Maternal- Fetal Respiratory Physiology and Pathophysiology

Obstetrical & Neonatal
Respiratory Issues
Mike Clark, M.D., M.B.A., M.S.
Obstetrics & Gynecology
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Maternal Topics
I. Normal Anatomical and Physiologic Respiratory Changes in
II. Maternal Respiratory Disorders in Pregnancy
A. Pulmonary Edema associated with Preeclampsia
B. Pulmonary Embolism in Pregnancy
C. Amniotic Fluid Embolism
D. Asthma in Pregnancy
E. Pneumonia in Pregnancy
F. Tuberculosis in Pregnancy
G. Idiopathic Pulmonary Fibrosis
H. Kyphoscoliosis
I. Sarcoidosis
J. Lung Cancer
Fetal and Neonatal Topics
III. Fetal and Neonatal Respiratory Problems
A. Fetal Distress diagnosed by Fetal Monitoring
B. Viability
C. Amniotic Fluid Testing for Lung Maturation
D. Respiratory Distress Syndrome of the Newborn
E. Meconium Aspiration
F. Hypoplastic Lungs
G. Asphyxiating Thoracic Dystrophy
H. Patent Ductus Arteriosus
I. Patent Foramen Ovale (Atrial Septal Defect)
J. Tetralogy of Fallot
K. Anomalous Venous Return
L. Transposition of the Great Vessels
Normal physiologic changes during pregnancy
Major hemodynamic alterations occur during
pregnancy, labor, delivery and the postpartum
period. These changes begin to take place
during the first 5 to 8 weeks of pregnancy and
reach their peak late in the second trimester.
In patients with preexisting cardiac disease,
cardiac decompensation often coincides with
this peak.
Uterine Changes in Pregnancy
Enlarging uterus decreases chest wall compliance
Figure 28.15
36 week fetus
Ribs and sternum
pushed out. Subcostal
angle widened.
Diaphragm pushed
Anatomical Respiratory Changes in Pregnancy (1)
• Capillary engorgement of the nasal and oropharyngeal
mucosae and larynx begins early in the first trimester and
increase progressively throughout pregnancy.
• Nasal breathing commonly becomes difficult, and epistaxis
may occur because of nasal mucosal engorgement.
Anatomical Respiratory Changes in Pregnancy (2)
• Airway conductance increases, indicating dilation of
the large airways below the larynx, mainly due to
direct effects of progesterone, cortisone, and
relaxin and possibly enhanced beta-adrenergic
activity induced by progesterone. However, FEV1
and FEV1/FVC does not change.
Flow = ΔP/R
R (Resistance) = 8ηL/πr4
r is the radius raised to the fourth power– thus dilation increases flow
Anatomical Respiratory Changes in Pregnancy (3)
• The thoracic cage increases in circumference by 5
to 7 cm during pregnancy because of increases in
both the anteroposterior and transverse
• Flaring of the ribs, which begins at the end of the
first trimester, results in an increase in the
subcostal angle from 68.5 degree to 103.5 degree
at term.
• The pregnant female becomes more barrel
• Lung compliance is decreased as the uterus
pushes up on the diaphragm
Jugular notch
Clavicular notch
Sternal angle
Intercostal spaces
Costal cartilage
Costal margin
Copyright © 2010 Pearson Education, Inc.
Floating ribs (11, 12)
• Pregnancy places a great demand on the
physiology of the maternal body – many
organ-systems are changed and stressed.
• Many preexisting medical conditions in
the female are exacerbated during
Physiological Changes
• Major hemodynamic alterations occur during
pregnancy, labor, and delivery and the
postpartum period. These changes begin to
take place during the first 5 to 8 weeks of
pregnancy and reach their peak late in the
second trimester. In patients with preexisting
respiratory disease, cardiac disease,
decompensation often coincides with this
Note that blood pressure generally goes down in pregnancy due to decreased vascular
Physiological Respiratory Changes in Pregnancy
Oxygen consumption:
• Several authors have reported that oxygen
consumption increases by 30% to 40% during
pregnancy, the progressive rise is due primary to
the metabolic needs of the fetus, uterus, and
placenta and secondarily to increased cardiac and
respiratory work. Carbon dioxide production shows
changes similar to those of oxygen consumption
• Minute ventilation increases by 45% during pregnancy, with increase
evident early in the first trimester, as a *result of increase in tidal volume.
Although respiratory rate declines slightly during mid gestation, it is
essentially unaltered during pregnancy. Some females complain of
*dyspnea as a result of no change in the respiratory rate.
• The increased ventilation during pregnancy results from hormonal
changes (particularly progesterone elevation) and increased carbon
dioxide production. Though there is increased CO2 production – the
increased minute ventilation actually drops the PaCO2 from 40 Hg in the
non-pregnant state to 32 – 34 Hg in the pregnant state.
• The central chemoreceptors become more sensitive to carbon dioxide
levels due to progesterone level increases.
• * Discussed on next slide
Physiologic Dyspnea
• The increased minute ventilation in pregnancy is
often perceived as a shortness in breath.
• Shortness of breath at rest or with mild exertion
is so common that it is often referred to a
“physiologic dyspnea.”
• About 75% of pregnant women have exertional
dyspnea by 30 weeks of gestation
• The proposed causes of dyspnea are increased
drive to breath and the load imposed by the
enlarging uterus
• Other factors are increased pulmonary blood
volume, anemia, and nasal congestion
The tidal volume expansion is a result of a
decrease in Expiratory Reserve Volume
Progesterone and Breathing
• Progesterone is a smooth muscle relaxant – thus it can dilate the
tracheal-bronchial tree – providing increased airway
• Progesterone is a known stimulant of respiration and respiratory
drive, and its levels rise gradually rise from approximately 25
ng/mL at six weeks to 150 ng/mL at term
• The respiratory centers in the brain appear to change their
homeostatic set points during pregnancy; this is probably a
function of the increasing levels of progesterone .
• The mechanism is thought to involve an increasing sensitivity of
the medulla (central chemoreceptor) to carbon dioxide such
that increases in PaCO2 elicit an exaggerated respiratory effort ,
although a direct effect of progesterone on the respiratory
center (DRG) cannot be excluded.
Maternal Respiratory Complications of
A. Pulmonary Edema associated with Preeclampsia
B. Pulmonary Embolism in Pregnancy
C. Amniotic Fluid Embolism
D. Asthma in Pregnancy
E. Pneumonia in Pregnancy
F. Tuberculosis in Pregnancy
G. Idiopathic Pulmonary Fibrosis
H. Kyphoscoliosis
I. Sarcoidosis
J. Lung Cancer
• A pregnancy-specific syndrome characterized by
new-onset hypertension and proteinuria, occurring
usually after 20 weeks' gestation – most commonly
after 34 weeks
• Diagnosis – BP of 140/90 mm Hg or greater after 20 weeks' gestation
in a women with previously normal blood pressure and
with proteinuria (>0.3 g protein in 24-h urine specimen).
