Lung Devo (both lectures) Flashcards by Meghan May

Precursor of: epithelial lining of the larnyx, trachea, bronchi and lungs

Endoderm

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Precursor of: cartilage, smooth muscle, elastic and fibrous CT of larynx, trachea and bronchi

Splanchnic mesoderm

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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)

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Anomalies Occurring During the Embryonic Phase
• Inadequate Partitioning perhaps due to abnormal or insufficient development of the

Tracheoesophageal Septum

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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

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• 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

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What is the most common type of esophageal atresia?

Listed as Type A in notes which = Gross type C

85%

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Symptoms and diagnosis of distal TEF

air in bowel on xray will confirm distal TEF, no contrast necessary

*perform a bronchoscopy to identify fistula

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Associated anomalies in TEF or EA

Occur in___% of patients
Most common with ______ and least common with_____

50%

isolated EA

isolated TEF

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In TEF and EA _________are main determinants of survival

Associated anomalies

(Smaller infants have more associated anomalies such as severe associated cardiac anomalies)

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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

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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

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During repart of TEF with EA, how do we access the trachea?

Via extra pleura right thoracotamy (watch for azygous vein!)

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Week 6-16 is the Psuedoglanular phase… what happens?

airway branching continues

increased epithelial-mesenchyme interactions and see pirmordia dev for respiratory passages.

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Respiratory diverticulum is made from:

endoderm

(surounded by splanchinc mesenchyme)

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Week 16-26 is the Canalicular Phase. What occurs?

Capillary density increases
Avelolar Cells (Pneumocytes) begin to differentiate

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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

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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

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Congenital Cystic Adenomatoid Malformation (CCAM) is an example of:

Congenital bronchopulmonary malformation

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Mass of pulmonary tissue in which there is proliferation of bronchial structures at the expense of alveolar development.

CCAM; Congenital Cystic Adenomatoid Malformation

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** 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

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Histology of CCAM:

Alveolar spaces lined by a combination of _______ and ______, forming
glandular (“adenomatoid”) architecture

both respiratory and mucus-secreting epithelium

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Classification of CCAM

Type I

Type II

Type III

Type I: large macroscopic cysts

Type II: small macro cysts

Type III: microscopic cysts

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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