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RS Pathology

Respiratory System Pathology-Atelactasis, Acute lung injury, and ARDS

What is Alectasis? The loss of lung volume caused by inadequate expansion of air spaces
What is the general consequence of atelactasis? Shunting of inadequately oxygenated blood from pulmonary arteries into veins, thus giving rise to hypoxia
What are the three forms of atelactasis? 1) Resorption 2) Compression 3) Contraction
When does resorption atelactasis occur? In the case of obstruction. preventing air from reaching distal airways
Why is it called resorption atelactasis? Because the air present gradually become absorbed and alveolar collapse follows
What part of the lung is affected by resorption atelactasis? Either an entire lung, a complete lobe, or one or more segments.
What is the most common cause of resorption collapse? Obstruction of a bronchus by a mucus or mucopurelent plug
In what cases can the bronchus be obstructed by a mucus or mucopurulent plug? 1) Postoperatively 2) Complicated bronchial asthma, bronchiectasis, or bronchitis
How else may the bronchus be obstructed? 1) Tumor 2) Foreign body aspiration (mainly in children)
What are some other names for compression atelactasis? Passive/ Relaxation atelactasis
How does compression atelactasis occur? Accumulation of fluid, blood, or air within the pleural cavity which mechanically collapses the adjacent lung
What is the most common cause of compression atelactasis? Pleural effusion, caused by congestive heart failure
What are some other causes of compression atelactasis? 1) Leakage of air into the pleural cavity (pneumothorax) 2) Hemothorax 3) Basal atelactasis resulting from the elevated position of the diaphragm
Basal atelactasis commonly occurs in: 1) Bedridden patients 2) Ascites
What is another name for contraction atelactasis? Cicatrization atelactasis
When does contraction atelactasis occur? When either local or generalized fibrotic changes in the lung or pleura or prevents expansion of air spaces
Which type(s) of atelactasis is/are reversible? Compression and Resorption
Which type(s) of atelactasis is/are irreversible? Contraction
Treating atelactasis early on prevents: Hypoxemia and superimposed infection of the collapsed lung
Acute lung injury includes: A spectrum of bilateral pulmonary damage (endothelial and epithelial) which can be initiated by numerous conditions
What are the clinical manifestations of Acute lung injury? 1) Acute onset of dyspnea 2) Decreased arterial oxygen pressure (hypoxemia) 3) Bilateral pulmonary infiltrates on the chest radiograph 4) Absence of clinical evidence of left sided heart failure
Accumulations in this type of injury are considered noncardiogenic pulmonary edema because: The pulmonary infiltrates in acute lung injury are caused by damage to the alveolar capillary membrane rather than by left sided heart failure
Acute lung injury can progress to: ARDS (Acute respiratory distress syndrome)
What is ARDS? A clinical syndrome caused by diffuse alveolar capillary and epithelial damagage
ARDS is usually characterized by: 1) Rapid onset of respiratory insufficiency (possibly fatal) 2) Severe arterial hypoxemia which is refractory to oxygen therapy and may progress to organ failure (multisystemic)
The histologic manifestation of ARDS is known as: DAD (Diffuse alveolar damage)
ARDS is associated with two types of lung injury. What are they? 1) Direct injury to the lung 2) Indirect injury in the setting of a systemic process
What are the common causes of direct lung injury? Pneumonia Aspiration of gastric contents
What are the uncommon causes of direct lung injury? Pulmonary contusion
What are the common causes of indirect lung injury? Sepsis Severe trauma with shock
What are the uncommon causes of indirect lung injury? Acute pancreatitis
What is the cause of ARDS in newborns? Primary deficiency of surfactant
What are the two barriers of the alveolar capillary membrane? 1) The microvascular endothelium 2) Alveolar epithelium
IN ARDS, what occurs to these barriers? The integrity of these barriers is compromised by either endothelial or epithelial injury, or both (the most common)
The acute consequences of damage to the alveolar capillary membrane include: 1) Increased vascular permeability and alveolar flooding 2) Loss of diffusion capacity 3) Widespread surfactant abnormalities (damage to type 2 pneumocytes)
In, ARDS, lung injury is caused by an imbalance of? Pro-inflammatory and anti-inflammatory mediators
As early as 30 minutes after an acute insult: 1) IL-8 synthesis increases (a neutrophil chemotactic and activating agent) by pulmonary macrophages 2) IL-1, TNF, and manily neutrophils released --> endothelial activation and damage 3) Neutrophils release oxidants, proteases, leukotrienes
Assault on the endothelium and epithelium increases: Vascular leakiness and loss of sufactant The alveaolar unit is unable to expand
The destructive neutrophilic forces can be counteracted by: Endogenous anti-Proteases, antioxidants, and inflammatory cytokines (IL-10)
The balance between the _____ and ______ factors determines the degree of tissue injury and clinical severity of ARDS Destructive/ Protective
Which type of cells are thought to have an important role in the pathenogenesis of ARDS? Neutrophils
Describe the general morphology of the lungs in acute ARDS Red, Firm, Airless, and heavy
Microscopic findings of ARDS affected lung: 1) Capillary congestion 2) Necrosis of alveolar epithelial cells 3) Interstitial and intra alveolar edema and hemorrhage 4) Increased neutrophils in vascular space, interstitium, and the alveoli
What is the most characteristic finding in ARDS? Hyaline membranes in the alveolar ducts
What do these hyaline membranes consist of? 1) Fibrin-rich edema fluid 2) Remnants of necrotic epithelial cells
In the organizing stage of ARDS, type 2 pneumocytes: Vigorously proliferate and attempt to regenerate the alveolar lining
Resolution of the lungs after ARDS is: Unusual
What happens instead of resolution? 1) Organization of fibrin exudates, with resultant intra alveolar fibrosis 2) Marked thickening of the alveolar septa, caused by proliferation of interstitial cells and deposition of collagen
How long does it take most patients to develop the clinical syndrome of acute lung injury or ARDS? (85%) Within 72 hours of the initiating insult
The mortality rate from ARDS has decreased from? 60-40%
Predictors of poor prognosis include: 1) Advanced age 2) Underlying bacteremia (sepsis) 3) Multi-system organ failure (especially cardiac, renal, or hepatic)
After the patient survives the acute stage: Diffuse interstitial fibrosis may occur with continued compromise of respiratory function
In patients who survive the acute insult and are spared the chronic stage: Normal respiratory function returns within 6-12 months
Created by: Ulaisl