Interstitial Lung Disease and ARDS - 1 Flashcards
Normally alveolar septae are very thin and composed of what?
single layer of pneumocytes
capillary and
small amount of connective tissue (mainly elastic fibers)
How do ILD’s affect alveolar interstitium?
add cells and fibrous tissue to the interstitium.
This:
Thickens and stiffens the septae and
Restricts stretching,
What is reduced lung compliance? (or rather what does it cause)
decreased filling of lungs upon inspiration
What does increased elasticity mean for the lungs? (upon expiration)
increased recoil of lungs on expiration
Restrictive lung diseases are characterized by what?
reduced lung compliance
What is the meaning of FEV 1?
forced expiratory volume in 1 second (FEV1) is the maximum amount of air that the subject can forcibly expel during the first second following maximal inhalation
What does FVC mean?
Forced vital capacity (FVC).
This is the amount of air exhaled forcefully and quickly after inhaling as much as you can.
Are obstructive diseases characterized by increased or decreased FEV 1/FVC ratios?
decreased
What are some C/F of interstitial lung disease?
- Stiff lung > increased effort of breathing > DYSPNEA
- DRY COUGH
- Ventilation perfusion abnormalities > Hypoxia > pulmonary hypertension > cor pulmonale >Respiratory failure
- All lung volumes and capacities are decreased
- Increased FEV 1sec / FVC ratio
What is the pathology of one with interstitial lung disease?
Diffuse fibrosis of alveolar interstitium
Upon completing a chest radiograph what would one find of a person with interstitial lung disease?
diffuse infiltrate (ground glass shadows)
What is this picture depicting?
Interstitial fibrosis
What is this picture depicting?
ground glass opacities (interstitial fibrosis)
What are the two classifications of restrictive lung disease?
acute: ARDS
chronic: Based on etiology
Classified into 2 major groups:
ILD with known cause
ILD with unknown cause
Chronic ILD comes from what exposure in general?
occupational and environmental exposures
Drug or treatment related
What are some inorganic exposures due to occupational and environmental exposures that could lead to chronic ILD?
pneumoconiosis:
asbestosis
silicosis
coal worker’s pneumoconiosis
berylliosis
What are some organic occupational and environmental exposure causes of chronic ILD?
Hypersensitivity pneumonitis
What are some drug related causes of chronic ILD?
Chemotherapeutic agents:
Busulfan, bleomycin, methotrexate
Ionizing radiation
What are some forms of ILD with unknown causes?
- Sarcoidosis
- Pulmonary hemorrhage syndrome
- Idiopathic pulmonary fibrosis
- Collagen vascular diseases
- Eosinophilic granuloma
What are some examples of pulmonary hemorrhage syndromes?
- Goodpasture syndrome
- Wegener’s granulomatosis
- Idiopathic hemosiderosis
ARDS is a clinical syndrome characterized by what?
Diffuse alveolar capillary damage with resultant
Increased capillary permeability causing leakage of protein rich fluid into alveoli and severe pulmonary edema.
What condition is being described?
Marked by formation of intra-alveolar hyaline membrane (composed of fibrin and cellular debris)
Results in severe impairment of gas exchange with consequent hypoxia (respiratory failure) refractory to oxygen therapy.
Patients present with: severe acute dyspnea and hypoxemia non responsive to 100% oxygen
ARDS acute respiratory distress syndrome
In simple words ARDS means what?
noncardiogenic pulmonary edema resulting from acute damage to alveoli
What are some synonyms for ARDS?
shock lung, diffuse alveolar damage (DAD)
What are some conditions associated with development of acute respiratory distress syndrome? (direct injury to lung)
Aspiration of gastric contents.
Smoke inhalation
Pneumonia
What are some conditions leading to indirect injury to the lung that are associate with development of acute respiratory distress syndrome?
Endotoxic or septic shock (most common cause)**
Severe trauma with shock
Drugs : heroin, bleomycin etc.
Toxemia of pregnancy
Amniotic fluid embolism
What are the 2 factors responsible for ARDS?
- Damage to alveolar capillary endothelium and alveolar epithelium
- Damage to type II pneumocytes
Describe pathogenesis of ARDS destroying alveolar capillary epithelium and type II pneumocytes.
Damage mediated by neutrophils and alveolar macrophages.
Alveolar macrophages release cytokines:
Cytokines are chemotactic to neutrophils
Neutrophils transmigrate into alveoli through pulmonary capillaries and damage type I and type II pneumocytes -Decrease in surfactant causes atelectasis
Capillary damage causes leakage of protein rich exudate producing hyaline membranes
What are the consequences of injury to pneumocytes and alveolar capillary endothelium?
- Damage to pulmonary capillaries (leaky capillary syndrome) > pulmonary edema, protein leakage
- Formation of hyaline membrane (from protein leakage)
- Damage of type II pneumocytes (loss of surfactant) > contributes to atelectasis (collapse of alveoli) …..In combination with pulmonary edema responsible for stiff lungs (chr or ARDS)
Gross morphology of lungs with ARDS?
lungs are dark red, airless and firm (liver-like)
Microscopy of early findings of lungs with ARDS?
Diffuse alveolar damage and necrosis
Alveolar edema, Collapsed alveoli
Some alveoli lined by hyaline membrane
What is the microscopic morphology of late findings (proliferative stage) of cells with ARDS?
Repair by type II pneumocytes
Progressive interstitial fibrosis (restrictive lung disease)
What is the pathogenesis of hyaline membrane formation?
Alveolar hyaline membranes consist of fibrin-rich edema fluid mixed with the cytoplasmic and lipid remnants of necrotic epithelial cells
How does the pathogenesis differ in hyaline membrane disease in newborns? (ARDS)
The mechanism of respiratory distress syndrome of the newborn is a deficiency of surfactant, whereas in ARDS the mechanism is damage to the alveolar epithelium (diffuse alveolar damage)
With continue proliferation in ARDS of fibroblasts, what type of lung disease develops in this patients?
While complete resolution may occur, hyperplasia of type II alveolar pneumocytes plus intra-alveolar fibrosis are common sequelae
Marked thickening of the alveolar walls and interstitial fibrosis may persist, giving rise to restrictive lung disease
What is the prognosis of patients with late stage ARDS?
mortality almost 60% even with improved methods
Compare and contrast FEV1/FVC ratio in restrictive vs obstructive lung diseases.
Obstructive FEV1 is really low compared to FVC > ratio < 80%
Restrictive FVC is much lower when compared to FEV1 and therefore ratio is > 80%
