Pediatric Lung Diseases Flashcards
Entire bronchial tree is developed by […] gestation.
16 weeks
Alveoli mostly form […].
after birth (begin forming at 37 weeks gestation).
Arterial development […] bronchial dvelopment.
lags behind
5 Important Growth Periods of the Embryonic Lung
- Embryonic (4th-7th weeks): Lung development begins as protrusion from foregut, which undergoes early branching into main and segmental bronchi.
- Pseudoglandular (7th-16th weeks): Smaller airways develop.
- Canalicular (16th-26th weeks): Acini develop, and vascularity increases.
- Saccular (26th-36th weeks): Development of saccules (primitive alveoli) occurs, and surfactant first appears.
- Alveolar (37th week +): True alveoli form and grow
Respiratory Distress Syndrome Definition
Respiratory distress syndrome (RDS) is a clinical syndrome characterized by respiratory dysfunction in infants, caused by deficiency of pulmonary surfactant. It was formerly known as “hyaline membrane disease” and that term is still commonly used by some physicians.
Respiratory Distress Syndrome
- Usually in premature infants.
- Diabetes and cesarean section are risk factors.
- Infant is OK at birth, but develops progressive respiratory distress within minutes to a few hours after birth.
- Infiltrates on chest film.
- If premature birth cannot be prevented, its severity can be reduced by antenatal steroid treatment to the mother (to accelerate maturation of type II pneumocytes in fetal lungs).
- After birth, treatment includes administration of artificial surfactant and respiratory support; many survive without sequelae.
Pathogenesis of RDS
deficiency in surfactant due to pulmonary immaturity
Pathology of RDS
atelectasis and hyaline membranes in the lungs
Complications of RDS
- Patent ductus arteriosus.
- Interventricular hemorrhage of brain (due to hypoxia).
- Necrotizing enterocolitis.
- Oxygen toxicity to lungs.
- Bronchopulmonary dysplasia.
Bronchopulmonary Dysplasia
- Chronic neonatal lung disease complicating unresolved RDS, causing persistent respiratory distress.
- Before surfactant therapy became available in the 1980s, the “old” form of BPD was caused by barotrauma (too much ventilatory pressure) and oxygen toxicity (too much oxygen); this is very rare now.
- “New” form of BPD in modern era results from disrupted lung development and alveolar hypoplasia (fewer and larger alveoli); the cause is poorly understood.
- May last for months to years or cause death.
- Pathology is persistent lung immaturity; chronic atelectasis, alveolar hypoplasia, and interstitial fibrosis may be seen.
Congenital Anomalies
- Bronchogenic (foregut cysts)
- Sequestrations
- Pulmonary Hypoplasia
Bronchogenic Cysts
pinched-off remnants of primitive esophagobronchial tissue that form a benign cyst in the lung, mediastinum, or next to the gut.
Sequestrations
portions of lung without a bronchial connection and with a systemic arterial (aortic) blood supply. Intralobar sequestrations are located within the visceral pleura (within one of the lungs), most commonly in the posterior segment of the left lower lobe. Extralobar sequestrations are invested by their own pleura, and are separate from the lungs; these may be in the thorax, but occasionally form in the abdomen beneath the diaphragm
Pulmonary Hypoplasia
is a condition characterized by underdevelopment of a lung, which largely lacks acinar development and typically is 1/2 normal size. Causes include:
a. External compression (rib cage anomalies, diaphragmatic hernia).
b. Renal agenesis or disease (Potter syndrome).
c. Oligohydramnios (decreased amniotic fluid).
d. Anencephaly.
e. Idiopathic.
f. Association with many complex malformation syndromes.
Cystic Fibrosis Definition
A multisystem genetic disease caused by abnormal transport of chloride across epithelial cell membranes, resulting in thickened, viscous secretions, which affects the lungs, digestive system, sweat glands, and reproductive organs.
CF is the most common “life shortening” […] genetic disease among […] populations.
Most common “life-shortening” autosomal recessive genetic disease among Caucasian populations.
CF is a widespread disorder of […] of all […] glands.
CF is a widespread disorder of secretory process of all exocrine glands.
CF is a defect in the regulation of […].
CF is a defect in the regulation of epithelial chloride transport (chloride channels).
CF Genetics
- Gene is on chromosome 7, which encodes the CFTR protein (cystic fibrosis transmembrane conductance regulator), a transmembrane protein that regulates transport of chloride across cell membranes.
- Over 200 mutations; most common (70%) mutation is delta F508 (deletion of 3 DNA bases coding for phenylalanine at amino acid residue position 508)
Major symptoms of CF
Major symptoms are due to pancreatic insufficiency and repeated respiratory infections.
Diagnosis of CF
Diagnosis usually includes sweat chloride test or genetic testing
CF Pulmonary Changes
Pulmonary changes are airway-based: mucous plugging, chronic bronchitis, bronchiectasis, and obliterative bronchiolitis.
Bacterial infections and CF
Secondary bacterial colonization of abnormal airways is essentially universal at an early age, and chronic bacterial infections are common, especially with Pseudomonas aeruginosa; these infections may be extr
Bronchiectasis Definition
Fixed dilatation of large airways (bronchi), usually due to a previous necrotizing inflammatory process in the airways resulting in permanent airway scarring.
Causes of Bronchiectasis
- Bronchial obstruction: Airways distended with secreted mucus, infection develops, and change is permanent if obstruction is not relieved.
- Congenital or hereditary conditions: Numerous congenital conditions can result in bronchiectasis. The classic example is cystic fibrosis, causing repeated airway infections (especially with Pseudomonas) and secondary bronchiectasis.
- Immunodeficiency states: Again a result of repeated airway infections.
- Ciliary abnormalities: Patients with defective ciliary action are more prone to retention of mucus and repeated infections of the airways, leading to bronchiectasis. A host of ciliary abnormalities have been identified. Typically, the defect is an autosomal recessive trait that involves the whole body. Primary ciliary dyskinesia (Kartagener syndrome) is the prototypical example, characterized by defects in ciliary structure and function, leading to bronchiectasis, sinusitis, and situs inversus.
- Necrotizing bronchopneumonia: Bronchiectasis can result as a secondary abnormality following severe infections, especially pertussis; fortunately this is no longer common.
Pathology of Bronchiectasis
- Gross pathology: Airways are dilated compared to normal and are typically thin-walled; may be symmetrically dilated or saccular.
- Microscopic pathology: Airway dilatation, absence of normal bronchial wall structures (glands, muscle, cartilage), fibrosis and chronic inflammation of airways, and sometimes superimposed acute infection.
- Clinical course: Chronic productive cough, occasional hemoptysis, episodes of acute infection, and eventually cor pulmonale (right heart failure) and cyanosis. Clubbing of the fingers is common.
Potter’s Syndrome
•lung hypoplasia with renal:
- agenesis (no kidneys)
- dysplasia (abnormally formed kidneys)
- infantile polycystic disease
Kartagener’s Syndrome
- Triad of situs inversus, bronchiectasis, and sinusitis
- Cilia are immotile or dyskinetic
- Autosomal recessive trait
- Males are infertile
