Lecture 11: COPD Flashcards
COPD definition
Collection of conditions characterized by persistent expiratory airflow limitation that is not fully reversible associated w/ enhanced inflammatory response and exacerbations
Big FEV1 / FVC difference between COPD and asthma
Ratio cannot NORMALIZE even after administration of bronchodilator
Chronic bronchitis definition
Chronic, productive cough on most days for at least 3 months a year
Chronic bronchitis pathology
Hypertrophy/hyperplasia of mucus glands, bronchial wall inflammation/fibrosis –> bronchial wall thickening (edema, BM thickening, increased SM) with decreased luminal size
Chronic bronchitis is a _________ dx; emphysema is a _________ dx
Clinical; pathological
Describe emphysema
Destruction of lung parenchyma and enlargement of air spaces distal to terminal bronchiole
Types of emphysema and description
Centrilobular (proximal acinar): predominantly involves respiraotry bronchiole and upper lungs, smokers; Panlobular (panacinar), lower lungs, see in alpha1-antitrypsin deficiency
What does alpha-1 antitrypsin do?
Inhibitor of neutrophil elastase, which is a proteolytic enzyme that degrades elastin
How does smoking involve the protease-antiprotease theory?
Inactivates alpha-1 antitrypsin and recruits neutrophils
Variants in alpha-1 antitrypsin disease and which is more dangerous and which is more common
Z-variant (more dangerous) and S-variant (more common)
Z-variant
Failure to form alpha-1 antitrypsin salt bridge leading to slowly folding protein that form globules that are never secreted and accumulate hepatocytes (cirrhosis)
S-variant
Renders alpha-1 antitrypsin more susceptible to proteolysis; not associated with intracellular accumulation
Emphysema: lung compliance increased or decreased
Increased!
What is the equal pressure point?
Point at which the pressure within the bronchus and within the chest cavity are equal
Why is there decreased trans pulmonary pressure in emphysema?
Because the lungs are more compliant (less stiff), they cannot withstand a strong pressure differential
Why does a decreased trans pulmonary pressure impact emphysema?
You reach the EPP earlier, meaning that on expiration, there is obstruction
What does decreased airway tethering mean?
Fewer “tethers” of the airways mean they cannot be open fully (decreased diameter)
FRC and TLC in ephysema. What about VC?
FRC is larger because of increased compliance, TLC is increased (hyperinflation); VC is reduced
Mechanical disadvantage in ephysema
Enlarged lungs –> flattened diaphragm –> less strength of diaphragm (dyspnea)
Describe dynamic hyperinflation in a patient with COPD during exercise
They struggle with breathing out, meaning less time to breath out, so their end expiratory lung volume INCREASES as minute vent increases
V/Q in chronic bronchitis
Problem with airway leads to V/Q mismatch
V/Q in emphysema
Destroyed whole unit (alveolus and capillary), so may not get hypoxemia
Alveolar hypoventilation in emphysema
Increased work of breathing –> decreased central ventilatory drive AND increased dead space due to tissue destruction (this area is ventilated but not perfused = V/Q mismatch)
Symptoms of COPD
Dyspnea, cough (w/ sputum), exacerbations
What precipitates an exacerbation?
Viral infections, pollution, bronchospasm
Exam findings with emphysema
Prolonged expiratory phase, decreased breath sounds, wheezing (expiratory), ronchi
Exam findings with severe emphysema/COPD
Barrel-shaped chest, purse-lipped breathing (increases pressure in airways to stent open airways), emaciation
How can you see emphysema on X-ray/CT?
Hyperinflation by counting ribs and “moth eaten” appearance on CT
Causes of pulmonary HT in COPD
Hypoxia and other vessel changes, thromboembolism, parenchymal destruction (decreased vessels), LV dysfunction, hyperinflation
Chronic bronchitis and smoking (3 histological changes)
Mucus hypertrophy and hyperplasia, broncial wall inflammation, impaired mucociliary clearance
Chronic emphysema and smoking (2 histological changes)
Increased number of neutrophils –> increased elastase, oxidation of alpha-1 antitrypsin –> decreased function
What are other risk factors for emphysema?
Occupational exposures and indoor air pollution (cooking with biomass fuels)
Blue bloater
Chronic bronchitis: overweight, cyanotic, elevated Hb, peripheral edema, ronchi and wheezing
Pink puffer
Emphysema: older and thin, severe dyspnea, quiet chest, xray: hyperinflation with flattened diaphragm
What is the diagnostic requirement for COPD?
Airflow obstruction: you can have ephysema and chronic bronchitis without COPD
How is COPD a systemic disease?
SYSTEMIC inflammation related to ischemic HD, osteoporosis, metabolic syndrome, depression via systemic inflammation
Emphysema tx
Proven survival benefit: smoking cessation and supplemental O2 for hypoxemic pts
Emphysema sx management
Inhaled bronchodilators and corticosteroids
Describe lung volume reduction surgery
Reduces lung volume to reduce physiologic dead-space, increases elastic recoil, improve mechanic functioning of diaphragm