– Eclampsia is defined as seizures that cannot be
attributable to other causes in a woman with
Preeclampsia can be mild, moderate or severe
Severe preeclampsia is defined as the presence of one of the
following symptoms or signs in the presence of
1. Systolic BP of 160 mm Hg or higher or diastolic BP of 110
mm Hg or higher on 2 occasions at least 6 hours apart
2. Proteinuria of more than 5 g in 24-hour period
3. Pulmonary edema
4. Oliguria (<400 mL in 24 h)
5. Persistent headaches
6. Epigastric pain and/or impaired liver function
7. Thrombocytopenia
8. Intrauterine growth restriction
Pulmonary Embolism in Pregnancy
• Pregnancy 5X increases the risk for Deep Venous
Thrombosis (DVT) and a subsequent PE
• Occurs in 1-5/1,000 deliveries
• Leading cause of maternal death
• DVT most common in left leg
• Clotting factor V seems to be most involved
• Difficult to diagnose since many pregnant patients
have lower extremity edema and dyspnea
• Perfusion scans generally used for diagnosis
• Primary Treatment is Heparin (Coumadin cannot be
used in pregnancy) Coumadin can cross the placenta
• Thrombolytic agents can be used but cautiously due
to increased bleeding
The Food and Drug Administration (FDA) created the
following rating system in 1979 to categorize the
potential risk to the fetus for a given drug.
Category A: Controlled human studies have
demonstrated no fetal risk
Category B: Animal studies indicate no fetal risk, but
no human studies OR adverse effects in animals , but
not in well- controlled human studies
Category C: No adequate human or animal studies,
OR adverse fetal effects in animal studies, but no
available human data.
Category D: Evidence of fetal risk, but benefits
outweigh risks.
Category X: Evidence of fetal risk. Risks outweigh any
Amniotic Fluid Embolus (1)
• Occurs in 1/ 8,000 – 1/ 80,000 Pregnancies
• Accounts for 10% of maternal deaths
• Major risk factors are maternal age and
• Lesser risk factors are amniotomy, cesarean
section, intrauterine fetal monitoring, induction
of labor, term pregnancy with an IUD in place
• Most occur during labor – but can happen during
any trimester, usually in the setting of uterine
manipulation or trauma
Amniotic Fluid Embolus (2)
Classic presenting signs and symptoms are;
1. Severe dyspnea and tachypnea
2. Pulmonary Edema
3. Tachycardia with cardiovascular collapse
4. Cyanosis
5. Disseminated Intravascular Coagulation (DIC)
The diagnosis is made clinically- may aspirate from right
• Respiratory treatment is supportive – maximize
oxygenation through mechanical ventilation with high
oxygen concentrations using low tidal volumes
• Cardiovascular treatment is to stabilize circulation using
inotropic agents and vasoactive agents. The goal is to
maximize cardiac output with the lowest possible left
ventricular end diastolic pressures
Asthma in Pregnancy (1)
• The prevalence of asthma in pregnancy is on the rise
• In the world the asthma incidence in pregnancy ranges
from 3.7 % - 13% (lower rate in U.S. and higher rate in the
• It is well known and widely reported that one third of
women experience worsening of asthma during pregnancy,
one third improve, and one third remain the same.
• Between 25 and 32 weeks gestation, there was a significant
increase in asthma symptoms for women that reported
asthma worsening – whereas those reporting asthma
improving – there was a decrease in wheezing
• In all women there was a significant improvement in
symptoms between 37 and 40 weeks
Asthma in Pregnancy (2)
• The improvement of some pregnant patients with
asthma is most likely due to increased levels of
cortisol and progesterone during pregnancy
• An interesting finding is that pregnant females
carrying boys have less asthma symptoms than
those with girls
• Another interesting finding is smoking is more
common among pregnant females with asthma
those without the condition
• Women having an exacerbation of their asthma
during pregnancy had a higher incidence of Low
Birth Weight babies– but not of premature babies
• Inhaled corticosteroids have proven to be the most
effective management of asthma in pregnancy
Sarcoidosis in Pregnancy
Sarcoidosis is a systemic
granulomatous inflammatory
disease characterized by
caseating granulomas (small
inflammatory nodules). Its
cause is unknown. Granulomas
most often appear in the lungs
or the lymph nodes, but
virtually any organ can be
affected. Normally the onset is
gradual. Sarcoidosis may be
asymptomatic or chronic and
may cause death.
Pneumonia in Pregnancy
• The most common cause of fatal non-obstetric infection
• Can have adverse consequences for both the mother and
her fetus, with certain infections (particularly viral and
fungal) assuming greater virulence and mortality than in
non-pregnant women of similar age
• The pathogens for Community-Acquired Pneumonia are
similar in pregnant and non-pregnant patients, with
Streptococcus pneumoniae, Haemophilus influenza,
Mycoplasma pneumoniae, Legionella spp., Chlamydophila
pneumoniae, and influenza A accounting for the majority
of cases
• However, reduction in cell mediated immunity particularly
in the third trimester increases the risk for more severe
pneumonia infections with organisms such as herpes,
varicella and coccidiomycosis
Pneumonia in Pregnancy
• The incidence of pneumonia in pregnancy is widely varied among studies in
different regions of the world – Finland has one of the higher rates and the
U.S. one of the lower rates
• The incidence of pneumonia in the U. S. has declined with the highest rate
being found in the large urban hospitals
• The onset of pneumonia can be at any time during gestation – with the
mean gestational age being 24 – 31 weeks.
• Major risk factors for pneumonia in pregnancy are anemia and history of
asthma, use of tocolytic (labor stopping) agents, cigarette smoking and drug
• Viral and fungal pneumonia bear more significance in pregnancy than the
bacterial pneumonias
• Pregnancies having a pneumonia complication have an increased chance
of preterm delivery and small for gestational age babies
Pregnancy changes predisposing to an increased incidence and
Mortality from Pneumonia
Immunologic changes
• Reduced lymphocyte proliferative response
• Delayed cell-mediated cytotoxicity
• Reduced number of T-helper cells
• Reduced lymphokine response to alloantigens
Physiologic changes
• Increase in Oxygen Consumption
• Increase in lung water
• Elevation of the diaphragm
• Aspiration more likely in labor and delivery
Coexisting illnesses
• Smoking
• Anemia
• Asthma
• Cystic Fibrosis
• Illicit Drug Use
• Immunosuppressive illness and therapy
• Placental Abruption
Pneumonia in Pregnancy
• The clinical presentation in pregnancy is not substantially
different from the non-pregnant presentation – fever, cough,
pleuritic chest pain, rigors, chills, and dyspnea
• Most women with pneumonia do not have multilobar
involvement – but when present does complicate the course of
• The Pneumonia Severity Index (PSI) is the most widely used tool
in the U.S. to determine if the patient needs inpatient care and
the need for the ICU.
