiratory insufficiency, cyanosis, severe arterial hypoxemia refactory to oxygen therapy, diffuse alveolar infiltrates
What type of cells produce surfactant?
Type II pneumocytes
What do these histo slides illustrate?
Fibrosis - honeycomb lung
What are the three causes of pulmonary edema?
- Hemodynamic disturbances (cardiogenic)
- Alveolar wall injury (microvascular or epithelial injury)
- Undetermined origin (head injury, high altitude)
What are some other causes of respiratory disress in the neonate?
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
What is the histological manifestation of acute lung injury?
diffuse alveolar damage (DAD)
What is acute interstitial pneumonia?
ALI/DAD of unknown etiology, rare, mean age of 59, acute respiratory failure following upper respiratory tract infection-like illness
What are the three types of complications associated with neonatal RDS?
Air leaks
Complications of oxygen therapy
Complications of prematurity
What is name for noncardiogenic pulmonary edema?
Acute Lung Injury, abrupt onset of significant hypoxemia and diffuse pulmonary infiltrates in the absence of cardiac failure
What are the different gestation ages and their corresponding rate of neonatal RDS?
<28 wks: 60% of infants born
28-34 wks: 30% of infants born
34 wks and beyond: under 5%
Describe how a deficiency in surfactant leads to neonatal respiratory distress.
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
