respiratory system: introduction, atelectasis, ards
TRANSCRIPT
INTRODUCTIONATELECTASIS, ARDS
Dr Vijay Shankar S
RESPIRATORY SYSTEM
OVERVIEW
• Congenital anomalies,Neonatal lung diseases
• Pulmonary infections• Obstructive vs Restrictive lung diseases
COPDs & Penumoconiosis• Pneumoconiosis• Lung tumors
TODAY
• Anatomy and histology• Functions• Congenital anomalies• Atelectasis and collapse• Hyaline membrane disease• ARDS
A 7-year-old boy accidentally inhales a small peanut, which lodges inone of his bronchi. A chest x-ray reveals the mediastinum to be shiftedtoward the side of the obstruction. Which of the following pulmonaryabnormalities is most likely present in this boy?
a. Absorptive atelectasisb. Compression atelectasisc. Contraction atelectasisd. Patchy atelectasise. Hyaline membrane disease
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1. Trachea
2. Bronchus (Right- or Left- Primary Bronchus)
3. Lobar Bronchus
4. Segmental Bronchus
5. Bronchus
6. Bronchiole
7. Terminal Bronciole
8. Respiratory Bronchiole
9. Alveolar Duct
10.
Alveolar Sac / Alveolus
Normal histology of alveolar septa
Paediatric lung disease
• Congenital • Bronchopulmonary sequestration• Hyaline membrane disease(NRDS)
ATELESTASIS/ COLLAPSE
• Greek word ἀτελής, "incomplete" + ἔκτασις, "extension"
• Defn: incomplete expansion of lung parenchyma ( neonatal/primary )– Etiology
prematurity, cerebral birth injury, CNS malformation and IUhypoxia
• Sec/acquired atelectasis – collapse of previously expanded lung
IRREVERSIBLE
SIGNIFICANCE
• Reduces oxygenation and predisposes to infection!
• Reversible except contraction type!
GROSS• Small, • dark blue,• fleshy and non-crepitant ( looks like a
liver)
Histology
• Alveolar space in the affected area– are small with thick interalveolar septa.– Contain proteinaceous fluid with scattered epithelial
squames & meconium.• Scattered aerated space
Neonatal respiratory distress syndrome
• Hyaline membrane disease
• Characterised by hyaline membrane formation
• Begins with dyspnoea a few after birth with tachypnoea, hypoxia and cyanosis and in severe case death occurs in few hours.
• More common in LBW babies
• Etiology.Preterm babyInfants born to diabetic mothersDelivery by caesarean section without preceding labourExcessive sedationBirth asphyxiaMale preponderance
PREMATURITY
Reduced SURFACTANT synthesis, storage and release
Decreased alveolar surfactant
Increased alveolar surface tension
Atelectasis
Uneven perfusion Hypoventilation
HYPOXEMIA + CO2 RETENTION
Acidosis
Pulmonary Vasoconstriction
Pulmonary hypoperfusion
Endothelial damage + Epithelial damage
Plasma leak into alveoliFIBRIN + NECROTIC CELLS ( HYALINE MEMBRANE)
Increased diffusion gradient
GROSS• The lungs are normal in size ,• Reddish purple in color.• Are solid and airless so that they sink in
water.
Acute lung injury
• Spectrum of endothelial and epithelial lesions
• Manifestations:congestionsurfactant disruptionatelectasis
Variable progression to:
• Pulmonary edema• Acute respiratory distress syndrome• Acute interstitial pneumonia
Microvascular injury
• Injury to endothelial or epithelial cells• Leakage of fluids and proteins into the interstitial
space → alveoli
• Localized: symptoms of infection• Diffuse: ARDS
Acute respiratory distress syndrome
ARDS / DAD / shock lung
ARDS
• Clinical syndrome caused by diffuse alveolar capillary damage
Clinically,• Severe life threatening respiratory insufficiency
of rapid onset• Cyanosis• Severe arterial hypoxemia refractory to o2
• Progress to multisystem organ failure
Infection SepsisDiffuse pulmonary infections – viral mycoplasma, PCP, miliary TBGastric aspiration
Physical injuryMechanical traumaPulmonary contusionsNear drowningFractures with fat embolismBurnsIonizing radiation
Inhaled irritantsOxygen toxicitySmokeIrritant gases & chemicals
Chemical injuryHeroin or methadone overdoseASABarbiturate overdose
Hematological conditionsMultiple transfusionsDIC
PancreatitisUremia, C-P bypass
PATHOGENESIS
Acute alveolar injury
Release of cytokines
By Macrophages(IL1, 8, TNF) By Activated neutrophils
(Protease, leukotrienes, PAF, Oxidases)
Local tissue damage, intra alveolar edema loss of diffusion capacity and damage to type II alveolar pneumocytes Surfactant inactivation
HYALINE MEMBRANE
STIFF LUNG
Clinical course
• Previously hospitalized pts develop tachypnea and dyspnea
• Increasing cyanosis and hypoxemia• Unresponsive to oxygen therapy• Respiratory acidosis develops
Chest X ray
• Diffuse alveolar infiltration
Morphology - Acute stage:
• Heavy, firm, red and boggy
• Congestion, intra-alveolar edema, inflammation and fibrin deposition
• Alveolar walls lined by waxy hyaline membranes
• Fibrin rich edema fluid mixed with cytoplasmic and lipid remnants of necrotic epithelial cells
Organizing stage
• Type II pneumocytes proliferate
• Organization of the exudate intra alveolar fibrosis
• Thickening of alveolar septa
• Proliferation of interstitial cells and deposition of collagen
• Fatal cases superimposed bronchopneumonia.
The blue arrows point to intralveolar macrophages and type II pneumocytes. • The green arrow identifies brightly eosinophilic hyaline membranes.
• The blue arrows point to the type II pneumocytes which are very prominent; their nuclei protruding into the alveolar space. • The arrows highlight the thickened septum. • The septum contains excess collagen, fibroblasts, and lymphocytes. • Hyaline membranes are not present.
A 7-year-old boy accidentally inhales a small peanut, which lodges in one of his bronchi. A chest x-ray reveals the mediastinum to be shifted toward the side of the obstruction. Which of the following pulmonary abnormalities is most likely present in this boy?
• a. Absorptive atelectasis• b. Compression atelectasis• c. Contraction atelectasis• d. Patchy atelectasis• e. Hyaline membrane disease