• The PSI uses demographics (whether someone is older, and is
male or female), the coexistence of co-morbid illnesses, findings
on physical examination and vital signs, and essential laboratory
findings. This study demonstrated that patients could be
stratified into five risk categories, Risk Classes I-V, and that these
classes could be used to predict 30-day survival.
Pneumonia in Pregnancy
• Initial treatment is towards Streptococcus
pneumoniae, Haemophilus influenza, Mycoplasma
pneumoniae, Legionella spp., Chlamydophila
pneumoniae – in that these are the most common
• Antibiotics that are safe in pregnancy against
Community-Acquired Pneumonia are the penicillins,
cephalosporins and erythromycin. Clindamycin may
also be safe – but not adequately tested.
• The fluoroquinolones should not be used in pregnancy
Antibiotics not to use in Pregnancy
“unless absolutely necessary‘’
• Fluoroquinolones – due to risk of arthropathy,
malformations, and carcinogenic (Baloxin, Raxar)
• Chloramphenicol – can cause bone marrow
suppression in fetus and if given near term can
cause “gray baby syndrome” with gray facies,
flaccidity and cardiovascular collapse
• Tetracyclines – mother at risk for fulminant
hepatitis and staining of teeth in newborn along
with other dental abnormalities
• Sulfa drugs can cause fetal kernicterus
• Aminoglycosides – can cause fetal ototoxicity
• Vancomycin poses a risk to the fetus in terms of
nephrotoxicity and ototoxicity
The Food and Drug Administration (FDA) created the
following rating system in 1979 to categorize the
potential risk to the fetus for a given drug.
Category A: Controlled human studies have
demonstrated no fetal risk
Category B: Animal studies indicate no fetal risk, but
no human studies OR adverse effects in animals , but
not in well- controlled human studies
Category C: No adequate human or animal studies,
OR adverse fetal effects in animal studies, but no
available human data.
Category D: Evidence of fetal risk, but benefits
outweigh risks.
Category X: Evidence of fetal risk. Risks outweigh any
Viral Pneumonia in Pregnancy
• The most common viral organism causing pneumonia is
influenza A although other viral infections can also occur
• Pregnant women are at increased risk for both acquiring
influenza, and developing complications of the infection
• Historically, influenza in pregnancy has been associated
with a higher rate of morbidity and mortality (with the
mortality highest in the last 3 months of pregnancy)
• The clinical presentation is not altered by pregnancy
• Antibiotics should be given to prevent secondary
bacterial infections
• Some antiviral medications can be given in pregnancy –
such as Amantadine
Fungal Pneumonia in Pregnancy
• Fungal pneumonia in pregnancy is rare – and if
the women is healthy normally resolves without
• If the fungal infection becomes widely
disseminated – it carries a more serious
• Cryptococcus neoformans, Histoplasma
capsulatum, Sporothrix Schenckii, Blastomyces
dermatitis, and Coccidioides immitis are the most
common fungal organisms
• For disseminated disease or severe pneumonia
treatment with intravenous amphotericin B
(pregnancy category B) is recommended followed
by oral fluconazole post-partum.
Tuberculosis in Pregnancy
Caused by infection with
Mycobacterium tuberculosis
• Attacks mostly the lungs – but can attack other
• 1/3 of the world’s population now carries the TB
• Not all that are infected with TB show signs (active
TB) -many have a latent infection (asymptomatic)
Tuberculosis in Pregnancy
• Two millennia ago – the Greeks believed that pregnancy
made TB get better – thus women with TB were
encouraged to get pregnant
• This idea persisted until the 19th and 20th centuries when
the concept completely changed – pregnancy is bad for TB
• Currently – the concept is pregnancy does not alter the
course of TB
• Testing for TB in pregnancy is the same as in the nonpregnant patient – PPD, Chest X-ray and sputum cultures
• Treatment for TB is virtually the same as in the nonpregnant state – Isoniazid (INH) and Rifampin
Tuberculosis in Pregnancy
• INH does cross the placenta – but causes no
problems in the fetus – however it does have some
degree of hepatoxicity in the mother during
pregnancy – thus if therapy can be delayed till after
pregnancy – that it preferable
• Treatment can generally be delayed if the patient
has latent TB
• Breast feeding while taking TB medication is OK if
the mother does not have active TB – if the mother
has active TB – it could be transferred to the
newborn in cough droplets while breast feeding
• Congenital transplacental transmission of TB is rare
and occurs most commonly through hematogenous
infection via the umbilical vein in mothers who have
active TB of the placenta or genital tract
C= ∆V ⁄∆P Idiopathic Pulmonary Fibrosis in Pregnancy
• Not common in pregnancy due to a higher incidence in males and usually
occurs in women past childbearing age
• The pregnancy outcome depends on the severity of the disease at the
time of conception
• In all restrictive lung diseases in pregnancy – patients experience
breathing difficulties as pregnancy progresses since the expected
increase in tidal volume is limited by the restrictive physiology and the
much needed increase in minute ventilation is then achieved by an
increase in respiratory rate.
• Patients with severe IPF should avoid pregnancy
• Epidural anesthesia is advised to minimize the stress of labor
Kyphoscoliosis in Pregnancy
The severity of spinal curvature is measured by the
Cobb angle, which is the angle formed by the
intersection of perpendicular lines drawn superior to
the highest vertebrae and the inferior angle to
The lower vertebrae involved in the curvature.
When the angle is greater than 100°, the vital capacity is reduced by
Historically, patients with this condition were cautioned against
pregnancy. However, studies of patients with a Cobb angle greater
than 60° - show successful vaginal deliveries in most cases.
Anesthetic considerations in pregnant patients during labor and
delivery follow the same principles as other patients with restrictive
lung disease.
Sarcoidosis in Pregnancy
• Account for approximately 0.02 – 0.06% of
normal deliveries
• Has not been associated with an increased risk
of fetal or maternal complications
• The effect of pregnancy on the course of the
disease is variable
• Treatment during pregnancy is the same as in
the non-pregnant state
Lung Cancer in Pregnancy (1)
• Lung cancer has surpassed colon cancer as the leading cause
of death in women
• There is an increased incidence of smoking among adolescent
• Evaluation for lung malignancy is generally delayed in
pregnancy due to signs and symptoms being misinterpreted
as respiratory changes of pregnancy and apprehension by
doctors to do radiographic studies during pregnancy
• Unfortunately many cases of lung cancer in pregnancy are
diagnosed once the disease is locally advanced or metastatic.
• Of 19 reported cases of lung cancer in pregnancy, placental
metastasis were found in 8.
• While the infant outcome is usually healthy – two reports
describe metastasis to the infant- found months after delivery
Lung Cancer in Pregnancy (2)
• Treatment depends on histologic cell type, gestational age at
the time of diagnosis, clinical stage, possibility of surgery, and
desires of the patient.
