6.5 Pathophysiology of COPD Flashcards
Define COPD
- Preventable, treatable
- Airflow limitation, not fully reversible
- Usually progressive
Symptoms that are suggestive of COPD
- Exertional breathlessness
- Cough
- Sputum
What history features could indicate increased risk of COPD?
- Smoking
- Exposure to other noxious agents
What is the FEV1/FVC ratio range that suggests COPD? What other condition is necessary for this?
- FEV1/FVC <0.70
- AND: bronchodilators have been given
What proportion of Australians over 45 have COPD?
1 in 20
What cardiovascular diagnosis is often used mistakenly instead of COPD?
Angina; since it commonly causes breathlessness.
List some childhood risk factors for COPD
- Low birth weight
- Smoking exposure
- Famine
Is there a genetic component to COPD?
Yes; there is basically one for every disease
Describe how epigenetic modification leads to inflammation in COPD
- Histone acetylation
- DNA is bound more loosely
- More transcription
- Production of inflammatory mediators
Clinical features of COPD
- Wheeze
- Dyspnoea
- Chest tightness/fullness
- Cough (more often in mornings)
- Sputum production
Common history signs of COPD
- Recurrent chest infections (often in winter)
- Tobacco
- Occupational exposure
- Hobbies
CXR signs of COPD
-Lungs are bigger
- Fewer lung markings visible
- Heart is pulled down
- Diaphragm is flattened
What does emphysema look like on a CT scan of the lungs?
Black holes in lungs
Why do people with obstructive lung diseases inhale less air?
- More air is trapped in the lung
- Less space for new air to be inhaled
Why are anxiety and depression common in COPD?
Breathlessness -> inactivity -> deconditioninng -> exercise intolerance -> disability/mortality
A vicious spiral downwards
Common viruses that exacerbate COPD
- Rhinoviruses
- Influenza viruses
Common bacteria that exacerbate COPD
- Haemophilus influenzaue
- Streptococcus pneumoniae
Effect of COPD exacerbations on mortality
Great increase in risk, even after first exacerbation
Four main signs of asthma in terms of pathophysiology
- Lung inflammation
- Airway hyper-responsiveness
- Airway remodelling
- Mucous hypersecretion
What happens during an asthma attack?
- Smooth muscle constricts
- More mucous is secreted
How does the ability of cilia to clear airways change in a person with asthma?
- Decreases
- Leads to more mucus lining the airways
Describe the airway remodelling that occurs during asthma
- Subepithelial fibrosis
- Angiogenesis
- Smooth muscle cell hyperplasia
Is airway remodelling more pronounced in chronic or acute asthma?
Chronic
What characterises allergic asthma?
Raised IgE levels
What characterises eosinophilic asthma?
Raised eosinophil count; greater than
What is type 2 inflammation?
Inflammation mediated by Th 2 cells
What type of asthma involves type 1 inflammation?
non-eosinophilic, non-allergic asthma
Describe early phase asthma response
- Typical asthma attack
- Inhaled allergen -> mast cell degranulation
- Reaction occurs within 10-15mins
Describe late phase asthma reactions
- Occurs 3-4 hours after initial exposure
- Involves T cells, eosinophils, and neutrophils
- Can have non-specific increased bronchial reactivity for up to 2 weeks
What are two of the most common types of COPD?
- Chronic bronchitis
- Emphysema
Describe emphysema
- Loss of elasticity
- Hyperinflation of lungs
- Increased airspaces (instead of many small ones), decreased SA:V
Describe COPD Pathophysiology. How does this link to exacerbation?
- Inhaled irritant/toxin
- Stimulates fibroblasts -> subendothelial fibrosis
- Complex inflammatory pathways -> alveolar and capillary damage
- Mucus hypersecretion in response to inflammation
- In exacerbation, an irritant such as a bacteria or a virus simply makes this worse than normal
What symptoms do patients present with during COPD exacerbation? Why?
- Increased breathlessness (airway narrowing, increased bronchospasm)
- Increased mucous production (goblet cell hyperplasia)
- Increased sputum thickness (recruitment of neutrophils or, more rarely, eosinophils)
Which is more likely to appear in older patients: COPD or asthma?
COPD
When is asthma typically worse throughout the day? Is this the same for COPD?
Asthma: typically worse at night
COPD: consistent (although can be characterised by increased cough in the mornings)
Which of asthma and COPD cause persistent vs variable decreases in lung function?
COPD: Consistent
Asthma: Variable
Time course of asthma vs that of COPD
Asthma: Seasonal; no worsening
COPD: Progressive worsening
CXR in asthma vs COPD
COPD: Hyperinflation
Asthma: Normal
