Respiratory System Pathology 2023

Questions and Answers

What condition is characterized by rapid onset of life-threatening respiratory insufficiency, cyanosis, and severe arterial hypoxemia?

Chronic Obstructive Pulmonary Disease

Acute Respiratory Distress Syndrome (correct)

Pneumonia

Bronchial Asthma

Which of the following is NOT considered a trigger for Acute Respiratory Distress Syndrome?

Sepsis

Trauma

Pneumonia

Asthma Attack (correct)

How is Acute Respiratory Distress Syndrome defined in terms of its onset?

Respiratory failure occurring within 1 week of a known clinical insult. (correct)

Respiratory distress within 48 hours of any injury.

Respiratory failure within 24 hours of a known insult.

Rapid respiratory decline occurring without any prior incident.

What histological condition is associated with extensive bilateral injury to alveoli in ARDS?

Diffuse Alveolar Damage Signup and view all the answers

What role do activated neutrophils play in the pathogenesis of ARDS?

They release reactive oxygen species that cause epithelial injury. Signup and view all the answers

What is the most characteristic histological finding in the acute phase of ARDS?

Hyaline membranes Signup and view all the answers

What is one way that the body attempts to counteract the destructive forces in ARDS?

Utilizing endogenous anti-proteases and anti-oxidants. Signup and view all the answers

Which condition is associated with a poor prognosis in patients with ARDS?

Bacteremia (sepsis) Signup and view all the answers

What imaging finding is typically associated with ARDS?

Bilateral opacities Signup and view all the answers

In the organizing stage of ARDS, what is one of the primary histological changes observed?

Proliferation of type II pneumocytes Signup and view all the answers

Which of the following factors does NOT fully explain the symptoms of ARDS?

Exposure to cold air Signup and view all the answers

What complication may arise in patients who survive the acute insult of ARDS?

Chronic respiratory insufficiency Signup and view all the answers

How is ARDS classified in relation to diffuse pulmonary diseases?

As a restrictive defect Signup and view all the answers

Which statement correctly describes the respiratory symptoms of ARDS patients?

Patients experience prolonged cyanosis and hypoxemia Signup and view all the answers

What histological feature indicates the presence of necrotic epithelial cells in ARDS?

Fibrin-rich edema fluid Signup and view all the answers

What percentage reflects the overall hospital mortality rate for ARDS?

38.5% Signup and view all the answers

What is the primary function of the lungs?

To replenish oxygen and remove carbon dioxide from blood Signup and view all the answers

Which type of pneumocyte is most abundant in the alveolar epithelium?

Type I pneumocytes Signup and view all the answers

What condition is characterized by loss of lung volume due to inadequate expansion of air spaces?

Atelectasis Signup and view all the answers

What is a common cause of resorption atelectasis?

Intrabronchial mucous plugs Signup and view all the answers

Which type of atelectasis occurs due to fluid accumulation in the pleural cavity?

Compression atelectasis Signup and view all the answers

What type of atelectasis is associated with local or generalized fibrosis of the lung or pleura?

Contraction atelectasis Signup and view all the answers

Which of the following is NOT a cause of resorption atelectasis?

Air leakage into the pleural space Signup and view all the answers

Alveolar macrophages are primarily involved in which function?

Phagocytosis within the alveolar space Signup and view all the answers

Study Notes

Objectives of the Lecture

Focus on the function and anatomy of the respiratory system, atelectasis, ARDS, and the distinction between restrictive and obstructive lung diseases.

Function and Anatomy of the Respiratory System

Main function: oxygen replenishment and carbon dioxide removal from the bloodstream.
Alveolar walls (septae) comprise:
- Capillary endothelium
- Basement membrane
- Pulmonary interstitium
- Alveolar epithelium made of:
  - Type I pneumocytes (flattened, 95%)
  - Type II pneumocytes (rounded, produce surfactant, repair Type I damage)
  - Alveolar macrophages (phagocytic cells within alveolar space)

Atelectasis

Defined as loss of lung volume due to inadequate air space expansion.
Three types of atelectasis:
- Resorption: due to total bronchial obstruction preventing air reach.
  - Common causes include bronchial obstruction from mucus, foreign bodies, lung diseases, and tumors.
- Compression: caused by accumulation of fluid, blood, or air in the pleural cavity.
  - Examples include pleural effusion and pneumothorax.
- Contraction: results from localized or generalized fibrosis in the lung or pleura.
Prompt treatment of atelectasis (except contraction) is crucial to prevent hypoxemia and infection.

Acute Respiratory Distress Syndrome (ARDS)

Evolving definition: respiratory failure occurring within one week post clinical insult with bilateral opacities on chest imaging.
Not explained by effusions, atelectasis, cardiac failure, or fluid overload.
Causes include pneumonia, sepsis, aspiration, trauma, pancreatitis, and transfusion reactions.
Severity graded based on arterial blood oxygenation.
Distinct from neonatal respiratory distress syndrome (surfactant deficiency due to prematurity).

Pathogenesis of ARDS

Compromise of the alveolar-capillary membrane from endothelial and epithelial injury.
Early increase in inflammatory mediators (IL-8, IL-1, TNF) by pulmonary macrophages leads to neutrophil activation in capillaries.
Activated neutrophils release damaging reactive oxygen species and proteases, resulting in vascular leakiness and surfactant loss.
Disease severity depends on the balance between destructive and protective factors.

Histology of ARDS

Acute phase characterized by hyaline membranes formed from fibrin-rich edema and necrotic epithelial cells.
Organizing stage features proliferation of Type II pneumocytes and intraalveolar fibrosis with thickening of alveolar septa.

Clinical Features of ARDS

Patients often hospitalized for predisposing conditions, presenting with profound dyspnea, tachypnea, cyanosis, and hypoxemia.
Diffuse bilateral infiltrates visible on radiographs.
Hypoxemia may resist oxygen therapy.

Outcomes and Prognosis

Overall hospital mortality rate near 38.5%.
Survivors may regain normal respiratory function within 6 to 12 months; some may develop chronic respiratory insufficiency.
Poor prognosis predictors include advanced age, bacteremia (sepsis), and multiorgan failure.

COVID-19 and ARDS

COVID-19 associated with variable presentations, with a significant number experiencing severe ARDS.
Ongoing research on pathogenesis and management in the context of aging populations.

Classification of Pulmonary Diseases

Obstructive airway diseases: characterized by airflow resistance from injury or obstruction.
Restrictive diseases: include reduced lung expansion and total lung capacity, encountered in:
- Chest wall disorders (e.g., obesity, pleural diseases, neuromuscular disorders).
- Interstitial lung diseases, with ARDS as a classic example of acute restrictive disease.

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Description

Explore the complexities of the respiratory system with a focus on pathology in this undergraduate quiz. Key topics include lung function, atelectasis, acute respiratory distress syndrome (ARDS), and the differences between restrictive and obstructive lung diseases.