Lung Devo (both lectures) Flashcards
Precursor of: epithelial lining of the larnyx, trachea, bronchi and lungs
Endoderm
Precursor of: cartilage, smooth muscle, elastic and fibrous CT of larynx, trachea and bronchi
Splanchnic mesoderm
Lung devo occurs in recognizable phases: What happens week 4-7?
(week 4 -7)
- Lung primordium appears from splanchnic mesoderm
- Initial airway branching
laryngotracheal tube–> seperated by transeosphageal septum into : primitive trachea and primitive esophagus (look at diagram)
Anomalies Occurring During the Embryonic Phase
• Inadequate Partitioning perhaps due to abnormal or insufficient development of the
Tracheoesophageal Septum
The following are all examples of :
absence of the lungs, extra lobes, ectopic lobes or absence of lobes, abnormal or insufficient branching, an accessory lung, bronchogenic cysts, pulmonary vascular anomalies
• Anatomic Anomalies
• 39 week male
• 3.2 kg
• Prenatal ultrasound –
normal
• Excess secretions and
respiratory distress 30
minutes after birth
• Unable to pass NGT
Problem with tracheoesophageal septum; could be cystic or atresia
What is the most common type of esophageal atresia?
Listed as Type A in notes which = Gross type C
85%
Symptoms and diagnosis of distal TEF
air in bowel on xray will confirm distal TEF, no contrast necessary
*perform a bronchoscopy to identify fistula
Associated anomalies in TEF or EA
- Occur in___% of patients
- Most common with ______ and least common with_____
50%
isolated EA
isolated TEF
In TEF and EA _________are main determinants of survival
Associated anomalies
(Smaller infants have more associated anomalies such as severe associated cardiac anomalies)
Newborn has distal TEF with EA. What makes them canidates for primary repair?
– Healthy
– Near Term
– No major cardiac anomalies
– No significant pulmonary disease
• Removes threat of aspiration PNA
Recomended pre-op mamagement for isolated EA
Gastrostomy for feeding
• Drain upper pouch
• Wait 6-12 weeks for pouch growth
• May utilize dilation methods to “stretch”pouch
• Re-evaluate the pouch prior to OR
During repart of TEF with EA, how do we access the trachea?
Via extra pleura right thoracotamy (watch for azygous vein!)
Week 6-16 is the Psuedoglanular phase… what happens?
airway branching continues
increased epithelial-mesenchyme interactions and see pirmordia dev for respiratory passages.
Respiratory diverticulum is made from:
endoderm
(surounded by splanchinc mesenchyme)
Week 16-26 is the Canalicular Phase. What occurs?
- Capillary density increases
- Avelolar Cells (Pneumocytes) begin to differentiate
What is the limit of extrauterine viability?
kid needs to be in for at least 22-24 weeks to support life outside and will need assistance
weeks 26-birth: Terminal Sac phase
What is going on during this phase?
• Distal airways dilate, forming Terminal Sacs (primitive alveoli)
surrounded by splanchinc mesenchyme
epithelium starts to thin
get elsatin fibers
Congenital Cystic Adenomatoid Malformation (CCAM) is an example of:
Congenital bronchopulmonary malformation
Mass of pulmonary tissue in which there is proliferation of bronchial structures at the expense of alveolar development.
CCAM; Congenital Cystic Adenomatoid Malformation
** Asynchronous maturation** of the developing lung bud and the surrounding mesenchyme between the 16th and 20th weeks, resulting in:
overgrowth of the terminal airway structures or CCAM
Histology of CCAM:
Alveolar spaces lined by a combination of _______ and ______, forming
glandular (“adenomatoid”) architecture
both respiratory and mucus-secreting epithelium
Classification of CCAM
Type I
Type II
Type III
Type I: large macroscopic cysts
Type II: small macro cysts
Type III: microscopic cysts
Clincal Presentaiton of CCAM
______ respiratory distress
_______pulmonary infections
asymptomatic but detected:
rarely respiratory distress
recurrent pulmonary infections
no symptoms but seen on x-tray or ultrasound
CCAM
ususally affects ______ lobe(s), has communication with ______ system and progressive air trapping leads to ________
affects single lobe
communicates with bronchial system
trapping air leads to distension
Respiratory distress as neonate
• Day of Life 1 in this infant with tachypnea and hypoxia, requiring intubation. CXR shows LLL hyperlucency with herniation across midline
What conclusions can be drawn from this vignette?