• Generally surgery is delayed till the second trimester after
organogenesis has been completed unless the patient opts for a
therapeutic abortion
• Low dose radiation with the abdomen shielded has not
produced deleterious outcomes for the fetus
• Overall chemotherapy is best reserved for the second or third
trimester ,if necessary
• If amniocentesis shows fetal lung maturity, early delivery may
be an option – particularly for women that do not want to risk
fetal exposure to radiation and/or chemotherapy
Date of Delivery ?
Trimester One
Trimester Two
Trimester Three
LMP till end of 12th week
Start of 13th week till 28th week
28th week till delivery
Fetal Cardiorespiratory
Development and Anatomy
Human Developmental Terms
• Normal length of pregnancy from the date of fertilization till the time
of delivery is 266 days (38 weeks)
• Since most women do not know when they actually got pregnant – the
term gestation period was introduced.
• Normal Gestation Period – starts with the Last Menstrual Period
(approximately two weeks before the women got pregnant) – thus two
weeks is added so approximately 40 weeks
• Normal Range for date of delivery using date of fertilization is 36 to 40
• Normal Range for date of delivery using LMP is 37 – 42 weeks.
• Before 37 weeks – preterm or premature
• After 42 weeks – postterm or post dates.
Human Developmental Terms
• Human embryonic period includes the first 8
weeks since date of fertilization – known as date
of conception
• Human fetal period – which is week 9 after date
of fertilization till birth
• The perinatal period is from week 20 of
gestation (some suggest week 28) till 1- 4 weeks
after the baby is born
• The neonatal period is the first 28 days after
• Antepartum – before birth
• Postpartum (postnatal) – after birth
• Parturition - birth
Human Heart Development
Sinus Venosus
Bulbus Cordis
Arterial end
Arterial end
Venous end
(a) Day 20:
(b) Day 22: (c) Day 24: Heart
continues to
tubes begin
elongate and
to fuse.
starts to bend.
Venous end
vena cava
(d) Day 28: Bending
continues as ventricle
moves caudally and
atrium moves cranially.
(e) Day 35: Bending
is complete.
The heart begins to beat on approximately the 22nd day since fertilization (5th week of
gestation). However, it only beats 3.3 beats per day. By week 9 it beats at 155 – 195 beats
Per minute – then by week 12 it goes into the normal recognizable rate of 120 – 160 BPM.
Fetal heart sounds can be generally initially heard with the Doppler at 9 – 10 weeks of
gestation - definitely heard with Doppler at 12 weeks – with fetoscope at 20 weeks.
Figure 18.23
Human Lung Development
Lung Development is subsumed into stages
(1) Embryonic stage ( 3 – 6 weeks)
(2) Fetal Pseudoglandular stage (7 – 17 weeks)
(3) Fetal Canalicular stage (18 – 24 weeks)
(4) Fetal Saccular stage ( 24 weeks till birth)
(5) Postnatal Alveolar Stage
Embryonic Stage ( 3 – 6 weeks)
Day 26 Tracheoesophageal septum develops
Day 28 Buds of mainstem bronchi appear
Day 33 Buds of lung lobes appear
Day 41 Bronchopulmonary segments develop and
lungs become lobulated
Main Fact – Lung develops to the level
of the Bronchopulmonary Segments.
Fetal Pseudoglandular stage
(7 – 17 weeks)
The pseudoglandular stage takes place during the first
three to four months of gestation. During this time,
the conducting airways are being formed inside what
looks like a gland-like structure. Tall columnar
epithelium cells grow inside these airways and form a
lining. Tubular branching continues to develop
throughout this stage. As early as two months into the
pseudoglandular stage, all of the bronchi segments
are present.
Main Fact: All of the bronchi segments are present
Fetal Canalicular stage (18 – 24 weeks)
• The canalicular stage of fetal lung development starts at the 16th
week of gestation and lasts until the 24th week.
• Further branchings of the lungs occur – with the start of the
formation of bronchioles.
• The capillaries that will later on allow for future gas exchange
• Surrounding lung muscles begin to take shape.
Main Fact: Bronchioles start to develop as well as lung vasculature
Fetal Saccular stage
(24 weeks till birth)
• The saccular stage starts at the 24th week and lasts until
the fetus comes to term. Airway development begins to
spread out and form airspaces, or saccules, within the
chambers. The airspace expands as saccules continue to
• Terminal bronchioles divide into three or four respiratory
• Type II pneumocytes, important in surfactant synthesis,
begin to proliferate during this phase
Main Fact: Respiratory bronchioles form and surfactant
production begins
Postnatal Alveolar Stage
• Begins approximately 1 – 2 months after birth.
• Alveoli are developed
Day 26
Day 28
Day 33
Day 41
Tracheoesophageal septum develops
Buds of mainstem bronchi appear
Buds of lung lobes appear
Bronchopulmonary segments develop and
lungs become lobulated
Day 52 Pleural cavity closed
Week 8 Pseudoglandular phase occurs
Week 16 Canalicular phase occurs
Week 24 Saccular phase occurs and continues until
2 months
2 years
7 years
8 years
15 years
Alveolar development begins
Regular growth begins in place of septal formation
Lung architecture remodeled to adult pattern
Alveolization ends; no further alveoli are formed during growth
Normal growth complete
Future mouth
(future mouth)
(a) 4 weeks: anterior
superficial view of
the embryo’s head
(b) 5 weeks: left lateral view of the developing lower
respiratory passageway mucosae
Figure 22.28
Respiratory Bronchiole
Normal Values
Respiratory Rates
Average respiratory rates, by age:
Newborns: Average 44 breaths per minute
Infants: 40-60 breaths per minute
Preschool children: 20–30 breaths per minute
Older children: 16–25 breaths per minute
Tidal Volume 6 – 8 ml/Kg (Adult 7 ml/kg)
Dead Space 2 – 2.5 ml/Kg (Adult 2.0)
Average newborn weight – 2.5 – 4 kg
Surfactant is secreted by the type II pneumocytes
Surfactant is composed of Lipids and Proteins
Lipid Composition
Over 90% of the surfactant is lipids; around half (50%) of
which is dipalmitoylphosphatidylcholine (DPPC) also known as
lecithin. Phosphatidylcholine molecules form ~85% of the
lipid in surfactant. Phosphatidylglycerol (PG) forms about 11%
of the lipids in surfactant, it has unsaturated fatty acid chains
that fluidize the lipid monolayer at the interface. Neutral lipids
and cholesterol are also present. The components for these
lipids diffuse from the blood into type II alveolar cells where
they are assembled and packaged for secretion into secretory
organelles called lamellar bodies.
Protein composition of Surfactant (1)
• Proteins make up the remaining 10% of surfactant. Half of this
10% is plasma proteins but the rest is formed by the apoproteins
SP-A (SFTPA1), B (SFTPB), C (SFTPC) and D (SFTPD). (SP standing
for "surfactant protein".)
• SP-A and SP-D confer innate immunity as they have carbohydrate
recognition domains that allow them to coat bacteria and viruses
promoting phagocytosis by macrophages. SP-A is also thought to
be involved in a negative feedback mechanism to control the
production of surfactant.
