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RTH 225 Respiratory Care Neonatology

RTH 225 Respiratory Care Neonatology. Fetal Development, Part II. Objectives. Define IRDS Describe the pathophysiology of IRDS Discuss Surfactant When it is formed Where it is formed Causes of decreased surfactant Describe tests which assess lung maturity L/S Ratio Shake Test.

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RTH 225 Respiratory Care Neonatology

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  1. RTH 225Respiratory Care Neonatology Fetal Development, Part II

  2. Objectives • Define IRDS • Describe the pathophysiology of IRDS • Discuss Surfactant • When it is formed • Where it is formed • Causes of decreased surfactant • Describe tests which assess lung maturity • L/S Ratio • Shake Test

  3. Immature surfactant production causes development of IRDS

  4. What is Surfactant?

  5. Surfactant Development • Takes place at 24 - 26 weeks gestation • Surfactant is a mixture of phospholipid & proteins. • Produced by type II pneumocytes . • LECITHIN is major & SPHINGOMYELINE is minor surfactant .

  6. Pathophysiology of IRDS

  7. Assessment of lung maturity • L/S Ratio • Shake Test

  8. L / S RATIO : • Collection of amniotic fluid amniocentesis needed to determine L/S Ratio • Helps to identify • sex of the fetus. • lung maturity • chromosomal defects & biochemical abnormalities .

  9. L / S RATIO • Greater than 2.0 = mature lungs • 1.0 - 2.0 = RDS may or may not developed • Less than 1.0 = RDS is likely due to immaturity

  10. The “L”: LECITHIN • It starts rising slowly at 18 weeks . • Surge abruptly at 34 weeks. • Peaks at 38 weeks . • Lecithin abrupt at 34 weeks • represents synthesis by more mature and stable fetal lung .

  11. The “S”: SPHINGOMYELINE • It is constant during early pregnancy. • Rises at about 18 weeks. • Peaks at about 30 weeks. • Declines after 30 weeks.

  12. SHAKE TEST • A screening test . • Mix amniotic fluid with alcohol . • Shake well to form bubbles at the surface. • After 15 minutes , if complete ring is developed, L/S ratio is considered 2.0 or greater • Indicates mature lungs. • Incomplete ring does not necessarily mean low L/S ratio .

  13. Early Lung Maturity(before 34 weeks gestation) • If L/S ratio is greater than normal for age (before 34 weeks gestation) • Toxemia of pregnancy . • Maternal hypertension [ PIH ] . • Maternal infection . • Severe diabetes . • PROM & placental insufficiency .

  14. Delayed Lung Maturity • Due to decreased surfactant • Mild diabetes, fetal Rh disease • Acidosis, hypoxemia • Prematurity, malnutrition • Smaller identical twin

  15. Steroid Therapy • Increases surfactant production & lung maturity . • Used in infants 24 - 34 weeks especially 24 - 30 weeks . • Given to mother 48 hours to 7 days prior to delivery . • e.g. Dexamethasone [ Decadrone ] Beclamethasone [ Becasone ]

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