Chapter 8b Flashcards
What are diffuse parenchymal lung diseases?
Group of lung diseases characterised by widespread inflammatory pathology, predominantly in the interstitium
What are two consequences of diffuse parenchymal lung diseases?
- Reduced compliance of lungs - edema and fibrosis of alveolar walls renders them rigid
- Thickening of alveolar walls also results in reduced gas exchange
What are 4 histological patterns of reaction in the lung following damage?
Hemorrhage and fibrin exudation into alveoli
Edema and inflammation of interstitium
Macrophage accumulation in alveolar spaces
Fibrosis in interstitium or alveolar spaces
What is the pathophysiology of ARDS?
- Damaging Stimulus to Lung
- Damage to alveolar lining cells (pneumocytes) & damage to alveolar capillary endothelium (pulmonary endothelium)
- Interstitial edema & protein exudation into alveoli (hyaline membranes) – causes significant decrease in lung compliance (death in 70%)
- Regeneration of Type 2 alveolar lining cells & inflammation of interstitium
- Organisation leading to interstitial fibrosis
- Mild focal fibrosis: recovery with minimal respiratory dysfunction (10%) OR marked interstitial fibrosis (honeycomb lung) leading to death due to chronic severe respiratory impairment (20%)
What are the two phases of ARDS?
- Acute Exudative Phase
- interstitial edema and high protein exudation into alveoli
(fibrin-rich fluid +. necrotic epithelial cells) - Late reorganisation phase
- regeneration of type 2 alveolar lining cells, organisation of hyaline membranes with fibrosis
- interstitium widened by mixture of inflammatory cells & scar tissue
How do COVID-19 patients die?
“cytokine storm” in response to the virus in the lung causes ARDS = stiff lungs
mechanical ventilation & 100% oxygen may not be sufficient to treat respiratory failure
What is the reslt of end stage of chronic pulmonary fibrosis?
Honeycomb Lung - small alveoli replaced by large cystic spaces
What is the consequence of end stage pulmonary fibrosis?
Chronic Respiratory Impairment and reduced diffusion capacity
Death due to combination of respiratory and cardiac failure
What histological pattern can be seen in acute damage to lungs? What modality is this seen on? What other imaging modality is used for diagnosis?
‘DAD’ diffuse alveolar damage in ARDS. Microscopy of lung biopsy. High resolution CT
What is idiopathic pulmonary fibrosis?
Commonest chronic diffuse parenchymal lung disease
no cause
Progressive restrictive lung disease
How does idiopathic pulmonary fibrosis present on microscope.
Usual interstitial pneumonia pattern
What is hypersensitivity pneumonitis/extrinsic allergic alveolitis?
Lung disease due to hypersensitivity to inhaled organic antigens
What is the cause of hypersensitivity pneumonitis/extrinsic allergic alveolits?
- Aninal Proteins
- Microbial Agents in vegetable matter 9fungi in mouldy crops, hay, compost)
When might symptoms of hypersensitivity pneumonitis/extrinsic allergic alveolits occur?
Acute (4-8h)
Chronic (insidious development of dyspnea and pulmonary fibrosis in patient with no acute symptoms)8
What is pneumoconiosis?
Disease of lungs caused by inhalation of dust
- silica
- coal dust
-asbestos
interaction of dust with defence mechanisms of lung, leading to inflammation, release of cytokines and stimulation of fibrosis
