Respiratory Distress Syndromes Flashcards
What is Acute Respiratory Distress Syndrome?
ARDS - Diffuse damage to the alveolar capillary interface (diffuse alveolar damage)
What is the pathogenesis of Acute Respiratory Distress Syndrome?
Leakage of protein-rich fluid leads to edema that combined with necrotic epithelial cells to form hyaline membranes in alveoli.
What is the seen in the alveoli of ARDS?
Hyaline membranes
What is seen in ARDS on CXR?
‘White-out’ of the lung
What are the symptoms associated with ARDS?
-Hypoxemia
-Cyanosis
. . .with respiratory distress
What causes the hypoxemia, cyanosis and respiratory distress seen in ARDS?
Thickened diffusion barrier and collapse of air sacs (increased surface tension) –> “sticky” air sacs
What is Acute Respiratory Distress Syndrome secondary to?
A variety of disease processes:
- Sepsis
- Infection
- Shock
- Trauma
- Aspiration
- Pancreatitis
- DIC
- Hypersensitivity reactions
- Drugs
What is the pathogenesis of ARDS caused by disease processes?
Activation of neutrophils induces protease and free radical-mediated damage of type I and II pneumocytes
How do you treat ARDS?
- Adress the underlying cause
2. Ventilation with positive end-expiratory pressure (PEEP)
What might recovery from ARDS be complicated by?
Interstitial fibrosis
What can cause interstitial fibrosis in ARDS recovery?
Damage and loss of type II pneumocytes leads to scarring and fibrosis
What does damage and loss of type II pneumocytes in ARDS cause?
Scarring and fibrosis
What are the two main functions of Type II pneumocytes?
- Stem cell of the lung
2. Produces surfactant
What is Neonatal Respiratory Distress Syndrome?
Respiratory distress due to inadequate sufactant levels
What makes surfactant?
Type II pneumocytes
What is the major component in surfactant?
Phosphatidylcholine (lecithin)
What is the purpose/function of surfactant?
Surfactant decreases surface tension in the lung, preventing collapse of alveolar air sacs after expiration.
What does lack of surfactant lead to?
Collapse of air sacs and formation of hyaline membranes.
What three situations is Neonatal Respiratory Distress Syndrome associated with?
- Prematurity
- Caesarian section delivery
- Maternal diabetes
When does surfactant production begin?
28 weeks
When are adequate surfactant levels reached?
34 weeks
What is used to screen for lung maturity?
Amniotic fluid lecithin to sphingomyelin ratio (L:S ratio)
How does the L:S ratio change through out pregnancy?
Lecithin increases from 28-34 weeks, but S stays the same!
What happens to lecithin and sphingomyelin as surfactant is produced?
- Phosphatidylcholine (lecithin) levels increase as surfactant is produced.
- Sphingomyelin remains constant
What L:S ratio indicates adequate surfactant production?
A ratio >2
How does Caesarian delivery cause Neonatal Respiratory Distress Syndrome?
Due to lack of stress-induced steroids
What do steroids provide the fetus during delivery?
- Steroids increase the synthesis of surfactant.
- They cause surfactant in type II pneumocytes to be released into the lung
How does Maternal diabetes lead to Neonatal Respiratory Distress Syndrome?
Insulin decreases surfactant production.
How does insulin lead to NRDS?
High blood sugar in mom —> goes to baby –> baby’s pancreas produces insulin –> insulin inhibits surfactant –> increases risk for NRDS
What happens to a NRDS baby at birth?
Increasing respiratory effort at birth, tachypnea with use of accessory muscles, and grunting
What are two other clinical signs of NRDS?
Hypoxemia and cyanosis
What is seen in an X-ray of NRDS?
-Diffuse granularity of the lung (‘ground-glass’) appearance
What is a complication related to hypoxemia in NRDS?
Hypoxemia increases risk for persistence of patent ductus arteriosus and necrotizing enterocolitis.
What complication is supplemental oxygen use in NRDS associated with?
Increased risk for free radical injury.
What specific damage can free radical injury in NRDS cause?
Retinal injury —> leads to blindness
Lung damage –> broncopulmonary dysplasia (lung didn’t form properly)
What used to be a major cause of blindness in neonates?
Use of O2 in NRDS
