Download stages of lung development

RSPT 2353 Neonatal
Pediatric Respiratory Care
STAGES OF FETAL LUNG
DEVELOPMENT
Objectives
• Discuss anatomy and physiology of fetal
circulation
• Compare and contrast fetal circulation to infant
circulation
• Define specialized structures of fetal circulation
• Discuss normal cardiac circulation (infant and
adult)
• Discuss cardiac defects
Stages of Lung Development
• Embroynal
26 -52 days
development of trachea and
major bronchi
• Pseudoglandular 52 daysweek 16 Development of
remaining conducting airways
• Canalicular week 17- week
28 Development of vascular
bed and acinus
• Saccular week 29 - week36
Increased complexity of
saccules
• Alveolar week 36 – Term 40
weeks Development of
alveoli sufficient to sustain gas
exchange
• Post Term > 41 weeks
Factors That Limit Normal Lung
Growth
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Hyperoxia
Cigarette smoking
Diaphragmatic hernia
Nutritional deprivation
Problems with
amniotic fluid
• Hormonal imbalances
• Drug abuse
• ETOH abuse
Surfactant
Surfactant Production
• Type II pneumocytes produces surfactant in the alveoli
• Alveoli must be formed to make surfactant
• < 33 weeks the alveoli are insufficient to form surfactant
Surfactant Function
• Decreases surface tension
• Maintains compliance and FRC
Tests for Adequate Surfactant Production
• Shake test
• LS Ratio test
• Amniocentisis
Fetal Lung Fluid
What happens to all that fluid that has been
filling the lungs for 9 months?
Fetal lung fluid is evacuated from the
newborns lungs via:
• Absorption- lymphatic system
• Clearance- pulmonary capillaries
• Contraction – birth canal, birth squeeze
Placenta
• Provides Gas
exchange & waste
removal.
• Supplies nutrient to
the fetus
• Placenta is the lung
for the fetus
Fetal Circulation
Fetal Circulation
• Cardiac development occurs between the 4th and 7th week of
gestation.
• The foramen ovale is a one-way flap in the atrial septal wall.
Blood bypasses the lungs because of the high right sided
pressures.
• The ductus arteriosis is a connection between the PA and the
Aorta - shunts blood away from the lungs.
• Fetal PVR is high, within 24hr after birth, PVR should fall to 1/2
SVR
• The ductus should close within 10-24 hrs after birth.
• Fetal CO is very high, therefore tissue hypoxia usually does not
occur, even when oxygen saturations are 60-70%
Fetal Circulation
• Low pressure circuit
• Gas Exchange occurs in the Placenta
• Fetal lungs do not participate in gas exchange
Roughly 10% of blood goes to lungs for
tissue development
Fetal Oxygenation
• Best-oxygenated blood
–Right atrium, Foramen ovale, Left
atrium
–Supplies the upper body,
specifically the brain
• Less-oxygenated blood supplies the rest of
the body via the Ductus Arteriosus
How Does Blood Bypass the
Lungs?
• High PVR in utero creates a desireable
R to L shunting
• Foramen Ovale
• Ductus Arteriosus
Question: Why is a R to L shunt desirable
in – utero ?
PaO2 in Fetal Circulation
• Large gradient between mom’s PaO2 and fetal
PaO2
– Promotes the transfer of O2
– Higher Hgb concentration in fetus
– Fetal Hgb
• Greater affinity for O2
• Higher SaO2 for the same PaO2 than adult Hgb
• Left shift of fetal oxyhemoglobin dissociation Curve
Conversion from Fetal to
Infant Circulation
• Cord is clamped - closing low pressure system
• SVR increases
• Lungs inflate w/ air (due to several factors, one of which is
atmospheric pressure changes)
• PVR decreases
– Lung inflation (only slightly changes it)
– Changes in O2, CO2 and pH
Conversion from Fetal to Infant
Circulation
• R to L shunting decreases
Increased pressures in LA results in:
–Closing of Foramen Ovale
–Closing of Ductus Arteriosus
• PaO2 changes
• Prostaglandin level changes
Overview of Conversion
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Umbilical cord is clamped
Loose placenta
Closure of ductus venosus
Blood is transported to liver and portal system
Loss of placenta also leads to first breath
Lungs expand and fluid is expelled
Decreased pulmonary vascular resistance
Increased systemic vascular resistance
Overview of Conversion
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Increased pressure in left atrium
Closure of foramen ovale
Loss of placenta
Increased systemic resistance
Pressure in right atrium decreased
Change from right to left shunting to left to right blood
flow
• Increased O2 levels in pulmonary circulation
• Closure of the ductus arteriosus
Fetal vs. Infant Circulation
