RESP - COPD Flashcards
What is COPD?
- Group of disorders characterised by airway inflammation and airflow limitation that is not fully reversible
- A progressive condition associated with an abnormal inflammatory response to noxious stimuli
- Fully reversible asthma is NOT COPD
Pathogenesis of COPD
Noxious agent -> inflammation ->
- Small airway disease
- airway inflammation
- airway remodelling
and/or
- Parenchymal destruction
- Loss of alveolar attachments
- Loss of elastic recoil
-> airflow limitation
- Inflammation in the airways, lung parenchyma and pulmonary vessels
- Neutrophils, macrophages, CD 8 cells
- Proteinase - antiproteinase imbalance
- Oxidative stress
(4) changes in lung parenchyma in COPD
- Alveolar wall destruction
- Loss of elasticity
- Destruction of pulmonary capillary bed
- Increased inflammatory cells; macrophages, CD8+ lymphocytes
Describe emphysema
- mechanism
- cells prominent
- (3) different patterns
- Mechanism: protease/antiprotease imbalance (proteases digest elastin and other structural proteins in alveolar wall; antiproteases protect against attack)
- Macrophages and T lymphocytes prominent
Different patterns in emphysema:
- Centriacinar (radiates from terminal bronchiole)
- Panacinar (more generalized)
- Bullae
Risk factors for COPD
- Smoking
- Occupational exposure to irritants
- Alpha-1 antitrypsin deficiency
- Bronchial hyper-responsiveness
- Passive smoking
- Air pollution (indoor and outdoor, esp biomass fuels)
- Recurrent RTIs in childhood
- Genetic predisposition
When should you consider the COPD diagnosis?
–any past or current smoker –chronic cough –productive cough –dyspnoea –history of exposure to other risk factors
How do you diagnose COPD?
•Spirometry is the best measure of airflow obstruction
•Measures time course of exhaled volume or flow
•FER = forced expiratory ratio
•FER = FEV1/FVC or FEV1/VC
–using the larger of FVC or VC
•FER less than 0.7 -> airflow obstruction
–this cut-off varies slightly with age
What is the cut off for airflow obstruction on spirometry?
Forced Expiratory Ratio (FEV1/FVC) LESS THAN 0.7
The cut off varies slightly with age
Compare COPD vs. Asthma
- timeline
- onset of symptoms
- smoking Hx
- airflow limitation reversible or irreversible
COPD:
- progressive
- late onset of symptoms
- moderate heavy smoking Hx
- airflow limitation not completely reversible
Asthma:
- variable course
- onset at young age
- no a/w smoking Hx
- airflow limitation substantially or completely reversible
NOTE: there is however overlap of respiratory symptoms b/w COPD & Asthma
Discuss the pathology of asthma
- inflammation?
- parts of airways affected
- involvement of lung parenchyma
- fibrosis?
- Inflammation (largely eosinophilic) affects ALL the airways (large and small) and doesn’t involve lung parenchyma
- Fibrosis is NOT a feature (sub-epithelial fibrosis may be present but is minimal compared with that seen in COPD)
Discuss the pathology of COPD
- inflammation?
- parts of airways affected
- involvement of lung parenchyma
- fibrosis?
- mucus?
- Neutrophilic inflammation
- In contrast with asthma, most of pathologic changes are in peripheral airways where there is also fibrosis leading to obliterative bronchiolitis
- Mucus hypersecretion is more prominent than in asthma
(4) cells involved in asthma
- Epithelial cells
- Mast cells
- CD4+ cells (Th2)
- Eosinophils
(4) cells involved in COPD
- Epithelial cells
- Alveolar macrophage
- CD8+ cells (Th1)
- Neutrophil
(2) main differences of inflammation consequences in asthma vs. COPD
Asthma:
- Bronchoconstriction
- Airway hyperresponsiveness
COPD:
- Small airway narrowing
- Alveolar destruction
List the GOLD classification of COPD severity
Stage I: Mild
FER less than 0.70
FEV1 > 80% predicted
Stage II: Moderate
FER less than 0.70
FEV1: 50-80% predicted
Stage III: Severe
FER less than 0.70
FEV1: 30-50% predicted
Stage IV: Very severe
FER less than 0.70
FEV1 less than 30% predicted OR
FEV1 less than 50% predicted + chronic respiratory failure
NOTE: Stages only differ by the % of FEV1 predicted. All stages have FER less than 0.70