1. Neonatal Physiology Teka Siebenaler RRT Cardiopulmonary Services
University of Minnesota Amplatz Children’s Hospital

2. Fetal Lung Stages of Development
Embryonic Stage 3rd-8th week
Neural Tube closure
Diaphragm and lung bud formation
Internal organs in primitive formation
stomach, liver, pancreas, gall bladder,
bladder and intestinal loop
Vascular systems appears

3. Most congenital malformations occur during the 4th-8th weeks
Anencephaly/Spina Bifida
Extremity deformities
Diaphragmatic hernia (85% on the left side)

4. Fetal Lung Development
7-16 weeks the formation of the bronchial tree
17-24 weeks primitive gas exchange surface forms
24-40 weeks alveolar development continues
35 weeks stable surfactant production

5. Postnatal Lung Development
Newborn
Airway branching complete
Alveolar formation is not complete
Age 1-10 years number of alveoli increase
Age 10 to young adult lung grows larger with little alveolar growth

6. Fun Facts
Surfactant is produced by alveolar epithelial cells (type II)
Surfactant production increases 2 weeks prior to normal birth
We are born with on 1/6th the number of alveoli we will need as an adult.

7. Surfactant Replacement
Creates a layer between the alveolar surface and the alveolar gas and reduces alveolar collapse by decreasing surface tension within the alveoli.
Given to patients with immature lungs, MAS, RDS, Pulmonary Hypoplasia and CDH
Curosurf vs. Infasurf vs. Survanta……

8. Cardiac Formation By 22 days a endocardial tube has formed
At 28 days aortic roots, primitive left atrium, pericardial cavity, left ventricle have formed
Blood begins to shunt from left to right during the 4th and 5th weeks of development
“Abnormalities in heart formation, the most common form of human birth defects, afflict nearly 1% of newborns, and their frequency in spontaneously aborted pregnancies is estimated to be tenfold higher”
Hoffman, J.I. Incidence of congenital heart disease: II. Prenatal incidence. Pediatr. Cardiol. 16, (1995).

9. Fetal Circulation Fetal Circulation
Oxygenated blood from placenta via umbilical vein
66% shunted past liver by DUCTUS VENOSUS to IVC
50% of this blood shunted from right atrium to left atrium via FORAMEN OVALE
This blood continues to left ventricle, ascending aorta, and arteries feeding head and right arm

10. Fetal Circulation cont’d
Venous blood from head (SVC) is directed via right atrium to right ventricle into the pulmonary artery
90% of blood in PA is shunted away from lungs and into descending aorta via the DUCTUS ARTERIOUS and returns to the placenta via the umbilical arteries.

11. Trace blood flow

12. Changes in Circulation, Respiration After Birth
Pulmonary vascular resistance decreases after birth due to:
Increased alveolar and arterial oxygen tensions, which increase nitric oxide
Lung expansion
Decrease in PaCO2
Increase in arterial pH
Pulmonary artery pressure decreases below systemic pressure; pulmonary blood flow increases
Left and right ventricles pump in series rather than in parallel as in the fetal circulatory pattern

13. “Normal Circulation”
Closure of Umbilical arteries w/in minutes after birth
Ligation of umbilical vein (clamped cord)
Closure of PDA (minutes to days)
Closure of Foramen Ovale due to increased pressure in Left Atrium and Decreased pressures in Right Atrium

14. Pulmonary Hypertension (PPHN)
Occurs in 2 out of every 1,000 born live infants
Complicates the course of 10% of infants with respiratory distress
Typically seen in infant’s >34 weeks
More common in babies that were hypoxic and acidemic around the time of birth (Venous cord Ph <7.20 and BE -8)
More prevalent in infants whose mothers took NSAIDS or SSRI’s during the 3rd trimester

15. “Due to a patent foramen ovale and patent ductus arteriosus, which are normally present early in life, elevated pulmonary vascular resistance in the newborn produces extrapulmonary shunting of blood, leading to severe and potentially unresponsive hypoxemia. With inadequate pulmonary perfusion, neonates are at risk for developing refractory hypoxemia, respiratory distress, and acidosis.”
Robin Steinhorn, MD

16. Cardiac Complications
Persistent pulmonary hypertension
Normal Circulation

17. PPHN
3 types:
Result of abnormally constricted pulmonary vasculature due to lung parenchymal diseases leading to hypoxia (mec aspiration, pneumonia, RDS)
Idopathic (10-20% of all affected infants)
Pulmonary hypoplasia or structural defects (CDH, PROM)
How do you know its PPHN? Hyperoxia test (PO2 >150 on 100% is good) and pre/post difference >5% and fetal echo

18. How do you know it is PPHN?
Cyanosis
Tachypnea
Grunting
Pre/post ductal split
Hypoxia/hypercapnea/acidosis
Response to oxygen and iNO
Cardiac Ultrasound

19. Treatment for PPHN Oxygen therapy Inhaled Nitric Oxide
Normal Lab Values
Blood Pressure support if needed
Mechanical Ventilation
ECMO
Time!

20. PPHN and ECMO Can be V-A or V-V ECMO Typically a short run (3-5 days)
Survival rates greater than 68% as compared with 40% in infants treated with conventional non-ECMO therapy
Patient needs time for the pulmonary vasculature to relax and for the patient’s heart is able to pump blood to the lungs

21. Congenital Diaphragmatic Hernia
Occurs in 1 of every live births and accounts for 8% of all major congenital anomalies. Mortality rates are 25-60%....
The diaphragm initially develops as a septum between the heart and liver, progresses posterolaterally, and closes at the left Bochdalek foramen at approximately 8-10 weeks' gestation.

22. A severe CDH is believed to occur during the pseudoglandular stage of lung development. Weeks 7-17 and this is when pulmonary circulation develops.
Lung compression results in pulmonary hypoplasia (both lungs may be abnormal). Pulmonary hypoplasia is associated with fewer bronchial generations, alveoli, and arterial generations.

23. Left Sided Congenital Diaphragmatic Hernia

24. Left CDH

25. CDH and ECMO Typically VA ECMO
Can be a difficult cannulation due to small vessels and cardiac anatomy
Average run time hours and 50% of patients with a CDH are treated with ECMO
Patients are often decannulated and immediately repaired on the NICU
If patient is not repaired by 14 days-survival rates rapidly decline

26. ECMO and Respiratory Failure
Meconium Aspiration Syndrome
Sepsis
Pneumonia
Alveolar Capillary Dysplasia
****All have a component of PPHN******

27. Alveolar Capillary Dysplasia
Very rare lethal congenital anomaly
Failure of formation of the normal air-blood diffusion barrier in the newborn lung. Alveolar Capillary Dysplasia is usually associated with "misalignment" of the pulmonary veins.

28. Patient will not repond to mechanical ventilation, iNO or ECMO
75% of these patients will have other organs affected
Longest reported survival is 2 months post ECMO run

29. Questions??????