they hyperlucency in LLL is indicitive of fluid in the lung (hydrops)
(CCAM will result in fluid filled cysts)
*child requires thoracotomy and lobectomy right away
Consequences of mass effect and timing of arrest of development from CCAM:
• pulmonary______ and _______
• distortion of______ and impaired _____
hypertension and hypoplasia
mediastinum
venous return
Can result in hydrops, severe respiratory failure,
pulmonary infection, or no symptoms
CCAMs
Tx options for PRE-natal hydrops
- Thoracentesis
- Thoraco-amniotic shunt
- Fetal lobectomy
- Induce delivery and perform resection
While doing rotations, a first time mother delivers a healthy apperaing baby. During a chest Xray, the baby was found to have CCAM in the LLL. The attending asks you if surgery is still required… your response?
- They will likely cause recurrent infections, making the resection of a symptomatic lesion more difficult.
- There is always some amount of diagnostic uncertainty before the pathologic specimen is available.
- There have been reports of cancers developing in CCAMs, at as little as 1 year of age.
- The procedure of choice is an anatomic lobectomy
What is the process for a nonemergent ‘elective’ Treatement of CCAM?
• Plain Film Chest Xray in neonatal period
• Follow – up CT Scan within 1-2 months
• Elective resection within first 3-6 months of life
– Thoracoscopic
– Open
Alveolar Phase (32 weeks - 8 years)
• Alveolar formation begins by ________
• Alveolar septum (walls) become_____
subdivision of terminal sacs - Septation
thinner
Postnatal Development
• Most alveoli form after birth
• Formation proportional to_____
body growth
Each phase of devo blends into the next phase in Lungs (T/F)
• Formation of airways in the lung proceeds in a proximal to distal direction or distal to proximal direction
True
devos in proximal to distal direction
The prenatal lung contains:
Fluid!
*insufficient fluid in lungs leads to HYPOPlastic lung
Prenatal lung has _____
Respiratory movements are ______
pulmonary vascular resistance is______
fluid
shallow, episodic
high resistance
What changes after birth allow breathing?
**Pulmonary Changes **
• Fluid replaced by air
Circulatory Changes
• Cardiac shunts close
• Pulmonary vessels fill
Neural
• Breathing
• Sympathetic activation
If a newborn has ‘wet lung’ or issues with fluid removal from the lungs, may get:
transient tachypnea
Characteristics of the new air/liquid interface within the alveoli
• Thin_____ wall
• Subjected to _____
compliant
surface tension
Production of surfactant by _____ begins toward the end of ______ period with a significant increase at ____ weeks
Type 2 pneumocytes
canalicular
35 weeks
What prevents a baby from breathing on it’s own if it’s born prior to 35 weeks?
insufficient pulmonary surfactant production
3 Functions of Pulmonary Surfactant
- Decrease surface tension
- Stabilize alveolar surface
- Decrease fluid transfer
Pulmonary Surfactant is a mixture of 3 Components
- Phospholipid
- Protein
- Antioxidant
- Rapid breathing (>60 breaths/min)
- Flaring nostrils
- Chest retractions
- Expiratory grunt
- Often cyanotic (blue)
- Rapid heart rate
- Anxious expression
Clinical Signs Respiratory Distress
***this is a MEDICAL EMERGENCY!**
Respiratory Distress Syndrome/Hyaline Membrane Diseas = clinical condition where newborn babies experience Respiratory Distress
• Are usually _____
• Have_____ Lungs
• Often develop a________in their lungs
Premature
Immature
Hyaline Membrane
HMD and RDS are two different diseases and yet…
these guys often overlap. Very likely that if you have one, you have the other
Hyaline membrane formation:
Type ____ alveolar injury–> breakdown of caplilary/air barrier–> ____ leaks into alveolar lumen–> hyaline forms and ____ is disrupted
Type I alveolar cells
Serum leaks to lumen
Surfactant fnx is disrupted
Cuases of Respiratory Distress Syndrome:
An inability to keep alveoli filled with air
A Decrease in Surfactant Production
- Poor Compliance of Lung Tissue
- Atelectasis due to alveolar collapse
- Engorgement of Pulmonary Capillaries
- Formation of a Hyaline Membrane
These are all from:
Decreased surfactant production
Premature infants who experience RDS may develop
Bronchopulmonary Dysplasia (chronic lung disease of infancy)
- 1.2-kg male infant born vaginally at 32 weeks EGA
- Apgars 6, 8
- Required bulb suctioning, brief PPV.