Protein composition of Surfactant (2)
SP-B and SP-C are hydrophobic membrane
proteins that increase the rate that surfactant
spreads over the surface. SP-B and SP-C are
required for proper biophysical function of the
lung. Humans and animals born with a
congenital absence of SP-B suffer from
intractable respiratory failure whereas those
born lacking SP-C tend to develop progressive
interstitial pneumonitis.
Respiratory Membrane
Figure 22.9c ,d
Chemical Stimulants of Surfactant Production
• Numerous agents such as Beta adrenergic
agonists, corticosteroids, activators of protein
Kinase C, leukotrienes and purinergic agonists
stimulate secretion of surfactant.
• Respiratory Distress of the Newborn is due to
lack of surfactant particularly the PG.
Surfactant Production Timeline
Lecithin and Phosphatidyl Glycerol (PG) increase as
pregnancy proceeds while PI (other phosphatidyl choline molecules)
Fetal Lung Fluid
During fetal life the lungs are filled with fluid
produced by the lungs themselves. Additionally
some fluid in the fetal lungs is amniotic fluid.
Amniotic fluid is produced initially by the
placenta then after the kidneys start to function –
they take over the job.
Fetal Lung Fluid
• The degree to which lungs are expanded by liquid is
vital for normal lung development. Reductions in
the degree of lung distension cause lung growth
and development to cease, whereas increases in
lung distension accelerate the normal growth and
development of the lung. At the time of birth,
however, this liquid must be cleared to enable the
newborn infant to initiate air breathing.
• Removal of lung fluid before birth is due to (1)
decrease production of lung fluid (2) resorption of
fluid and (3) vaginal squeeze
Oligohydramnios due to urinary
track obstruction. Note the poor
lung development.
5. Blood travels
from the left ventricle
to the Aorta – which
gives blood to perfuse
the organs.
6. Blood then enters
the very low resistance
umbilical arteries on its
way back to the placenta.
1. Oxygenated blood comes
from the placenta traveling
to the fetus in the umbilical
2. The umbilical vein dumps
50% of blood into the inferior
Vena Cava – through the Ductus
Venosus and the other 50%
Of the blood enters the inferior
Margin of the liver
3. The blood from the inferior
Vena Cava enters into the right
4. Since the placenta is supplying
Oxygen to the fetus – much blood is
Shunted away from the lungs through
The Foramen Ovale and the Ductus
Figure 28.13a
In the fetal periodpulmonary vascular
resistance is high causing
right sided heart
pressure to be higher
than left sided heart
pressure. Thus blood
Is shunted from the
right side to the left
through the Foramen
Ovale and Ductus
The Foramen Ovale is an
opening between the
right atrium and left.
The Ductus Arteriosus is
an opening between the
pulmonary artery and
Respiratory Transition at Birth
• With birth the following sequence occurs:
• The placental circulation is removed and systemic vascular
resistance increases. This in turn, increases pressures in the left
ventricle and left atrium.
– The foramen will tend to close when pulmonary blood flow increases as
increased pulmonary flow will increase the blood volume entering the
left atrium and in so doing, increase left atrial pressure
– Increased left atrial pressure (more than right atrial pressure) results in
functional closure of the foramen ovale
• With the onset of ventilation, the oxygen tension in the alveolus and
in arterial blood increases.
– as alveolar PaO2 increases, pulmonary vasoconstriction relaxes and
pulmonary vascular resistance becomes less than systemic vascular
– increased oxygenation also results in constriction of the ductus
• The onset of ventilation also represents the onset of lung expansion
resulting in the straightening out of mechanically compressed vessels
• The end result of these changes is a closure of the fetal conduits that
carried blood by the lungs, but not into them
The Ductus Arteriosus
after closure becomes
the Ligamentum Arteriosum
The Foramen Ovale after
closure becomes the Fossa
Closure of the Ductus Venosus
becomes the Ligamentum
Figure 28.13b
Fetal and Neonatal Respiratory
A. Fetal Distress diagnosed by Fetal Monitoring
B. Viability
C. Amniotic Fluid Testing for Lung Maturation
D. Respiratory Distress Syndrome of the Newborn
E. Meconium Aspiration
F. Hypoplastic Lungs
G. Asphyxiating Thoracic Dystrophy
H. Patent Ductus Arteriosus
I. Patent Foramen Ovale (Atrial Septal Defect)
J. Tetralogy of Fallot
K. Anomalous Venous Return
L. Transposition of the Great Vessels
Fetal Monitoring
• Electronic fetal monitoring is used to evaluate
fetal well being and to assess labor progress.
• The main goal is to rule out fetal distress
• Fetal heart rate in association with uterine
contractions are measured
• Fetal heart rate and uterine contractions are
monitored using an external electronic device
until the amniotic fluid bag breaks – then
internal electronic monitoring can be
Normal Fetal Heart Rate –
120 – 160 BPM
Look For
1. Variability
2. Early Deceleration
(Head compression)
3. Variable Deceleration
(Cord Compression)
4. Late Deceleration
insufficiency )
APGAR (Postpartum analysis)
• The Apgar score was devised in 1952 by Dr.
Virginia Apgar as a simple and repeatable method
to quickly and summarily assess the health of
newborn children immediately after birth
• The Apgar score is determined by evaluating the
newborn baby on five simple criteria on a scale
from zero to two, then summing up the five
values thus obtained. The resulting Apgar score
ranges from zero to 10. The five criteria
(Appearance, Pulse, Grimace, Activity,
Respiration) are used as a mnemonic learning aid.
The test is generally done at one and five minutes
after birth, and may be repeated later if the score is
and remains low. Scores 3 and below are generally
regarded as critically low, 4 to 6 fairly low, and 7 to 10
generally normal.
• Viability is the ability of a fetus to survive outside the
• There is no sharp limit of development, age, or weight at
which a fetus automatically becomes viable.
• According to data years 2003-2005, 20 to 35 percent of
babies born at 23 weeks of gestation survive,
• while 50 to 70 percent of babies born at 24 to 25 weeks,
• and more than 90 percent born at 26 to 27 weeks, survive.
• It is rare for a baby weighing less than 500 gm to survive.
Legal Issues of Viability
• The Supreme Court stated in Roe v. Wade (1973) that viability
(i.e., the "interim point at which the fetus becomes ...
potentially able to live outside the mother's womb, albeit with
artificial aid") "is usually placed at about seven months (28
weeks) but may occur earlier, even at 24 weeks."The 28-week
definition became part of the "trimester framework" marking
the point at which the "compelling state interest" (under the
doctrine of strict scrutiny) in preserving potential life became
possibly controlling, permitting states to freely regulate and
even ban abortion after the 28th week. The subsequent
Planned Parenthood v. Casey (1992) modified the "trimester
framework," permitting the states to regulate abortion in
ways not posing an "undue burden" on the right of the
mother to an abortion at any point before and after viability;
on account of technological developments between 1973 and
1992, viability itself was legally dissociated from the hard line
of 28 weeks, leaving the point at which "undue burdens" were
permissible variable depending on the technology of the time
and the judgment of the state legislatures.