Fetal
• Low pressure system
• Right to left shunting
• Lungs non-functional
• Increased pulmonary
resistance
• Decreased systemic
resistance
Infant
• High pressure system
• Left to right blood flow
• Lungs functional
• Decreased pulmonary
resistance
• Increased systemic
resistance
NORMAL HEART
Antenatal Assessment and
High-Risk Delivery
Fetal and Newborn Assessment
in the L and D
Objectives
At the completion of this lecture the student
will:
• Be able to discuss relevant points
concerning Antenatal Assessment
• Be able to ID the L and D cases which
may present a high-risk delivery
• Know the parameters on which to base
antenatal/perinatal assessments
Antenatal Assessment and
High- Risk Delivery
Indications of a High-Risk Delivery:
• Incompetent Cervix
• Toxic habits in Pregnancy
• Hypertension and Diabetes Mellitus
• Preclampsia
• Severe Preclampsia
• Infectious Disease
• Multiple birth
Antenatal Assessment and
High- Risk Delivery
Indications of a High-Risk Delivery:
•Long cord, Nuchal cord, cord knots
•Placenta Abruption
•Placenta Previa
•Disorders of aminiotoic fluid
•Abnormalities of Umbilical cord
•Oligohydraminos, Polyhydraminos
Antenatal Assessment
Antenatal = Around birth time, usually considered
prior to L and D
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Ultrasound
Amniocentesis
Shake test
Fetal Biophysical profile
Preterm Pregnancy
Less than 37 weeks
Indications of High-Risk Delivery
• Magnesium sulfate is given to stop
contractions
• Blood gas with Ph less than 7.15 can be
an indication of asphyxia
• Post-term Labor
• Pregnancy continued beyond 42 weeks
• Pre-term less than 33 weeks ges age
• Lack of prenatal care
Neonatal Assessment and
Resuscitation
Neonatal Resuscitation Considerations While
Assessing the Patient
• Maintain warmth
• Cold stress increases oxygen consumption
• Maintain an airway
• Placing a small roll under the shoulders will
correct the position
• Suction the airway
• Stimulation
• Obtain vascular access
• Provide resuscitative drugs PRN
Assessing the Neonate
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Vital signs
Apgar score
Neonatal resuscitation
When is Positive pressure ventilation
Indicated?
• When is Intubation Indicated?
• When are chest compressions indicated?
• When are Medications indicated?
Resuscitation of New Born
Supportive
Care
Routine Care
Provide warmth
Clear Airway
Dry
Breathing
Birth
Clear of Meconium?
Breathing or Crying?
Good Muscle Tone?
Color Pink ?
Term gestation?
Approximate Time
30 sec
Ventilating
HR >100
Pink
Yes
Provide warmth
Position
Clear Airway
NO (as necessary)
Dry, stimulate
Reposition,
Give O2
Ongoing care
Evaluate:
Respirations
Heart rate
Color
HR >100
Pink
PPV
Apnea or
HR<100
30 sec
HR < 60
PPV
Chest Compressions
Administer
Epinephrine
HR <60
HR >60
Time
30 sec
Assessment of Neonatal Patient
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Vital signs
Skin
Mottling
Irregular areas of dusky skin alternating with pale skin
Capillary refill
Respiratory Function
Assessment
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Apnea
Periodic breathing
Grunting
Nasal flaring
Retractions
Silverman score
Stridor
X-ray
Nasal Flaring and Sub-sternal
Retractions
Nasal Flaring and Substernal
Retractions
Silverman score
Cardiac Assessment
Heart, how is it working?
• HR, RR,BP
• Cardiac murmur – PDA
• Weak pulse Coarctation of Aorta
• Hypo plastic Left heart syndrome
• Adequate MBP= gestational age + 5
Abdomen
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Diaphramatic hernia
Omphalocele
Gastroschisis
Umblical cord
A single umblical artery
Congenital anomalies
Thin cord
Thick cord-diabetics
Head and Neck Assessment
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Microstomia-small mouth
Micrognathia-small jaw
T-E fistula
Pierre robin syndrome
Choanal Artesia
Macroglossia
Assess an Infant’s Cry
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Loud and vigorous- healthy infant
Grunting cry- RDS
Hoarse cry-laryngeal edema
Cat like cry- chromosme abnormality
High-pitched cry- neurological deficit
Pediatric Assessment
Pedi assessment is focused on different
indications:
• History and assessment
• Chief complaint
• Medical history
• Family history
• Environmental history
Elements of Pediatric Physical
Assessment
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Assessment
Inspection
RR
Retractions
AP diameter
Digital clubbing
Palpation
Tactile fremitus
Position of trachea
Percussion
Auscultation