Neonatal Physiology
Teka Siebenaler RRT
Cardiopulmonary Services
University of Minnesota Amplatz Children’s Hospital
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
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• Most congenital malformations occur during
the 4th-8th weeks
• Anencephaly/Spina Bifida
• Extremity deformities
• Diaphragmatic hernia (85% on the left side)
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
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
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.
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……
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, 155-165 (1995).
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
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.
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
“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
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
• “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
Cardiac Complications
• Persistent pulmonary
hypertension
• Normal Circulation
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 it is PPHN?
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Cyanosis
Tachypnea
Grunting
Pre/post ductal split
Hypoxia/hypercapnea/acidosis
Response to oxygen and iNO
Cardiac Ultrasound
Treatment for PPHN
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Oxygen therapy
Inhaled Nitric Oxide
Normal Lab Values
Blood Pressure support if needed
Mechanical Ventilation
ECMO
Time!
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 nonECMO therapy
• Patient needs time for the pulmonary
vasculature to relax and for the patient’s heart
is able to pump blood to the lungs
Congenital Diaphragmatic Hernia
• Occurs in 1 of every 2000-3000 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.
• 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.
Left Sided Congenital Diaphragmatic
Hernia
Left CDH
CDH and ECMO
• Typically VA ECMO
• Can be a difficult cannulation due to small
vessels and cardiac anatomy
• Average run time 181-197 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
ECMO and Respiratory Failure
• Meconium Aspiration Syndrome
• Sepsis
• Pneumonia
• Alveolar Capillary Dysplasia
****All have a component of PPHN******
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.
• 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
• Questions??????