Amniotic Fluid Testing for Lung
Because the amount of amniotic fluid
and the concentration of material in it
may vary between pregnancies,
lecithin levels are generally expressed
as a ratio against sphingomyelin
(present in cell membranes) , a nonpulmonary lipid whose concentration is
relatively constant in amniotic fluid.
Other test for lung maturity
are also gaining acceptance
– but the L/S ratio remains
the standard for now.
Phosphatidylglycerol (PG) is a second
lipid that shows a similar time course: it
is undetectable in amniotic fluid until
lung maturity just prior to birth. The
RDS risk is about 2% if PG is present.
Surfactant Production Timeline
Lecithin and Phosphatidyl Glycerol (PG) increase as
pregnancy proceeds while PI (other phosphatidyl choline molecules)
Respiratory Distress Syndrome of the
• A syndrome caused in premature infants by
developmental insufficiency of surfactant
production and structural immaturity in the lungs. It
can also result from a genetic problem with the
production of surfactant associated proteins – in
particular surfactant protein B (SP-B).
• The characteristic pathology seen in babies who die
from RDS was the source of the name "hyaline
membrane disease". These waxy-appearing layers
line the collapsed tiny air sacs of the lung.
Normal Neonatal Lung
Air Bronchograms
RDS Lung
Note the opacities in the lung
fields indicating atelectasis
Respiratory Distress Syndrome
• RDS affects about 1% of newborn infants and
is the leading cause of death in preterm
infants. The incidence decreases with
advancing gestational age, from about 50% in
babies born at 26–28 weeks, to about 25% at
30–31 weeks. The syndrome is more frequent
in infants of diabetic mothers and in the
second born of premature twins.
Surfactant Production Timeline
Lecithin and Phosphatidyl Glycerol (PG) increase as
pregnancy proceeds while PI (other phosphatidyl choline molecules)
Respiratory Distress Syndrome
Clinical course
• Respiratory distress syndrome begins shortly after birth and is manifest by
tachypnea, tachycardia, chest wall retractions , expiratory grunting, flaring
of the nostrils and cyanosis during breathing efforts.
• As the disease progresses, the baby may develop ventilatory failure and
prolonged cessations of breathing.
• Whether treated or not, the clinical course for the acute disease lasts
about 2 to 3 days. During the first, the patient worsens and requires more
support. During the second the baby may be remarkably stable on
adequate support and resolution is noted during the third day, heralded
by a prompt diuresis.
• Despite huge advances in care, RDS remains the most common single
cause of death in the first month of life of the developed world.
• Complications include metabolic disorders (acidosis, low blood sugar),
patent ductus arteriosus, low blood pressure, chronic lung changes, and
intracranial hemorrhage.
Respiratory Distress Syndrome
• The main preventive measure is to deliver a baby
at term
• If, for some reason, the baby must be delivered
early an amniocentesis to determine lung
maturity (L/S ratio and PG) is ideally performed if
greater than 30 weeks of gestation
• Another preventive technique is to inject the
mother with glucocorticoids if less than 34 weeks
of gestation. Glucocorticoids accelerate
surfactant production.
Treatment for RDS
Treatment depends on the severity of the
• Mild Condition – O2, CPAP, Intravenous fluids to
stabilize blood sugar, electrolytes and blood
• Moderate to Severe– Endotracheal tube, PEEP,
exogenous surfactant through the endotracheal
• ECMO – not generally used even in severe cases
in that a neonate under 4.5 pounds (2 Kg) –
does not have blood vessels large enough to
adequately cannulate
Over Oxygenation
• Bronchopulmonary Dysplasia
• Retrolental Fibroplasia
Hyperoxia conditions
• Bronchopulmonary dysplasia (BPD; formerly Chronic Lung
Disease of Infancy) is a chronic lung disorder that is most
common among children who were born prematurely, with
low birth weights and who received prolonged mechanical
ventilation to treat respiratory distress syndrome. BPD is
clinically defined as oxygen dependence at 36 weeks'
postmenstrual age.
• BPD is characterized by inflammation and scarring in the
lungs. More specifically, the high pressures of oxygen delivery
result in necrotizing bronchiolitis and alveolar septal injury,
further compromising oxygenation of blood.
Hyperoxia conditions
• Retinopathy of prematurity (ROP), previously known
as retrolental fibroplasia (RLF), is an eye disease that
affects prematurely born babies. It is thought to be
caused by disorganized growth of retinal blood
vessels which may result in scarring and retinal
detachment. ROP can be mild and may resolve
spontaneously, but may lead to blindness in serious
cases. As such, all preterm babies are at risk for ROP,
and very low birth weight is an additional risk factor.
Both oxygen toxicity and relative hypoxia can
contribute to the development of ROP.
• Normally, maturation of the retina proceeds in-utero and at
term, the mature infant has fully vascularized retina. However,
in preterm infants, the retina is often not fully vascularized.
ROP occurs when the development of the retinal vasculature
is arrested and then proceeds abnormally. The key disease
element is fibrovascular proliferation. Associated with the
growth of these new vessels is fibrous tissue (scar tissue) that
may contract to cause retinal detachment. Supplemental
oxygen exposure, while a risk factor, is not the main risk factor
for development of this disease. Restricting supplemental
oxygen use does not necessarily reduce the rate of ROP, and
may raise the risk of other hypoxia-related systemic
Meconium Aspiration
• It occurs when meconium is present in their lungs
during or before delivery. Meconium is the first stool of
an infant, composed of materials ingested during the
time the infant spends in the uterus – which mainly are
substances in the amniotic fluid.
• Meconium is normally stored in the infant's intestines
until after birth, but sometimes (often in response to
fetal distress) it is expelled into the amniotic fluid prior
to birth, or during labor. If the baby then inhales the
contaminated fluid, respiratory problems may occur.
Meconium Signs and Symptoms
• The most obvious sign that meconium has been passed during or before
labor is the greenish or yellowish appearance of the amniotic fluid. The
infant's skin, umbilical cord, or nail beds may be stained green if the
meconium was passed a considerable amount of time before birth.
These symptoms alone do not necessarily indicate that the baby has
inhaled in the fluid by gasping in utero or after birth.
• After birth, rapid or labored breathing, cyanosis, slow heartbeat, a
barrel-shaped chest or low Apgar score are all signs of the syndrome.
Inhalation can be confirmed by one or more tests such as using a
stethoscope to listen for abnormal lung sounds (diffuse crackles and
rhonchi), performing blood gas tests to confirm a severe loss of lung
function, and using chest X-rays to look for patchy or streaked areas on
the lungs.
• Infants who have inhaled meconium may develop respiratory distress
syndrome often requiring ventilatory support. Complications of MAS
include pneumothorax and persistent pulmonary hypertension.