- Grunting, retractions, nasal flaring, acrocyanosisimmediately after birth.
- VS: HR 178, RR 79, Mean BP 39 mmHg. O2 74-78% in room air
What is concerning for RDS?
Grunting, retractions, nasal flaring, acrocyanosis
low O2 saturation
increased RR and low BP
born at 32 weeks
What is the pathology of RDS?
Due to structural and functional immaturity of lungs.
• Underdeveloped parenchyma
• Surfactant deficiency–:Type II pneumatocytes
• Results in decreased lung compliance, unstable alveoli
- Prematurity
- <28 weeks GA (≈100%)
- 28-34 weeks GA (33%)
- >34 weeks GA (5%)
- Perinatal depression
- Male predominance
- Maternal diabetes
- C-section
- Multiple birth
What do you see on chest xray in infant with RDS?
• Low lung volumes
• Diffuse atelectasis: “ground
glass opacities”
• Air bronchograms
• Difficult to distinguish from
pneumonia
Lab findings concerning for RDS?
- Moderate hypoxia
- Respiratory acidosis
- Metabolic acidosis (delayed)
Tx for RDS in infant?
- Oxygen supplementation
- Assisted ventilation
- nCPAP
- mechanical ventilation
- FiO2 > .40
- Exogenous surfactant replacement
- Fluid restriction
Prevention of RSD
- Antenatal bethamethasone
- Arrest of preterm labor
- Peak severity ___days
- Recovery coincides with____ beginning at 72 hrs
- Severe cases evolve into _________
1-3
diuresis (getting water out of lungs)
bronchopulmonarydysplasia (chronic lung disease)
- Tachypnea immediately after birth or within two hours, with other predictable signs of respiratory distress.
- Symptoms can last few hours to two days
Transient tachypnea
What do we see in xray in TTN?
Chest radiography shows diffuse parenchymal infiltrates, a “ wet silhouette” around heart, or intralobar fluid accumulation
Meconium Aspiration Syndrome is seen in _____% in term or post term infants.
Why is it a bad deal?
1.5- 2
- Meconium is locally irritative, obstructive & medium for for bacterial culture
- Meconium aspiration causes significant respiratory distress. Hypoxia occurs because aspiration occurs in utero.
- CXR- Patchy atelectasis or consolidation.
What does xray for child with RDS look like compared to normal?
RDS has patchy, whitish looking lungs while normal lungs are clear
Issues with RDS when we have premature lungs with insufficient surfactant. We can measure this using:
Lecithin/sphingomyelin ratio (Phosphatidylglyerol ismore accurate measurement)
LS ratios
>2.0 is 98%:
1.5-1.9 is 50%:
<1.5 is 73%:
normal
RDS
RDS
How can doctors enhance fetal lung maturation?
- Administer glucocorticoids to the mother before delivery
- Administer artificial surfactant to the newborn
• The lower portion of the respiratory system develops from a
ventral foregut diverticulum (endoderm)
Interaction between endoderm and splanchnic mesoderm results in
airway branching which proceeds
proximal-distal
- A air/liquid interface is established in alveoli which is subject to_____
- Adequate surfactant reduces the surface tension
surface tension
Inadequate____ levels lead to immature lungs and respiratory distress syndrome (hyaline membrane disease
surfactant