Cause of Meconium Staining
• Fetal Distress (not necessarily RDS) during labor
causes intestinal contractions, as well relaxation
of the anal sphincter, which allows meconium to
pass into the amniotic fluid and contaminate the
amniotic fluid.
• Meconium passage into the amniotic fluid occurs
in about 5-20 percent of all births and more
common in overdue births.
• Of the cases where meconium is found in the
amniotic fluid, meconium aspiration syndrome
develops less than 5 percent of the time.
• Amniotic fluid is normally clear, but becomes
greenish if it is tinted with meconium.
Treatment of Meconium Aspiration
• Amnioinfusion has not shown a benefit in treating MAS .
• Until recently it had been recommended that the throat and nose of the
baby be suctioned by the delivery attendant as soon as the head is
delivered. However, new studies have shown that this is not useful and the
revised Neonatal Resuscitation Guidelines published by the American
Academy of Pediatrics no longer recommend it.
• When meconium staining of the amniotic fluid is present and the baby is
born depressed, it is recommended by the guidelines that an individual
trained in neonatal intubation use a laryngoscope and endotracheal tube
to suction meconium from below the vocal cords.
• If the condition worsens to a point where treatments are not affecting the
newborn as they should, ECMO can be necessary to keep the infant alive.
• Surfaxin (Lucinactant) is used as a treatment of MAS.
Hypoplastic Lungs
Pulmonary hypoplasia is part of the
spectrum of malformations characterized
by incomplete development of lung tissue.
Chest radiograph of a
newborn with primary
pulmonary hypoplasia
of the right lung
showing shift of the
mediastinum to the
right hemithorax.
Chest radiograph of a
newborn with primary
pulmonary hypoplasia
of the right lung
showing shift of the
mediastinum to the
right hemithorax.
Hypoplastic Lungs
• The severity of the lesion depends on the
timing of the insult in relation to the stage of
lung development and the presence of other
anatomic anomalies.
• The hypoplastic lung consists of a carina, a
malformed bronchial stump, and absent or
poorly differentiated distal lung tissue.
• In more than 50% of these cases, coexisting
cardiac, GI, genitourinary, and skeletal
malformations are present, as well as
variations in the bronchopulmonary
Normal Tracheobronchial tree
Carina and Bronchial Stump
Hypoplastic Lung
• In order for adequate development of the lung
physical space in the fetal thoracic cavity must
be adequate, proper fluid levels in the lung
from lung secretions and amniotic fluid must
be present, proper genetics and proper kidney
• The kidney provides amniotic fluid and
provides proline which is important in lung
Hypoplastic Lung
• Hypoplastic Lung may be primary, but generally it is secondary,
manifested by a small fetal thoracic volume due to some
compression in the hemithorax.
• Some compression conditions are congenital diaphragmatic
hernia, pleural effusion with fetal hydrops, abdominal mass
lesions, malformation lesions (e.g.. Asphyxiating thoracic
• Other causes are prolonged oligohydramnios (low amniotic
fluid), early rupture of membranes, longer latent period
before delivery, decreased fetal breathing
• Congenital heart disease with poor pulmonary flow is also a
cause – conditions such a Tetralogy of Fallot, Hypoplastic Right
Heart, Pulmonary Artery Hypoplasia , Trisomies 18, 13 and 21
Asphyxiating Thoracic Dystrophy
Asphyxiating thoracic dystrophy, also known as
Jeune syndrome, is an inherited disorder of bone
growth characterized by a small chest, short ribs,
and shortened bones in the arms and legs.
Additional skeletal abnormalities can include
unusually shaped pelvic bones and extra fingers
and/or toes (polydactyly).
Infants with this condition are born with an
extremely narrow, bell-shaped chest that can
restrict the growth and expansion of the lungs.
Life-threatening problems with breathing often
result, and most people with asphyxiating thoracic
dystrophy live only into infancy or early childhood.
Incidence of 1 in 100,000 to 130,000 people
Extremely narrow – bell shaped chest
Patent Ductus Arteriosus
• A congenital disorder of the heart wherein a neonate's
ductus arteriosus fails to close after birth.
• Early symptoms are uncommon, but in the first year of
life include increased work of breathing and poor weight
gain. With age, the PDA may lead to congestive heart
failure if left uncorrected.
• A patent ductus arteriosus can be idiopathic, or
secondary to another condition. Some common
contributing factors in humans include:
• Preterm birth
• Congenital Rubella Syndrome
• Chromosomal abnormalities such as Down’s Syndrome
Patent Ductus Arteriosus
• At birth pulmonary vascular resistance decreases such that
the right heart and pulmonary vasculature becomes less
pressured than the left heart and aorta.
• Shortly after birth, the lungs release bradykinin to
constrict the smooth muscle wall of the DA and reduce
blood flow through the DA as it narrows and completely
closes, usually within the first few weeks of life. The main
stimulus to cause the release of bradykinin is an increased
oxygen content of the neonate’s blood.
• In normal newborns, the DA is substantially closed within
12-24 hours after birth, and is completely sealed after
three weeks.
• Withdrawal from maternal circulating prostaglandins also
contributes to ductal closure.
Patent Ductus Arteriosus
Some mild PDAs are asymptomatic but common
symptoms include:
respiratory problems
Shortness of breath
continuous machine-like murmur
Enlarged heart
Left subclavicular thrill
Bounding pulse
Widened pulse pressure
Patent Ductus Arteriosus (Diagnosis)
• PDA is usually diagnosed using non-invasive
techniques. Echocardiography and associated
Doppler studies are the primary methods of
detecting PDA.
• Electrocardiography (EKG )is not particularly
helpful as there are no specific rhythms or ECG
patterns which can be used to detect PDA.
• A chest X-ray may be taken. A small PDA most
often shows a normal sized heart and normal
blood flow to the lungs. A large PDA generally
shows an enlarged cardiac silhouette and
increased blood flow to the lungs.
Patent Ductus Arteriosus (Treatment)
• Neonates without adverse symptoms may simply be
monitored as outpatients, while symptomatic PDA can
be treated with both surgical and non-surgical
• Surgically, the DA may be closed by ligation, wherein
the DA is manually tied shut, or with intravascular coils
or plugs that leads to formation of a thrombus in the
• Because Prostaglandin E2 is responsible for keeping the
ductus patent, NSAIDS (inhibitors of prostaglandin
synthesis) such as indomethacin or a special form of
ibuprofen have been used to help close a PDA. This is
an especially viable alternative for premature infants.
Patent Foramen Ovale
A condition in which the fetal opening (Foramen Ovale)
between the right and left atria does properly close –
thus creating an Atrial Septal Defect (ASD).
Patent Foramen Ovale
• After birth when the pulmonary vascular resistance drops
– giving the left atrium more pressure than the right – a
left to right shunt of blood forms
• This extra blood from the left atrium may cause a volume
overload of both the right atrium and the right ventricle,
which if left untreated, can result in enlargement of the
right side of the heart and ultimately heart failure.
• The right ventricle will have to push out more blood than
the left ventricle due to the left-to-right shunt. This
constant overload of the right side of the heart will cause
an overload of the entire pulmonary vasculature.
Eventually the pulmonary vasculature will develop
pulmonary hypertension to try to divert the extra blood
volume away from the lungs.
Patent Foramen Ovale (ASD)
• There are different types of Atrial Septal DefectsPatent Foramen Ovale is the common type
• As a group, atrial septal defects are detected in 1
child per 1500 live births. PFO are quite common
(appearing in 10 - 20% of adults) but
asymptomatic and therefore undiagnosed.
• ASDs make up 30 to 40% of all congenital heart
disease that is seen in adults.
• The ostium secundum atrial septal defect
accounts for 7% of all congenital heart lesions.
This lesion shows a female preponderance, with a
male : female ratio of 1:2.
Patent Foramen Ovale (ASD)
• Most individuals with a significant ASD are
diagnosed in utero or in early childhood with the
use of ultrasonography or auscultation of the
heart sounds during physical examination
• Once someone is found to have an atrial septal
defect, a determination of whether it should be
corrected has to be made.
• Surgical mortality due to closure of an ASD is
lowest when the procedure is performed prior to
the development of significant pulmonary
hypertension. The lowest mortality rates are
achieved in individuals with a pulmonary artery
systolic pressure of less than *40 mmHg.
Aortic Pressure
Pulmonary Artery Wedge Pressure
4 -12 mm Hg (indirect measurement
Of Left Atrial Pressure
PAP 15-25 mmHg/5-15 mmHg
LAP 6 – 12 mmHg
LVP 120/0- 8 mm Hg
RVP 15 – 25 mm Hg/0 -8 mmHg
Tetralogy of Fallot
A congenital heart defect which is classically
understood to involve four anatomical
abnormalities (although only three of them
are always present). It is the most common
cyanotic heart defect, and the most common
cause of blue baby syndrome.
A. Pulmonary Stenosis – the major cause of the
malformation, with the other associated
malformations acting as a compensatory
mechanism to the pulmonic stenosis. The degree
of stenosis varies between individuals with TOF,
and is the primary determinant of symptoms and
B. Overriding Aorta - An aortic valve with
biventricular connection, that is, it is situated
above the ventricular septal defect and
connected to both the right and the left ventricle.
The degree to which the aorta is attached to the
right ventricle is referred to as its degree of
"override“ – range from 5 – 95%
C. Ventricular Septal Defect - A hole between the
two bottom chambers (ventricles) of the heart.
The defect is centered around the most superior
aspect of the ventricular septum (the outlet
septum), and in the majority of cases is single and
large. In some cases thickening of the septum
(septal hypertrophy) can narrow the margins of
the defect .
D. Right Ventricular Hypertrophy - The right
ventricle is more muscular than normal. The right
ventricular wall increases in size to deal with the
increased obstruction to the right outflow tract
(Pulmonic Stenosis) . This feature is now generally
agreed to be a secondary anomaly, as the level of
hypertrophy generally increases with age
1. Overriding Aorta – notice
how the aorta is shifted
more rightward –
allowing some blood
from the right ventricle to
2. Ventricular Septal Defect
4. Right Ventricular Hypertrophy 3. Pulmonic Stenosis
Additional Anomalies can sometimes
occur in Tetralogy of Fallot
• stenosis of the left pulmonary artery , in 40% of
• a bicuspid pulmonary valve, in 40% of patients
• Right sided aortic arch, in 25% of patients
• Coronary artery anomalies, in 10% of patients
• a patent foramen ovale or atrial septal defect, in
which case the syndrome is sometimes called a
pentalogy of Fallot
• partially or totally anomalous pulmonary venous
return (discussed in later PowerPoint Slide)
• forked ribs and scoliosis
Tetralogy of Fallot results in low oxygenation
of blood due to the mixing of oxygenated and
deoxygenated blood in the left ventricle via
the VSD and preferential flow of the mixed
blood from both ventricles through the aorta
because of the obstruction to flow through
the pulmonary valve. This is known as a rightto- left shunt. The primary symptom is low
blood oxygen saturation with or without
cyanosis from birth or developing in the first
year of life.
Main Treatment - Surgery
Total repair of Tetralogy of Fallot initially carried a
high mortality risk. This risk has gone down
steadily over the years. Surgery is now often
carried out in infants one year of age or younger
with less than 5% perioperative mortality. The
open-heart surgery is designed (1) to relieve the
right ventricular outflow tract stenosis by careful
resection of muscle and (2) to repair the VSD.
• Untreated, tetralogy of Fallot rapidly results in
progressive right ventricular hypertrophy. This
progresses to heart failure (dilated
cardiomyopathy) which begins in the right heart
and often leads to left heart failure.
• Actuarial survival for untreated tetralogy of Fallot
is approximately 75% after the first year of life,
60% by four years, 30% by ten years, and 5% by
forty years.
• Patients who have undergone total surgical repair
of tetralogy of Fallot have improved
hemodynamics and often have good to excellent
cardiac function.
Anomalous Pulmonary Venous Return
• A Partial anomalous pulmonary venous
connection is a congenital defect where right
atrium is the point of return for the blood
from some (but not all) of the pulmonary
• A Total anomalous pulmonary venous
connection is a rare cyanotic congenital heart
defect in which all four pulmonary veins are
malpositioned and make anomalous
connections to the systemic venous
Only Right upper pulmonary vein
Entering the superior Vena Cava
Partial Anomalous Pulmonary Venous Return
Transposition of the Great Vessels
• Transposition of the great vessels is a group of
congenital heart defects involving an abnormal
spatial arrangement of any of the primary blood
vessels: superior and/or inferior vena cava,
pulmonary artery, pulmonary veins, and aorta.
• Transposition of the great arteries is a subcategory of Transposition of the Great Vessels in
which the right ventricle empties into the aorta
and the left ventricle empties into the pulmonary
Transposition of the Great Vessels
(Transposition of the Great Arteries)
Transposition of the Great Vessels
Factors in the mother that may increase the risk of
this condition include:
Age over 40
Poor nutrition during pregnancy (prenatal nutrition)
Rubella or other viral illness during pregnancy
• In many cases, TGV is accompanied by other heart
defects, the most common type being intracardiac
shunts such as atrial septal defect, ventricular septal
defect , and patent ductus arteriosus. Stenosis, or
other defects, of valves and/or vessels may also be
Treatment for Transposition of the
Great Vessels
• Immediate IV prostaglandin infusion to keep the
ductus arteriosus open which allows some
mixing of the two blood circulations.
• A balloon atrial septostomy may be needed to
create a large hole in the atrial septum to allow
blood to mix.
• A surgery called an arterial switch procedure is
used to permanently correct the problem within
the baby's first week of life. This surgery switches
the great arteries back to the normal position and
keeps the coronary arteries attached to the aorta
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